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Home on zfs: some software stopped working #512

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mgiammarco opened this issue Jan 3, 2012 · 9 comments
Closed

Home on zfs: some software stopped working #512

mgiammarco opened this issue Jan 3, 2012 · 9 comments
Milestone
0.6.0-rc11

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@mgiammarco
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Hello,
I have ubuntu oneiric and zfs unstable. I have put my home on zfs. All seems to work enough well now apart ubuntu-one, nomachine and x2go that have stopped working.

Mario
@dajhorn
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dajhorn commented Jan 3, 2012

Are you using ppa:zfs-native/stable or ppa:zfs-native/daily?

@mgiammarco
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The daily one, the stable had some serious bugs.

@dajhorn
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dajhorn commented Jan 3, 2012

Okay, I will install ubuntu-one on my workstation to check what happens.

@mgiammarco
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I suggest you to install also www.nomachine.com or x2go. They write a lot
of files in their dot directory.

2012/1/3 Darik Horn <
[email protected]

Okay, I will install ubuntu-one on my workstation to check what happens.

Reply to this email directly or view it on GitHub:
#512 (comment)

@mgiammarco
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Situation is getting worse. After today update (0.6.0-43) eclipse and intellij idea fails to start many times.
Eclipse complains that a .project has disappeared and periodically complains about "could not write metadata for project xxx". It seems to me that this bug happens when there are applications that write a lot in dot files or that do synchronous writes.

@mgiammarco
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I confirm zfs is losing files and they are all .filename

@mgiammarco
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I add an example of an eclipse error message:

Problems occurred while trying to save the state of the workbench.
Could not write metadata for '/camel-example-aggregate'.
/home/mgiammarco/workspace/.metadata/.plugins/org.eclipse.core.resources/.projects/camel-example-aggregate/.markers (File o directory non esistente)

@behlendorf
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I can't see how zfs could loose a file. But what might be happening is these applications are attempting to update a dot file by unlinking it and writing a new one. But for some reason the new file fails to get written because zfs returns an error on write. It would be interesting to see one of these file updates under strace to see what flags its using and what error zfs is returning.

@behlendorf
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Closing issue, this issue is stale and I've heard of no similar issues

ryao added a commit to ryao/zfs that referenced this issue Oct 9, 2014
@ryao
vdev_raidz_io_start: Ignore empty writes
0489068 
The below excerpt of a backtrace is from a ztest failure when running
ZoL's ztest.

/openzfs#453 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#454 0x00007f03c806106e in vdev_queue_io (zio=zio@entry=0x7f0350003de0) at ../../module/zfs/vdev_queue.c:747
/openzfs#455 0x00007f03c80818c1 in zio_vdev_io_start (zio=0x7f0350003de0) at ../../module/zfs/zio.c:2659
/openzfs#456 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003de0) at ../../module/zfs/zio.c:1399
/openzfs#457 zio_nowait (zio=0x7f0350003de0) at ../../module/zfs/zio.c:1456
/openzfs#458 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350003a10) at ../../module/zfs/vdev_mirror.c:374
/openzfs#459 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003a10) at ../../module/zfs/zio.c:1399
/openzfs#460 zio_nowait (zio=0x7f0350003a10) at ../../module/zfs/zio.c:1456
/openzfs#461 0x00007f03c806464c in vdev_raidz_io_start (zio=0x7f0350003380) at ../../module/zfs/vdev_raidz.c:1607
/openzfs#462 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003380) at ../../module/zfs/zio.c:1399
/openzfs#463 zio_nowait (zio=0x7f0350003380) at ../../module/zfs/zio.c:1456
/openzfs#464 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350002fb0) at ../../module/zfs/vdev_mirror.c:374
/openzfs#465 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002fb0) at ../../module/zfs/zio.c:1399
/openzfs#466 zio_nowait (zio=0x7f0350002fb0) at ../../module/zfs/zio.c:1456
/openzfs#467 0x00007f03c805ed43 in vdev_mirror_io_done (zio=0x7f033957ebf0) at ../../module/zfs/vdev_mirror.c:499
/openzfs#468 0x00007f03c807a0c0 in zio_vdev_io_done (zio=0x7f033957ebf0) at ../../module/zfs/zio.c:2707
/openzfs#469 0x00007f03c808285b in __zio_execute (zio=0x7f033957ebf0) at ../../module/zfs/zio.c:1399
/openzfs#470 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f0390001330, pio=0x7f033957ebf0) at ../../module/zfs/zio.c:547
/openzfs#471 zio_done (zio=0x7f0390001330) at ../../module/zfs/zio.c:3278
/openzfs#472 0x00007f03c808285b in __zio_execute (zio=0x7f0390001330) at ../../module/zfs/zio.c:1399
/openzfs#473 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4013a00, pio=0x7f0390001330) at ../../module/zfs/zio.c:547
/openzfs#474 zio_done (zio=0x7f03b4013a00) at ../../module/zfs/zio.c:3278
/openzfs#475 0x00007f03c808285b in __zio_execute (zio=0x7f03b4013a00) at ../../module/zfs/zio.c:1399
/openzfs#476 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4014210, pio=0x7f03b4013a00) at ../../module/zfs/zio.c:547
/openzfs#477 zio_done (zio=0x7f03b4014210) at ../../module/zfs/zio.c:3278
/openzfs#478 0x00007f03c808285b in __zio_execute (zio=0x7f03b4014210) at ../../module/zfs/zio.c:1399
/openzfs#479 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4014620, pio=0x7f03b4014210) at ../../module/zfs/zio.c:547
/openzfs#480 zio_done (zio=0x7f03b4014620) at ../../module/zfs/zio.c:3278
/openzfs#481 0x00007f03c807a6d3 in __zio_execute (zio=0x7f03b4014620) at ../../module/zfs/zio.c:1399
/openzfs#482 zio_execute (zio=zio@entry=0x7f03b4014620) at ../../module/zfs/zio.c:1337
/openzfs#483 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#484 0x00007f03c806106e in vdev_queue_io (zio=zio@entry=0x7f0350002be0) at ../../module/zfs/vdev_queue.c:747
/openzfs#485 0x00007f03c80818c1 in zio_vdev_io_start (zio=0x7f0350002be0) at ../../module/zfs/zio.c:2659
/openzfs#486 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002be0) at ../../module/zfs/zio.c:1399
/openzfs#487 zio_nowait (zio=0x7f0350002be0) at ../../module/zfs/zio.c:1456
/openzfs#488 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350002810) at ../../module/zfs/vdev_mirror.c:374
/openzfs#489 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002810) at ../../module/zfs/zio.c:1399
/openzfs#490 zio_nowait (zio=0x7f0350002810) at ../../module/zfs/zio.c:1456
/openzfs#491 0x00007f03c8064593 in vdev_raidz_io_start (zio=0x7f0350001270) at ../../module/zfs/vdev_raidz.c:1591
/openzfs#492 0x00007f03c807f243 in __zio_execute (zio=0x7f0350001270) at ../../module/zfs/zio.c:1399
/openzfs#493 zio_nowait (zio=0x7f0350001270) at ../../module/zfs/zio.c:1456
/openzfs#494 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350001e60) at ../../module/zfs/vdev_mirror.c:374
/openzfs#495 0x00007f03c807f243 in __zio_execute (zio=0x7f0350001e60) at ../../module/zfs/zio.c:1399
/openzfs#496 zio_nowait (zio=0x7f0350001e60) at ../../module/zfs/zio.c:1456
/openzfs#497 0x00007f03c805ed43 in vdev_mirror_io_done (zio=0x7f033a0c39c0) at ../../module/zfs/vdev_mirror.c:499
/openzfs#498 0x00007f03c807a0c0 in zio_vdev_io_done (zio=0x7f033a0c39c0) at ../../module/zfs/zio.c:2707
/openzfs#499 0x00007f03c808285b in __zio_execute (zio=0x7f033a0c39c0) at ../../module/zfs/zio.c:1399
/openzfs#500 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03a8003c00, pio=0x7f033a0c39c0) at ../../module/zfs/zio.c:547
/openzfs#501 zio_done (zio=0x7f03a8003c00) at ../../module/zfs/zio.c:3278
/openzfs#502 0x00007f03c808285b in __zio_execute (zio=0x7f03a8003c00) at ../../module/zfs/zio.c:1399
/openzfs#503 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800c400, pio=0x7f03a8003c00) at ../../module/zfs/zio.c:547
/openzfs#504 zio_done (zio=0x7f038800c400) at ../../module/zfs/zio.c:3278
/openzfs#505 0x00007f03c808285b in __zio_execute (zio=0x7f038800c400) at ../../module/zfs/zio.c:1399
/openzfs#506 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800da00, pio=0x7f038800c400) at ../../module/zfs/zio.c:547
/openzfs#507 zio_done (zio=0x7f038800da00) at ../../module/zfs/zio.c:3278
/openzfs#508 0x00007f03c808285b in __zio_execute (zio=0x7f038800da00) at ../../module/zfs/zio.c:1399
/openzfs#509 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800fd80, pio=0x7f038800da00) at ../../module/zfs/zio.c:547
/openzfs#510 zio_done (zio=0x7f038800fd80) at ../../module/zfs/zio.c:3278
/openzfs#511 0x00007f03c807a6d3 in __zio_execute (zio=0x7f038800fd80) at ../../module/zfs/zio.c:1399
/openzfs#512 zio_execute (zio=zio@entry=0x7f038800fd80) at ../../module/zfs/zio.c:1337
/openzfs#513 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#514 0x00007f03c806119d in vdev_queue_io_done (zio=zio@entry=0x7f03a0010950) at ../../module/zfs/vdev_queue.c:775
/openzfs#515 0x00007f03c807a0e8 in zio_vdev_io_done (zio=0x7f03a0010950) at ../../module/zfs/zio.c:2686
/openzfs#516 0x00007f03c807a6d3 in __zio_execute (zio=0x7f03a0010950) at ../../module/zfs/zio.c:1399
/openzfs#517 zio_execute (zio=0x7f03a0010950) at ../../module/zfs/zio.c:1337
/openzfs#518 0x00007f03c7fcd0c4 in taskq_thread (arg=0x966d50) at ../../lib/libzpool/taskq.c:215
/openzfs#519 0x00007f03c7fc7937 in zk_thread_helper (arg=0x967e90) at ../../lib/libzpool/kernel.c:135
/openzfs#520 0x00007f03c78890a3 in start_thread (arg=0x7f03c2703700) at pthread_create.c:309
/openzfs#521 0x00007f03c75c50fd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

The backtrace was an infinite loop of `vdev_queue_io_to_issue()` invoking
`zio_execute()` until it overran the stack. vdev_queue_io_to_issue() will ony
invoke `zio_execute()` on raidz vdevs when aggregation I/Os are generated to
improve aggregation continuity. These I/Os do not trigger any writes. However,
it appears that they can be generated in such a way that they recurse
infinitely upon return to `vdev_queue_io_to_issue()`. As a consequence, we see
the number of parents by 1 each time the recursion returns to
`vdev_raidz_io_start()`.

Signed-off-by: Richard Yao <[email protected]>
@ryao ryao mentioned this issue Oct 9, 2014
Closed
ryao added a commit to ryao/zfs that referenced this issue Oct 9, 2014
@ryao
vdev_raidz_io_start: Ignore empty writes
0bd246f 
The below excerpt of a backtrace is from a ztest failure when running
ZoL's ztest.

