[PATCH 08/27] xfs: scrub the shape of a metadata btree

Darrick J. Wong
2017-09-21T00:18:28Z

Create a function that can check the shape of a btree -- each block
passes basic inspection and all the pointers look ok. In the next patch
we'll add the ability to check the actual keys and records stored within
the btree. Add some helper functions so that we report detailed scrub
errors in a uniform manner in dmesg. These are helper functions for
subsequent patches.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
fs/xfs/libxfs/xfs_btree.c | 16 +++
fs/xfs/libxfs/xfs_btree.h | 7 +
fs/xfs/scrub/btree.c | 236 +++++++++++++++++++++++++++++++++++++++++++++
fs/xfs/scrub/common.h | 13 ++
4 files changed, 268 insertions(+), 4 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_btree.c b/fs/xfs/libxfs/xfs_btree.c
index 5bfb882..c4d8b47 100644
--- a/fs/xfs/libxfs/xfs_btree.c
+++ b/fs/xfs/libxfs/xfs_btree.c
@@ -1027,7 +1027,7 @@ xfs_btree_setbuf(
}
}

-STATIC int
+bool
xfs_btree_ptr_is_null(
struct xfs_btree_cur *cur,
union xfs_btree_ptr *ptr)
@@ -1052,7 +1052,7 @@ xfs_btree_set_ptr_null(
/*
* Get/set/init sibling pointers
*/
-STATIC void
+void
xfs_btree_get_sibling(
struct xfs_btree_cur *cur,
struct xfs_btree_block *block,
@@ -4914,3 +4914,15 @@ xfs_btree_count_blocks(
return xfs_btree_visit_blocks(cur, xfs_btree_count_blocks_helper,
blocks);
}
+
+/* Compare two btree pointers. */
+int64_t
+xfs_btree_diff_two_ptrs(
+ struct xfs_btree_cur *cur,
+ const union xfs_btree_ptr *a,
+ const union xfs_btree_ptr *b)
+{
+ if (cur->bc_flags & XFS_BTREE_LONG_PTRS)
+ return (int64_t)be64_to_cpu(a->l) - be64_to_cpu(b->l);
+ return (int64_t)be32_to_cpu(a->s) - be32_to_cpu(b->s);
+}
diff --git a/fs/xfs/libxfs/xfs_btree.h b/fs/xfs/libxfs/xfs_btree.h
index f2a88c3..0daf524 100644
--- a/fs/xfs/libxfs/xfs_btree.h
+++ b/fs/xfs/libxfs/xfs_btree.h
@@ -517,5 +517,12 @@ int xfs_btree_lookup_get_block(struct xfs_btree_cur *cur, int level,
union xfs_btree_ptr *pp, struct xfs_btree_block **blkp);
struct xfs_btree_block *xfs_btree_get_block(struct xfs_btree_cur *cur,
int level, struct xfs_buf **bpp);
+bool xfs_btree_ptr_is_null(struct xfs_btree_cur *cur, union xfs_btree_ptr *ptr);
+int64_t xfs_btree_diff_two_ptrs(struct xfs_btree_cur *cur,
+ const union xfs_btree_ptr *a,
+ const union xfs_btree_ptr *b);
+void xfs_btree_get_sibling(struct xfs_btree_cur *cur,
+ struct xfs_btree_block *block,
+ union xfs_btree_ptr *ptr, int lr);

#endif /* __XFS_BTREE_H__ */
diff --git a/fs/xfs/scrub/btree.c b/fs/xfs/scrub/btree.c
index adf5d09..a9c2bf3 100644
--- a/fs/xfs/scrub/btree.c
+++ b/fs/xfs/scrub/btree.c
@@ -94,6 +94,152 @@ xfs_scrub_btree_check_ok(
return fs_ok;
}

