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Fix kernel panic due to tsd_exit in ZFS_EXIT(zsb) 

The following panic would occur under certain heavy load:
[ 4692.202686] Kernel panic - not syncing: thread ffff8800c4f5dd60 terminating with rrw lock ffff8800da1b9c40 held
[ 4692.228053] CPU: 1 PID: 6250 Comm: mmap_deadlock Tainted: P           OE  3.18.10 #7

The culprit is that ZFS_EXIT(zsb) would call tsd_exit() every time, which
would purge all tsd data for the thread. However, ZFS_ENTER is designed to be
reentrant, so we cannot allow ZFS_EXIT to blindly purge tsd data.

Instead, we rely on the new behavior of tsd_set. When NULL is passed as the
new value to tsd_set, it will automatically remove the tsd entry specified the
the key for the current thread.

rrw_tsd_key and zfs_allow_log_key already calls tsd_set(key, NULL) when
they're done. The zfs_fsyncer_key relied on ZFS_EXIT(zsb) to call tsd_exit() to
do clean up. Now we explicitly call tsd_set(key, NULL) on them.

Signed-off-by: Chunwei Chen <tuxoko@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #3247
This commit is contained in:
Chunwei Chen 2015-04-02 02:18:05 +08:00 committed by Brian Behlendorf
parent 59199d9083
commit 07012da668
2 changed files with 2 additions and 1 deletions
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1
include/sys/zfs_znode.h
View File

@ -263,7 +263,6 @@ typedef struct znode {
#define ZFS_EXIT(zsb) \ #define ZFS_EXIT(zsb) \
{ \ { \
rrw_exit(&(zsb)->z_teardown_lock, FTAG); \ rrw_exit(&(zsb)->z_teardown_lock, FTAG); \
tsd_exit(); \
} }
/* Verifies the znode is valid */ /* Verifies the znode is valid */

2
module/zfs/zfs_vnops.c
View File

@ -2156,6 +2156,8 @@ zfs_fsync(struct inode *ip, int syncflag, cred_t *cr)
zil_commit(zsb->z_log, zp->z_id); zil_commit(zsb->z_log, zp->z_id);
ZFS_EXIT(zsb); ZFS_EXIT(zsb);
} }
tsd_set(zfs_fsyncer_key, NULL);
return (0); return (0);
} }
EXPORT_SYMBOL(zfs_fsync); EXPORT_SYMBOL(zfs_fsync);