Commit add46b3b authored by Darrick J. Wong's avatar Darrick J. Wong
Browse files

xfs: set buffer ops when repair probes for btree type 



In xrep_findroot_block, we work out the btree type and correctness of a
given block by calling different btree verifiers on root block
candidates.  However, we leave the NULL b_ops while ->verify_read
validates the block, which means that if the verifier calls
xfs_buf_verifier_error it'll crash on the null b_ops.  Fix it to set
b_ops before calling the verifier and unsetting it if the verifier
fails.

Furthermore, improve the documentation around xfs_buf_ensure_ops, which
is the function that is responsible for cleaning up the b_ops state of
buffers that go through xrep_findroot_block but don't match anything.

Signed-off-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: default avatarBrian Foster <bfoster@redhat.com>
parent 465fa17f

fs/xfs/scrub/repair.c

+8 −3
Original line number Diff line number Diff line
@@ -768,18 +768,23 @@ xrep_findroot_block( 
		if (!uuid_equal(&btblock->bb_u.s.bb_uuid,

				&mp->m_sb.sb_meta_uuid))

			goto out;

		/*

		 * Read verifiers can reference b_ops, so we set the pointer

		 * here.  If the verifier fails we'll reset the buffer state

		 * to what it was before we touched the buffer.

		 */

		bp->b_ops = fab->buf_ops;

		fab->buf_ops->verify_read(bp);

		if (bp->b_error) {

			bp->b_ops = NULL;

			bp->b_error = 0;

			goto out;

		}



		/*

		 * Some read verifiers will (re)set b_ops, so we must be

		 * careful not to blow away any such assignment.

		 * careful not to change b_ops after running the verifier.

		 */

		if (!bp->b_ops)

			bp->b_ops = fab->buf_ops;

	}



	/*

fs/xfs/xfs_buf.c

+16 −0
Original line number Diff line number Diff line
@@ -776,10 +776,26 @@ _xfs_buf_read( 
}



/*

 * Set buffer ops on an unchecked buffer and validate it, if possible.

 *

 * If the caller passed in an ops structure and the buffer doesn't have ops

 * assigned, set the ops and use them to verify the contents.  If the contents

 * cannot be verified, we'll clear XBF_DONE.  We assume the buffer has no

 * recorded errors and is already in XBF_DONE state.

 *

 * Under normal operations, every in-core buffer must have buffer ops assigned

 * to them when the buffer is read in from disk so that we can validate the

 * metadata.

 *

 * However, there are two scenarios where one can encounter in-core buffers

 * that don't have buffer ops.  The first is during log recovery of buffers on

 * a V4 filesystem, though these buffers are purged at the end of recovery.

 *

 * The other is online repair, which tries to match arbitrary metadata blocks

 * with btree types in order to find the root.  If online repair doesn't match

 * the buffer with /any/ btree type, the buffer remains in memory in DONE state

 * with no ops, and a subsequent read_buf call from elsewhere will not set the

 * ops.  This function helps us fix this situation.

 */

int

xfs_buf_ensure_ops(

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