[20/23] xfs_repair: correctly account for free space btree shrinks when fixing freelist

Commit Message

Darrick J. Wong March 1, 2019, 11:28 p.m. UTC

From: Darrick J. Wong <[e-mail]>

When we fix the freelist at the end of build_agf_agfl in phase 5 of
repair, we need to create incore rmap records for the blocks that get
added to the AGFL.  We can't let the regular freelist fixing code use
the regular on-disk rmapbt update code because the rmapbt isn't fully
set up yet.

Unfortunately, the original code fails to account for the fact that the
free space btrees can shrink when we allocate blocks to fix the
freelist; those blocks are also put on the freelist, but there are
already incore rmaps for all the free space btree blocks.  We must not
create (redundant) incore rmaps for those blocks.  If we do, repair
fails with a complaint that rebuilding the rmapbt failed during phase 5.
xfs/137 on a 1k block size occasionally triggers this bug.

To fix the problem, construct a bitmap of all OWN_AG blocks that we know
about before traversing the AGFL, and only create new incore rmaps for
those AGFL blocks that are not already tracked in the bitmap.

Signed-off-by: Darrick J. Wong <[e-mail]>
---
 repair/rmap.c |   54 ++++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 44 insertions(+), 10 deletions(-)

Patch

diff --git a/repair/rmap.c b/repair/rmap.c
index d0156f9d..19cceca3 100644
--- a/repair/rmap.c
+++ b/repair/rmap.c
@@ -12,6 +12,7 @@ 
 #include "dinode.h"
 #include "slab.h"
 #include "rmap.h"
+#include "bitmap.h"
 
 #undef RMAP_DEBUG
 
@@ -450,15 +451,16 @@  rmap_store_ag_btree_rec(
 	struct xfs_buf		*agflbp = NULL;
 	struct xfs_trans	*tp;
 	__be32			*agfl_bno, *b;
+	struct xfs_ag_rmap	*ag_rmap = &ag_rmaps[agno];
+	struct bitmap		*own_ag_bitmap = NULL;
 	int			error = 0;
 
 	if (!xfs_sb_version_hasrmapbt(&mp->m_sb))
 		return 0;
 
 	/* Release the ar_rmaps; they were put into the rmapbt during p5. */
-	free_slab(&ag_rmaps[agno].ar_rmaps);
-	error = init_slab(&ag_rmaps[agno].ar_rmaps,
-				  sizeof(struct xfs_rmap_irec));
+	free_slab(&ag_rmap->ar_rmaps);
+	error = init_slab(&ag_rmap->ar_rmaps, sizeof(struct xfs_rmap_irec));
 	if (error)
 		goto err;
 
@@ -478,19 +480,50 @@  rmap_store_ag_btree_rec(
 	 * rmap, we only need to add rmap records for AGFL blocks past
 	 * that point in the AGFL because those blocks are a result of a
 	 * no-rmap no-shrink freelist fixup that we did earlier.
+	 *
+	 * However, some blocks end up on the AGFL because the free space
+	 * btrees shed blocks as a result of allocating space to fix the
+	 * freelist.  We already created in-core rmap records for the free
+	 * space btree blocks, so we must be careful not to create those
+	 * records again.  Create a bitmap of already-recorded OWN_AG rmaps.
 	 */
+	error = init_slab_cursor(ag_rmap->ar_raw_rmaps, rmap_compare, &rm_cur);
+	if (error)
+		goto err;
+	if (!bitmap_init(&own_ag_bitmap)) {
+		error = -ENOMEM;
+		goto err_slab;
+	}
+	while ((rm_rec = pop_slab_cursor(rm_cur)) != NULL) {
+		if (rm_rec->rm_owner != XFS_RMAP_OWN_AG)
+			continue;
+		if (!bitmap_set(own_ag_bitmap, rm_rec->rm_startblock,
+					rm_rec->rm_blockcount)) {
+			error = EFSCORRUPTED;
+			goto err_slab;
+		}
+	}
+	free_slab_cursor(&rm_cur);
+
+	/* Create rmaps for any AGFL blocks that aren't already rmapped. */
 	agfl_bno = XFS_BUF_TO_AGFL_BNO(mp, agflbp);
-	b = agfl_bno + ag_rmaps[agno].ar_flcount;
+	b = agfl_bno + ag_rmap->ar_flcount;
 	while (*b != cpu_to_be32(NULLAGBLOCK) &&
 	       b - agfl_bno < libxfs_agfl_size(mp)) {
-		error = rmap_add_ag_rec(mp, agno, be32_to_cpu(*b), 1,
-				XFS_RMAP_OWN_AG);
-		if (error)
-			goto err;
+		xfs_agblock_t	agbno;
+
+		agbno = be32_to_cpu(*b);
+		if (!bitmap_test(own_ag_bitmap, agbno, 1)) {
+			error = rmap_add_ag_rec(mp, agno, agbno, 1,
+					XFS_RMAP_OWN_AG);
+			if (error)
+				goto err;
+		}
 		b++;
 	}
 	libxfs_putbuf(agflbp);
 	agflbp = NULL;
+	bitmap_free(&own_ag_bitmap);
 
 	/* Merge all the raw rmaps into the main list */
 	error = rmap_fold_raw_recs(mp, agno);
@@ -498,8 +531,7 @@  rmap_store_ag_btree_rec(
 		goto err;
 
 	/* Create cursors to refcount structures */
-	error = init_slab_cursor(ag_rmaps[agno].ar_rmaps, rmap_compare,
-			&rm_cur);
+	error = init_slab_cursor(ag_rmap->ar_rmaps, rmap_compare, &rm_cur);
 	if (error)
 		goto err;
 
@@ -542,6 +574,8 @@  rmap_store_ag_btree_rec(
 err:
 	if (agflbp)
 		libxfs_putbuf(agflbp);
+	if (own_ag_bitmap)
+		bitmap_free(&own_ag_bitmap);
 	return error;
 }