/openzfs#453 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#454 0x00007f03c806106e in vdev_queue_io (zio=zio@entry=0x7f0350003de0) at ../../module/zfs/vdev_queue.c:747
/openzfs#455 0x00007f03c80818c1 in zio_vdev_io_start (zio=0x7f0350003de0) at ../../module/zfs/zio.c:2659
/openzfs#456 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003de0) at ../../module/zfs/zio.c:1399
/openzfs#457 zio_nowait (zio=0x7f0350003de0) at ../../module/zfs/zio.c:1456
/openzfs#458 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350003a10) at ../../module/zfs/vdev_mirror.c:374
/openzfs#459 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003a10) at ../../module/zfs/zio.c:1399
/openzfs#460 zio_nowait (zio=0x7f0350003a10) at ../../module/zfs/zio.c:1456
/openzfs#461 0x00007f03c806464c in vdev_raidz_io_start (zio=0x7f0350003380) at ../../module/zfs/vdev_raidz.c:1607
/openzfs#462 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003380) at ../../module/zfs/zio.c:1399
/openzfs#463 zio_nowait (zio=0x7f0350003380) at ../../module/zfs/zio.c:1456
/openzfs#464 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350002fb0) at ../../module/zfs/vdev_mirror.c:374
/openzfs#465 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002fb0) at ../../module/zfs/zio.c:1399
/openzfs#466 zio_nowait (zio=0x7f0350002fb0) at ../../module/zfs/zio.c:1456
/openzfs#467 0x00007f03c805ed43 in vdev_mirror_io_done (zio=0x7f033957ebf0) at ../../module/zfs/vdev_mirror.c:499
/openzfs#468 0x00007f03c807a0c0 in zio_vdev_io_done (zio=0x7f033957ebf0) at ../../module/zfs/zio.c:2707
/openzfs#469 0x00007f03c808285b in __zio_execute (zio=0x7f033957ebf0) at ../../module/zfs/zio.c:1399
/openzfs#470 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f0390001330, pio=0x7f033957ebf0) at ../../module/zfs/zio.c:547
/openzfs#471 zio_done (zio=0x7f0390001330) at ../../module/zfs/zio.c:3278
/openzfs#472 0x00007f03c808285b in __zio_execute (zio=0x7f0390001330) at ../../module/zfs/zio.c:1399
/openzfs#473 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4013a00, pio=0x7f0390001330) at ../../module/zfs/zio.c:547
/openzfs#474 zio_done (zio=0x7f03b4013a00) at ../../module/zfs/zio.c:3278
/openzfs#475 0x00007f03c808285b in __zio_execute (zio=0x7f03b4013a00) at ../../module/zfs/zio.c:1399
/openzfs#476 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4014210, pio=0x7f03b4013a00) at ../../module/zfs/zio.c:547
/openzfs#477 zio_done (zio=0x7f03b4014210) at ../../module/zfs/zio.c:3278
/openzfs#478 0x00007f03c808285b in __zio_execute (zio=0x7f03b4014210) at ../../module/zfs/zio.c:1399
/openzfs#479 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4014620, pio=0x7f03b4014210) at ../../module/zfs/zio.c:547
/openzfs#480 zio_done (zio=0x7f03b4014620) at ../../module/zfs/zio.c:3278
/openzfs#481 0x00007f03c807a6d3 in __zio_execute (zio=0x7f03b4014620) at ../../module/zfs/zio.c:1399
/openzfs#482 zio_execute (zio=zio@entry=0x7f03b4014620) at ../../module/zfs/zio.c:1337
/openzfs#483 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#484 0x00007f03c806106e in vdev_queue_io (zio=zio@entry=0x7f0350002be0) at ../../module/zfs/vdev_queue.c:747
/openzfs#485 0x00007f03c80818c1 in zio_vdev_io_start (zio=0x7f0350002be0) at ../../module/zfs/zio.c:2659
/openzfs#486 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002be0) at ../../module/zfs/zio.c:1399
/openzfs#487 zio_nowait (zio=0x7f0350002be0) at ../../module/zfs/zio.c:1456
/openzfs#488 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350002810) at ../../module/zfs/vdev_mirror.c:374
/openzfs#489 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002810) at ../../module/zfs/zio.c:1399
/openzfs#490 zio_nowait (zio=0x7f0350002810) at ../../module/zfs/zio.c:1456
/openzfs#491 0x00007f03c8064593 in vdev_raidz_io_start (zio=0x7f0350001270) at ../../module/zfs/vdev_raidz.c:1591
/openzfs#492 0x00007f03c807f243 in __zio_execute (zio=0x7f0350001270) at ../../module/zfs/zio.c:1399
/openzfs#493 zio_nowait (zio=0x7f0350001270) at ../../module/zfs/zio.c:1456
/openzfs#494 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350001e60) at ../../module/zfs/vdev_mirror.c:374
/openzfs#495 0x00007f03c807f243 in __zio_execute (zio=0x7f0350001e60) at ../../module/zfs/zio.c:1399
/openzfs#496 zio_nowait (zio=0x7f0350001e60) at ../../module/zfs/zio.c:1456
/openzfs#497 0x00007f03c805ed43 in vdev_mirror_io_done (zio=0x7f033a0c39c0) at ../../module/zfs/vdev_mirror.c:499
/openzfs#498 0x00007f03c807a0c0 in zio_vdev_io_done (zio=0x7f033a0c39c0) at ../../module/zfs/zio.c:2707
/openzfs#499 0x00007f03c808285b in __zio_execute (zio=0x7f033a0c39c0) at ../../module/zfs/zio.c:1399
/openzfs#500 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03a8003c00, pio=0x7f033a0c39c0) at ../../module/zfs/zio.c:547
/openzfs#501 zio_done (zio=0x7f03a8003c00) at ../../module/zfs/zio.c:3278
/openzfs#502 0x00007f03c808285b in __zio_execute (zio=0x7f03a8003c00) at ../../module/zfs/zio.c:1399
/openzfs#503 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800c400, pio=0x7f03a8003c00) at ../../module/zfs/zio.c:547
/openzfs#504 zio_done (zio=0x7f038800c400) at ../../module/zfs/zio.c:3278
/openzfs#505 0x00007f03c808285b in __zio_execute (zio=0x7f038800c400) at ../../module/zfs/zio.c:1399
/openzfs#506 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800da00, pio=0x7f038800c400) at ../../module/zfs/zio.c:547
/openzfs#507 zio_done (zio=0x7f038800da00) at ../../module/zfs/zio.c:3278
/openzfs#508 0x00007f03c808285b in __zio_execute (zio=0x7f038800da00) at ../../module/zfs/zio.c:1399
/openzfs#509 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800fd80, pio=0x7f038800da00) at ../../module/zfs/zio.c:547
/openzfs#510 zio_done (zio=0x7f038800fd80) at ../../module/zfs/zio.c:3278
/openzfs#511 0x00007f03c807a6d3 in __zio_execute (zio=0x7f038800fd80) at ../../module/zfs/zio.c:1399
/openzfs#512 zio_execute (zio=zio@entry=0x7f038800fd80) at ../../module/zfs/zio.c:1337
/openzfs#513 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#514 0x00007f03c806119d in vdev_queue_io_done (zio=zio@entry=0x7f03a0010950) at ../../module/zfs/vdev_queue.c:775
/openzfs#515 0x00007f03c807a0e8 in zio_vdev_io_done (zio=0x7f03a0010950) at ../../module/zfs/zio.c:2686
/openzfs#516 0x00007f03c807a6d3 in __zio_execute (zio=0x7f03a0010950) at ../../module/zfs/zio.c:1399
/openzfs#517 zio_execute (zio=0x7f03a0010950) at ../../module/zfs/zio.c:1337
/openzfs#518 0x00007f03c7fcd0c4 in taskq_thread (arg=0x966d50) at ../../lib/libzpool/taskq.c:215
/openzfs#519 0x00007f03c7fc7937 in zk_thread_helper (arg=0x967e90) at ../../lib/libzpool/kernel.c:135
/openzfs#520 0x00007f03c78890a3 in start_thread (arg=0x7f03c2703700) at pthread_create.c:309
/openzfs#521 0x00007f03c75c50fd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

The backtrace was an infinite loop of `vdev_queue_io_to_issue()` invoking
`zio_execute()` until it overran the stack. vdev_queue_io_to_issue() will ony
invoke `zio_execute()` on raidz vdevs when aggregation I/Os are generated to
improve aggregation continuity. These I/Os do not trigger any writes. However,
it appears that they can be generated in such a way that they recurse
infinitely upon return to `vdev_queue_io_to_issue()`. As a consequence, we see
the number of parents by 1 each time the recursion returns to
`vdev_raidz_io_start()`.

Signed-off-by: Richard Yao <[email protected]>
ryao added a commit to ryao/zfs that referenced this issue Oct 9, 2014
@ryao
vdev_raidz_io_start: Ignore empty writes
7fbb0cb 
The below excerpt of a backtrace is from a ztest failure when running
ZoL's ztest.

/openzfs#453 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#454 0x00007f03c806106e in vdev_queue_io (zio=zio@entry=0x7f0350003de0) at ../../module/zfs/vdev_queue.c:747
/openzfs#455 0x00007f03c80818c1 in zio_vdev_io_start (zio=0x7f0350003de0) at ../../module/zfs/zio.c:2659
/openzfs#456 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003de0) at ../../module/zfs/zio.c:1399
/openzfs#457 zio_nowait (zio=0x7f0350003de0) at ../../module/zfs/zio.c:1456
/openzfs#458 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350003a10) at ../../module/zfs/vdev_mirror.c:374
/openzfs#459 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003a10) at ../../module/zfs/zio.c:1399
/openzfs#460 zio_nowait (zio=0x7f0350003a10) at ../../module/zfs/zio.c:1456
/openzfs#461 0x00007f03c806464c in vdev_raidz_io_start (zio=0x7f0350003380) at ../../module/zfs/vdev_raidz.c:1607
/openzfs#462 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003380) at ../../module/zfs/zio.c:1399
/openzfs#463 zio_nowait (zio=0x7f0350003380) at ../../module/zfs/zio.c:1456
/openzfs#464 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350002fb0) at ../../module/zfs/vdev_mirror.c:374
/openzfs#465 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002fb0) at ../../module/zfs/zio.c:1399
/openzfs#466 zio_nowait (zio=0x7f0350002fb0) at ../../module/zfs/zio.c:1456
/openzfs#467 0x00007f03c805ed43 in vdev_mirror_io_done (zio=0x7f033957ebf0) at ../../module/zfs/vdev_mirror.c:499
/openzfs#468 0x00007f03c807a0c0 in zio_vdev_io_done (zio=0x7f033957ebf0) at ../../module/zfs/zio.c:2707
/openzfs#469 0x00007f03c808285b in __zio_execute (zio=0x7f033957ebf0) at ../../module/zfs/zio.c:1399
/openzfs#470 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f0390001330, pio=0x7f033957ebf0) at ../../module/zfs/zio.c:547
/openzfs#471 zio_done (zio=0x7f0390001330) at ../../module/zfs/zio.c:3278
/openzfs#472 0x00007f03c808285b in __zio_execute (zio=0x7f0390001330) at ../../module/zfs/zio.c:1399
/openzfs#473 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4013a00, pio=0x7f0390001330) at ../../module/zfs/zio.c:547
/openzfs#474 zio_done (zio=0x7f03b4013a00) at ../../module/zfs/zio.c:3278
/openzfs#475 0x00007f03c808285b in __zio_execute (zio=0x7f03b4013a00) at ../../module/zfs/zio.c:1399
/openzfs#476 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4014210, pio=0x7f03b4013a00) at ../../module/zfs/zio.c:547
/openzfs#477 zio_done (zio=0x7f03b4014210) at ../../module/zfs/zio.c:3278
/openzfs#478 0x00007f03c808285b in __zio_execute (zio=0x7f03b4014210) at ../../module/zfs/zio.c:1399
/openzfs#479 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4014620, pio=0x7f03b4014210) at ../../module/zfs/zio.c:547
/openzfs#480 zio_done (zio=0x7f03b4014620) at ../../module/zfs/zio.c:3278
/openzfs#481 0x00007f03c807a6d3 in __zio_execute (zio=0x7f03b4014620) at ../../module/zfs/zio.c:1399
/openzfs#482 zio_execute (zio=zio@entry=0x7f03b4014620) at ../../module/zfs/zio.c:1337
/openzfs#483 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#484 0x00007f03c806106e in vdev_queue_io (zio=zio@entry=0x7f0350002be0) at ../../module/zfs/vdev_queue.c:747
/openzfs#485 0x00007f03c80818c1 in zio_vdev_io_start (zio=0x7f0350002be0) at ../../module/zfs/zio.c:2659
/openzfs#486 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002be0) at ../../module/zfs/zio.c:1399
/openzfs#487 zio_nowait (zio=0x7f0350002be0) at ../../module/zfs/zio.c:1456
/openzfs#488 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350002810) at ../../module/zfs/vdev_mirror.c:374
/openzfs#489 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002810) at ../../module/zfs/zio.c:1399
/openzfs#490 zio_nowait (zio=0x7f0350002810) at ../../module/zfs/zio.c:1456
/openzfs#491 0x00007f03c8064593 in vdev_raidz_io_start (zio=0x7f0350001270) at ../../module/zfs/vdev_raidz.c:1591
/openzfs#492 0x00007f03c807f243 in __zio_execute (zio=0x7f0350001270) at ../../module/zfs/zio.c:1399
/openzfs#493 zio_nowait (zio=0x7f0350001270) at ../../module/zfs/zio.c:1456
/openzfs#494 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350001e60) at ../../module/zfs/vdev_mirror.c:374
/openzfs#495 0x00007f03c807f243 in __zio_execute (zio=0x7f0350001e60) at ../../module/zfs/zio.c:1399
/openzfs#496 zio_nowait (zio=0x7f0350001e60) at ../../module/zfs/zio.c:1456
/openzfs#497 0x00007f03c805ed43 in vdev_mirror_io_done (zio=0x7f033a0c39c0) at ../../module/zfs/vdev_mirror.c:499
/openzfs#498 0x00007f03c807a0c0 in zio_vdev_io_done (zio=0x7f033a0c39c0) at ../../module/zfs/zio.c:2707
/openzfs#499 0x00007f03c808285b in __zio_execute (zio=0x7f033a0c39c0) at ../../module/zfs/zio.c:1399
/openzfs#500 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03a8003c00, pio=0x7f033a0c39c0) at ../../module/zfs/zio.c:547
/openzfs#501 zio_done (zio=0x7f03a8003c00) at ../../module/zfs/zio.c:3278
/openzfs#502 0x00007f03c808285b in __zio_execute (zio=0x7f03a8003c00) at ../../module/zfs/zio.c:1399
/openzfs#503 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800c400, pio=0x7f03a8003c00) at ../../module/zfs/zio.c:547
/openzfs#504 zio_done (zio=0x7f038800c400) at ../../module/zfs/zio.c:3278
/openzfs#505 0x00007f03c808285b in __zio_execute (zio=0x7f038800c400) at ../../module/zfs/zio.c:1399
/openzfs#506 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800da00, pio=0x7f038800c400) at ../../module/zfs/zio.c:547
/openzfs#507 zio_done (zio=0x7f038800da00) at ../../module/zfs/zio.c:3278
/openzfs#508 0x00007f03c808285b in __zio_execute (zio=0x7f038800da00) at ../../module/zfs/zio.c:1399
/openzfs#509 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800fd80, pio=0x7f038800da00) at ../../module/zfs/zio.c:547
/openzfs#510 zio_done (zio=0x7f038800fd80) at ../../module/zfs/zio.c:3278
/openzfs#511 0x00007f03c807a6d3 in __zio_execute (zio=0x7f038800fd80) at ../../module/zfs/zio.c:1399
/openzfs#512 zio_execute (zio=zio@entry=0x7f038800fd80) at ../../module/zfs/zio.c:1337
/openzfs#513 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#514 0x00007f03c806119d in vdev_queue_io_done (zio=zio@entry=0x7f03a0010950) at ../../module/zfs/vdev_queue.c:775
/openzfs#515 0x00007f03c807a0e8 in zio_vdev_io_done (zio=0x7f03a0010950) at ../../module/zfs/zio.c:2686
/openzfs#516 0x00007f03c807a6d3 in __zio_execute (zio=0x7f03a0010950) at ../../module/zfs/zio.c:1399
/openzfs#517 zio_execute (zio=0x7f03a0010950) at ../../module/zfs/zio.c:1337
/openzfs#518 0x00007f03c7fcd0c4 in taskq_thread (arg=0x966d50) at ../../lib/libzpool/taskq.c:215
/openzfs#519 0x00007f03c7fc7937 in zk_thread_helper (arg=0x967e90) at ../../lib/libzpool/kernel.c:135
/openzfs#520 0x00007f03c78890a3 in start_thread (arg=0x7f03c2703700) at pthread_create.c:309
/openzfs#521 0x00007f03c75c50fd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

