xfs: refactor stale buffer scanning for repairs

In an upcoming patch, we will need to be able to look for xfs_buf
objects caching file-based metadata blocks without needing to walk the
(possibly corrupt) structures to find all the buffers.  Repair already
has most of the code needed to scan the buffer cache, so hoist these
utility functions.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>

1 files changed, 51 insertions, 22 deletions

diff --git a/fs/xfs/scrub/reap.c b/fs/xfs/scrub/reap.c
index 265866891830..34f1e166498b 100644
--- a/fs/xfs/scrub/reap.c
+++ b/fs/xfs/scrub/reap.c
@@ -209,6 +209,48 @@ static inline void xreap_defer_finish_reset(struct xreap_state *rs)
 	rs->force_roll = false;
 }
 
+/*
+ * Compute the maximum length of a buffer cache scan (in units of sectors),
+ * given a quantity of fs blocks.
+ */
+xfs_daddr_t
+xrep_bufscan_max_sectors(
+	struct xfs_mount	*mp,
+	xfs_extlen_t		fsblocks)
+{
+	int			max_fsbs;
+
+	/* Remote xattr values are the largest buffers that we support. */
+	max_fsbs = xfs_attr3_rmt_blocks(mp, XFS_XATTR_SIZE_MAX);
+
+	return XFS_FSB_TO_BB(mp, min_t(xfs_extlen_t, fsblocks, max_fsbs));
+}
+
+/*
+ * Return an incore buffer from a sector scan, or NULL if there are no buffers
+ * left to return.
+ */
+struct xfs_buf *
+xrep_bufscan_advance(
+	struct xfs_mount	*mp,
+	struct xrep_bufscan	*scan)
+{
+	scan->__sector_count += scan->daddr_step;
+	while (scan->__sector_count <= scan->max_sectors) {
+		struct xfs_buf	*bp = NULL;
+		int		error;
+
+		error = xfs_buf_incore(mp->m_ddev_targp, scan->daddr,
+				scan->__sector_count, XBF_BCACHE_SCAN, &bp);
+		if (!error)
+			return bp;
+
+		scan->__sector_count += scan->daddr_step;
+	}
+
+	return NULL;
+}
+
 /* Try to invalidate the incore buffers for an extent that we're freeing. */
 STATIC void
 xreap_agextent_binval(
@@ -239,28 +281,15 @@ xreap_agextent_binval(
 	 * of any plausible size.
 	 */
 	while (bno < agbno_next) {
-		xfs_agblock_t	fsbcount;
-		xfs_agblock_t	max_fsbs;
-
-		/*
-		 * Max buffer size is the max remote xattr buffer size, which
-		 * is one fs block larger than 64k.
-		 */
-		max_fsbs = min_t(xfs_agblock_t, agbno_next - bno,
-				xfs_attr3_rmt_blocks(mp, XFS_XATTR_SIZE_MAX));
-
-		for (fsbcount = 1; fsbcount < max_fsbs; fsbcount++) {
-			struct xfs_buf	*bp = NULL;
-			xfs_daddr_t	daddr;
-			int		error;
-
-			daddr = XFS_AGB_TO_DADDR(mp, agno, bno);
-			error = xfs_buf_incore(mp->m_ddev_targp, daddr,
-					XFS_FSB_TO_BB(mp, fsbcount),
-					XBF_BCACHE_SCAN, &bp);
-			if (error)
-				continue;
-
+		struct xrep_bufscan	scan = {
+			.daddr		= XFS_AGB_TO_DADDR(mp, agno, bno),
+			.max_sectors	= xrep_bufscan_max_sectors(mp,
+							agbno_next - bno),
+			.daddr_step	= XFS_FSB_TO_BB(mp, 1),
+		};
+		struct xfs_buf	*bp;
+
+		while ((bp = xrep_bufscan_advance(mp, &scan)) != NULL) {
 			xfs_trans_bjoin(sc->tp, bp);
 			xfs_trans_binval(sc->tp, bp);
 			rs->invalidated++;