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Fix empty xattr dir causing lockup

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During zfs_rmnode on a xattr dir, if the system crash just after
dmu_free_long_range, we would get empty xattr dir in delete queue. This would
cause blkid=0 be passed into zap_get_leaf_byblk when doing zfs_purgedir during
mount, and would try to do rw_enter on a wrong structure and cause system
lockup.

We fix this by returning ENOENT when blkid is zero in zap_get_leaf_byblk.

Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #4114
Closes #4052
Closes #4006
Closes #3018
Closes #2861
This commit is contained in:
Chunwei Chen 2015-12-18 11:39:41 -08:00 committed by Brian Behlendorf
parent 2ebc7b72b3
commit 29572ccdef
1 changed files with 10 additions and 0 deletions
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10
module/zfs/zap.c
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@ -504,6 +504,16 @@ zap_get_leaf_byblk(zap_t *zap, uint64_t blkid, dmu_tx_t *tx, krw_t lt,
ASSERT(RW_LOCK_HELD(&zap->zap_rwlock));
/*
* If system crashed just after dmu_free_long_range in zfs_rmnode, we
* would be left with an empty xattr dir in delete queue. blkid=0
* would be passed in when doing zfs_purgedir. If that's the case we
* should just return immediately. The underlying objects should
* already be freed, so this should be perfectly fine.
*/
if (blkid == 0)
return (ENOENT);
err = dmu_buf_hold(zap->zap_objset, zap->zap_object,
blkid << bs, NULL, &db, DMU_READ_NO_PREFETCH);
if (err)