The backtrace was an infinite loop of `vdev_queue_io_to_issue()` invoking
`zio_execute()` until it overran the stack. vdev_queue_io_to_issue() will ony
invoke `zio_execute()` on raidz vdevs when aggregation I/Os are generated to
improve aggregation continuity. These I/Os do not trigger any writes. However,
it appears that they can be generated in such a way that they recurse
infinitely upon return to `vdev_queue_io_to_issue()`.

Signed-off-by: Richard Yao <[email protected]>
ryao added a commit to ryao/zfs that referenced this issue Oct 10, 2014
@ryao
Redispatch ZIOs in deep notification call graphs
8d523a5 
The below excerpt of a backtrace is from a ztest failure when running ZoL's
ztest:

/openzfs#453 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#454 0x00007f03c806106e in vdev_queue_io (zio=zio@entry=0x7f0350003de0) at ../../module/zfs/vdev_queue.c:747
/openzfs#455 0x00007f03c80818c1 in zio_vdev_io_start (zio=0x7f0350003de0) at ../../module/zfs/zio.c:2659
/openzfs#456 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003de0) at ../../module/zfs/zio.c:1399
/openzfs#457 zio_nowait (zio=0x7f0350003de0) at ../../module/zfs/zio.c:1456
/openzfs#458 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350003a10) at ../../module/zfs/vdev_mirror.c:374
/openzfs#459 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003a10) at ../../module/zfs/zio.c:1399
/openzfs#460 zio_nowait (zio=0x7f0350003a10) at ../../module/zfs/zio.c:1456
/openzfs#461 0x00007f03c806464c in vdev_raidz_io_start (zio=0x7f0350003380) at ../../module/zfs/vdev_raidz.c:1607
/openzfs#462 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003380) at ../../module/zfs/zio.c:1399
/openzfs#463 zio_nowait (zio=0x7f0350003380) at ../../module/zfs/zio.c:1456
/openzfs#464 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350002fb0) at ../../module/zfs/vdev_mirror.c:374
/openzfs#465 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002fb0) at ../../module/zfs/zio.c:1399
/openzfs#466 zio_nowait (zio=0x7f0350002fb0) at ../../module/zfs/zio.c:1456
/openzfs#467 0x00007f03c805ed43 in vdev_mirror_io_done (zio=0x7f033957ebf0) at ../../module/zfs/vdev_mirror.c:499
/openzfs#468 0x00007f03c807a0c0 in zio_vdev_io_done (zio=0x7f033957ebf0) at ../../module/zfs/zio.c:2707
/openzfs#469 0x00007f03c808285b in __zio_execute (zio=0x7f033957ebf0) at ../../module/zfs/zio.c:1399
/openzfs#470 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f0390001330, pio=0x7f033957ebf0) at ../../module/zfs/zio.c:547
/openzfs#471 zio_done (zio=0x7f0390001330) at ../../module/zfs/zio.c:3278
/openzfs#472 0x00007f03c808285b in __zio_execute (zio=0x7f0390001330) at ../../module/zfs/zio.c:1399
/openzfs#473 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4013a00, pio=0x7f0390001330) at ../../module/zfs/zio.c:547
/openzfs#474 zio_done (zio=0x7f03b4013a00) at ../../module/zfs/zio.c:3278
/openzfs#475 0x00007f03c808285b in __zio_execute (zio=0x7f03b4013a00) at ../../module/zfs/zio.c:1399
/openzfs#476 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4014210, pio=0x7f03b4013a00) at ../../module/zfs/zio.c:547
/openzfs#477 zio_done (zio=0x7f03b4014210) at ../../module/zfs/zio.c:3278
/openzfs#478 0x00007f03c808285b in __zio_execute (zio=0x7f03b4014210) at ../../module/zfs/zio.c:1399
/openzfs#479 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4014620, pio=0x7f03b4014210) at ../../module/zfs/zio.c:547
/openzfs#480 zio_done (zio=0x7f03b4014620) at ../../module/zfs/zio.c:3278
/openzfs#481 0x00007f03c807a6d3 in __zio_execute (zio=0x7f03b4014620) at ../../module/zfs/zio.c:1399
/openzfs#482 zio_execute (zio=zio@entry=0x7f03b4014620) at ../../module/zfs/zio.c:1337
/openzfs#483 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#484 0x00007f03c806106e in vdev_queue_io (zio=zio@entry=0x7f0350002be0) at ../../module/zfs/vdev_queue.c:747
/openzfs#485 0x00007f03c80818c1 in zio_vdev_io_start (zio=0x7f0350002be0) at ../../module/zfs/zio.c:2659
/openzfs#486 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002be0) at ../../module/zfs/zio.c:1399
/openzfs#487 zio_nowait (zio=0x7f0350002be0) at ../../module/zfs/zio.c:1456
/openzfs#488 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350002810) at ../../module/zfs/vdev_mirror.c:374
/openzfs#489 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002810) at ../../module/zfs/zio.c:1399
/openzfs#490 zio_nowait (zio=0x7f0350002810) at ../../module/zfs/zio.c:1456
/openzfs#491 0x00007f03c8064593 in vdev_raidz_io_start (zio=0x7f0350001270) at ../../module/zfs/vdev_raidz.c:1591
/openzfs#492 0x00007f03c807f243 in __zio_execute (zio=0x7f0350001270) at ../../module/zfs/zio.c:1399
/openzfs#493 zio_nowait (zio=0x7f0350001270) at ../../module/zfs/zio.c:1456
/openzfs#494 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350001e60) at ../../module/zfs/vdev_mirror.c:374
/openzfs#495 0x00007f03c807f243 in __zio_execute (zio=0x7f0350001e60) at ../../module/zfs/zio.c:1399
/openzfs#496 zio_nowait (zio=0x7f0350001e60) at ../../module/zfs/zio.c:1456
/openzfs#497 0x00007f03c805ed43 in vdev_mirror_io_done (zio=0x7f033a0c39c0) at ../../module/zfs/vdev_mirror.c:499
/openzfs#498 0x00007f03c807a0c0 in zio_vdev_io_done (zio=0x7f033a0c39c0) at ../../module/zfs/zio.c:2707
/openzfs#499 0x00007f03c808285b in __zio_execute (zio=0x7f033a0c39c0) at ../../module/zfs/zio.c:1399
/openzfs#500 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03a8003c00, pio=0x7f033a0c39c0) at ../../module/zfs/zio.c:547
/openzfs#501 zio_done (zio=0x7f03a8003c00) at ../../module/zfs/zio.c:3278
/openzfs#502 0x00007f03c808285b in __zio_execute (zio=0x7f03a8003c00) at ../../module/zfs/zio.c:1399
/openzfs#503 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800c400, pio=0x7f03a8003c00) at ../../module/zfs/zio.c:547
/openzfs#504 zio_done (zio=0x7f038800c400) at ../../module/zfs/zio.c:3278
/openzfs#505 0x00007f03c808285b in __zio_execute (zio=0x7f038800c400) at ../../module/zfs/zio.c:1399
/openzfs#506 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800da00, pio=0x7f038800c400) at ../../module/zfs/zio.c:547
/openzfs#507 zio_done (zio=0x7f038800da00) at ../../module/zfs/zio.c:3278
/openzfs#508 0x00007f03c808285b in __zio_execute (zio=0x7f038800da00) at ../../module/zfs/zio.c:1399
/openzfs#509 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800fd80, pio=0x7f038800da00) at ../../module/zfs/zio.c:547
/openzfs#510 zio_done (zio=0x7f038800fd80) at ../../module/zfs/zio.c:3278
/openzfs#511 0x00007f03c807a6d3 in __zio_execute (zio=0x7f038800fd80) at ../../module/zfs/zio.c:1399
/openzfs#512 zio_execute (zio=zio@entry=0x7f038800fd80) at ../../module/zfs/zio.c:1337
/openzfs#513 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#514 0x00007f03c806119d in vdev_queue_io_done (zio=zio@entry=0x7f03a0010950) at ../../module/zfs/vdev_queue.c:775
/openzfs#515 0x00007f03c807a0e8 in zio_vdev_io_done (zio=0x7f03a0010950) at ../../module/zfs/zio.c:2686
/openzfs#516 0x00007f03c807a6d3 in __zio_execute (zio=0x7f03a0010950) at ../../module/zfs/zio.c:1399
/openzfs#517 zio_execute (zio=0x7f03a0010950) at ../../module/zfs/zio.c:1337
/openzfs#518 0x00007f03c7fcd0c4 in taskq_thread (arg=0x966d50) at ../../lib/libzpool/taskq.c:215
/openzfs#519 0x00007f03c7fc7937 in zk_thread_helper (arg=0x967e90) at ../../lib/libzpool/kernel.c:135
/openzfs#520 0x00007f03c78890a3 in start_thread (arg=0x7f03c2703700) at pthread_create.c:309
/openzfs#521 0x00007f03c75c50fd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

This occurred when ztest was simulating a scrub under heavy I/O load. Under
those circumstances, it was possible for a mix of noop I/Os for aggregation
continuity and the I/O elevator to generate arbitrarily deep recursion.

This patch modifies ZFS to propapage a recursion counter inside the zio_t
objects such that IOs will be redispatched upon reaching a given recursion
depth.  We can detect long call chains and dispatch to another ZIO taskq. We
cut in-line when we do this to minimize the potential for taskq exhaustion that
can prevent a zio from notifying its parent.

