xfs: remove the agfl_bno member from struct xfs_agfl

struct xfs_agfl is a header in front of the AGFL entries that exists
for CRC enabled file systems.  For not CRC enabled file systems the AGFL
is simply a list of agbno.  Make the CRC case similar to that by just
using the list behind the new header.  This indirectly solves a problem
with modern gcc versions that warn about taking addresses of packed
structures (and we have to pack the AGFL given that gcc rounds up
structure sizes).  Also replace the helper macro to get from a buffer
with an inline function in xfs_alloc.h to make the code easier to
read.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/libxfs/xfs_ag.c

@@ -301,7 +301,7 @@ xfs_agflblock_init(
 		uuid_copy(&agfl->agfl_uuid, &mp->m_sb.sb_meta_uuid);
 	}
 
-	agfl_bno = XFS_BUF_TO_AGFL_BNO(mp, bp);
+	agfl_bno = xfs_buf_to_agfl_bno(bp);
 	for (bucket = 0; bucket < xfs_agfl_size(mp); bucket++)
 		agfl_bno[bucket] = cpu_to_be32(NULLAGBLOCK);
 }

fs/xfs/libxfs/xfs_alloc.c

@@ -589,6 +589,7 @@ xfs_agfl_verify(
 {
 	struct xfs_mount *mp = bp->b_mount;
 	struct xfs_agfl	*agfl = XFS_BUF_TO_AGFL(bp);
+	__be32		*agfl_bno = xfs_buf_to_agfl_bno(bp);
 	int		i;
 
 	/*
@@ -614,8 +615,8 @@ xfs_agfl_verify(
 		return __this_address;
 
 	for (i = 0; i < xfs_agfl_size(mp); i++) {
-		if (be32_to_cpu(agfl->agfl_bno[i]) != NULLAGBLOCK &&
+		if (be32_to_cpu(agfl_bno[i]) != NULLAGBLOCK &&
-		    be32_to_cpu(agfl->agfl_bno[i]) >= mp->m_sb.sb_agblocks)
+		    be32_to_cpu(agfl_bno[i]) >= mp->m_sb.sb_agblocks)
 			return __this_address;
 	}
 
@@ -2684,7 +2685,7 @@ xfs_alloc_get_freelist(
 	/*
 	 * Get the block number and update the data structures.
 	 */
-	agfl_bno = XFS_BUF_TO_AGFL_BNO(mp, agflbp);
+	agfl_bno = xfs_buf_to_agfl_bno(agflbp);
 	bno = be32_to_cpu(agfl_bno[be32_to_cpu(agf->agf_flfirst)]);
 	be32_add_cpu(&agf->agf_flfirst, 1);
 	xfs_trans_brelse(tp, agflbp);
@@ -2820,7 +2821,7 @@ xfs_alloc_put_freelist(
 
 	ASSERT(be32_to_cpu(agf->agf_flcount) <= xfs_agfl_size(mp));
 
-	agfl_bno = XFS_BUF_TO_AGFL_BNO(mp, agflbp);
+	agfl_bno = xfs_buf_to_agfl_bno(agflbp);
 	blockp = &agfl_bno[be32_to_cpu(agf->agf_fllast)];
 	*blockp = cpu_to_be32(bno);
 	startoff = (char *)blockp - (char *)agflbp->b_addr;
@@ -3424,7 +3425,7 @@ xfs_agfl_walk(
 	unsigned int		i;
 	int			error;
 
-	agfl_bno = XFS_BUF_TO_AGFL_BNO(mp, agflbp);
+	agfl_bno = xfs_buf_to_agfl_bno(agflbp);
 	i = be32_to_cpu(agf->agf_flfirst);
 
 	/* Nothing to walk in an empty AGFL. */

fs/xfs/libxfs/xfs_alloc.h

@@ -236,4 +236,13 @@ typedef int (*xfs_agfl_walk_fn)(struct xfs_mount *mp, xfs_agblock_t bno,
 int xfs_agfl_walk(struct xfs_mount *mp, struct xfs_agf *agf,
 		struct xfs_buf *agflbp, xfs_agfl_walk_fn walk_fn, void *priv);
 
+static inline __be32 *
+xfs_buf_to_agfl_bno(
+	struct xfs_buf		*bp)
+{
+	if (xfs_sb_version_hascrc(&bp->b_mount->m_sb))
+		return bp->b_addr + sizeof(struct xfs_agfl);
+	return bp->b_addr;
+}
+
 #endif	/* __XFS_ALLOC_H__ */

fs/xfs/libxfs/xfs_format.h

@@ -785,18 +785,12 @@ typedef struct xfs_agi {
 #define	XFS_AGFL_BLOCK(mp)	XFS_HDR_BLOCK(mp, XFS_AGFL_DADDR(mp))
 #define	XFS_BUF_TO_AGFL(bp)	((xfs_agfl_t *)((bp)->b_addr))
 
-#define XFS_BUF_TO_AGFL_BNO(mp, bp) \
-	(xfs_sb_version_hascrc(&((mp)->m_sb)) ? \
-		&(XFS_BUF_TO_AGFL(bp)->agfl_bno[0]) : \
-		(__be32 *)(bp)->b_addr)
-
 typedef struct xfs_agfl {
 	__be32		agfl_magicnum;
 	__be32		agfl_seqno;
 	uuid_t		agfl_uuid;
 	__be64		agfl_lsn;
 	__be32		agfl_crc;
-	__be32		agfl_bno[];	/* actually xfs_agfl_size(mp) */
 } __attribute__((packed)) xfs_agfl_t;
 
 #define XFS_AGFL_CRC_OFF	offsetof(struct xfs_agfl, agfl_crc)

fs/xfs/scrub/agheader_repair.c

@@ -602,7 +602,7 @@ xrep_agfl_init_header(
 	 * step.
 	 */
 	fl_off = 0;
-	agfl_bno = XFS_BUF_TO_AGFL_BNO(mp, agfl_bp);
+	agfl_bno = xfs_buf_to_agfl_bno(agfl_bp);
 	for_each_xfs_bitmap_extent(br, n, agfl_extents) {
 		agbno = XFS_FSB_TO_AGBNO(mp, br->start);