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authorDarrick J. Wong <djwong@kernel.org>2022-03-16 11:54:18 -0700
committerDarrick J. Wong <djwong@kernel.org>2022-03-28 08:38:43 -0700
commitc8c568259772751a14e969b7230990508de73d9d (patch)
treeb04ccdf6673b85d23f84b0f1b31937894df20b6f /fs/xfs/xfs_mount.c
parent93defd5a15dd74791532692cc59be3a1aaa045fe (diff)
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xfs: don't include bnobt blocks when reserving free block pool
xfs_reserve_blocks controls the size of the user-visible free space reserve pool. Given the difference between the current and requested pool sizes, it will try to reserve free space from fdblocks. However, the amount requested from fdblocks is also constrained by the amount of space that we think xfs_mod_fdblocks will give us. If we forget to subtract m_allocbt_blks before calling xfs_mod_fdblocks, it will will return ENOSPC and we'll hang the kernel at mount due to the infinite loop. In commit fd43cf600cf6, we decided that xfs_mod_fdblocks should not hand out the "free space" used by the free space btrees, because some portion of the free space btrees hold in reserve space for future btree expansion. Unfortunately, xfs_reserve_blocks' estimation of the number of blocks that it could request from xfs_mod_fdblocks was not updated to include m_allocbt_blks, so if space is extremely low, the caller hangs. Fix this by creating a function to estimate the number of blocks that can be reserved from fdblocks, which needs to exclude the set-aside and m_allocbt_blks. Found by running xfs/306 (which formats a single-AG 20MB filesystem) with an fstests configuration that specifies a 1k blocksize and a specially crafted log size that will consume 7/8 of the space (17920 blocks, specifically) in that AG. Cc: Brian Foster <bfoster@redhat.com> Fixes: fd43cf600cf6 ("xfs: set aside allocation btree blocks from block reservation") Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Brian Foster <bfoster@redhat.com> Reviewed-by: Dave Chinner <dchinner@redhat.com>
Diffstat (limited to 'fs/xfs/xfs_mount.c')
-rw-r--r--fs/xfs/xfs_mount.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index bed73e8002a5..29ffa8c42795 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -1146,7 +1146,7 @@ xfs_mod_fdblocks(
* problems (i.e. transaction abort, pagecache discards, etc.) than
* slightly premature -ENOSPC.
*/
- set_aside = mp->m_alloc_set_aside + atomic64_read(&mp->m_allocbt_blks);
+ set_aside = xfs_fdblocks_unavailable(mp);
percpu_counter_add_batch(&mp->m_fdblocks, delta, batch);
if (__percpu_counter_compare(&mp->m_fdblocks, set_aside,
XFS_FDBLOCKS_BATCH) >= 0) {