Re: [PATCH] xfs: verify buffer contents when we skip log replay

[Dave Chinner <david@fromorbit.com>]

On Wed, Apr 12, 2023 at 05:18:07AM -0700, Christoph Hellwig wrote:
> On Tue, Apr 11, 2023 at 04:31:59PM -0700, Darrick J. Wong wrote:
> > Unfortunately, the ondisk buffer is corrupt, but recovery just read the
> > buffer with no buffer ops specified:
> > 
> > 	error = xfs_buf_read(mp->m_ddev_targp, buf_f->blf_blkno,
> > 			buf_f->blf_len, buf_flags, &bp, NULL);
> 
> > +
> > +		/*
> > +		 * We're skipping replay of this buffer log item due to the log
> > +		 * item LSN being behind the ondisk buffer.  Verify the buffer
> > +		 * contents since we aren't going to run the write verifier.
> > +		 */
> > +		if (bp->b_ops) {
> > +			bp->b_ops->verify_read(bp);
> > +			error = bp->b_error;
> > +		}
> 
> How do we end up with ops attached here if xfs_buf_read doesn't
> attach them?  The buf type specific recover routines later attach
> ops, but this is called before we reach them.

The line of context above this hunk you cut out does exactly
that. i.e. this call:

		xlog_recover_validate_buf_type(mp, bp, buf_f, NULLCOMMITLSN);

-Dave.
-- 
Dave Chinner
david@fromorbit.com