Re: [PATCH v2] xfs_repair: handling a block with bad crc, bad uuid, and bad magic number needs fixing

["Darrick J. Wong" <djwong@kernel.org>]

On Fri, Mar 21, 2025 at 03:36:39PM -0500, Bill O'Donnell wrote:
> On Fri, Mar 21, 2025 at 08:27:25AM -0700, Darrick J. Wong wrote:
> > On Fri, Mar 21, 2025 at 09:28:49AM -0500, bodonnel@redhat.com wrote:
> > > From: Bill O'Donnell <bodonnel@redhat.com>
> > > 
> > > In certain cases, if a block is so messed up that crc, uuid and magic
> > > number are all bad, we need to not only detect in phase3 but fix it
> > > properly in phase6. In the current code, the mechanism doesn't work
> > > in that it only pays attention to one of the parameters.
> > > 
> > > Note: in this case, the nlink inode link count drops to 1, but
> > > re-running xfs_repair fixes it back to 2. This is a side effect that
> > > should probably be handled in update_inode_nlinks() with separate patch.
> > > Regardless, running xfs_repair twice fixes the issue. Also, this patch
> > > fixes the issue with v5, but not v4 xfs.
> > > 
> > > Signed-off-by: Bill O'Donnell <bodonnel@redhat.com>
> > 
> > That makes sense.
> > Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
> > 
> > Bonus question: does longform_dir2_check_leaf need a similar correction
> > for:
> > 
> > 	if (leafhdr.magic == XFS_DIR3_LEAF1_MAGIC) {
> > 		error = check_da3_header(mp, bp, ip->i_ino);
> > 		if (error) {
> > 			libxfs_buf_relse(bp);
> > 			return error;
> > 		}
> > 	}
> > --D
> > 
> 
> I believe so, yes. Basing the v4/v5 decisions on an assumed correct
> magic number is not so good. I'll fix it in a new version or separate
> patch if preferred.

It's up to you, but since this fix has already earned its review, how
about a separate patch? :)

--D

> Thanks-
> Bill
> 
> 
> > > 
> > > v2: remove superfluous wantmagic logic
> > > 
> > > ---
> > >  repair/phase6.c | 5 +----
> > >  1 file changed, 1 insertion(+), 4 deletions(-)
> > > 
> > > diff --git a/repair/phase6.c b/repair/phase6.c
> > > index 4064a84b2450..9cffbb1f4510 100644
> > > --- a/repair/phase6.c
> > > +++ b/repair/phase6.c
> > > @@ -2364,7 +2364,6 @@ longform_dir2_entry_check(
> > >  	     da_bno = (xfs_dablk_t)next_da_bno) {
> > >  		const struct xfs_buf_ops *ops;
> > >  		int			 error;
> > > -		struct xfs_dir2_data_hdr *d;
> > >  
> > >  		next_da_bno = da_bno + mp->m_dir_geo->fsbcount - 1;
> > >  		if (bmap_next_offset(ip, &next_da_bno)) {
> > > @@ -2404,9 +2403,7 @@ longform_dir2_entry_check(
> > >  		}
> > >  
> > >  		/* check v5 metadata */
> > > -		d = bp->b_addr;
> > > -		if (be32_to_cpu(d->magic) == XFS_DIR3_BLOCK_MAGIC ||
> > > -		    be32_to_cpu(d->magic) == XFS_DIR3_DATA_MAGIC) {
> > > +		if (xfs_has_crc(mp)) {
> > >  			error = check_dir3_header(mp, bp, ino);
> > >  			if (error) {
> > >  				fixit++;
> > > -- 
> > > 2.48.1
> > > 
> > > 
> > 
>