Signed-off-by: Richard Yao <[email protected]>
@ryao ryao mentioned this issue Oct 10, 2014
Closed
ryao added a commit to ryao/zfs that referenced this issue Oct 10, 2014
@ryao
Redispatch ZIOs in deep call graphs
a726161 
The below excerpt of a backtrace is from a ztest failure when running ZoL's
ztest:

/openzfs#453 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#454 0x00007f03c806106e in vdev_queue_io (zio=zio@entry=0x7f0350003de0) at ../../module/zfs/vdev_queue.c:747
/openzfs#455 0x00007f03c80818c1 in zio_vdev_io_start (zio=0x7f0350003de0) at ../../module/zfs/zio.c:2659
/openzfs#456 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003de0) at ../../module/zfs/zio.c:1399
/openzfs#457 zio_nowait (zio=0x7f0350003de0) at ../../module/zfs/zio.c:1456
/openzfs#458 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350003a10) at ../../module/zfs/vdev_mirror.c:374
/openzfs#459 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003a10) at ../../module/zfs/zio.c:1399
/openzfs#460 zio_nowait (zio=0x7f0350003a10) at ../../module/zfs/zio.c:1456
/openzfs#461 0x00007f03c806464c in vdev_raidz_io_start (zio=0x7f0350003380) at ../../module/zfs/vdev_raidz.c:1607
/openzfs#462 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003380) at ../../module/zfs/zio.c:1399
/openzfs#463 zio_nowait (zio=0x7f0350003380) at ../../module/zfs/zio.c:1456
/openzfs#464 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350002fb0) at ../../module/zfs/vdev_mirror.c:374
/openzfs#465 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002fb0) at ../../module/zfs/zio.c:1399
/openzfs#466 zio_nowait (zio=0x7f0350002fb0) at ../../module/zfs/zio.c:1456
/openzfs#467 0x00007f03c805ed43 in vdev_mirror_io_done (zio=0x7f033957ebf0) at ../../module/zfs/vdev_mirror.c:499
/openzfs#468 0x00007f03c807a0c0 in zio_vdev_io_done (zio=0x7f033957ebf0) at ../../module/zfs/zio.c:2707
/openzfs#469 0x00007f03c808285b in __zio_execute (zio=0x7f033957ebf0) at ../../module/zfs/zio.c:1399
/openzfs#470 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f0390001330, pio=0x7f033957ebf0) at ../../module/zfs/zio.c:547
/openzfs#471 zio_done (zio=0x7f0390001330) at ../../module/zfs/zio.c:3278
/openzfs#472 0x00007f03c808285b in __zio_execute (zio=0x7f0390001330) at ../../module/zfs/zio.c:1399
/openzfs#473 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4013a00, pio=0x7f0390001330) at ../../module/zfs/zio.c:547
/openzfs#474 zio_done (zio=0x7f03b4013a00) at ../../module/zfs/zio.c:3278
/openzfs#475 0x00007f03c808285b in __zio_execute (zio=0x7f03b4013a00) at ../../module/zfs/zio.c:1399
/openzfs#476 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4014210, pio=0x7f03b4013a00) at ../../module/zfs/zio.c:547
/openzfs#477 zio_done (zio=0x7f03b4014210) at ../../module/zfs/zio.c:3278
/openzfs#478 0x00007f03c808285b in __zio_execute (zio=0x7f03b4014210) at ../../module/zfs/zio.c:1399
/openzfs#479 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4014620, pio=0x7f03b4014210) at ../../module/zfs/zio.c:547
/openzfs#480 zio_done (zio=0x7f03b4014620) at ../../module/zfs/zio.c:3278
/openzfs#481 0x00007f03c807a6d3 in __zio_execute (zio=0x7f03b4014620) at ../../module/zfs/zio.c:1399
/openzfs#482 zio_execute (zio=zio@entry=0x7f03b4014620) at ../../module/zfs/zio.c:1337
/openzfs#483 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#484 0x00007f03c806106e in vdev_queue_io (zio=zio@entry=0x7f0350002be0) at ../../module/zfs/vdev_queue.c:747
/openzfs#485 0x00007f03c80818c1 in zio_vdev_io_start (zio=0x7f0350002be0) at ../../module/zfs/zio.c:2659
/openzfs#486 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002be0) at ../../module/zfs/zio.c:1399
/openzfs#487 zio_nowait (zio=0x7f0350002be0) at ../../module/zfs/zio.c:1456
/openzfs#488 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350002810) at ../../module/zfs/vdev_mirror.c:374
/openzfs#489 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002810) at ../../module/zfs/zio.c:1399
/openzfs#490 zio_nowait (zio=0x7f0350002810) at ../../module/zfs/zio.c:1456
/openzfs#491 0x00007f03c8064593 in vdev_raidz_io_start (zio=0x7f0350001270) at ../../module/zfs/vdev_raidz.c:1591
/openzfs#492 0x00007f03c807f243 in __zio_execute (zio=0x7f0350001270) at ../../module/zfs/zio.c:1399
/openzfs#493 zio_nowait (zio=0x7f0350001270) at ../../module/zfs/zio.c:1456
/openzfs#494 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350001e60) at ../../module/zfs/vdev_mirror.c:374
/openzfs#495 0x00007f03c807f243 in __zio_execute (zio=0x7f0350001e60) at ../../module/zfs/zio.c:1399
/openzfs#496 zio_nowait (zio=0x7f0350001e60) at ../../module/zfs/zio.c:1456
/openzfs#497 0x00007f03c805ed43 in vdev_mirror_io_done (zio=0x7f033a0c39c0) at ../../module/zfs/vdev_mirror.c:499
/openzfs#498 0x00007f03c807a0c0 in zio_vdev_io_done (zio=0x7f033a0c39c0) at ../../module/zfs/zio.c:2707
/openzfs#499 0x00007f03c808285b in __zio_execute (zio=0x7f033a0c39c0) at ../../module/zfs/zio.c:1399
/openzfs#500 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03a8003c00, pio=0x7f033a0c39c0) at ../../module/zfs/zio.c:547
/openzfs#501 zio_done (zio=0x7f03a8003c00) at ../../module/zfs/zio.c:3278
/openzfs#502 0x00007f03c808285b in __zio_execute (zio=0x7f03a8003c00) at ../../module/zfs/zio.c:1399
/openzfs#503 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800c400, pio=0x7f03a8003c00) at ../../module/zfs/zio.c:547
/openzfs#504 zio_done (zio=0x7f038800c400) at ../../module/zfs/zio.c:3278
/openzfs#505 0x00007f03c808285b in __zio_execute (zio=0x7f038800c400) at ../../module/zfs/zio.c:1399
/openzfs#506 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800da00, pio=0x7f038800c400) at ../../module/zfs/zio.c:547
/openzfs#507 zio_done (zio=0x7f038800da00) at ../../module/zfs/zio.c:3278
/openzfs#508 0x00007f03c808285b in __zio_execute (zio=0x7f038800da00) at ../../module/zfs/zio.c:1399
/openzfs#509 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800fd80, pio=0x7f038800da00) at ../../module/zfs/zio.c:547
/openzfs#510 zio_done (zio=0x7f038800fd80) at ../../module/zfs/zio.c:3278
/openzfs#511 0x00007f03c807a6d3 in __zio_execute (zio=0x7f038800fd80) at ../../module/zfs/zio.c:1399
/openzfs#512 zio_execute (zio=zio@entry=0x7f038800fd80) at ../../module/zfs/zio.c:1337
/openzfs#513 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#514 0x00007f03c806119d in vdev_queue_io_done (zio=zio@entry=0x7f03a0010950) at ../../module/zfs/vdev_queue.c:775
/openzfs#515 0x00007f03c807a0e8 in zio_vdev_io_done (zio=0x7f03a0010950) at ../../module/zfs/zio.c:2686
/openzfs#516 0x00007f03c807a6d3 in __zio_execute (zio=0x7f03a0010950) at ../../module/zfs/zio.c:1399
/openzfs#517 zio_execute (zio=0x7f03a0010950) at ../../module/zfs/zio.c:1337
/openzfs#518 0x00007f03c7fcd0c4 in taskq_thread (arg=0x966d50) at ../../lib/libzpool/taskq.c:215
/openzfs#519 0x00007f03c7fc7937 in zk_thread_helper (arg=0x967e90) at ../../lib/libzpool/kernel.c:135
/openzfs#520 0x00007f03c78890a3 in start_thread (arg=0x7f03c2703700) at pthread_create.c:309
/openzfs#521 0x00007f03c75c50fd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

This occurred when ztest was simulating a scrub under heavy I/O load. Under
those circumstances, it was possible for a mix of noop I/Os for aggregation
continuity and the I/O elevator to generate arbitrarily deep recursion.

This patch modifies ZFS to propapage a recursion counter inside the zio_t
objects such that IOs will be redispatched upon reaching a given recursion
depth.  We can detect long call chains and dispatch to another ZIO taskq. We
cut in-line when we do this to minimize the potential for taskq exhaustion that
can prevent a zio from notifying its parent.

Signed-off-by: Richard Yao <[email protected]>
ryao added a commit to ryao/zfs that referenced this issue Oct 10, 2014
@ryao
Redispatch ZIOs in deep call graphs
efb4636 
The below excerpt of a backtrace is from a ztest failure when running ZoL's
ztest:

