xfs: rename buffer cache index variable b_bn

To stop external users from using b_bn as the disk address of the
buffer, rename it to b_rhash_key to indicate that it is the buffer
cache index, not the block number of the buffer. Code that needs the
disk address should use xfs_buf_daddr() to obtain it.

Do the rename and clean up any of the remaining internal b_bn users.
Also clean up any remaining b_bn cruft that is now unused.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index c1bb6e4..047bd6e 100644 (file)
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -251,7 +251,7 @@ _xfs_buf_alloc(
                return error;
        }
 
-       bp->b_bn = map[0].bm_bn;
+       bp->b_rhash_key = map[0].bm_bn;
        bp->b_length = 0;
        for (i = 0; i < nmaps; i++) {
                bp->b_maps[i].bm_bn = map[i].bm_bn;
@@ -459,7 +459,7 @@ _xfs_buf_obj_cmp(
         */
        BUILD_BUG_ON(offsetof(struct xfs_buf_map, bm_bn) != 0);
 
-       if (bp->b_bn != map->bm_bn)
+       if (bp->b_rhash_key != map->bm_bn)
                return 1;
 
        if (unlikely(bp->b_length != map->bm_len)) {
@@ -481,7 +481,7 @@ static const struct rhashtable_params xfs_buf_hash_params = {
        .min_size               = 32,   /* empty AGs have minimal footprint */
        .nelem_hint             = 16,
        .key_len                = sizeof(xfs_daddr_t),
-       .key_offset             = offsetof(struct xfs_buf, b_bn),
+       .key_offset             = offsetof(struct xfs_buf, b_rhash_key),
        .head_offset            = offsetof(struct xfs_buf, b_rhash_head),
        .automatic_shrinking    = true,
        .obj_cmpfn              = _xfs_buf_obj_cmp,
@@ -853,7 +853,9 @@ xfs_buf_readahead_map(
 
 /*
  * Read an uncached buffer from disk. Allocates and returns a locked
- * buffer containing the disk contents or nothing.
+ * buffer containing the disk contents or nothing. Uncached buffers always have
+ * a cache index of XFS_BUF_DADDR_NULL so we can easily determine if the buffer
+ * is cached or uncached during fault diagnosis.
  */
 int
 xfs_buf_read_uncached(
@@ -875,7 +877,7 @@ xfs_buf_read_uncached(
 
        /* set up the buffer for a read IO */
        ASSERT(bp->b_map_count == 1);
-       bp->b_bn = XFS_BUF_DADDR_NULL;  /* always null for uncached buffers */
+       bp->b_rhash_key = XFS_BUF_DADDR_NULL;
        bp->b_maps[0].bm_bn = daddr;
        bp->b_flags |= XBF_READ;
        bp->b_ops = ops;
@@ -1513,7 +1515,7 @@ _xfs_buf_ioapply(
                                                   SHUTDOWN_CORRUPT_INCORE);
                                return;
                        }
-               } else if (bp->b_bn != XFS_BUF_DADDR_NULL) {
+               } else if (bp->b_rhash_key != XFS_BUF_DADDR_NULL) {
                        struct xfs_mount *mp = bp->b_mount;
 
                        /*
@@ -1523,7 +1525,8 @@ _xfs_buf_ioapply(
                        if (xfs_has_crc(mp)) {
                                xfs_warn(mp,
                                        "%s: no buf ops on daddr 0x%llx len %d",
-                                       __func__, bp->b_bn, bp->b_length);
+                                       __func__, xfs_buf_daddr(bp),
+                                       bp->b_length);
                                xfs_hex_dump(bp->b_addr,
                                                XFS_CORRUPTION_DUMP_LEN);
                                dump_stack();
@@ -1793,7 +1796,7 @@ xfs_buftarg_drain(
                                xfs_buf_alert_ratelimited(bp,
                                        "XFS: Corruption Alert",
 "Corruption Alert: Buffer at daddr 0x%llx had permanent write failures!",
-                                       (long long)bp->b_bn);
+                                       (long long)xfs_buf_daddr(bp));
                        }
                        xfs_buf_rele(bp);
                }

diff --git a/fs/xfs/xfs_buf.h b/fs/xfs/xfs_buf.h
index 6db2fba..6b0200b 100644 (file)
--- a/fs/xfs/xfs_buf.h
+++ b/fs/xfs/xfs_buf.h
@@ -134,11 +134,7 @@ struct xfs_buf {
         */
        struct rhash_head       b_rhash_head;   /* pag buffer hash node */
 
-       /*
-        * b_bn is the cache index. Do not use directly, use b_maps[0].bm_bn
-        * for the buffer disk address instead.
-        */
-       xfs_daddr_t             b_bn;
+       xfs_daddr_t             b_rhash_key;    /* buffer cache index */
        int                     b_length;       /* size of buffer in BBs */
        atomic_t                b_hold;         /* reference count */
        atomic_t                b_lru_ref;      /* lru reclaim ref count */
@@ -301,18 +297,6 @@ extern int xfs_buf_delwri_pushbuf(struct xfs_buf *, struct list_head *);
 extern int xfs_buf_init(void);
 extern void xfs_buf_terminate(void);
 
-/*
- * 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_SET_ADDR(bp, bno)      ((bp)->b_maps[0].bm_bn = (xfs_daddr_t)(bno))
-
 static inline xfs_daddr_t xfs_buf_daddr(struct xfs_buf *bp)
 {
        return bp->b_maps[0].bm_bn;