xfs: turn XFS_ATTR3_RMT_BUF_SPACE into a function

Turn this into a properly typechecked function, and actually use the
correct blocksize for extended attributes.  The function cannot be
static inline because xfsprogs userspace uses it.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Andrey Albershteyn <aalbersh@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/xfs/libxfs/xfs_attr_remote.c

@@ -43,6 +43,19 @@
  * the logging system and therefore never have a log item.
  */
 
+/* How many bytes can be stored in a remote value buffer? */
+inline unsigned int
+xfs_attr3_rmt_buf_space(
+	struct xfs_mount	*mp)
+{
+	unsigned int		blocksize = mp->m_attr_geo->blksize;
+
+	if (xfs_has_crc(mp))
+		return blocksize - sizeof(struct xfs_attr3_rmt_hdr);
+
+	return blocksize;
+}
+
 /*
  * Each contiguous block has a header, so it is not just a simple attribute
  * length to FSB conversion.
@@ -53,7 +66,7 @@ xfs_attr3_rmt_blocks(
 	unsigned int		attrlen)
 {
 	if (xfs_has_crc(mp)) {
-		unsigned int buflen = XFS_ATTR3_RMT_BUF_SPACE(mp, mp->m_sb.sb_blocksize);
+		unsigned int buflen = xfs_attr3_rmt_buf_space(mp);
 		return (attrlen + buflen - 1) / buflen;
 	}
 	return XFS_B_TO_FSB(mp, attrlen);
@@ -293,7 +306,7 @@ xfs_attr_rmtval_copyout(
 
 	while (len > 0 && *valuelen > 0) {
 		unsigned int hdr_size = 0;
-		unsigned int byte_cnt = XFS_ATTR3_RMT_BUF_SPACE(mp, blksize);
+		unsigned int byte_cnt = xfs_attr3_rmt_buf_space(mp);
 
 		byte_cnt = min(*valuelen, byte_cnt);
 
@@ -342,7 +355,7 @@ xfs_attr_rmtval_copyin(
 
 	while (len > 0 && *valuelen > 0) {
 		unsigned int hdr_size;
-		unsigned int byte_cnt = XFS_ATTR3_RMT_BUF_SPACE(mp, blksize);
+		unsigned int byte_cnt = xfs_attr3_rmt_buf_space(mp);
 
 		byte_cnt = min(*valuelen, byte_cnt);
 		hdr_size = xfs_attr3_rmt_hdr_set(mp, dst, ino, *offset,

fs/xfs/libxfs/xfs_da_format.h

@@ -880,9 +880,7 @@ struct xfs_attr3_rmt_hdr {
 
 #define XFS_ATTR3_RMT_CRC_OFF	offsetof(struct xfs_attr3_rmt_hdr, rm_crc)
 
-#define XFS_ATTR3_RMT_BUF_SPACE(mp, bufsize)	\
-	((bufsize) - (xfs_has_crc((mp)) ? \
-			sizeof(struct xfs_attr3_rmt_hdr) : 0))
+unsigned int xfs_attr3_rmt_buf_space(struct xfs_mount *mp);
 
 /* Number of bytes in a directory block. */
 static inline unsigned int xfs_dir2_dirblock_bytes(struct xfs_sb *sbp)