+/* Check a btree pointer. */
+static int
+xfs_scrub_btree_ptr(
+ struct xfs_scrub_btree *bs,
+ int level,
+ union xfs_btree_ptr *ptr)
+{
+ struct xfs_btree_cur *cur = bs->cur;
+ xfs_daddr_t daddr;
+ xfs_daddr_t eofs;
+
+ if (!xfs_scrub_btree_check_ok(bs->sc, cur, level,
+ !xfs_btree_ptr_is_null(cur, ptr)))
+ goto corrupt;
+ if (cur->bc_flags & XFS_BTREE_LONG_PTRS) {
+ daddr = XFS_FSB_TO_DADDR(cur->bc_mp, be64_to_cpu(ptr->l));
+ } else {
+ if (!xfs_scrub_btree_check_ok(bs->sc, cur, level,
+ cur->bc_private.a.agno != NULLAGNUMBER))
+ goto corrupt;
+
+ daddr = XFS_AGB_TO_DADDR(cur->bc_mp, cur->bc_private.a.agno,
+ be32_to_cpu(ptr->s));
+ }
+ eofs = XFS_FSB_TO_BB(cur->bc_mp, cur->bc_mp->m_sb.sb_dblocks);
+ if (!xfs_scrub_btree_check_ok(bs->sc, cur, level,
+ daddr != 0 && daddr < eofs))
+ goto corrupt;
+
+ return 0;
+
+corrupt:
+ return -EFSCORRUPTED;
+}
+
+/* Check that a btree block's sibling matches what we expect it. */
+STATIC int
+xfs_scrub_btree_block_check_sibling(
+ struct xfs_scrub_btree *bs,
+ int level,
+ int direction,
+ union xfs_btree_ptr *sibling)
+{
+ struct xfs_btree_cur *cur = bs->cur;
+ struct xfs_btree_block *pblock;
+ struct xfs_buf *pbp;
+ struct xfs_btree_cur *ncur;
+ union xfs_btree_ptr *pp;
+ int success;
+ int error;
+
+ if (xfs_btree_ptr_is_null(cur, sibling))
+ return 0;
+
+ error = xfs_btree_dup_cursor(cur, &ncur);
+ if (error)
+ return error;
+
+ if (direction > 0)
+ error = xfs_btree_increment(ncur, level + 1, &success);
+ else
+ error = xfs_btree_decrement(ncur, level + 1, &success);
+ if (!xfs_scrub_btree_op_ok(bs->sc, cur, level + 1, &error) ||
+ !xfs_scrub_btree_check_ok(bs->sc, cur, level + 1, success))
+ goto out;
+
+ pblock = xfs_btree_get_block(ncur, level + 1, &pbp);
+ pp = xfs_btree_ptr_addr(ncur, ncur->bc_ptrs[level + 1], pblock);
+ error = xfs_scrub_btree_ptr(bs, level + 1, pp);
+ if (error) {
+ /*
+ * _scrub_btree_ptr already recorded a garbage sibling.
+ * Don't let the EFSCORRUPTED bubble up and prevent more
+ * scanning of the data structure.
+ */
+ error = 0;
+ goto out;
+ }
+
+ xfs_scrub_btree_check_ok(bs->sc, cur, level,
+ !xfs_btree_diff_two_ptrs(cur, pp, sibling));
+out:
+ xfs_btree_del_cursor(ncur, XFS_BTREE_ERROR);
+ return error;
+}
+
+/* Check the siblings of a btree block. */
+STATIC int
+xfs_scrub_btree_block_check_siblings(
+ struct xfs_scrub_btree *bs,
+ struct xfs_btree_block *block)
+{
+ struct xfs_btree_cur *cur = bs->cur;
+ union xfs_btree_ptr leftsib;
+ union xfs_btree_ptr rightsib;
+ int level;
+ int error = 0;
+
+ xfs_btree_get_sibling(cur, block, &leftsib, XFS_BB_LEFTSIB);
+ xfs_btree_get_sibling(cur, block, &rightsib, XFS_BB_RIGHTSIB);
+ level = xfs_btree_get_level(block);
+
+ /* Root block should never have siblings. */
+ if (level == cur->bc_nlevels - 1) {
+ xfs_scrub_btree_check_ok(bs->sc, cur, level,
+ xfs_btree_ptr_is_null(cur, &leftsib) &&
+ xfs_btree_ptr_is_null(cur, &rightsib));
+ goto out;
+ }
+
+ /* Does the left sibling match the parent level left block? */
+ error = xfs_scrub_btree_block_check_sibling(bs, level, -1, &leftsib);
+ if (error)
+ return error;
+
+ /* Does the right sibling match the parent level right block? */
+ error = xfs_scrub_btree_block_check_sibling(bs, level, 1, &rightsib);
+ if (error)
+ return error;
+out:
+ return error;
+}
+
+/* Grab and scrub a btree block. */
+STATIC int
+xfs_scrub_btree_block(
+ struct xfs_scrub_btree *bs,
+ int level,
+ union xfs_btree_ptr *pp,
+ struct xfs_btree_block **pblock,