/openzfs#453 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#454 0x00007f03c806106e in vdev_queue_io (zio=zio@entry=0x7f0350003de0) at ../../module/zfs/vdev_queue.c:747
/openzfs#455 0x00007f03c80818c1 in zio_vdev_io_start (zio=0x7f0350003de0) at ../../module/zfs/zio.c:2659
/openzfs#456 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003de0) at ../../module/zfs/zio.c:1399
/openzfs#457 zio_nowait (zio=0x7f0350003de0) at ../../module/zfs/zio.c:1456
/openzfs#458 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350003a10) at ../../module/zfs/vdev_mirror.c:374
/openzfs#459 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003a10) at ../../module/zfs/zio.c:1399
/openzfs#460 zio_nowait (zio=0x7f0350003a10) at ../../module/zfs/zio.c:1456
/openzfs#461 0x00007f03c806464c in vdev_raidz_io_start (zio=0x7f0350003380) at ../../module/zfs/vdev_raidz.c:1607
/openzfs#462 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003380) at ../../module/zfs/zio.c:1399
/openzfs#463 zio_nowait (zio=0x7f0350003380) at ../../module/zfs/zio.c:1456
/openzfs#464 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350002fb0) at ../../module/zfs/vdev_mirror.c:374
/openzfs#465 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002fb0) at ../../module/zfs/zio.c:1399
/openzfs#466 zio_nowait (zio=0x7f0350002fb0) at ../../module/zfs/zio.c:1456
/openzfs#467 0x00007f03c805ed43 in vdev_mirror_io_done (zio=0x7f033957ebf0) at ../../module/zfs/vdev_mirror.c:499
/openzfs#468 0x00007f03c807a0c0 in zio_vdev_io_done (zio=0x7f033957ebf0) at ../../module/zfs/zio.c:2707
/openzfs#469 0x00007f03c808285b in __zio_execute (zio=0x7f033957ebf0) at ../../module/zfs/zio.c:1399
/openzfs#470 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f0390001330, pio=0x7f033957ebf0) at ../../module/zfs/zio.c:547
/openzfs#471 zio_done (zio=0x7f0390001330) at ../../module/zfs/zio.c:3278
/openzfs#472 0x00007f03c808285b in __zio_execute (zio=0x7f0390001330) at ../../module/zfs/zio.c:1399
/openzfs#473 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4013a00, pio=0x7f0390001330) at ../../module/zfs/zio.c:547
/openzfs#474 zio_done (zio=0x7f03b4013a00) at ../../module/zfs/zio.c:3278
/openzfs#475 0x00007f03c808285b in __zio_execute (zio=0x7f03b4013a00) at ../../module/zfs/zio.c:1399
/openzfs#476 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4014210, pio=0x7f03b4013a00) at ../../module/zfs/zio.c:547
/openzfs#477 zio_done (zio=0x7f03b4014210) at ../../module/zfs/zio.c:3278
/openzfs#478 0x00007f03c808285b in __zio_execute (zio=0x7f03b4014210) at ../../module/zfs/zio.c:1399
/openzfs#479 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4014620, pio=0x7f03b4014210) at ../../module/zfs/zio.c:547
/openzfs#480 zio_done (zio=0x7f03b4014620) at ../../module/zfs/zio.c:3278
/openzfs#481 0x00007f03c807a6d3 in __zio_execute (zio=0x7f03b4014620) at ../../module/zfs/zio.c:1399
/openzfs#482 zio_execute (zio=zio@entry=0x7f03b4014620) at ../../module/zfs/zio.c:1337
/openzfs#483 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#484 0x00007f03c806106e in vdev_queue_io (zio=zio@entry=0x7f0350002be0) at ../../module/zfs/vdev_queue.c:747
/openzfs#485 0x00007f03c80818c1 in zio_vdev_io_start (zio=0x7f0350002be0) at ../../module/zfs/zio.c:2659
/openzfs#486 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002be0) at ../../module/zfs/zio.c:1399
/openzfs#487 zio_nowait (zio=0x7f0350002be0) at ../../module/zfs/zio.c:1456
/openzfs#488 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350002810) at ../../module/zfs/vdev_mirror.c:374
/openzfs#489 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002810) at ../../module/zfs/zio.c:1399
/openzfs#490 zio_nowait (zio=0x7f0350002810) at ../../module/zfs/zio.c:1456
/openzfs#491 0x00007f03c8064593 in vdev_raidz_io_start (zio=0x7f0350001270) at ../../module/zfs/vdev_raidz.c:1591
/openzfs#492 0x00007f03c807f243 in __zio_execute (zio=0x7f0350001270) at ../../module/zfs/zio.c:1399
/openzfs#493 zio_nowait (zio=0x7f0350001270) at ../../module/zfs/zio.c:1456
/openzfs#494 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350001e60) at ../../module/zfs/vdev_mirror.c:374
/openzfs#495 0x00007f03c807f243 in __zio_execute (zio=0x7f0350001e60) at ../../module/zfs/zio.c:1399
/openzfs#496 zio_nowait (zio=0x7f0350001e60) at ../../module/zfs/zio.c:1456
/openzfs#497 0x00007f03c805ed43 in vdev_mirror_io_done (zio=0x7f033a0c39c0) at ../../module/zfs/vdev_mirror.c:499
/openzfs#498 0x00007f03c807a0c0 in zio_vdev_io_done (zio=0x7f033a0c39c0) at ../../module/zfs/zio.c:2707
/openzfs#499 0x00007f03c808285b in __zio_execute (zio=0x7f033a0c39c0) at ../../module/zfs/zio.c:1399
/openzfs#500 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03a8003c00, pio=0x7f033a0c39c0) at ../../module/zfs/zio.c:547
/openzfs#501 zio_done (zio=0x7f03a8003c00) at ../../module/zfs/zio.c:3278
/openzfs#502 0x00007f03c808285b in __zio_execute (zio=0x7f03a8003c00) at ../../module/zfs/zio.c:1399
/openzfs#503 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800c400, pio=0x7f03a8003c00) at ../../module/zfs/zio.c:547
/openzfs#504 zio_done (zio=0x7f038800c400) at ../../module/zfs/zio.c:3278
/openzfs#505 0x00007f03c808285b in __zio_execute (zio=0x7f038800c400) at ../../module/zfs/zio.c:1399
/openzfs#506 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800da00, pio=0x7f038800c400) at ../../module/zfs/zio.c:547
/openzfs#507 zio_done (zio=0x7f038800da00) at ../../module/zfs/zio.c:3278
/openzfs#508 0x00007f03c808285b in __zio_execute (zio=0x7f038800da00) at ../../module/zfs/zio.c:1399
/openzfs#509 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800fd80, pio=0x7f038800da00) at ../../module/zfs/zio.c:547
/openzfs#510 zio_done (zio=0x7f038800fd80) at ../../module/zfs/zio.c:3278
/openzfs#511 0x00007f03c807a6d3 in __zio_execute (zio=0x7f038800fd80) at ../../module/zfs/zio.c:1399
/openzfs#512 zio_execute (zio=zio@entry=0x7f038800fd80) at ../../module/zfs/zio.c:1337
/openzfs#513 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#514 0x00007f03c806119d in vdev_queue_io_done (zio=zio@entry=0x7f03a0010950) at ../../module/zfs/vdev_queue.c:775
/openzfs#515 0x00007f03c807a0e8 in zio_vdev_io_done (zio=0x7f03a0010950) at ../../module/zfs/zio.c:2686
/openzfs#516 0x00007f03c807a6d3 in __zio_execute (zio=0x7f03a0010950) at ../../module/zfs/zio.c:1399
/openzfs#517 zio_execute (zio=0x7f03a0010950) at ../../module/zfs/zio.c:1337
/openzfs#518 0x00007f03c7fcd0c4 in taskq_thread (arg=0x966d50) at ../../lib/libzpool/taskq.c:215
/openzfs#519 0x00007f03c7fc7937 in zk_thread_helper (arg=0x967e90) at ../../lib/libzpool/kernel.c:135
/openzfs#520 0x00007f03c78890a3 in start_thread (arg=0x7f03c2703700) at pthread_create.c:309
/openzfs#521 0x00007f03c75c50fd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

This occurred when ztest was simulating a scrub under heavy I/O load. Under
those circumstances, it was possible for a mix of noop I/Os for aggregation
continuity and the I/O elevator to generate arbitrarily deep recursion.

This patch modifies ZFS to propapage a recursion counter inside the zio_t
objects such that IOs will be redispatched upon reaching a given recursion
depth.  We can detect long call chains and dispatch to another ZIO taskq. We
cut in-line when we do this to minimize the potential for taskq exhaustion that
can prevent a zio from notifying its parent.

Signed-off-by: Richard Yao <[email protected]>
ryao added a commit to ryao/zfs that referenced this issue Oct 10, 2014
@ryao
Redispatch ZIOs in deep call graphs
5300bd4 
The below excerpt of a backtrace is from a ztest failure when running ZoL's
ztest:

/openzfs#453 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#454 0x00007f03c806106e in vdev_queue_io (zio=zio@entry=0x7f0350003de0) at ../../module/zfs/vdev_queue.c:747
/openzfs#455 0x00007f03c80818c1 in zio_vdev_io_start (zio=0x7f0350003de0) at ../../module/zfs/zio.c:2659
/openzfs#456 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003de0) at ../../module/zfs/zio.c:1399
/openzfs#457 zio_nowait (zio=0x7f0350003de0) at ../../module/zfs/zio.c:1456
/openzfs#458 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350003a10) at ../../module/zfs/vdev_mirror.c:374
/openzfs#459 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003a10) at ../../module/zfs/zio.c:1399
/openzfs#460 zio_nowait (zio=0x7f0350003a10) at ../../module/zfs/zio.c:1456
/openzfs#461 0x00007f03c806464c in vdev_raidz_io_start (zio=0x7f0350003380) at ../../module/zfs/vdev_raidz.c:1607
/openzfs#462 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003380) at ../../module/zfs/zio.c:1399
/openzfs#463 zio_nowait (zio=0x7f0350003380) at ../../module/zfs/zio.c:1456
/openzfs#464 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350002fb0) at ../../module/zfs/vdev_mirror.c:374
/openzfs#465 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002fb0) at ../../module/zfs/zio.c:1399
/openzfs#466 zio_nowait (zio=0x7f0350002fb0) at ../../module/zfs/zio.c:1456
/openzfs#467 0x00007f03c805ed43 in vdev_mirror_io_done (zio=0x7f033957ebf0) at ../../module/zfs/vdev_mirror.c:499
/openzfs#468 0x00007f03c807a0c0 in zio_vdev_io_done (zio=0x7f033957ebf0) at ../../module/zfs/zio.c:2707
/openzfs#469 0x00007f03c808285b in __zio_execute (zio=0x7f033957ebf0) at ../../module/zfs/zio.c:1399
/openzfs#470 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f0390001330, pio=0x7f033957ebf0) at ../../module/zfs/zio.c:547
/openzfs#471 zio_done (zio=0x7f0390001330) at ../../module/zfs/zio.c:3278
/openzfs#472 0x00007f03c808285b in __zio_execute (zio=0x7f0390001330) at ../../module/zfs/zio.c:1399
/openzfs#473 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4013a00, pio=0x7f0390001330) at ../../module/zfs/zio.c:547
/openzfs#474 zio_done (zio=0x7f03b4013a00) at ../../module/zfs/zio.c:3278
/openzfs#475 0x00007f03c808285b in __zio_execute (zio=0x7f03b4013a00) at ../../module/zfs/zio.c:1399
/openzfs#476 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4014210, pio=0x7f03b4013a00) at ../../module/zfs/zio.c:547
/openzfs#477 zio_done (zio=0x7f03b4014210) at ../../module/zfs/zio.c:3278
/openzfs#478 0x00007f03c808285b in __zio_execute (zio=0x7f03b4014210) at ../../module/zfs/zio.c:1399
/openzfs#479 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4014620, pio=0x7f03b4014210) at ../../module/zfs/zio.c:547
/openzfs#480 zio_done (zio=0x7f03b4014620) at ../../module/zfs/zio.c:3278
/openzfs#481 0x00007f03c807a6d3 in __zio_execute (zio=0x7f03b4014620) at ../../module/zfs/zio.c:1399
/openzfs#482 zio_execute (zio=zio@entry=0x7f03b4014620) at ../../module/zfs/zio.c:1337
/openzfs#483 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#484 0x00007f03c806106e in vdev_queue_io (zio=zio@entry=0x7f0350002be0) at ../../module/zfs/vdev_queue.c:747
/openzfs#485 0x00007f03c80818c1 in zio_vdev_io_start (zio=0x7f0350002be0) at ../../module/zfs/zio.c:2659
/openzfs#486 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002be0) at ../../module/zfs/zio.c:1399
/openzfs#487 zio_nowait (zio=0x7f0350002be0) at ../../module/zfs/zio.c:1456
/openzfs#488 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350002810) at ../../module/zfs/vdev_mirror.c:374
/openzfs#489 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002810) at ../../module/zfs/zio.c:1399
/openzfs#490 zio_nowait (zio=0x7f0350002810) at ../../module/zfs/zio.c:1456
/openzfs#491 0x00007f03c8064593 in vdev_raidz_io_start (zio=0x7f0350001270) at ../../module/zfs/vdev_raidz.c:1591
/openzfs#492 0x00007f03c807f243 in __zio_execute (zio=0x7f0350001270) at ../../module/zfs/zio.c:1399
/openzfs#493 zio_nowait (zio=0x7f0350001270) at ../../module/zfs/zio.c:1456
/openzfs#494 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350001e60) at ../../module/zfs/vdev_mirror.c:374
/openzfs#495 0x00007f03c807f243 in __zio_execute (zio=0x7f0350001e60) at ../../module/zfs/zio.c:1399
/openzfs#496 zio_nowait (zio=0x7f0350001e60) at ../../module/zfs/zio.c:1456
/openzfs#497 0x00007f03c805ed43 in vdev_mirror_io_done (zio=0x7f033a0c39c0) at ../../module/zfs/vdev_mirror.c:499
/openzfs#498 0x00007f03c807a0c0 in zio_vdev_io_done (zio=0x7f033a0c39c0) at ../../module/zfs/zio.c:2707
/openzfs#499 0x00007f03c808285b in __zio_execute (zio=0x7f033a0c39c0) at ../../module/zfs/zio.c:1399
/openzfs#500 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03a8003c00, pio=0x7f033a0c39c0) at ../../module/zfs/zio.c:547
/openzfs#501 zio_done (zio=0x7f03a8003c00) at ../../module/zfs/zio.c:3278
/openzfs#502 0x00007f03c808285b in __zio_execute (zio=0x7f03a8003c00) at ../../module/zfs/zio.c:1399
/openzfs#503 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800c400, pio=0x7f03a8003c00) at ../../module/zfs/zio.c:547
/openzfs#504 zio_done (zio=0x7f038800c400) at ../../module/zfs/zio.c:3278
/openzfs#505 0x00007f03c808285b in __zio_execute (zio=0x7f038800c400) at ../../module/zfs/zio.c:1399
/openzfs#506 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800da00, pio=0x7f038800c400) at ../../module/zfs/zio.c:547
/openzfs#507 zio_done (zio=0x7f038800da00) at ../../module/zfs/zio.c:3278
/openzfs#508 0x00007f03c808285b in __zio_execute (zio=0x7f038800da00) at ../../module/zfs/zio.c:1399
/openzfs#509 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800fd80, pio=0x7f038800da00) at ../../module/zfs/zio.c:547
/openzfs#510 zio_done (zio=0x7f038800fd80) at ../../module/zfs/zio.c:3278
/openzfs#511 0x00007f03c807a6d3 in __zio_execute (zio=0x7f038800fd80) at ../../module/zfs/zio.c:1399
/openzfs#512 zio_execute (zio=zio@entry=0x7f038800fd80) at ../../module/zfs/zio.c:1337
/openzfs#513 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#514 0x00007f03c806119d in vdev_queue_io_done (zio=zio@entry=0x7f03a0010950) at ../../module/zfs/vdev_queue.c:775
/openzfs#515 0x00007f03c807a0e8 in zio_vdev_io_done (zio=0x7f03a0010950) at ../../module/zfs/zio.c:2686
/openzfs#516 0x00007f03c807a6d3 in __zio_execute (zio=0x7f03a0010950) at ../../module/zfs/zio.c:1399
/openzfs#517 zio_execute (zio=0x7f03a0010950) at ../../module/zfs/zio.c:1337
/openzfs#518 0x00007f03c7fcd0c4 in taskq_thread (arg=0x966d50) at ../../lib/libzpool/taskq.c:215
/openzfs#519 0x00007f03c7fc7937 in zk_thread_helper (arg=0x967e90) at ../../lib/libzpool/kernel.c:135
/openzfs#520 0x00007f03c78890a3 in start_thread (arg=0x7f03c2703700) at pthread_create.c:309
/openzfs#521 0x00007f03c75c50fd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

This occurred when ztest was simulating a scrub under heavy I/O load. Under
those circumstances, it was possible for a mix of noop I/Os for aggregation
continuity and the I/O elevator to generate arbitrarily deep recursion.

