From d6e8deb14cbea11d8f265537f7163428717b93fb Mon Sep 17 00:00:00 2001 From: Brian Foster Date: Tue, 15 Sep 2020 15:59:38 -0400 Subject: [PATCH] xfs: fix off-by-one in inode alloc block reservation calculation Source kernel 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 Reviewed-by: Darrick J. Wong Signed-off-by: Darrick J. Wong Signed-off-by: Eric Sandeen --- libxfs/xfs_ialloc.c | 4 ++-- libxfs/xfs_trans_space.h | 2 +- 2 files changed, 3 insertions(+), 3 deletions(-) diff --git a/libxfs/xfs_ialloc.c b/libxfs/xfs_ialloc.c index 5f09ff5af..ce73feed9 100644 --- a/libxfs/xfs_ialloc.c +++ b/libxfs/xfs_ialloc.c @@ -683,7 +683,7 @@ 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; @@ -731,7 +731,7 @@ 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/libxfs/xfs_trans_space.h b/libxfs/xfs_trans_space.h index c6df01a2a..7ad3659c5 100644 --- a/libxfs/xfs_trans_space.h +++ b/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. -- 2.47.2