On Sun, Dec 15, 2019 at 04:05:41PM -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 the computation code from xfs_repair and teach mount to avoid the > ondisk update if it would cause problems for repair. We allow the mount > to proceed (and new allocations will reflect this new geometry) because > we've never screened this kind of thing before. > > [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> > --- > v3: actually check the alignment check function return value > v2: v2: refactor the agfl length calculations, clarify the fsgeometry ioctl > behavior, fix a bunch of the comments and make it clearer how we compute > the rootino location > --- > fs/xfs/libxfs/xfs_alloc.c | 18 ++++++-- > fs/xfs/libxfs/xfs_ialloc.c | 70 +++++++++++++++++++++++++++++++ > fs/xfs/libxfs/xfs_ialloc.h | 1 > fs/xfs/xfs_mount.c | 99 +++++++++++++++++++++++++++++++------------- > fs/xfs/xfs_trace.h | 21 +++++++++ > 5 files changed, 175 insertions(+), 34 deletions(-) > ... > diff --git a/fs/xfs/libxfs/xfs_ialloc.c b/fs/xfs/libxfs/xfs_ialloc.c > index 988cde7744e6..7b4e76c75c58 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; > + > + /* > + * 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 happens with filesystems that only have a single s/happens/happen/ > + * 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 ... > @@ -359,15 +359,55 @@ 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; > +} I ran a quick test changing swidth (not sunit) and otherwise using mkfs defaults: [root@localhost ~]# mkfs.xfs -f /dev/test/scratch -dsunit=8,swidth=8 meta-data=/dev/test/scratch isize=512 agcount=16, agsize=245760 blks = sectsz=512 attr=2, projid32bit=1 = crc=1 finobt=1, sparse=1, rmapbt=0 = reflink=1 data = bsize=4096 blocks=3932160, imaxpct=25 = sunit=1 swidth=1 blks naming =version 2 bsize=4096 ascii-ci=0, ftype=1 log =internal log bsize=4096 blocks=2560, version=2 = sectsz=512 sunit=1 blks, lazy-count=1 realtime =none extsz=4096 blocks=0, rtextents=0 [root@localhost ~]# mount /dev/test/scratch /mnt/ [root@localhost ~]# stat -c %i /mnt/ 128 [root@localhost ~]# umount /mnt/ [root@localhost ~]# mount /dev/test/scratch /mnt/ -o sunit=8,swidth=16 I see the following trace output on the mount above, which suggests this would have moved rootino: <...>-1007 [002] ...1 516.719543: xfs_check_new_dalign: dev 253:4 new_dalign 1 sb_rootino 128 calc_rootino 80 But if I start with that geometry, that's not what I see from mkfs: [root@localhost ~]# mkfs.xfs -f /dev/test/scratch -dsunit=8,swidth=16 meta-data=/dev/test/scratch isize=512 agcount=16, agsize=245759 blks = sectsz=512 attr=2, projid32bit=1 = crc=1 finobt=1, sparse=1, rmapbt=0 = reflink=1 data = bsize=4096 blocks=3932144, imaxpct=25 = sunit=1 swidth=2 blks naming =version 2 bsize=4096 ascii-ci=0, ftype=1 log =internal log bsize=4096 blocks=2560, version=2 = sectsz=512 sunit=1 blks, lazy-count=1 realtime =none extsz=4096 blocks=0, rtextents=0 [root@localhost ~]# mount /dev/test/scratch /mnt/ [root@localhost ~]# stat -c %i /mnt/ 128 I did notice the AG size changes slightly in the second mkfs, but it doesn't seem to make a difference if I set it back to the original value. Hm? BTW, given the subtle effect of this patch and potential for varying behavior, I wonder if we should have an fstest to format with some different alignments and make sure mount DTRT in various cases. Brian > + > /* > * Update alignment values based on mount options and sb values > */ > STATIC int > -xfs_update_alignment(xfs_mount_t *mp) > +xfs_update_alignment( > + struct xfs_mount *mp) > { > - xfs_sb_t *sbp = &(mp->m_sb); > + struct xfs_sb *sbp = &mp->m_sb; > > if (mp->m_dalign) { > + bool update_sb; > + int error; > + > /* > * If stripe unit and stripe width are not multiples > * of the fs blocksize turn off alignment. > @@ -398,28 +438,28 @@ xfs_update_alignment(xfs_mount_t *mp) > } > } > > - /* > - * Update superblock with new values > - * and log changes > - */ > - if (xfs_sb_version_hasdalign(sbp)) { > - if (sbp->sb_unit != mp->m_dalign) { > - sbp->sb_unit = mp->m_dalign; > - mp->m_update_sb = true; > - } > - if (sbp->sb_width != mp->m_swidth) { > - sbp->sb_width = mp->m_swidth; > - mp->m_update_sb = true; > - } > - } else { > + /* Update superblock with new values and log changes. */ > + if (!xfs_sb_version_hasdalign(sbp)) { > xfs_warn(mp, > "cannot change alignment: superblock does not support data alignment"); > return -EINVAL; > } > + > + 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; > } else if ((mp->m_flags & XFS_MOUNT_NOALIGN) != XFS_MOUNT_NOALIGN && > xfs_sb_version_hasdalign(&mp->m_sb)) { > - mp->m_dalign = sbp->sb_unit; > - mp->m_swidth = sbp->sb_width; > + mp->m_dalign = sbp->sb_unit; > + mp->m_swidth = sbp->sb_width; > } > > return 0; > @@ -647,16 +687,6 @@ xfs_mountfs( > mp->m_update_sb = true; > } > > - /* > - * Check if sb_agblocks is aligned at stripe boundary > - * If sb_agblocks is NOT aligned turn off m_dalign since > - * allocator alignment is within an ag, therefore ag has > - * to be aligned at stripe boundary. > - */ > - error = xfs_update_alignment(mp); > - if (error) > - goto out; > - > xfs_alloc_compute_maxlevels(mp); > xfs_bmap_compute_maxlevels(mp, XFS_DATA_FORK); > xfs_bmap_compute_maxlevels(mp, XFS_ATTR_FORK); > @@ -664,6 +694,17 @@ xfs_mountfs( > xfs_rmapbt_compute_maxlevels(mp); > xfs_refcountbt_compute_maxlevels(mp); > > + /* > + * Check if sb_agblocks is aligned at stripe boundary. If sb_agblocks > + * is NOT aligned turn off m_dalign since allocator alignment is within > + * an ag, therefore ag has to be aligned at stripe boundary. Note that > + * we must compute the free space and rmap btree geometry before doing > + * this. > + */ > + error = xfs_update_alignment(mp); > + if (error) > + goto out; > + > /* enable fail_at_unmount as default */ > mp->m_fail_unmount = 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 >