This patch modifies ZFS to propapage a recursion counter inside the zio_t
objects such that IOs will be redispatched upon reaching a given recursion
depth.  We can detect long call chains and dispatch to another ZIO taskq. We
cut in-line when we do this to minimize the potential for taskq exhaustion that
can prevent a zio from notifying its parent.

Signed-off-by: Richard Yao <[email protected]>
ryao added a commit to ryao/zfs that referenced this issue Oct 10, 2014
@ryao
Redispatch ZIOs in deep call graphs
373534d 
The below excerpt of a backtrace is from a ztest failure when running ZoL's
ztest:

/openzfs#453 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#454 0x00007f03c806106e in vdev_queue_io (zio=zio@entry=0x7f0350003de0) at ../../module/zfs/vdev_queue.c:747
/openzfs#455 0x00007f03c80818c1 in zio_vdev_io_start (zio=0x7f0350003de0) at ../../module/zfs/zio.c:2659
/openzfs#456 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003de0) at ../../module/zfs/zio.c:1399
/openzfs#457 zio_nowait (zio=0x7f0350003de0) at ../../module/zfs/zio.c:1456
/openzfs#458 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350003a10) at ../../module/zfs/vdev_mirror.c:374
/openzfs#459 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003a10) at ../../module/zfs/zio.c:1399
/openzfs#460 zio_nowait (zio=0x7f0350003a10) at ../../module/zfs/zio.c:1456
/openzfs#461 0x00007f03c806464c in vdev_raidz_io_start (zio=0x7f0350003380) at ../../module/zfs/vdev_raidz.c:1607
/openzfs#462 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003380) at ../../module/zfs/zio.c:1399
/openzfs#463 zio_nowait (zio=0x7f0350003380) at ../../module/zfs/zio.c:1456
/openzfs#464 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350002fb0) at ../../module/zfs/vdev_mirror.c:374
/openzfs#465 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002fb0) at ../../module/zfs/zio.c:1399
/openzfs#466 zio_nowait (zio=0x7f0350002fb0) at ../../module/zfs/zio.c:1456
/openzfs#467 0x00007f03c805ed43 in vdev_mirror_io_done (zio=0x7f033957ebf0) at ../../module/zfs/vdev_mirror.c:499
/openzfs#468 0x00007f03c807a0c0 in zio_vdev_io_done (zio=0x7f033957ebf0) at ../../module/zfs/zio.c:2707
/openzfs#469 0x00007f03c808285b in __zio_execute (zio=0x7f033957ebf0) at ../../module/zfs/zio.c:1399
/openzfs#470 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f0390001330, pio=0x7f033957ebf0) at ../../module/zfs/zio.c:547
/openzfs#471 zio_done (zio=0x7f0390001330) at ../../module/zfs/zio.c:3278
/openzfs#472 0x00007f03c808285b in __zio_execute (zio=0x7f0390001330) at ../../module/zfs/zio.c:1399
/openzfs#473 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4013a00, pio=0x7f0390001330) at ../../module/zfs/zio.c:547
/openzfs#474 zio_done (zio=0x7f03b4013a00) at ../../module/zfs/zio.c:3278
/openzfs#475 0x00007f03c808285b in __zio_execute (zio=0x7f03b4013a00) at ../../module/zfs/zio.c:1399
/openzfs#476 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4014210, pio=0x7f03b4013a00) at ../../module/zfs/zio.c:547
/openzfs#477 zio_done (zio=0x7f03b4014210) at ../../module/zfs/zio.c:3278
/openzfs#478 0x00007f03c808285b in __zio_execute (zio=0x7f03b4014210) at ../../module/zfs/zio.c:1399
/openzfs#479 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4014620, pio=0x7f03b4014210) at ../../module/zfs/zio.c:547
/openzfs#480 zio_done (zio=0x7f03b4014620) at ../../module/zfs/zio.c:3278
/openzfs#481 0x00007f03c807a6d3 in __zio_execute (zio=0x7f03b4014620) at ../../module/zfs/zio.c:1399
/openzfs#482 zio_execute (zio=zio@entry=0x7f03b4014620) at ../../module/zfs/zio.c:1337
/openzfs#483 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#484 0x00007f03c806106e in vdev_queue_io (zio=zio@entry=0x7f0350002be0) at ../../module/zfs/vdev_queue.c:747
/openzfs#485 0x00007f03c80818c1 in zio_vdev_io_start (zio=0x7f0350002be0) at ../../module/zfs/zio.c:2659
/openzfs#486 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002be0) at ../../module/zfs/zio.c:1399
/openzfs#487 zio_nowait (zio=0x7f0350002be0) at ../../module/zfs/zio.c:1456
/openzfs#488 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350002810) at ../../module/zfs/vdev_mirror.c:374
/openzfs#489 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002810) at ../../module/zfs/zio.c:1399
/openzfs#490 zio_nowait (zio=0x7f0350002810) at ../../module/zfs/zio.c:1456
/openzfs#491 0x00007f03c8064593 in vdev_raidz_io_start (zio=0x7f0350001270) at ../../module/zfs/vdev_raidz.c:1591
/openzfs#492 0x00007f03c807f243 in __zio_execute (zio=0x7f0350001270) at ../../module/zfs/zio.c:1399
/openzfs#493 zio_nowait (zio=0x7f0350001270) at ../../module/zfs/zio.c:1456
/openzfs#494 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350001e60) at ../../module/zfs/vdev_mirror.c:374
/openzfs#495 0x00007f03c807f243 in __zio_execute (zio=0x7f0350001e60) at ../../module/zfs/zio.c:1399
/openzfs#496 zio_nowait (zio=0x7f0350001e60) at ../../module/zfs/zio.c:1456
/openzfs#497 0x00007f03c805ed43 in vdev_mirror_io_done (zio=0x7f033a0c39c0) at ../../module/zfs/vdev_mirror.c:499
/openzfs#498 0x00007f03c807a0c0 in zio_vdev_io_done (zio=0x7f033a0c39c0) at ../../module/zfs/zio.c:2707
/openzfs#499 0x00007f03c808285b in __zio_execute (zio=0x7f033a0c39c0) at ../../module/zfs/zio.c:1399
/openzfs#500 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03a8003c00, pio=0x7f033a0c39c0) at ../../module/zfs/zio.c:547
/openzfs#501 zio_done (zio=0x7f03a8003c00) at ../../module/zfs/zio.c:3278
/openzfs#502 0x00007f03c808285b in __zio_execute (zio=0x7f03a8003c00) at ../../module/zfs/zio.c:1399
/openzfs#503 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800c400, pio=0x7f03a8003c00) at ../../module/zfs/zio.c:547
/openzfs#504 zio_done (zio=0x7f038800c400) at ../../module/zfs/zio.c:3278
/openzfs#505 0x00007f03c808285b in __zio_execute (zio=0x7f038800c400) at ../../module/zfs/zio.c:1399
/openzfs#506 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800da00, pio=0x7f038800c400) at ../../module/zfs/zio.c:547
/openzfs#507 zio_done (zio=0x7f038800da00) at ../../module/zfs/zio.c:3278
/openzfs#508 0x00007f03c808285b in __zio_execute (zio=0x7f038800da00) at ../../module/zfs/zio.c:1399
/openzfs#509 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800fd80, pio=0x7f038800da00) at ../../module/zfs/zio.c:547
/openzfs#510 zio_done (zio=0x7f038800fd80) at ../../module/zfs/zio.c:3278
/openzfs#511 0x00007f03c807a6d3 in __zio_execute (zio=0x7f038800fd80) at ../../module/zfs/zio.c:1399
/openzfs#512 zio_execute (zio=zio@entry=0x7f038800fd80) at ../../module/zfs/zio.c:1337
/openzfs#513 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#514 0x00007f03c806119d in vdev_queue_io_done (zio=zio@entry=0x7f03a0010950) at ../../module/zfs/vdev_queue.c:775
/openzfs#515 0x00007f03c807a0e8 in zio_vdev_io_done (zio=0x7f03a0010950) at ../../module/zfs/zio.c:2686
/openzfs#516 0x00007f03c807a6d3 in __zio_execute (zio=0x7f03a0010950) at ../../module/zfs/zio.c:1399
/openzfs#517 zio_execute (zio=0x7f03a0010950) at ../../module/zfs/zio.c:1337
/openzfs#518 0x00007f03c7fcd0c4 in taskq_thread (arg=0x966d50) at ../../lib/libzpool/taskq.c:215
/openzfs#519 0x00007f03c7fc7937 in zk_thread_helper (arg=0x967e90) at ../../lib/libzpool/kernel.c:135
/openzfs#520 0x00007f03c78890a3 in start_thread (arg=0x7f03c2703700) at pthread_create.c:309
/openzfs#521 0x00007f03c75c50fd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

This occurred when ztest was simulating a scrub under heavy I/O load. Under
those circumstances, it was possible for a mix of noop I/Os for aggregation
continuity and the I/O elevator to generate arbitrarily deep recursion.

This patch modifies ZFS to propapage a recursion counter inside the zio_t
objects such that IOs will be redispatched upon reaching a given recursion
depth.  We can detect long call chains and dispatch to another ZIO taskq. We
cut in-line when we do this to minimize the potential for taskq exhaustion that
can prevent a zio from notifying its parent.

Signed-off-by: Richard Yao <[email protected]>
ryao added a commit to ryao/zfs that referenced this issue Oct 10, 2014
@ryao
Redispatch ZIOs in deep call graphs
ddf4bde 
The below excerpt of a backtrace is from a ztest failure when running ZoL's
ztest:

