Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Avoid memory copies during mirror scrub. #13606

Merged
merged 1 commit into from
Jul 5, 2022
Merged

Avoid memory copies during mirror scrub. #13606

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
131 changes: 61 additions & 70 deletions module/zfs/vdev_mirror.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -436,36 +436,6 @@ vdev_mirror_child_done(zio_t *zio)
{
mirror_child_t *mc = zio->io_private;

/* See scrubbing read comment in vdev_mirror_io_start() */
if (zio->io_flags & ZIO_FLAG_SCRUB && zio->io_bp == NULL)
mc->mc_abd = zio->io_abd;

mc->mc_error = zio->io_error;
mc->mc_tried = 1;
mc->mc_skipped = 0;
}

static void
vdev_mirror_scrub_done(zio_t *zio)
{
mirror_child_t *mc = zio->io_private;

if (zio->io_error == 0) {
zio_t *pio;
zio_link_t *zl = NULL;

mutex_enter(&zio->io_lock);
while ((pio = zio_walk_parents(zio, &zl)) != NULL) {
mutex_enter(&pio->io_lock);
ASSERT3U(zio->io_size, >=, pio->io_size);
abd_copy(pio->io_abd, zio->io_abd, pio->io_size);
mutex_exit(&pio->io_lock);
}
mutex_exit(&zio->io_lock);
}

abd_free(zio->io_abd);

mc->mc_error = zio->io_error;
mc->mc_tried = 1;
mc->mc_skipped = 0;
Expand Down Expand Up @@ -645,15 +615,13 @@ vdev_mirror_io_start(zio_t *zio)
if (zio->io_type == ZIO_TYPE_READ) {
if ((zio->io_flags & ZIO_FLAG_SCRUB) && !mm->mm_resilvering) {
/*
* For scrubbing reads we need to allocate a buffer
* for each child and issue reads to all children.
* If we can verify the checksum here, as indicated
* by io_bp being non-NULL, the data will be copied
* into zio->io_data in vdev_mirror_scrub_done().
* If not, then vdev_mirror_io_done() will compare
* all of the read buffers and return a checksum
* error if they aren't all identical.
* For scrubbing reads we need to issue reads to all
* children. One child can reuse parent buffer, but
* for others we have to allocate separate ones to
* verify checksums if io_bp is non-NULL, or compare
* them in vdev_mirror_io_done() otherwise.
*/
boolean_t first = B_TRUE;
for (c = 0; c < mm->mm_children; c++) {
mc = &mm->mm_child[c];

Expand All @@ -665,13 +633,15 @@ vdev_mirror_io_start(zio_t *zio)
continue;
}

zio_nowait(zio_vdev_child_io(zio, zio->io_bp,
mc->mc_vd, mc->mc_offset,
mc->mc_abd = first ? zio->io_abd :
abd_alloc_sametype(zio->io_abd,
zio->io_size), zio->io_size,
zio->io_type, zio->io_priority, 0,
zio->io_bp ? vdev_mirror_scrub_done :
zio->io_size);
zio_nowait(zio_vdev_child_io(zio, zio->io_bp,
mc->mc_vd, mc->mc_offset, mc->mc_abd,
zio->io_size, zio->io_type,
zio->io_priority, 0,
vdev_mirror_child_done, mc));
first = B_FALSE;
}
zio_execute(zio);
return;
Expand Down Expand Up @@ -802,55 +772,76 @@ vdev_mirror_io_done(zio_t *zio)
return;
}

/*
* If we're scrubbing but don't have a BP available (because this
* vdev is under a raidz or draid vdev) then the best we can do is
* compare all of the copies read. If they're not identical then
* return a checksum error and the most likely correct data. The
* raidz code will issue a repair I/O if possible.
*/
if (zio->io_flags & ZIO_FLAG_SCRUB && zio->io_bp == NULL) {
abd_t *last_good_abd;

ASSERT(zio->io_vd->vdev_ops == &vdev_replacing_ops ||
zio->io_vd->vdev_ops == &vdev_spare_ops);
if (zio->io_flags & ZIO_FLAG_SCRUB && !mm->mm_resilvering) {
abd_t *best_abd = NULL;
if (last_good_copy >= 0)
best_abd = mm->mm_child[last_good_copy].mc_abd;

if (good_copies > 1) {
last_good_abd = mm->mm_child[last_good_copy].mc_abd;
abd_t *best_abd = NULL;
/*
* If we're scrubbing but don't have a BP available (because
* this vdev is under a raidz or draid vdev) then the best we
* can do is compare all of the copies read. If they're not
* identical then return a checksum error and the most likely
* correct data. The raidz code will issue a repair I/O if
* possible.
*/
if (zio->io_bp == NULL) {
ASSERT(zio->io_vd->vdev_ops == &vdev_replacing_ops ||
zio->io_vd->vdev_ops == &vdev_spare_ops);

abd_t *pref_abd = NULL;
for (c = 0; c < last_good_copy; c++) {
mc = &mm->mm_child[c];

if (mc->mc_error || !mc->mc_tried)
continue;

if (abd_cmp(mc->mc_abd, last_good_abd) != 0)
if (abd_cmp(mc->mc_abd, best_abd) != 0)
zio->io_error = SET_ERROR(ECKSUM);

/*
* The distributed spare is always prefered
* by vdev_mirror_child_select() so it's
* considered to be the best candidate.
*/
if (best_abd == NULL &&
if (pref_abd == NULL &&
mc->mc_vd->vdev_ops ==
&vdev_draid_spare_ops) {
&vdev_draid_spare_ops)
pref_abd = mc->mc_abd;

/*
* In the absence of a preferred copy, use
* the parent pointer to avoid a memory copy.
*/
if (mc->mc_abd == zio->io_abd)
best_abd = mc->mc_abd;
}
}
if (pref_abd)
best_abd = pref_abd;
} else {

abd_copy(zio->io_abd, best_abd ? best_abd :
last_good_abd, zio->io_size);

} else if (good_copies == 1) {
last_good_abd = mm->mm_child[last_good_copy].mc_abd;
abd_copy(zio->io_abd, last_good_abd, zio->io_size);
/*
* If we have a BP available, then checksums are
* already verified and we just need a buffer
* with valid data, preferring parent one to
* avoid a memory copy.
*/
for (c = 0; c < last_good_copy; c++) {
mc = &mm->mm_child[c];
if (mc->mc_error || !mc->mc_tried)
continue;
if (mc->mc_abd == zio->io_abd) {
best_abd = mc->mc_abd;
break;
}
}
}

if (best_abd && best_abd != zio->io_abd)
abd_copy(zio->io_abd, best_abd, zio->io_size);
for (c = 0; c < mm->mm_children; c++) {
mc = &mm->mm_child[c];
abd_free(mc->mc_abd);
if (mc->mc_abd != zio->io_abd)
abd_free(mc->mc_abd);
mc->mc_abd = NULL;
}
}
Expand Down