Re: [External] Re: [PATCH 2/2] xfs: update dir3 leaf block metadata after swap

[Zhang Tianci]

On Wed, Nov 29, 2023 at 2:34 PM Darrick J. Wong <djwong@xxxxxxxxxx> wrote:
>
> On Wed, Nov 29, 2023 at 10:15:52AM +1100, Dave Chinner wrote:
> > On Tue, Nov 28, 2023 at 01:32:02PM +0800, Jiachen Zhang wrote:
> > > From: Zhang Tianci <zhangtianci.1997@xxxxxxxxxxxxx>
> > >
> > > xfs_da3_swap_lastblock() copy the last block content to the dead block,
> > > but do not update the metadata in it. We need update some metadata
> > > for some kinds of type block, such as dir3 leafn block records its
> > > blkno, we shall update it to the dead block blkno. Otherwise,
> > > before write the xfs_buf to disk, the verify_write() will fail in
> > > blk_hdr->blkno != xfs_buf->b_bn, then xfs will be shutdown.
> > >
> > > We will get this warning:
> > >
> > >   XFS (dm-0): Metadata corruption detected at xfs_dir3_leaf_verify+0xa8/0xe0 [xfs], xfs_dir3_leafn block 0x178
> > >   XFS (dm-0): Unmount and run xfs_repair
> > >   XFS (dm-0): First 128 bytes of corrupted metadata buffer:
> > >   00000000e80f1917: 00 80 00 0b 00 80 00 07 3d ff 00 00 00 00 00 00  ........=.......
> > >   000000009604c005: 00 00 00 00 00 00 01 a0 00 00 00 00 00 00 00 00  ................
> > >   000000006b6fb2bf: e4 44 e3 97 b5 64 44 41 8b 84 60 0e 50 43 d9 bf  .D...dDA..`.PC..
> > >   00000000678978a2: 00 00 00 00 00 00 00 83 01 73 00 93 00 00 00 00  .........s......
> > >   00000000b28b247c: 99 29 1d 38 00 00 00 00 99 29 1d 40 00 00 00 00  .).8.....).@....
> > >   000000002b2a662c: 99 29 1d 48 00 00 00 00 99 49 11 00 00 00 00 00  .).H.....I......
> > >   00000000ea2ffbb8: 99 49 11 08 00 00 45 25 99 49 11 10 00 00 48 fe  .I....E%.I....H.
> > >   0000000069e86440: 99 49 11 18 00 00 4c 6b 99 49 11 20 00 00 4d 97  .I....Lk.I. ..M.
> > >   XFS (dm-0): xfs_do_force_shutdown(0x8) called from line 1423 of file fs/xfs/xfs_buf.c.  Return address = 00000000c0ff63c1
> > >   XFS (dm-0): Corruption of in-memory data detected.  Shutting down filesystem
> > >   XFS (dm-0): Please umount the filesystem and rectify the problem(s)
> > >
> > > From the log above, we know xfs_buf->b_no is 0x178, but the block's hdr record
> > > its blkno is 0x1a0.
> > >
> > > Fixes: 24df33b45ecf ("xfs: add CRC checking to dir2 leaf blocks")
> > > Signed-off-by: Zhang Tianci <zhangtianci.1997@xxxxxxxxxxxxx>
> > > ---
> > >  fs/xfs/libxfs/xfs_da_btree.c | 12 +++++++++++-
> > >  1 file changed, 11 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/fs/xfs/libxfs/xfs_da_btree.c b/fs/xfs/libxfs/xfs_da_btree.c
> > > index e576560b46e9..35f70e4c6447 100644
> > > --- a/fs/xfs/libxfs/xfs_da_btree.c
> > > +++ b/fs/xfs/libxfs/xfs_da_btree.c
> > > @@ -2318,8 +2318,18 @@ xfs_da3_swap_lastblock(
> > >      * Copy the last block into the dead buffer and log it.
> > >      */
> > >     memcpy(dead_buf->b_addr, last_buf->b_addr, args->geo->blksize);
> > > -   xfs_trans_log_buf(tp, dead_buf, 0, args->geo->blksize - 1);
> > >     dead_info = dead_buf->b_addr;
> > > +   /*
> > > +    * Update the moved block's blkno if it's a dir3 leaf block
> > > +    */
> > > +   if (dead_info->magic == cpu_to_be16(XFS_DIR3_LEAF1_MAGIC) ||
> > > +       dead_info->magic == cpu_to_be16(XFS_DIR3_LEAFN_MAGIC) ||
> > > +       dead_info->magic == cpu_to_be16(XFS_ATTR3_LEAF_MAGIC)) {
>
> On second thought, does this code have to handle XFS_DA3_NODE_MAGIC as
> well?

I think the node block is not too possible the last block, but it's
harmless to add this check.

I would use Dave's suggestion to check xfs's crc-feature rather than
magic. I think it's equivalent
in this function.

We will send the v2 patchset soon.

Thanks.

>
> >
> > a.k.a.
> >
> >       if (xfs_has_crc(mp)) {
> >
> > i.e. this is not specific to the buffer type being processed, it's
> > specific to v4 vs v5 on-disk format. Hence it's a fs-feature check,
> > not a block magic number check.
>
> in which case Dave's comment is correct, yes?
>
> --D
>
> > Cheers,
> >
> > Dave.
> > --
> > Dave Chinner
> > david@xxxxxxxxxxxxx
> >