On 1/26/17 1:26 PM, Brian Foster wrote:
> Quotacheck runs at mount time in situations where quota accounting must
> be recalculated. In doing so, it uses bulkstat to visit every inode in
> the filesystem. Historically, every inode processed during quotacheck
> was released and immediately tagged for reclaim because quotacheck runs
> before the superblock is marked active by the VFS. In other words,
> the final iput() lead to an immediate ->destroy_inode() call, which
> allowed the XFS background reclaim worker to start reclaiming inodes.
>
> Commit 17c12bcd3 ("xfs: when replaying bmap operations, don't let
> unlinked inodes get reaped") marks the XFS superblock active sooner as
> part of the mount process to support caching inodes processed during log
> recovery. This occurs before quotacheck and thus means all inodes
> processed by quotacheck are inserted to the LRU on release. The
> s_umount lock is held until the mount has completed and thus prevents
> the shrinkers from operating on the sb. This means that quotacheck can
> excessively populate the inode LRU and lead to OOM conditions on systems
> without sufficient RAM.
>
> Update the quotacheck bulkstat handler to set XFS_IGET_DONTCACHE on
> inodes processed by quotacheck. This causes ->drop_inode() to return 1
> and in turn causes iput_final() to evict the inode. This preserves the
> original quotacheck behavior and prevents it from overloading the LRU
> and running out of memory.
>
> CC: stable@xxxxxxxxxxxxxxx # v4.9
> Reported-by: Martin Svec <martin.svec@xxxxxxxx>
> Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
Makes sense, thanks for digging into this!
Reviewed-by: Eric Sandeen <sandeen@xxxxxxxxxx>
> ---
> fs/xfs/xfs_qm.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/xfs/xfs_qm.c b/fs/xfs/xfs_qm.c
> index 45e50ea..b669b12 100644
> --- a/fs/xfs/xfs_qm.c
> +++ b/fs/xfs/xfs_qm.c
> @@ -1177,7 +1177,8 @@ xfs_qm_dqusage_adjust(
> * the case in all other instances. It's OK that we do this because
> * quotacheck is done only at mount time.
> */
> - error = xfs_iget(mp, NULL, ino, 0, XFS_ILOCK_EXCL, &ip);
> + error = xfs_iget(mp, NULL, ino, XFS_IGET_DONTCACHE, XFS_ILOCK_EXCL,
> + &ip);
> if (error) {
> *res = BULKSTAT_RV_NOTHING;
> return error;
>
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