/openzfs#453 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#454 0x00007f03c806106e in vdev_queue_io (zio=zio@entry=0x7f0350003de0) at ../../module/zfs/vdev_queue.c:747
/openzfs#455 0x00007f03c80818c1 in zio_vdev_io_start (zio=0x7f0350003de0) at ../../module/zfs/zio.c:2659
/openzfs#456 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003de0) at ../../module/zfs/zio.c:1399
/openzfs#457 zio_nowait (zio=0x7f0350003de0) at ../../module/zfs/zio.c:1456
/openzfs#458 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350003a10) at ../../module/zfs/vdev_mirror.c:374
/openzfs#459 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003a10) at ../../module/zfs/zio.c:1399
/openzfs#460 zio_nowait (zio=0x7f0350003a10) at ../../module/zfs/zio.c:1456
/openzfs#461 0x00007f03c806464c in vdev_raidz_io_start (zio=0x7f0350003380) at ../../module/zfs/vdev_raidz.c:1607
/openzfs#462 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003380) at ../../module/zfs/zio.c:1399
/openzfs#463 zio_nowait (zio=0x7f0350003380) at ../../module/zfs/zio.c:1456
/openzfs#464 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350002fb0) at ../../module/zfs/vdev_mirror.c:374
/openzfs#465 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002fb0) at ../../module/zfs/zio.c:1399
/openzfs#466 zio_nowait (zio=0x7f0350002fb0) at ../../module/zfs/zio.c:1456
/openzfs#467 0x00007f03c805ed43 in vdev_mirror_io_done (zio=0x7f033957ebf0) at ../../module/zfs/vdev_mirror.c:499
/openzfs#468 0x00007f03c807a0c0 in zio_vdev_io_done (zio=0x7f033957ebf0) at ../../module/zfs/zio.c:2707
/openzfs#469 0x00007f03c808285b in __zio_execute (zio=0x7f033957ebf0) at ../../module/zfs/zio.c:1399
/openzfs#470 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f0390001330, pio=0x7f033957ebf0) at ../../module/zfs/zio.c:547
/openzfs#471 zio_done (zio=0x7f0390001330) at ../../module/zfs/zio.c:3278
/openzfs#472 0x00007f03c808285b in __zio_execute (zio=0x7f0390001330) at ../../module/zfs/zio.c:1399
/openzfs#473 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4013a00, pio=0x7f0390001330) at ../../module/zfs/zio.c:547
/openzfs#474 zio_done (zio=0x7f03b4013a00) at ../../module/zfs/zio.c:3278
/openzfs#475 0x00007f03c808285b in __zio_execute (zio=0x7f03b4013a00) at ../../module/zfs/zio.c:1399
/openzfs#476 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4014210, pio=0x7f03b4013a00) at ../../module/zfs/zio.c:547
/openzfs#477 zio_done (zio=0x7f03b4014210) at ../../module/zfs/zio.c:3278
/openzfs#478 0x00007f03c808285b in __zio_execute (zio=0x7f03b4014210) at ../../module/zfs/zio.c:1399
/openzfs#479 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4014620, pio=0x7f03b4014210) at ../../module/zfs/zio.c:547
/openzfs#480 zio_done (zio=0x7f03b4014620) at ../../module/zfs/zio.c:3278
/openzfs#481 0x00007f03c807a6d3 in __zio_execute (zio=0x7f03b4014620) at ../../module/zfs/zio.c:1399
/openzfs#482 zio_execute (zio=zio@entry=0x7f03b4014620) at ../../module/zfs/zio.c:1337
/openzfs#483 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#484 0x00007f03c806106e in vdev_queue_io (zio=zio@entry=0x7f0350002be0) at ../../module/zfs/vdev_queue.c:747
/openzfs#485 0x00007f03c80818c1 in zio_vdev_io_start (zio=0x7f0350002be0) at ../../module/zfs/zio.c:2659
/openzfs#486 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002be0) at ../../module/zfs/zio.c:1399
/openzfs#487 zio_nowait (zio=0x7f0350002be0) at ../../module/zfs/zio.c:1456
/openzfs#488 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350002810) at ../../module/zfs/vdev_mirror.c:374
/openzfs#489 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002810) at ../../module/zfs/zio.c:1399
/openzfs#490 zio_nowait (zio=0x7f0350002810) at ../../module/zfs/zio.c:1456
/openzfs#491 0x00007f03c8064593 in vdev_raidz_io_start (zio=0x7f0350001270) at ../../module/zfs/vdev_raidz.c:1591
/openzfs#492 0x00007f03c807f243 in __zio_execute (zio=0x7f0350001270) at ../../module/zfs/zio.c:1399
/openzfs#493 zio_nowait (zio=0x7f0350001270) at ../../module/zfs/zio.c:1456
/openzfs#494 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350001e60) at ../../module/zfs/vdev_mirror.c:374
/openzfs#495 0x00007f03c807f243 in __zio_execute (zio=0x7f0350001e60) at ../../module/zfs/zio.c:1399
/openzfs#496 zio_nowait (zio=0x7f0350001e60) at ../../module/zfs/zio.c:1456
/openzfs#497 0x00007f03c805ed43 in vdev_mirror_io_done (zio=0x7f033a0c39c0) at ../../module/zfs/vdev_mirror.c:499
/openzfs#498 0x00007f03c807a0c0 in zio_vdev_io_done (zio=0x7f033a0c39c0) at ../../module/zfs/zio.c:2707
/openzfs#499 0x00007f03c808285b in __zio_execute (zio=0x7f033a0c39c0) at ../../module/zfs/zio.c:1399
/openzfs#500 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03a8003c00, pio=0x7f033a0c39c0) at ../../module/zfs/zio.c:547
/openzfs#501 zio_done (zio=0x7f03a8003c00) at ../../module/zfs/zio.c:3278
/openzfs#502 0x00007f03c808285b in __zio_execute (zio=0x7f03a8003c00) at ../../module/zfs/zio.c:1399
/openzfs#503 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800c400, pio=0x7f03a8003c00) at ../../module/zfs/zio.c:547
/openzfs#504 zio_done (zio=0x7f038800c400) at ../../module/zfs/zio.c:3278
/openzfs#505 0x00007f03c808285b in __zio_execute (zio=0x7f038800c400) at ../../module/zfs/zio.c:1399
/openzfs#506 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800da00, pio=0x7f038800c400) at ../../module/zfs/zio.c:547
/openzfs#507 zio_done (zio=0x7f038800da00) at ../../module/zfs/zio.c:3278
/openzfs#508 0x00007f03c808285b in __zio_execute (zio=0x7f038800da00) at ../../module/zfs/zio.c:1399
/openzfs#509 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800fd80, pio=0x7f038800da00) at ../../module/zfs/zio.c:547
/openzfs#510 zio_done (zio=0x7f038800fd80) at ../../module/zfs/zio.c:3278
/openzfs#511 0x00007f03c807a6d3 in __zio_execute (zio=0x7f038800fd80) at ../../module/zfs/zio.c:1399
/openzfs#512 zio_execute (zio=zio@entry=0x7f038800fd80) at ../../module/zfs/zio.c:1337
/openzfs#513 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#514 0x00007f03c806119d in vdev_queue_io_done (zio=zio@entry=0x7f03a0010950) at ../../module/zfs/vdev_queue.c:775
/openzfs#515 0x00007f03c807a0e8 in zio_vdev_io_done (zio=0x7f03a0010950) at ../../module/zfs/zio.c:2686
/openzfs#516 0x00007f03c807a6d3 in __zio_execute (zio=0x7f03a0010950) at ../../module/zfs/zio.c:1399
/openzfs#517 zio_execute (zio=0x7f03a0010950) at ../../module/zfs/zio.c:1337
/openzfs#518 0x00007f03c7fcd0c4 in taskq_thread (arg=0x966d50) at ../../lib/libzpool/taskq.c:215
/openzfs#519 0x00007f03c7fc7937 in zk_thread_helper (arg=0x967e90) at ../../lib/libzpool/kernel.c:135
/openzfs#520 0x00007f03c78890a3 in start_thread (arg=0x7f03c2703700) at pthread_create.c:309
/openzfs#521 0x00007f03c75c50fd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

This occurred when ztest was simulating a scrub under heavy I/O load. Under
those circumstances, it was possible for a mix of noop I/Os for aggregation
continuity and the I/O elevator to generate arbitrarily deep recursion.

This patch modifies ZFS to propapage a recursion counter inside the zio_t
objects such that IOs will be redispatched upon reaching a given recursion
depth.  We can detect long call chains and dispatch to another ZIO taskq. We
cut in-line when we do this to minimize the potential for taskq exhaustion that
can prevent a zio from notifying its parent.

Signed-off-by: Richard Yao <[email protected]>
ryao added a commit to ryao/zfs that referenced this issue Oct 11, 2014
@ryao
Redispatch ZIOs in deep call graphs
a7d6be6 
The below excerpt of a backtrace is from a ztest failure when running ZoL's
ztest:

/openzfs#453 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#454 0x00007f03c806106e in vdev_queue_io (zio=zio@entry=0x7f0350003de0) at ../../module/zfs/vdev_queue.c:747
/openzfs#455 0x00007f03c80818c1 in zio_vdev_io_start (zio=0x7f0350003de0) at ../../module/zfs/zio.c:2659
/openzfs#456 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003de0) at ../../module/zfs/zio.c:1399
/openzfs#457 zio_nowait (zio=0x7f0350003de0) at ../../module/zfs/zio.c:1456
/openzfs#458 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350003a10) at ../../module/zfs/vdev_mirror.c:374
/openzfs#459 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003a10) at ../../module/zfs/zio.c:1399
/openzfs#460 zio_nowait (zio=0x7f0350003a10) at ../../module/zfs/zio.c:1456
/openzfs#461 0x00007f03c806464c in vdev_raidz_io_start (zio=0x7f0350003380) at ../../module/zfs/vdev_raidz.c:1607
/openzfs#462 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003380) at ../../module/zfs/zio.c:1399
/openzfs#463 zio_nowait (zio=0x7f0350003380) at ../../module/zfs/zio.c:1456
/openzfs#464 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350002fb0) at ../../module/zfs/vdev_mirror.c:374
/openzfs#465 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002fb0) at ../../module/zfs/zio.c:1399
/openzfs#466 zio_nowait (zio=0x7f0350002fb0) at ../../module/zfs/zio.c:1456
/openzfs#467 0x00007f03c805ed43 in vdev_mirror_io_done (zio=0x7f033957ebf0) at ../../module/zfs/vdev_mirror.c:499
/openzfs#468 0x00007f03c807a0c0 in zio_vdev_io_done (zio=0x7f033957ebf0) at ../../module/zfs/zio.c:2707
/openzfs#469 0x00007f03c808285b in __zio_execute (zio=0x7f033957ebf0) at ../../module/zfs/zio.c:1399
/openzfs#470 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f0390001330, pio=0x7f033957ebf0) at ../../module/zfs/zio.c:547
/openzfs#471 zio_done (zio=0x7f0390001330) at ../../module/zfs/zio.c:3278
/openzfs#472 0x00007f03c808285b in __zio_execute (zio=0x7f0390001330) at ../../module/zfs/zio.c:1399
/openzfs#473 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4013a00, pio=0x7f0390001330) at ../../module/zfs/zio.c:547
/openzfs#474 zio_done (zio=0x7f03b4013a00) at ../../module/zfs/zio.c:3278
/openzfs#475 0x00007f03c808285b in __zio_execute (zio=0x7f03b4013a00) at ../../module/zfs/zio.c:1399
/openzfs#476 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4014210, pio=0x7f03b4013a00) at ../../module/zfs/zio.c:547
/openzfs#477 zio_done (zio=0x7f03b4014210) at ../../module/zfs/zio.c:3278
/openzfs#478 0x00007f03c808285b in __zio_execute (zio=0x7f03b4014210) at ../../module/zfs/zio.c:1399
/openzfs#479 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4014620, pio=0x7f03b4014210) at ../../module/zfs/zio.c:547
/openzfs#480 zio_done (zio=0x7f03b4014620) at ../../module/zfs/zio.c:3278
/openzfs#481 0x00007f03c807a6d3 in __zio_execute (zio=0x7f03b4014620) at ../../module/zfs/zio.c:1399
/openzfs#482 zio_execute (zio=zio@entry=0x7f03b4014620) at ../../module/zfs/zio.c:1337
/openzfs#483 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#484 0x00007f03c806106e in vdev_queue_io (zio=zio@entry=0x7f0350002be0) at ../../module/zfs/vdev_queue.c:747
/openzfs#485 0x00007f03c80818c1 in zio_vdev_io_start (zio=0x7f0350002be0) at ../../module/zfs/zio.c:2659
/openzfs#486 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002be0) at ../../module/zfs/zio.c:1399
/openzfs#487 zio_nowait (zio=0x7f0350002be0) at ../../module/zfs/zio.c:1456
/openzfs#488 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350002810) at ../../module/zfs/vdev_mirror.c:374
/openzfs#489 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002810) at ../../module/zfs/zio.c:1399
/openzfs#490 zio_nowait (zio=0x7f0350002810) at ../../module/zfs/zio.c:1456
/openzfs#491 0x00007f03c8064593 in vdev_raidz_io_start (zio=0x7f0350001270) at ../../module/zfs/vdev_raidz.c:1591
/openzfs#492 0x00007f03c807f243 in __zio_execute (zio=0x7f0350001270) at ../../module/zfs/zio.c:1399
/openzfs#493 zio_nowait (zio=0x7f0350001270) at ../../module/zfs/zio.c:1456
/openzfs#494 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350001e60) at ../../module/zfs/vdev_mirror.c:374
/openzfs#495 0x00007f03c807f243 in __zio_execute (zio=0x7f0350001e60) at ../../module/zfs/zio.c:1399
/openzfs#496 zio_nowait (zio=0x7f0350001e60) at ../../module/zfs/zio.c:1456
/openzfs#497 0x00007f03c805ed43 in vdev_mirror_io_done (zio=0x7f033a0c39c0) at ../../module/zfs/vdev_mirror.c:499
/openzfs#498 0x00007f03c807a0c0 in zio_vdev_io_done (zio=0x7f033a0c39c0) at ../../module/zfs/zio.c:2707
/openzfs#499 0x00007f03c808285b in __zio_execute (zio=0x7f033a0c39c0) at ../../module/zfs/zio.c:1399
/openzfs#500 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03a8003c00, pio=0x7f033a0c39c0) at ../../module/zfs/zio.c:547
/openzfs#501 zio_done (zio=0x7f03a8003c00) at ../../module/zfs/zio.c:3278
/openzfs#502 0x00007f03c808285b in __zio_execute (zio=0x7f03a8003c00) at ../../module/zfs/zio.c:1399
/openzfs#503 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800c400, pio=0x7f03a8003c00) at ../../module/zfs/zio.c:547
/openzfs#504 zio_done (zio=0x7f038800c400) at ../../module/zfs/zio.c:3278
/openzfs#505 0x00007f03c808285b in __zio_execute (zio=0x7f038800c400) at ../../module/zfs/zio.c:1399
/openzfs#506 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800da00, pio=0x7f038800c400) at ../../module/zfs/zio.c:547
/openzfs#507 zio_done (zio=0x7f038800da00) at ../../module/zfs/zio.c:3278
/openzfs#508 0x00007f03c808285b in __zio_execute (zio=0x7f038800da00) at ../../module/zfs/zio.c:1399
/openzfs#509 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800fd80, pio=0x7f038800da00) at ../../module/zfs/zio.c:547
/openzfs#510 zio_done (zio=0x7f038800fd80) at ../../module/zfs/zio.c:3278
/openzfs#511 0x00007f03c807a6d3 in __zio_execute (zio=0x7f038800fd80) at ../../module/zfs/zio.c:1399
/openzfs#512 zio_execute (zio=zio@entry=0x7f038800fd80) at ../../module/zfs/zio.c:1337
/openzfs#513 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#514 0x00007f03c806119d in vdev_queue_io_done (zio=zio@entry=0x7f03a0010950) at ../../module/zfs/vdev_queue.c:775
/openzfs#515 0x00007f03c807a0e8 in zio_vdev_io_done (zio=0x7f03a0010950) at ../../module/zfs/zio.c:2686
/openzfs#516 0x00007f03c807a6d3 in __zio_execute (zio=0x7f03a0010950) at ../../module/zfs/zio.c:1399
/openzfs#517 zio_execute (zio=0x7f03a0010950) at ../../module/zfs/zio.c:1337
/openzfs#518 0x00007f03c7fcd0c4 in taskq_thread (arg=0x966d50) at ../../lib/libzpool/taskq.c:215
/openzfs#519 0x00007f03c7fc7937 in zk_thread_helper (arg=0x967e90) at ../../lib/libzpool/kernel.c:135
/openzfs#520 0x00007f03c78890a3 in start_thread (arg=0x7f03c2703700) at pthread_create.c:309
/openzfs#521 0x00007f03c75c50fd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

