From 1b0819edded7b0df7efdbb885bb42acb7441b998 Mon Sep 17 00:00:00 2001 From: "Darrick J. Wong" Date: Wed, 22 Jan 2020 11:29:46 -0500 Subject: [PATCH] xfs: don't commit sunit/swidth updates to disk if that would cause repair failures Source kernel commit: 13eaec4b2adf2657b8167b67e27c97cc7314d923 Alex Lyakas reported[1] that mounting an xfs filesystem with new sunit and swidth values could cause xfs_repair to fail loudly. The problem here is that repair calculates the where mkfs should have allocated the root inode, based on the superblock geometry. The allocation decisions depend on sunit, which means that we really can't go updating sunit if it would lead to a subsequent repair failure on an otherwise correct filesystem. Port from xfs_repair some code that computes the location of the root inode and teach mount to skip the ondisk update if it would cause problems for repair. Along the way we'll update the documentation, provide a function for computing the minimum AGFL size instead of open-coding it, and cut down some indenting in the mount code. Note that we allow the mount to proceed (and new allocations will reflect this new geometry) because we've never screened this kind of thing before. We'll have to wait for a new future incompat feature to enforce correct behavior, alas. Note that the geometry reporting always uses the superblock values, not the incore ones, so that is what xfs_info and xfs_growfs will report. [1] https://lore.kernel.org/linux-xfs/20191125130744.GA44777@bfoster/T/#m00f9594b511e076e2fcdd489d78bc30216d72a7d Reported-by: Alex Lyakas Signed-off-by: Darrick J. Wong Reviewed-by: Brian Foster Signed-off-by: Eric Sandeen --- libxfs/xfs_ialloc.c | 64 +++++++++++++++++++++++++++++++++++++++++++++ libxfs/xfs_ialloc.h | 1 + 2 files changed, 65 insertions(+) diff --git a/libxfs/xfs_ialloc.c b/libxfs/xfs_ialloc.c index 71e7d0f6d..23bcc8c9b 100644 --- a/libxfs/xfs_ialloc.c +++ b/libxfs/xfs_ialloc.c @@ -2903,3 +2903,67 @@ xfs_ialloc_setup_geometry( else igeo->ialloc_align = 0; } + +/* Compute the location of the root directory inode that is laid out by mkfs. */ +xfs_ino_t +xfs_ialloc_calc_rootino( + struct xfs_mount *mp, + int sunit) +{ + struct xfs_ino_geometry *igeo = M_IGEO(mp); + xfs_agblock_t first_bno; + + /* + * Pre-calculate the geometry of AG 0. We know what it looks like + * because libxfs knows how to create allocation groups now. + * + * first_bno is the first block in which mkfs could possibly have + * allocated the root directory inode, once we factor in the metadata + * that mkfs formats before it. Namely, the four AG headers... + */ + first_bno = howmany(4 * mp->m_sb.sb_sectsize, mp->m_sb.sb_blocksize); + + /* ...the two free space btree roots... */ + first_bno += 2; + + /* ...the inode btree root... */ + first_bno += 1; + + /* ...the initial AGFL... */ + first_bno += xfs_alloc_min_freelist(mp, NULL); + + /* ...the free inode btree root... */ + if (xfs_sb_version_hasfinobt(&mp->m_sb)) + first_bno++; + + /* ...the reverse mapping btree root... */ + if (xfs_sb_version_hasrmapbt(&mp->m_sb)) + first_bno++; + + /* ...the reference count btree... */ + if (xfs_sb_version_hasreflink(&mp->m_sb)) + first_bno++; + + /* + * ...and the log, if it is allocated in the first allocation group. + * + * This can happen with filesystems that only have a single + * allocation group, or very odd geometries created by old mkfs + * versions on very small filesystems. + */ + if (mp->m_sb.sb_logstart && + XFS_FSB_TO_AGNO(mp, mp->m_sb.sb_logstart) == 0) + first_bno += mp->m_sb.sb_logblocks; + + /* + * Now round first_bno up to whatever allocation alignment is given + * by the filesystem or was passed in. + */ + if (xfs_sb_version_hasdalign(&mp->m_sb) && igeo->ialloc_align > 0) + first_bno = roundup(first_bno, sunit); + else if (xfs_sb_version_hasalign(&mp->m_sb) && + mp->m_sb.sb_inoalignmt > 1) + first_bno = roundup(first_bno, mp->m_sb.sb_inoalignmt); + + return XFS_AGINO_TO_INO(mp, 0, XFS_AGB_TO_AGINO(mp, first_bno)); +} diff --git a/libxfs/xfs_ialloc.h b/libxfs/xfs_ialloc.h index 323592d56..72b3468b9 100644 --- a/libxfs/xfs_ialloc.h +++ b/libxfs/xfs_ialloc.h @@ -152,5 +152,6 @@ int xfs_inobt_insert_rec(struct xfs_btree_cur *cur, uint16_t holemask, int xfs_ialloc_cluster_alignment(struct xfs_mount *mp); void xfs_ialloc_setup_geometry(struct xfs_mount *mp); +xfs_ino_t xfs_ialloc_calc_rootino(struct xfs_mount *mp, int sunit); #endif /* __XFS_IALLOC_H__ */ -- 2.50.1