[PATCH 6.18.y 1/2] xfs: refactor directory data block walking loops in scrub

[Sasha Levin <sashal@kernel.org>]

From: "Darrick J. Wong" <djwong@kernel.org>

[ Upstream commit 19b5653cc870788df71e7fcf2dd7b6131d8868dc ]

Hoist the inner loop code of the directory data block walking code in
the directory scrub and repair code to separate functions in preparation
for strengthening the validation in a subsequent patch.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
Stable-dep-of: 5d470234d04d ("xfs: improve dirent bounds checking in scrub and repair")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/xfs/scrub/dir.c        | 56 ++++++++++++++++++++++++++----
 fs/xfs/scrub/dir_repair.c | 73 ++++++++++++++++++++++++++++-----------
 2 files changed, 102 insertions(+), 27 deletions(-)

diff --git a/fs/xfs/scrub/dir.c b/fs/xfs/scrub/dir.c
index 7b0a9d2aea3ec..2f73baee0f0b4 100644
--- a/fs/xfs/scrub/dir.c
+++ b/fs/xfs/scrub/dir.c
@@ -313,6 +313,45 @@ xchk_dir_actor(
 	return error;
 }
 
+/*
+ * Deal with an unused directory entry.  Returns a positive number of bytes to
+ * advance in the directory block, zero to stop processing, or -1 if corruption
+ * was found.
+ */
+static int
+xchk_dir_check_unused(
+	struct xchk_da_btree		*ds,
+	struct xfs_buf			*bp,
+	unsigned int			iter_off,
+	unsigned int			end)
+{
+	struct xfs_dir2_data_unused	*dup = bp->b_addr + iter_off;
+
+	return be16_to_cpu(dup->length);
+}
+
+/*
+ * Check a directory entry.  Returns a positive number of bytes to advance
+ * in the directory block, zero to stop processing, or -1 if corruption was
+ * found.
+ */
+static int
+xchk_dir_check_entry(
+	struct xchk_da_btree		*ds,
+	struct xfs_buf			*bp,
+	unsigned int			iter_off,
+	unsigned int			end,
+	struct xfs_dir2_data_entry	*dent)
+{
+	struct xfs_dir2_data_entry	*dep = bp->b_addr + iter_off;
+	struct xfs_mount		*mp = ds->state->mp;
+
+	if (dep == dent)
+		return 0;
+
+	return xfs_dir2_data_entsize(mp, dep->namelen);
+}
+
 /* Scrub a directory btree record. */
 STATIC int
 xchk_dir_rec(
@@ -389,21 +428,24 @@ xchk_dir_rec(
 		goto out_relse;
 	}
 	for (;;) {
-		struct xfs_dir2_data_entry	*dep = bp->b_addr + iter_off;
 		struct xfs_dir2_data_unused	*dup = bp->b_addr + iter_off;
+		int				advance;
 
 		if (iter_off >= end) {
 			xchk_fblock_set_corrupt(ds->sc, XFS_DATA_FORK, rec_bno);
 			goto out_relse;
 		}
 
-		if (be16_to_cpu(dup->freetag) == XFS_DIR2_DATA_FREE_TAG) {
-			iter_off += be16_to_cpu(dup->length);
-			continue;
-		}
-		if (dep == dent)
+		if (dup->freetag == cpu_to_be16(XFS_DIR2_DATA_FREE_TAG))
+			advance = xchk_dir_check_unused(ds, bp, iter_off, end);
+		else
+			advance = xchk_dir_check_entry(ds, bp, iter_off, end,
+					dent);
+		if (advance < 0)
+			goto out_relse;
+		if (!advance)
 			break;
-		iter_off += xfs_dir2_data_entsize(mp, dep->namelen);
+		iter_off += advance;
 	}
 
 	/* Retrieve the entry, sanity check it, and compare hashes. */
diff --git a/fs/xfs/scrub/dir_repair.c b/fs/xfs/scrub/dir_repair.c
index 9aafe5c31cbe3..f8e88b638c43d 100644
--- a/fs/xfs/scrub/dir_repair.c
+++ b/fs/xfs/scrub/dir_repair.c
@@ -462,6 +462,52 @@ xrep_dir_salvage_data_entry(
 	return xrep_dir_salvage_entry(rd, dep->name, dep->namelen, ino);
 }
 
+/*
+ * Deal with an unused directory entry.  Returns a positive number of bytes to
+ * advance in the directory block, or zero to stop processing.
+ */
+static int
+xrep_dir_recover_unused(
+	struct xfs_buf			*bp,
+	unsigned int			offset,
+	unsigned int			end)
+{
+	struct xfs_dir2_data_unused	*dup = bp->b_addr + offset;
+
+	return be16_to_cpu(dup->length);
+}
+
+/*
+ * Salvage a directory entry.  Returns a positive number of bytes to advance
+ * in the directory block, zero to stop processing, or a negative errno.
+ */
+static int
+xrep_dir_recover_entry(
+	struct xrep_dir			*rd,
+	struct xfs_buf			*bp,
+	unsigned int			offset,
+	unsigned int			end)
+{
+	struct xfs_dir2_data_entry	*dep = bp->b_addr + offset;
+	unsigned int			advance;
+	int				error;
+
+	/* Don't walk off the end of the block. */
+	advance = xfs_dir2_data_entsize(rd->sc->mp, dep->namelen);
+	if (!advance)
+		return 0;
+	if (offset + advance > end)
+		return 0;
+
+	/* Ok, let's save this entry. */
+	error = xrep_dir_salvage_data_entry(rd, dep);
+	if (error < 0)
+		return error;
+
+	return advance;
+}
+
+
 /* Try to recover block/data format directory entries. */
 STATIC int
 xrep_dir_recover_data(
@@ -483,33 +529,20 @@ xrep_dir_recover_data(
 
 	while (offset < end) {
 		struct xfs_dir2_data_unused	*dup = bp->b_addr + offset;
-		struct xfs_dir2_data_entry	*dep = bp->b_addr + offset;
-		unsigned int			advance;
+		int				advance;
 
 		if (xchk_should_terminate(rd->sc, &error))
 			return error;
 
-		/* Skip unused entries. */
-		if (be16_to_cpu(dup->freetag) == XFS_DIR2_DATA_FREE_TAG) {
-			if (!dup->length)
-				break;
-			offset += be16_to_cpu(dup->length);
-			continue;
-		}
-
-		/* Don't walk off the end of the block. */
-		advance = xfs_dir2_data_entsize(rd->sc->mp, dep->namelen);
+		if (dup->freetag == cpu_to_be16(XFS_DIR2_DATA_FREE_TAG))
+			advance = xrep_dir_recover_unused(bp, offset, end);
+		else
+			advance = xrep_dir_recover_entry(rd, bp, offset, end);
+		if (advance < 0)
+			return advance;
 		if (!advance)
 			break;
 		offset += advance;
-		if (offset > end)
-			break;
-
-		/* Ok, let's save this entry. */
-		error = xrep_dir_salvage_data_entry(rd, dep);
-		if (error)
-			return error;
-
 	}
 
 	return 0;
-- 
2.53.0