On Wed, Dec 18, 2019 at 11:37:41AM -0800, Darrick J. Wong wrote: > From: Darrick J. Wong <darrick.wong@xxxxxxxxxx> > > 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 <alex@xxxxxxxxxx> > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx> > --- > fs/xfs/libxfs/xfs_ialloc.c | 70 ++++++++++++++++++++++++++++++++++++++++++++ > fs/xfs/libxfs/xfs_ialloc.h | 1 + > fs/xfs/xfs_mount.c | 45 ++++++++++++++++++++++++++++ > fs/xfs/xfs_trace.h | 21 +++++++++++++ > 4 files changed, 136 insertions(+), 1 deletion(-) > > > diff --git a/fs/xfs/libxfs/xfs_ialloc.c b/fs/xfs/libxfs/xfs_ialloc.c > index 988cde7744e6..eeec7c8d93fd 100644 > --- a/fs/xfs/libxfs/xfs_ialloc.c > +++ b/fs/xfs/libxfs/xfs_ialloc.c > @@ -2909,3 +2909,73 @@ xfs_ialloc_setup_geometry( > else > igeo->ialloc_align = 0; > } > + > +/* > + * Compute the location of the root directory inode that is laid out by mkfs. > + * The @sunit parameter will be copied from the superblock if it is negative. > + */ > +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; > + > + if (sunit < 0) > + sunit = mp->m_sb.sb_unit; What's the purpose of this check? Can this actually happen? That question aside, the rest LGTM: Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx> > + > + /* > + * 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/fs/xfs/libxfs/xfs_ialloc.h b/fs/xfs/libxfs/xfs_ialloc.h > index 323592d563d5..72b3468b97b1 100644 > --- a/fs/xfs/libxfs/xfs_ialloc.h > +++ b/fs/xfs/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__ */ > diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c > index 3750f0074c74..7f94c6b20920 100644 > --- a/fs/xfs/xfs_mount.c > +++ b/fs/xfs/xfs_mount.c > @@ -31,7 +31,7 @@ > #include "xfs_reflink.h" > #include "xfs_extent_busy.h" > #include "xfs_health.h" > - > +#include "xfs_trace.h" > > static DEFINE_MUTEX(xfs_uuid_table_mutex); > static int xfs_uuid_table_size; > @@ -359,6 +359,42 @@ xfs_readsb( > return error; > } > > +/* > + * If the sunit/swidth change would move the precomputed root inode value, we > + * must reject the ondisk change because repair will stumble over that. > + * However, we allow the mount to proceed because we never rejected this > + * combination before. Returns true to update the sb, false otherwise. > + */ > +static inline int > +xfs_check_new_dalign( > + struct xfs_mount *mp, > + int new_dalign, > + bool *update_sb) > +{ > + struct xfs_sb *sbp = &mp->m_sb; > + xfs_ino_t calc_ino; > + > + calc_ino = xfs_ialloc_calc_rootino(mp, new_dalign); > + trace_xfs_check_new_dalign(mp, new_dalign, calc_ino); > + > + if (sbp->sb_rootino == calc_ino) { > + *update_sb = true; > + return 0; > + } > + > + xfs_warn(mp, > +"Cannot change stripe alignment; would require moving root inode."); > + > + /* > + * XXX: Next time we add a new incompat feature, this should start > + * returning -EINVAL to fail the mount. Until then, spit out a warning > + * that we're ignoring the administrator's instructions. > + */ > + xfs_warn(mp, "Skipping superblock stripe alignment update."); > + *update_sb = false; > + return 0; > +} > + > /* > * If we were provided with new sunit/swidth values as mount options, make sure > * that they pass basic alignment and superblock feature checks, and convert > @@ -422,10 +458,17 @@ xfs_update_alignment( > struct xfs_sb *sbp = &mp->m_sb; > > if (mp->m_dalign) { > + bool update_sb; > + int error; > + > if (sbp->sb_unit == mp->m_dalign && > sbp->sb_width == mp->m_swidth) > return 0; > > + error = xfs_check_new_dalign(mp, mp->m_dalign, &update_sb); > + if (error || !update_sb) > + return error; > + > sbp->sb_unit = mp->m_dalign; > sbp->sb_width = mp->m_swidth; > mp->m_update_sb = true; > diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h > index c13bb3655e48..a86be7f807ee 100644 > --- a/fs/xfs/xfs_trace.h > +++ b/fs/xfs/xfs_trace.h > @@ -3573,6 +3573,27 @@ DEFINE_KMEM_EVENT(kmem_alloc_large); > DEFINE_KMEM_EVENT(kmem_realloc); > DEFINE_KMEM_EVENT(kmem_zone_alloc); > > +TRACE_EVENT(xfs_check_new_dalign, > + TP_PROTO(struct xfs_mount *mp, int new_dalign, xfs_ino_t calc_rootino), > + TP_ARGS(mp, new_dalign, calc_rootino), > + TP_STRUCT__entry( > + __field(dev_t, dev) > + __field(int, new_dalign) > + __field(xfs_ino_t, sb_rootino) > + __field(xfs_ino_t, calc_rootino) > + ), > + TP_fast_assign( > + __entry->dev = mp->m_super->s_dev; > + __entry->new_dalign = new_dalign; > + __entry->sb_rootino = mp->m_sb.sb_rootino; > + __entry->calc_rootino = calc_rootino; > + ), > + TP_printk("dev %d:%d new_dalign %d sb_rootino %llu calc_rootino %llu", > + MAJOR(__entry->dev), MINOR(__entry->dev), > + __entry->new_dalign, __entry->sb_rootino, > + __entry->calc_rootino) > +) > + > #endif /* _TRACE_XFS_H */ > > #undef TRACE_INCLUDE_PATH >
