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Linux: Fix ZFS_ENTER/ZFS_EXIT/ZFS_VERFY_ZP usage
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The ZFS_ENTER/ZFS_EXIT/ZFS_VERFY_ZP macros should not be used
in the Linux zpl_*.c source files.  They return a positive error
value which is correct for the common code, but not for the Linux
specific kernel code which expects a negative return value.  The
ZPL_ENTER/ZPL_EXIT/ZPL_VERFY_ZP macros should be used instead.

Furthermore, the ZPL_EXIT macro has been updated to not call the
zfs_exit_fs() function.  This prevents a possible deadlock which
can occur when a snapshot is automatically unmounted because the
zpl_show_devname() must never wait on in progress automatic
snapshot unmounts.

Reviewed-by: Adam Moss <[email protected]>
Reviewed-by: Ryan Moeller <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Closes #11169 
Closes #11201
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behlendorf committed Nov 14, 2020
1 parent 435dc4b commit d02fc15
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Showing 4 changed files with 23 additions and 19 deletions.
6 changes: 5 additions & 1 deletion include/os/linux/zfs/sys/zfs_znode_impl.h
Original file line number Diff line number Diff line change
Expand Up @@ -90,7 +90,11 @@ do { \
zfs_exit_fs(zfsvfs); \
rrm_exit(&(zfsvfs)->z_teardown_lock, FTAG); \
} while (0)
#define ZPL_EXIT(zfsvfs) ZFS_EXIT(zfsvfs)

#define ZPL_EXIT(zfsvfs) \
do { \
rrm_exit(&(zfsvfs)->z_teardown_lock, FTAG); \
} while (0)

/* Verifies the znode is valid. */
#define ZFS_VERIFY_ZP_ERROR(zp, error) \
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22 changes: 11 additions & 11 deletions module/os/linux/zfs/zpl_ctldir.c
Original file line number Diff line number Diff line change
Expand Up @@ -55,7 +55,7 @@ zpl_root_iterate(struct file *filp, zpl_dir_context_t *ctx)
zfsvfs_t *zfsvfs = ITOZSB(file_inode(filp));
int error = 0;

ZFS_ENTER(zfsvfs);
ZPL_ENTER(zfsvfs);

if (!zpl_dir_emit_dots(filp, ctx))
goto out;
Expand All @@ -76,7 +76,7 @@ zpl_root_iterate(struct file *filp, zpl_dir_context_t *ctx)
ctx->pos++;
}
out:
ZFS_EXIT(zfsvfs);
ZPL_EXIT(zfsvfs);

return (error);
}
Expand Down Expand Up @@ -242,7 +242,7 @@ zpl_snapdir_iterate(struct file *filp, zpl_dir_context_t *ctx)
uint64_t id, pos;
int error = 0;

ZFS_ENTER(zfsvfs);
ZPL_ENTER(zfsvfs);
cookie = spl_fstrans_mark();

if (!zpl_dir_emit_dots(filp, ctx))
Expand All @@ -266,7 +266,7 @@ zpl_snapdir_iterate(struct file *filp, zpl_dir_context_t *ctx)
}
out:
spl_fstrans_unmark(cookie);
ZFS_EXIT(zfsvfs);
ZPL_EXIT(zfsvfs);

if (error == -ENOENT)
return (0);
Expand Down Expand Up @@ -369,13 +369,13 @@ zpl_snapdir_getattr_impl(const struct path *path, struct kstat *stat,
struct inode *ip = path->dentry->d_inode;
zfsvfs_t *zfsvfs = ITOZSB(ip);

ZFS_ENTER(zfsvfs);
ZPL_ENTER(zfsvfs);
generic_fillattr(ip, stat);

stat->nlink = stat->size = 2;
stat->ctime = stat->mtime = dmu_objset_snap_cmtime(zfsvfs->z_os);
stat->atime = current_time(ip);
ZFS_EXIT(zfsvfs);
ZPL_EXIT(zfsvfs);

return (0);
}
Expand Down Expand Up @@ -453,7 +453,7 @@ zpl_shares_iterate(struct file *filp, zpl_dir_context_t *ctx)
znode_t *dzp;
int error = 0;

