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Fix z_xattr_lock/z_teardown_lock lock inversion 

There exists a lock inversion between the z_xattr_lock and the
z_teardown_lock.  Detect this case and return EBUSY so zfs_resume_fs()
will mark the inode stale and it can be safely revalidated on next
access.

* process-1
zpl_xattr_get -> Takes zp->z_xattr_lock
  __zpl_xattr_get
    zfs_lookup -> Takes zsb->z_teardown_lock in ZFS_ENTER macro

* process-2
zfs_ioc_recv -> Takes zsb->z_teardown_lock in zfs_suspend_fs()
  zfs_resume_fs
    zfs_rezget -> Takes zp->z_xattr_lock

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Closes #3969
This commit is contained in:
Brian Behlendorf 2015-12-16 14:17:49 -08:00
parent 2727b9d3b6
commit a8ad3bf02c
1 changed files with 10 additions and 1 deletions
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11
module/zfs/zfs_znode.c
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@ -1012,7 +1012,16 @@ zfs_rezget(znode_t *zp)
} }
mutex_exit(&zp->z_acl_lock); mutex_exit(&zp->z_acl_lock);
rw_enter(&zp->z_xattr_lock, RW_WRITER); /*
* Lock inversion with zpl_xattr_get->__zpl_xattr_get->zfs_lookup
* between z_xattr_lock and z_teardown_lock. Detect this case and
* return EBUSY so zfs_resume_fs() will mark the inode stale and it
* will safely be revalidated on next access.
*/
err = rw_tryenter(&zp->z_xattr_lock, RW_WRITER);
if (!err)
return (SET_ERROR(EBUSY));
if (zp->z_xattr_cached) { if (zp->z_xattr_cached) {
nvlist_free(zp->z_xattr_cached); nvlist_free(zp->z_xattr_cached);
zp->z_xattr_cached = NULL; zp->z_xattr_cached = NULL;