This occurred when ztest was simulating a scrub under heavy I/O load. Under
those circumstances, it was possible for a mix of noop I/Os for aggregation
continuity and the I/O elevator to generate arbitrarily deep recursion.

This patch modifies ZFS to propapage a recursion counter inside the zio_t
objects such that IOs will be redispatched upon reaching a given recursion
depth.  We can detect long call chains and dispatch to another ZIO taskq. We
cut in-line when we do this to minimize the potential for taskq exhaustion that
can prevent a zio from notifying its parent.

Signed-off-by: Richard Yao <[email protected]>
ryao added a commit to ryao/zfs that referenced this issue Oct 11, 2014
@ryao
Redispatch ZIOs in deep call graphs
2d33ca8 
The below excerpt of a backtrace is from a ztest failure when running ZoL's
ztest:

/openzfs#453 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#454 0x00007f03c806106e in vdev_queue_io (zio=zio@entry=0x7f0350003de0) at ../../module/zfs/vdev_queue.c:747
/openzfs#455 0x00007f03c80818c1 in zio_vdev_io_start (zio=0x7f0350003de0) at ../../module/zfs/zio.c:2659
/openzfs#456 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003de0) at ../../module/zfs/zio.c:1399
/openzfs#457 zio_nowait (zio=0x7f0350003de0) at ../../module/zfs/zio.c:1456
/openzfs#458 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350003a10) at ../../module/zfs/vdev_mirror.c:374
/openzfs#459 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003a10) at ../../module/zfs/zio.c:1399
/openzfs#460 zio_nowait (zio=0x7f0350003a10) at ../../module/zfs/zio.c:1456
/openzfs#461 0x00007f03c806464c in vdev_raidz_io_start (zio=0x7f0350003380) at ../../module/zfs/vdev_raidz.c:1607
/openzfs#462 0x00007f03c807f243 in __zio_execute (zio=0x7f0350003380) at ../../module/zfs/zio.c:1399
/openzfs#463 zio_nowait (zio=0x7f0350003380) at ../../module/zfs/zio.c:1456
/openzfs#464 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350002fb0) at ../../module/zfs/vdev_mirror.c:374
/openzfs#465 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002fb0) at ../../module/zfs/zio.c:1399
/openzfs#466 zio_nowait (zio=0x7f0350002fb0) at ../../module/zfs/zio.c:1456
/openzfs#467 0x00007f03c805ed43 in vdev_mirror_io_done (zio=0x7f033957ebf0) at ../../module/zfs/vdev_mirror.c:499
/openzfs#468 0x00007f03c807a0c0 in zio_vdev_io_done (zio=0x7f033957ebf0) at ../../module/zfs/zio.c:2707
/openzfs#469 0x00007f03c808285b in __zio_execute (zio=0x7f033957ebf0) at ../../module/zfs/zio.c:1399
/openzfs#470 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f0390001330, pio=0x7f033957ebf0) at ../../module/zfs/zio.c:547
/openzfs#471 zio_done (zio=0x7f0390001330) at ../../module/zfs/zio.c:3278
/openzfs#472 0x00007f03c808285b in __zio_execute (zio=0x7f0390001330) at ../../module/zfs/zio.c:1399
/openzfs#473 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4013a00, pio=0x7f0390001330) at ../../module/zfs/zio.c:547
/openzfs#474 zio_done (zio=0x7f03b4013a00) at ../../module/zfs/zio.c:3278
/openzfs#475 0x00007f03c808285b in __zio_execute (zio=0x7f03b4013a00) at ../../module/zfs/zio.c:1399
/openzfs#476 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4014210, pio=0x7f03b4013a00) at ../../module/zfs/zio.c:547
/openzfs#477 zio_done (zio=0x7f03b4014210) at ../../module/zfs/zio.c:3278
/openzfs#478 0x00007f03c808285b in __zio_execute (zio=0x7f03b4014210) at ../../module/zfs/zio.c:1399
/openzfs#479 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03b4014620, pio=0x7f03b4014210) at ../../module/zfs/zio.c:547
/openzfs#480 zio_done (zio=0x7f03b4014620) at ../../module/zfs/zio.c:3278
/openzfs#481 0x00007f03c807a6d3 in __zio_execute (zio=0x7f03b4014620) at ../../module/zfs/zio.c:1399
/openzfs#482 zio_execute (zio=zio@entry=0x7f03b4014620) at ../../module/zfs/zio.c:1337
/openzfs#483 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#484 0x00007f03c806106e in vdev_queue_io (zio=zio@entry=0x7f0350002be0) at ../../module/zfs/vdev_queue.c:747
/openzfs#485 0x00007f03c80818c1 in zio_vdev_io_start (zio=0x7f0350002be0) at ../../module/zfs/zio.c:2659
/openzfs#486 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002be0) at ../../module/zfs/zio.c:1399
/openzfs#487 zio_nowait (zio=0x7f0350002be0) at ../../module/zfs/zio.c:1456
/openzfs#488 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350002810) at ../../module/zfs/vdev_mirror.c:374
/openzfs#489 0x00007f03c807f243 in __zio_execute (zio=0x7f0350002810) at ../../module/zfs/zio.c:1399
/openzfs#490 zio_nowait (zio=0x7f0350002810) at ../../module/zfs/zio.c:1456
/openzfs#491 0x00007f03c8064593 in vdev_raidz_io_start (zio=0x7f0350001270) at ../../module/zfs/vdev_raidz.c:1591
/openzfs#492 0x00007f03c807f243 in __zio_execute (zio=0x7f0350001270) at ../../module/zfs/zio.c:1399
/openzfs#493 zio_nowait (zio=0x7f0350001270) at ../../module/zfs/zio.c:1456
/openzfs#494 0x00007f03c805f71b in vdev_mirror_io_start (zio=0x7f0350001e60) at ../../module/zfs/vdev_mirror.c:374
/openzfs#495 0x00007f03c807f243 in __zio_execute (zio=0x7f0350001e60) at ../../module/zfs/zio.c:1399
/openzfs#496 zio_nowait (zio=0x7f0350001e60) at ../../module/zfs/zio.c:1456
/openzfs#497 0x00007f03c805ed43 in vdev_mirror_io_done (zio=0x7f033a0c39c0) at ../../module/zfs/vdev_mirror.c:499
/openzfs#498 0x00007f03c807a0c0 in zio_vdev_io_done (zio=0x7f033a0c39c0) at ../../module/zfs/zio.c:2707
/openzfs#499 0x00007f03c808285b in __zio_execute (zio=0x7f033a0c39c0) at ../../module/zfs/zio.c:1399
/openzfs#500 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f03a8003c00, pio=0x7f033a0c39c0) at ../../module/zfs/zio.c:547
/openzfs#501 zio_done (zio=0x7f03a8003c00) at ../../module/zfs/zio.c:3278
/openzfs#502 0x00007f03c808285b in __zio_execute (zio=0x7f03a8003c00) at ../../module/zfs/zio.c:1399
/openzfs#503 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800c400, pio=0x7f03a8003c00) at ../../module/zfs/zio.c:547
/openzfs#504 zio_done (zio=0x7f038800c400) at ../../module/zfs/zio.c:3278
/openzfs#505 0x00007f03c808285b in __zio_execute (zio=0x7f038800c400) at ../../module/zfs/zio.c:1399
/openzfs#506 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800da00, pio=0x7f038800c400) at ../../module/zfs/zio.c:547
/openzfs#507 zio_done (zio=0x7f038800da00) at ../../module/zfs/zio.c:3278
/openzfs#508 0x00007f03c808285b in __zio_execute (zio=0x7f038800da00) at ../../module/zfs/zio.c:1399
/openzfs#509 zio_notify_parent (wait=ZIO_WAIT_DONE, zio=0x7f038800fd80, pio=0x7f038800da00) at ../../module/zfs/zio.c:547
/openzfs#510 zio_done (zio=0x7f038800fd80) at ../../module/zfs/zio.c:3278
/openzfs#511 0x00007f03c807a6d3 in __zio_execute (zio=0x7f038800fd80) at ../../module/zfs/zio.c:1399
/openzfs#512 zio_execute (zio=zio@entry=0x7f038800fd80) at ../../module/zfs/zio.c:1337
/openzfs#513 0x00007f03c8060b35 in vdev_queue_io_to_issue (vq=vq@entry=0x99f8a8) at ../../module/zfs/vdev_queue.c:706
/openzfs#514 0x00007f03c806119d in vdev_queue_io_done (zio=zio@entry=0x7f03a0010950) at ../../module/zfs/vdev_queue.c:775
/openzfs#515 0x00007f03c807a0e8 in zio_vdev_io_done (zio=0x7f03a0010950) at ../../module/zfs/zio.c:2686
/openzfs#516 0x00007f03c807a6d3 in __zio_execute (zio=0x7f03a0010950) at ../../module/zfs/zio.c:1399
/openzfs#517 zio_execute (zio=0x7f03a0010950) at ../../module/zfs/zio.c:1337
/openzfs#518 0x00007f03c7fcd0c4 in taskq_thread (arg=0x966d50) at ../../lib/libzpool/taskq.c:215
/openzfs#519 0x00007f03c7fc7937 in zk_thread_helper (arg=0x967e90) at ../../lib/libzpool/kernel.c:135
/openzfs#520 0x00007f03c78890a3 in start_thread (arg=0x7f03c2703700) at pthread_create.c:309
/openzfs#521 0x00007f03c75c50fd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

This occurred when ztest was simulating a scrub under heavy I/O load. Under
those circumstances, it was possible for a mix of noop I/Os for aggregation
continuity and the I/O elevator to generate arbitrarily deep recursion.

This patch modifies ZFS to propapage a recursion counter inside the zio_t
objects such that IOs will be redispatched upon reaching a given recursion
depth.  We can detect long call chains and dispatch to another ZIO taskq. We
cut in-line when we do this to minimize the potential for taskq exhaustion that
can prevent a zio from notifying its parent.

Signed-off-by: Richard Yao <[email protected]>
behlendorf added a commit to behlendorf/zfs that referenced this issue May 21, 2018
@behlendorf
Add spl_kmem_cache_kmem_threads man page entry
d297a5a 
The spl_kmem_cache_kmem_threads module option was accidentally
omitted from the documentation.  Add it.

Signed-off-by: Brian Behlendorf <[email protected]>
Closes openzfs#512
pcd1193182 added a commit to pcd1193182/zfs that referenced this issue Sep 26, 2023
@pcd1193182
DLPX-81923 zfs object agent panicked while retrieving blob and is not…
9ed4bb6 
… recoverable (blob doesn't exist) (openzfs#512)

Signed-off-by: Paul Dagnelie <[email protected]>
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@mgiammarco @behlendorf @dajhorn