[PATCH 1/2] xfs: use b_maps[] for discontiguous buffers

[Mark Tinguely <tinguely@xxxxxxx>]

This patch sets all the b_bmap accesses to be b_maps[0]. b_maps[0]
works for single and multiple segment buffers.

This fixes a bug where xfs_trans_buf_item_match() could not find a
multi-segment buffer associated with the transaction because it was
looking for the block number in the single segment location
b_map.bm.bn rather than the new generic b_maps[0].bm.bn. This
resulted in recursive buffer lock that can never be satisfied.

Signed-off-by: Mark Tinguely <tinguely@xxxxxxx>

---
 fs/xfs/xfs_buf.c |    8 ++++----
 fs/xfs/xfs_buf.h |    4 ++--
 2 files changed, 6 insertions(+), 6 deletions(-)

Index: b/fs/xfs/xfs_buf.c
===================================================================
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -377,8 +377,8 @@ xfs_buf_allocate_memory(
        }
 
 use_alloc_page:
-       start = BBTOB(bp->b_map.bm_bn) >> PAGE_SHIFT;
-       end = (BBTOB(bp->b_map.bm_bn + bp->b_length) + PAGE_SIZE - 1)
+       start = BBTOB(bp->b_maps[0].bm_bn) >> PAGE_SHIFT;
+       end = (BBTOB(bp->b_maps[0].bm_bn + bp->b_length) + PAGE_SIZE - 1)
                                                                >> PAGE_SHIFT;
        page_count = end - start;
        error = _xfs_buf_get_pages(bp, page_count, flags);
@@ -640,7 +640,7 @@ _xfs_buf_read(
        xfs_buf_flags_t         flags)
 {
        ASSERT(!(flags & XBF_WRITE));
-       ASSERT(bp->b_map.bm_bn != XFS_BUF_DADDR_NULL);
+       ASSERT(bp->b_maps[0].bm_bn != XFS_BUF_DADDR_NULL);
 
        bp->b_flags &= ~(XBF_WRITE | XBF_ASYNC | XBF_READ_AHEAD);
        bp->b_flags |= flags & (XBF_READ | XBF_ASYNC | XBF_READ_AHEAD);
@@ -1709,7 +1709,7 @@ xfs_buf_cmp(
        struct xfs_buf  *bp = container_of(b, struct xfs_buf, b_list);
        xfs_daddr_t             diff;
 
-       diff = ap->b_map.bm_bn - bp->b_map.bm_bn;
+       diff = ap->b_maps[0].bm_bn - bp->b_maps[0].bm_bn;
        if (diff < 0)
                return -1;
        if (diff > 0)
Index: b/fs/xfs/xfs_buf.h
===================================================================
--- a/fs/xfs/xfs_buf.h
+++ b/fs/xfs/xfs_buf.h
@@ -330,8 +330,8 @@ void xfs_buf_stale(struct xfs_buf *bp);
  * In future, uncached buffers will pass the block number directly to the io
  * request function and hence these macros will go away at that point.
  */
-#define XFS_BUF_ADDR(bp)               ((bp)->b_map.bm_bn)
-#define XFS_BUF_SET_ADDR(bp, bno)      ((bp)->b_map.bm_bn = (xfs_daddr_t)(bno))
+#define XFS_BUF_ADDR(bp)               ((bp)->b_maps[0].bm_bn)
+#define XFS_BUF_SET_ADDR(bp, bno)      ((bp)->b_maps[0].bm_bn = 
(xfs_daddr_t)(bno))
 
 static inline void xfs_buf_set_ref(struct xfs_buf *bp, int lru_ref)
 {