From: Brian Foster bfoster@redhat.com
[ Upstream commit 657f101930bc6c5b41bd7d6c22565c4302a80d33 ]
The inode chunk allocation transaction reserves inobt_maxlevels-1 blocks to accommodate a full split of the inode btree. A full split requires an allocation for every existing level and a new root block, which means inobt_maxlevels is the worst case block requirement for a transaction that inserts to the inobt. This can lead to a transaction block reservation overrun when tmpfile creation allocates an inode chunk and expands the inobt to its maximum depth. This problem has been observed in conjunction with overlayfs, which makes frequent use of tmpfiles internally.
The existing reservation code goes back as far as the Linux git repo history (v2.6.12). It was likely never observed as a problem because the traditional file/directory creation transactions also include worst case block reservation for directory modifications, which most likely is able to make up for a single block deficiency in the inode allocation portion of the calculation. tmpfile support is relatively more recent (v3.15), less heavily used, and only includes the inode allocation block reservation as tmpfiles aren't linked into the directory tree on creation.
Fix up the inode alloc block reservation macro and a couple of the block allocator minleft parameters that enforce an allocation to leave enough free blocks in the AG for a full inobt split.
Signed-off-by: Brian Foster bfoster@redhat.com Reviewed-by: Darrick J. Wong darrick.wong@oracle.com Signed-off-by: Darrick J. Wong darrick.wong@oracle.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/xfs/libxfs/xfs_ialloc.c | 4 ++-- fs/xfs/libxfs/xfs_trans_space.h | 2 +- 2 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/fs/xfs/libxfs/xfs_ialloc.c b/fs/xfs/libxfs/xfs_ialloc.c index 7fcf62b324b0d..8c1a7cc484b65 100644 --- a/fs/xfs/libxfs/xfs_ialloc.c +++ b/fs/xfs/libxfs/xfs_ialloc.c @@ -688,7 +688,7 @@ xfs_ialloc_ag_alloc( args.minalignslop = igeo->cluster_align - 1;
/* Allow space for the inode btree to split. */ - args.minleft = igeo->inobt_maxlevels - 1; + args.minleft = igeo->inobt_maxlevels; if ((error = xfs_alloc_vextent(&args))) return error;
@@ -736,7 +736,7 @@ xfs_ialloc_ag_alloc( /* * Allow space for the inode btree to split. */ - args.minleft = igeo->inobt_maxlevels - 1; + args.minleft = igeo->inobt_maxlevels; if ((error = xfs_alloc_vextent(&args))) return error; } diff --git a/fs/xfs/libxfs/xfs_trans_space.h b/fs/xfs/libxfs/xfs_trans_space.h index c6df01a2a1585..7ad3659c5d2a9 100644 --- a/fs/xfs/libxfs/xfs_trans_space.h +++ b/fs/xfs/libxfs/xfs_trans_space.h @@ -58,7 +58,7 @@ #define XFS_IALLOC_SPACE_RES(mp) \ (M_IGEO(mp)->ialloc_blks + \ ((xfs_sb_version_hasfinobt(&mp->m_sb) ? 2 : 1) * \ - (M_IGEO(mp)->inobt_maxlevels - 1))) + M_IGEO(mp)->inobt_maxlevels))
/* * Space reservation values for various transactions.