+ struct xfs_buf **pbp)
+{
+ int error;
+
+ error = xfs_btree_lookup_get_block(bs->cur, level, pp, pblock);
+ if (error)
+ return error;
+
+ xfs_btree_get_block(bs->cur, level, pbp);
+ error = xfs_btree_check_block(bs->cur, *pblock, level, *pbp);
+ if (error)
+ return error;
+
+ return xfs_scrub_btree_block_check_siblings(bs, *pblock);
+}
+
/*
* Visit all nodes and leaves of a btree. Check that all pointers and
* records are in order, that the keys reflect the records, and use a callback
@@ -109,6 +255,92 @@ xfs_scrub_btree(
struct xfs_owner_info *oinfo,
void *private)
{
- xfs_scrub_btree_op_ok(sc, cur, 0, false);
- return -EOPNOTSUPP;
+ struct xfs_scrub_btree bs = {0};
+ union xfs_btree_ptr ptr;
+ union xfs_btree_ptr *pp;
+ struct xfs_btree_block *block;
+ int level;
+ struct xfs_buf *bp;
+ int i;
+ int error = 0;
+
+ /* Initialize scrub state */
+ bs.cur = cur;
+ bs.scrub_rec = scrub_fn;
+ bs.oinfo = oinfo;
+ bs.firstrec = true;
+ bs.private = private;
+ bs.sc = sc;
+ for (i = 0; i < XFS_BTREE_MAXLEVELS; i++)
+ bs.firstkey[i] = true;
+ INIT_LIST_HEAD(&bs.to_check);
+
+ /* Don't try to check a tree with a height we can't handle. */
+ if (!xfs_scrub_btree_check_ok(sc, cur, 0, cur->bc_nlevels > 0 &&
+ cur->bc_nlevels <= XFS_BTREE_MAXLEVELS))
+ goto out;
+
+ /* Make sure the root isn't in the superblock. */
+ if (!(cur->bc_flags & XFS_BTREE_ROOT_IN_INODE)) {
+ cur->bc_ops->init_ptr_from_cur(cur, &ptr);
+ error = xfs_scrub_btree_ptr(&bs, cur->bc_nlevels, &ptr);
+ if (!xfs_scrub_btree_op_ok(sc, cur, cur->bc_nlevels - 1, &error))
+ goto out;
+ }
+
+ /* Load the root of the btree. */
+ level = cur->bc_nlevels - 1;
+ cur->bc_ops->init_ptr_from_cur(cur, &ptr);
+ error = xfs_scrub_btree_block(&bs, level, &ptr, &block, &bp);
+ if (!xfs_scrub_btree_op_ok(sc, cur, cur->bc_nlevels - 1, &error))
+ goto out;
+
+ cur->bc_ptrs[level] = 1;
+
+ while (level < cur->bc_nlevels) {
+ block = xfs_btree_get_block(cur, level, &bp);
+
+ if (level == 0) {
+ /* End of leaf, pop back towards the root. */
+ if (cur->bc_ptrs[level] >
+ be16_to_cpu(block->bb_numrecs)) {
+ if (level < cur->bc_nlevels - 1)
+ cur->bc_ptrs[level + 1]++;
+ level++;
+ continue;
+ }
+
+ if (xfs_scrub_should_terminate(&error))
+ break;
+
+ cur->bc_ptrs[level]++;
+ continue;
+ }
+
+ /* End of node, pop back towards the root. */
+ if (cur->bc_ptrs[level] > be16_to_cpu(block->bb_numrecs)) {
+ if (level < cur->bc_nlevels - 1)
+ cur->bc_ptrs[level + 1]++;
+ level++;
+ continue;
+ }
+
+ /* Drill another level deeper. */
+ pp = xfs_btree_ptr_addr(cur, cur->bc_ptrs[level], block);
+ error = xfs_scrub_btree_ptr(&bs, level, pp);
+ if (error) {
+ error = 0;
+ cur->bc_ptrs[level]++;
+ continue;
+ }
+ level--;
+ error = xfs_scrub_btree_block(&bs, level, pp, &block, &bp);
+ if (!xfs_scrub_btree_op_ok(sc, cur, level, &error))
+ goto out;
+
+ cur->bc_ptrs[level] = 1;
+ }
+
+out:
+ return error;
}
diff --git a/fs/xfs/scrub/common.h b/fs/xfs/scrub/common.h
index e1bb14b..9920488 100644
--- a/fs/xfs/scrub/common.h
+++ b/fs/xfs/scrub/common.h
@@ -20,6 +20,19 @@
#ifndef __XFS_SCRUB_COMMON_H__
#define __XFS_SCRUB_COMMON_H__

+/* Should we end the scrub early? */
+static inline bool
+xfs_scrub_should_terminate(
+ int *error)
+{
+ if (fatal_signal_pending(current)) {
+ if (*error == 0)
+ *error = -EAGAIN;
+ return true;
+ }
+ return false;
+}
+
/*
* Grab a transaction. If we're going to repair something, we need to
* ensure there's enough reservation to make all the changes. If not,