xfs: refactor attr scrub memory allocation function

Move the code that allocates memory buffers for the extended attribute
scrub code into a separate function so we can reduce memory allocations
in the next patch.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>

fs/xfs/scrub/attr.c

@@ -20,26 +20,41 @@
 #include "scrub/dabtree.h"
 #include "scrub/attr.h"
 
-/* Set us up to scrub an inode's extended attributes. */
+/* Allocate enough memory to hold an attr value and attr block bitmaps. */
 int
-xchk_setup_xattr(
+xchk_setup_xattr_buf(
 	struct xfs_scrub	*sc,
-	struct xfs_inode	*ip)
+	size_t			value_size)
 {
 	size_t			sz;
 
 	/*
-	 * Allocate the buffer without the inode lock held.  We need enough
-	 * space to read every xattr value in the file or enough space to
-	 * hold three copies of the xattr free space bitmap.  (Not both at
-	 * the same time.)
+	 * We need enough space to read an xattr value from the file or enough
+	 * space to hold three copies of the xattr free space bitmap.  We don't
+	 * need the buffer space for both purposes at the same time.
 	 */
-	sz = max_t(size_t, XATTR_SIZE_MAX, 3 * sizeof(long) *
-			BITS_TO_LONGS(sc->mp->m_attr_geo->blksize));
+	sz = 3 * sizeof(long) * BITS_TO_LONGS(sc->mp->m_attr_geo->blksize);
+	sz = max_t(size_t, sz, value_size);
+
 	sc->buf = kmem_zalloc_large(sz, KM_SLEEP);
 	if (!sc->buf)
 		return -ENOMEM;
 
+	return 0;
+}
+
+/* Set us up to scrub an inode's extended attributes. */
+int
+xchk_setup_xattr(
+	struct xfs_scrub	*sc,
+	struct xfs_inode	*ip)
+{
+	int			error;
+
+	error = xchk_setup_xattr_buf(sc, XATTR_SIZE_MAX);
+	if (error)
+		return error;
+
 	return xchk_setup_inode_contents(sc, ip, 0);
 }
 

fs/xfs/scrub/attr.h

@@ -62,4 +62,6 @@ xchk_xattr_dstmap(
 			BITS_TO_LONGS(sc->mp->m_attr_geo->blksize);
 }
 
+int xchk_setup_xattr_buf(struct xfs_scrub *sc, size_t value_size);
+
 #endif	/* __XFS_SCRUB_ATTR_H__ */