Re: [PATCH v3] xfs: add agf freeblocks verify in xfs_agf_verify

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Sat, Feb 29, 2020 at 07:21:17PM +0800, zhengbin (A) wrote:
> Hi, is this ok?

Yes.  I'll update for-next next week once my prepared branch finishes
running through torture testing.

--D

> On 2020/2/21 23:38, Darrick J. Wong wrote:
> > On Fri, Feb 21, 2020 at 12:47:15PM +0800, Zheng Bin wrote:
> >> We recently used fuzz(hydra) to test XFS and automatically generate
> >> tmp.img(XFS v5 format, but some metadata is wrong)
> >>
> >> xfs_repair information(just one AG):
> >> agf_freeblks 0, counted 3224 in ag 0
> >> agf_longest 536874136, counted 3224 in ag 0
> >> sb_fdblocks 613, counted 3228
> >>
> >> Test as follows:
> >> mount tmp.img tmpdir
> >> cp file1M tmpdir
> >> sync
> >>
> >> In 4.19-stable, sync will stuck, the reason is:
> >> xfs_mountfs
> >>   xfs_check_summary_counts
> >>     if ((!xfs_sb_version_haslazysbcount(&mp->m_sb) ||
> >>        XFS_LAST_UNMOUNT_WAS_CLEAN(mp)) &&
> >>        !xfs_fs_has_sickness(mp, XFS_SICK_FS_COUNTERS))
> >> 	return 0;  -->just return, incore sb_fdblocks still be 613
> >>     xfs_initialize_perag_data
> >>
> >> cp file1M tmpdir -->ok(write file to pagecache)
> >> sync -->stuck(write pagecache to disk)
> >> xfs_map_blocks
> >>   xfs_iomap_write_allocate
> >>     while (count_fsb != 0) {
> >>       nimaps = 0;
> >>       while (nimaps == 0) { --> endless loop
> >>          nimaps = 1;
> >>          xfs_bmapi_write(..., &nimaps) --> nimaps becomes 0 again
> >> xfs_bmapi_write
> >>   xfs_bmap_alloc
> >>     xfs_bmap_btalloc
> >>       xfs_alloc_vextent
> >>         xfs_alloc_fix_freelist
> >>           xfs_alloc_space_available -->fail(agf_freeblks is 0)
> >>
> >> In linux-next, sync not stuck, cause commit c2b3164320b5 ("xfs:
> >> use the latest extent at writeback delalloc conversion time") remove
> >> the above while, dmesg is as follows:
> >> [   55.250114] XFS (loop0): page discard on page ffffea0008bc7380, inode 0x1b0c, offset 0.
> >>
> >> Users do not know why this page is discard, the better soultion is:
> >> 1. Like xfs_repair, make sure sb_fdblocks is equal to counted
> >> (xfs_initialize_perag_data did this, who is not called at this mount)
> >> 2. Add agf verify, if fail, will tell users to repair
> >>
> >> This patch use the second soultion.
> >>
> >> Signed-off-by: Zheng Bin <zhengbin13@huawei.com>
> >> Signed-off-by: Ren Xudong <renxudong1@huawei.com>
> > Looks ok, will give this a run through fuzz testing...
> > Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
> >
> > --D
> >
> >> ---
> >>
> >> v1->v2: modify comment, add more agf verify
> >> v2->v3: modify code which is suggested by hellwig & darrick
> >> besides, remove the agf_freeblks < sb_fdblocks check, sb_fdblocks may not be true,
> >> if we have lazysbcount or not umount clean. If we check this, we need to add
> >> if ((!xfs_sb_version_haslazysbcount(&mp->m_sb) ||
> >>     XFS_LAST_UNMOUNT_WAS_CLEAN(mp)) &&
> >>     !xfs_fs_has_sickness(mp, XFS_SICK_FS_COUNTERS))
> >> like function xfs_check_summary_counts does.
> >>
> >>  fs/xfs/libxfs/xfs_alloc.c | 16 ++++++++++++++++
> >>  1 file changed, 16 insertions(+)
> >>
> >> diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
> >> index d8053bc..183dc25 100644
> >> --- a/fs/xfs/libxfs/xfs_alloc.c
> >> +++ b/fs/xfs/libxfs/xfs_alloc.c
> >> @@ -2858,6 +2858,13 @@ xfs_agf_verify(
> >>  	      be32_to_cpu(agf->agf_flcount) <= xfs_agfl_size(mp)))
> >>  		return __this_address;
> >>
> >> +	if (be32_to_cpu(agf->agf_length) > mp->m_sb.sb_dblocks)
> >> +		return __this_address;
> >> +
> >> +	if (be32_to_cpu(agf->agf_freeblks) < be32_to_cpu(agf->agf_longest) ||
> >> +	    be32_to_cpu(agf->agf_freeblks) > be32_to_cpu(agf->agf_length))
> >> +		return __this_address;
> >> +
> >>  	if (be32_to_cpu(agf->agf_levels[XFS_BTNUM_BNO]) < 1 ||
> >>  	    be32_to_cpu(agf->agf_levels[XFS_BTNUM_CNT]) < 1 ||
> >>  	    be32_to_cpu(agf->agf_levels[XFS_BTNUM_BNO]) > XFS_BTREE_MAXLEVELS ||
> >> @@ -2869,6 +2876,10 @@ xfs_agf_verify(
> >>  	     be32_to_cpu(agf->agf_levels[XFS_BTNUM_RMAP]) > XFS_BTREE_MAXLEVELS))
> >>  		return __this_address;
> >>
> >> +	if (xfs_sb_version_hasrmapbt(&mp->m_sb) &&
> >> +	    be32_to_cpu(agf->agf_rmap_blocks) > be32_to_cpu(agf->agf_length))
> >> +		return __this_address;
> >> +
> >>  	/*
> >>  	 * during growfs operations, the perag is not fully initialised,
> >>  	 * so we can't use it for any useful checking. growfs ensures we can't
> >> @@ -2883,6 +2894,11 @@ xfs_agf_verify(
> >>  		return __this_address;
> >>
> >>  	if (xfs_sb_version_hasreflink(&mp->m_sb) &&
> >> +	    be32_to_cpu(agf->agf_refcount_blocks) >
> >> +	    be32_to_cpu(agf->agf_length))
> >> +		return __this_address;
> >> +
> >> +	if (xfs_sb_version_hasreflink(&mp->m_sb) &&
> >>  	    (be32_to_cpu(agf->agf_refcount_level) < 1 ||
> >>  	     be32_to_cpu(agf->agf_refcount_level) > XFS_BTREE_MAXLEVELS))
> >>  		return __this_address;
> >> --
> >> 2.7.4
> >>
> > .
> >
>