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Wait iput_async before evict_inodes to prevent race 

Wait for iput_async before entering evict_inodes in
generic_shutdown_super. The reason we must finish before
evict_inodes is when lazytime is on, or when zfs_purgedir calls
zfs_zget, iput would bump i_count from 0 to 1. This would race
with the i_count check in evict_inodes.  This means it could
destroy the inode while we are still using it.

Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #4854
This commit is contained in:
Chunwei Chen 2016-07-14 17:31:00 -07:00 committed by Brian Behlendorf
parent b756ff2445
commit 1d9b3bd8fb
1 changed files with 18 additions and 0 deletions
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18
module/zfs/zfs_vfsops.c
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@ -1415,6 +1415,24 @@ zfs_preumount(struct super_block *sb)
if (zsb)
zfsctl_destroy(sb->s_fs_info);
/*
* Wait for iput_async before entering evict_inodes in
* generic_shutdown_super. The reason we must finish before
* evict_inodes is when lazytime is on, or when zfs_purgedir calls
* zfs_zget, iput would bump i_count from 0 to 1. This would race
* with the i_count check in evict_inodes. This means it could
* destroy the inode while we are still using it.
*
* We wait for two passes. xattr directories in the first pass may
* add xattr entries in zfs_purgedir, so in the second pass we wait
* for them. We don't use taskq_wait here because it is a pool wide
* taskq. Other mounted filesystems can constantly do iput_async
* and there's no guarantee when taskq will be empty.
*/
taskq_wait_outstanding(dsl_pool_iput_taskq(
dmu_objset_pool(zsb->z_os)), 0);
taskq_wait_outstanding(dsl_pool_iput_taskq(
dmu_objset_pool(zsb->z_os)), 0);
}
EXPORT_SYMBOL(zfs_preumount);