1 files changed, 23 insertions, 4 deletions

diff --git a/fs/xfs/xfs_buf.h b/fs/xfs/xfs_buf.h
index 7f1d1392ce37..c9c2ba90c53c 100644
--- a/fs/xfs/xfs_buf.h
+++ b/fs/xfs/xfs_buf.h
@@ -58,6 +58,7 @@ typedef enum {
 #define _XBF_PAGES      (1 << 20)/* backed by refcounted pages */
 #define _XBF_KMEM       (1 << 21)/* backed by heap memory */
 #define _XBF_DELWRI_Q   (1 << 22)/* buffer on a delwri queue */
+#define _XBF_COMPOUND   (1 << 23)/* compound buffer */
 
 typedef unsigned int xfs_buf_flags_t;
 
@@ -75,7 +76,8 @@ typedef unsigned int xfs_buf_flags_t;
         { XBF_UNMAPPED,         "UNMAPPED" },   /* ditto */\
         { _XBF_PAGES,           "PAGES" }, \
         { _XBF_KMEM,            "KMEM" }, \
-        { _XBF_DELWRI_Q,        "DELWRI_Q" }
+        { _XBF_DELWRI_Q,        "DELWRI_Q" }, \
+        { _XBF_COMPOUND,        "COMPOUND" }
 
 typedef struct xfs_buftarg {
         dev_t                   bt_dev;
@@ -98,6 +100,11 @@ typedef void (*xfs_buf_iodone_t)(struct xfs_buf *);
 
 #define XB_PAGES        2
 
+struct xfs_buf_map {
+        xfs_daddr_t             bm_bn;  /* block number for I/O */
+        int                     bm_len; /* size of I/O */
+};
+
 typedef struct xfs_buf {
         /*
          * first cacheline holds all the fields needed for an uncontended cache
@@ -107,7 +114,7 @@ typedef struct xfs_buf {
          * fast-path on locking.
          */
         struct rb_node          b_rbnode;       /* rbtree node */
-        xfs_daddr_t             b_bn;           /* block number for I/O */
+        xfs_daddr_t             b_bn;           /* block number of buffer */
         int                     b_length;       /* size of buffer in BBs */
         atomic_t                b_hold;         /* reference count */
         atomic_t                b_lru_ref;      /* lru reclaim ref count */
@@ -127,12 +134,14 @@ typedef struct xfs_buf {
         struct xfs_trans        *b_transp;
         struct page             **b_pages;      /* array of page pointers */
         struct page             *b_page_array[XB_PAGES]; /* inline pages */
+        struct xfs_buf_map      b_map;          /* compound buffer map */
         int                     b_io_length;    /* IO size in BBs */
         atomic_t                b_pin_count;    /* pin count */
         atomic_t                b_io_remaining; /* #outstanding I/O requests */
         unsigned int            b_page_count;   /* size of page array */
         unsigned int            b_offset;       /* page offset in first page */
         unsigned short          b_error;        /* error code on I/O */
+
 #ifdef XFS_BUF_LOCK_TRACKING
         int                     b_last_holder;
 #endif
@@ -233,8 +242,18 @@ void xfs_buf_stale(struct xfs_buf *bp);
 #define XFS_BUF_UNWRITE(bp)     ((bp)->b_flags &= ~XBF_WRITE)
 #define XFS_BUF_ISWRITE(bp)     ((bp)->b_flags & XBF_WRITE)
 
-#define XFS_BUF_ADDR(bp)                ((bp)->b_bn)
-#define XFS_BUF_SET_ADDR(bp, bno)       ((bp)->b_bn = (xfs_daddr_t)(bno))
+/*
+ * These macros use the IO block map rather than b_bn. b_bn is now really
+ * just for the buffer cache index for cached buffers. As IO does not use b_bn
+ * anymore, uncached buffers do not use b_bn at all and hence must modify the IO
+ * map directly. Uncached buffers are not allowed to be discontiguous, so this
+ * is safe to do.
+ *
+ * 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))
 
 static inline void xfs_buf_set_ref(struct xfs_buf *bp, int lru_ref)
 {