xfs: only allocate free space bitmap for xattr scrub if neededscrub-fix-xattr-memory-mgmt_2022-11-09

The free space bitmap is only required if we're going to check the
bestfree space at the end of an xattr leaf block.  Therefore, we can
reduce the memory requirements of this scrubber if we can determine that
the xattr is in short format.

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

1 files changed, 28 insertions, 3 deletions

diff --git a/fs/xfs/scrub/attr.c b/fs/xfs/scrub/attr.c
index 2c86a76977f3..0dbfc2aca29c 100644
--- a/fs/xfs/scrub/attr.c
+++ b/fs/xfs/scrub/attr.c
@@ -38,6 +38,29 @@ xchk_xattr_buf_cleanup(
 }
 
 /*
+ * Allocate the free space bitmap if we're trying harder; there are leaf blocks
+ * in the attr fork; or we can't tell if there are leaf blocks.
+ */
+static inline bool
+xchk_xattr_want_freemap(
+	struct xfs_scrub	*sc)
+{
+	struct xfs_ifork	*ifp;
+
+	if (sc->flags & XCHK_TRY_HARDER)
+		return true;
+
+	if (!sc->ip)
+		return true;
+
+	ifp = xfs_ifork_ptr(sc->ip, XFS_ATTR_FORK);
+	if (!ifp)
+		return false;
+
+	return xfs_ifork_has_extents(ifp);
+}
+
+/*
  * Allocate enough memory to hold an attr value and attr block bitmaps,
  * reallocating the buffer if necessary.  Buffer contents are not preserved
  * across a reallocation.
@@ -66,9 +89,11 @@ xchk_setup_xattr_buf(
 	if (!ab->usedmap)
 		return -ENOMEM;
 
-	ab->freemap = kvmalloc(bmp_sz, XCHK_GFP_FLAGS);
-	if (!ab->freemap)
-		return -ENOMEM;
+	if (xchk_xattr_want_freemap(sc)) {
+		ab->freemap = kvmalloc(bmp_sz, XCHK_GFP_FLAGS);
+		if (!ab->freemap)
+			return -ENOMEM;
+	}
 
 resize_value:
 	if (ab->value_sz >= value_size)