ZFS_ENTER(zfsvfs);
ZPL_ENTER(zfsvfs);
cookie = spl_fstrans_mark();

if (zfsvfs->z_shares_dir == 0) {
Expand All @@ -472,7 +472,7 @@ zpl_shares_iterate(struct file *filp, zpl_dir_context_t *ctx)
iput(ZTOI(dzp));
out:
spl_fstrans_unmark(cookie);
ZFS_EXIT(zfsvfs);
ZPL_EXIT(zfsvfs);
ASSERT3S(error, <=, 0);

return (error);
Expand Down Expand Up @@ -503,13 +503,13 @@ zpl_shares_getattr_impl(const struct path *path, struct kstat *stat,
znode_t *dzp;
int error;

ZFS_ENTER(zfsvfs);
ZPL_ENTER(zfsvfs);

if (zfsvfs->z_shares_dir == 0) {
generic_fillattr(path->dentry->d_inode, stat);
stat->nlink = stat->size = 2;
stat->atime = current_time(ip);
ZFS_EXIT(zfsvfs);
ZPL_EXIT(zfsvfs);
return (0);
}

Expand All @@ -519,7 +519,7 @@ zpl_shares_getattr_impl(const struct path *path, struct kstat *stat,
iput(ZTOI(dzp));
}

ZFS_EXIT(zfsvfs);
ZPL_EXIT(zfsvfs);
ASSERT3S(error, <=, 0);

return (error);
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10 changes: 5 additions & 5 deletions module/os/linux/zfs/zpl_file.c
Original file line number Diff line number Diff line change
Expand Up @@ -675,10 +675,10 @@ zpl_writepages(struct address_space *mapping, struct writeback_control *wbc)
enum writeback_sync_modes sync_mode;
int result;

ZFS_ENTER(zfsvfs);
ZPL_ENTER(zfsvfs);
if (zfsvfs->z_os->os_sync == ZFS_SYNC_ALWAYS)
wbc->sync_mode = WB_SYNC_ALL;
ZFS_EXIT(zfsvfs);
ZPL_EXIT(zfsvfs);
sync_mode = wbc->sync_mode;

/*
Expand All @@ -691,11 +691,11 @@ zpl_writepages(struct address_space *mapping, struct writeback_control *wbc)
wbc->sync_mode = WB_SYNC_NONE;
result = write_cache_pages(mapping, wbc, zpl_putpage, mapping);
if (sync_mode != wbc->sync_mode) {
ZFS_ENTER(zfsvfs);
ZFS_VERIFY_ZP(zp);
ZPL_ENTER(zfsvfs);
ZPL_VERIFY_ZP(zp);
if (zfsvfs->z_log != NULL)
zil_commit(zfsvfs->z_log, zp->z_id);
ZFS_EXIT(zfsvfs);
ZPL_EXIT(zfsvfs);

/*
* We need to call write_cache_pages() again (we can't just
Expand Down
4 changes: 2 additions & 2 deletions module/os/linux/zfs/zpl_super.c
Original file line number Diff line number Diff line change
Expand Up @@ -185,7 +185,7 @@ zpl_remount_fs(struct super_block *sb, int *flags, char *data)
static int
__zpl_show_devname(struct seq_file *seq, zfsvfs_t *zfsvfs)
{
ZFS_ENTER(zfsvfs);
ZPL_ENTER(zfsvfs);

char *fsname = kmem_alloc(ZFS_MAX_DATASET_NAME_LEN, KM_SLEEP);
dmu_objset_name(zfsvfs->z_os, fsname);
Expand All @@ -205,7 +205,7 @@ __zpl_show_devname(struct seq_file *seq, zfsvfs_t *zfsvfs)

kmem_free(fsname, ZFS_MAX_DATASET_NAME_LEN);

ZFS_EXIT(zfsvfs);
ZPL_EXIT(zfsvfs);

return (0);
}
Expand Down

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