xfs: break up xfs_buf_find() into individual pieces

xfs_buf_find() is made up of three main parts: lookup, insert and
locking. The interactions with xfs_buf_get_map() require it to be
called twice - once for a pure lookup, and again on lookup failure
so the insert path can be run. We want to simplify this down a lot,
so split it into a fast path lookup, a slow path insert and a "lock
the found buffer" helper. This will then let us integrate these
operations more effectively into xfs_buf_get_map() in future
patches.

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

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 143e1c7..9a44048 100644 (file)
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -503,6 +503,98 @@ xfs_buf_hash_destroy(
        rhashtable_destroy(&pag->pag_buf_hash);
 }
 
+static int
+xfs_buf_map_verify(
+       struct xfs_buftarg      *btp,
+       struct xfs_buf_map      *map)
+{
+       xfs_daddr_t             eofs;
+
+       /* Check for IOs smaller than the sector size / not sector aligned */
+       ASSERT(!(BBTOB(map->bm_len) < btp->bt_meta_sectorsize));
+       ASSERT(!(BBTOB(map->bm_bn) & (xfs_off_t)btp->bt_meta_sectormask));
+
+       /*
+        * Corrupted block numbers can get through to here, unfortunately, so we
+        * have to check that the buffer falls within the filesystem bounds.
+        */
+       eofs = XFS_FSB_TO_BB(btp->bt_mount, btp->bt_mount->m_sb.sb_dblocks);
+       if (map->bm_bn < 0 || map->bm_bn >= eofs) {
+               xfs_alert(btp->bt_mount,
+                         "%s: daddr 0x%llx out of range, EOFS 0x%llx",
+                         __func__, map->bm_bn, eofs);
+               WARN_ON(1);
+               return -EFSCORRUPTED;
+       }
+       return 0;
+}
+
+static int
+xfs_buf_find_lock(
+       struct xfs_buf          *bp,
+       xfs_buf_flags_t         flags)
+{
+       if (!xfs_buf_trylock(bp)) {
+               if (flags & XBF_TRYLOCK) {
+                       XFS_STATS_INC(bp->b_mount, xb_busy_locked);
+                       xfs_buf_rele(bp);
+                       return -EAGAIN;
+               }
+               xfs_buf_lock(bp);
+               XFS_STATS_INC(bp->b_mount, xb_get_locked_waited);
+       }
+
+       /*
+        * if the buffer is stale, clear all the external state associated with
+        * it. We need to keep flags such as how we allocated the buffer memory
+        * intact here.
+        */
+       if (bp->b_flags & XBF_STALE) {
+               ASSERT((bp->b_flags & _XBF_DELWRI_Q) == 0);
+               bp->b_flags &= _XBF_KMEM | _XBF_PAGES;
+               bp->b_ops = NULL;
+       }
+       return 0;
+}
+
+static inline struct xfs_buf *
+xfs_buf_lookup(
+       struct xfs_perag        *pag,
+       struct xfs_buf_map      *map)
+{
+       struct xfs_buf          *bp;
+
+       bp = rhashtable_lookup(&pag->pag_buf_hash, map, xfs_buf_hash_params);
+       if (!bp)
+               return NULL;
+       atomic_inc(&bp->b_hold);
+       return bp;
+}
+
+/*
+ * Insert the new_bp into the hash table. This consumes the perag reference
+ * taken for the lookup.
+ */
+static int
+xfs_buf_find_insert(
+       struct xfs_buftarg      *btp,
+       struct xfs_perag        *pag,
+       struct xfs_buf          *new_bp)
+{
+       /* No match found */
+       if (!new_bp) {
+               xfs_perag_put(pag);
+               XFS_STATS_INC(btp->bt_mount, xb_miss_locked);
+               return -ENOENT;
+       }
+
+       /* the buffer keeps the perag reference until it is freed */
+       new_bp->b_pag = pag;
+       rhashtable_insert_fast(&pag->pag_buf_hash, &new_bp->b_rhash_head,
+                              xfs_buf_hash_params);
+       return 0;
+}
+
 /*
  * Look up a buffer in the buffer cache and return it referenced and locked
  * in @found_bp.
@@ -533,7 +625,7 @@ xfs_buf_find(
        struct xfs_perag        *pag;
        struct xfs_buf          *bp;
        struct xfs_buf_map      cmap = { .bm_bn = map[0].bm_bn };
-       xfs_daddr_t             eofs;
+       int                     error;
        int                     i;
 
        *found_bp = NULL;
@@ -541,47 +633,22 @@ xfs_buf_find(
        for (i = 0; i < nmaps; i++)
                cmap.bm_len += map[i].bm_len;
 
-       /* Check for IOs smaller than the sector size / not sector aligned */
-       ASSERT(!(BBTOB(cmap.bm_len) < btp->bt_meta_sectorsize));
-       ASSERT(!(BBTOB(cmap.bm_bn) & (xfs_off_t)btp->bt_meta_sectormask));
-
-       /*
-        * Corrupted block numbers can get through to here, unfortunately, so we
-        * have to check that the buffer falls within the filesystem bounds.
-        */
-       eofs = XFS_FSB_TO_BB(btp->bt_mount, btp->bt_mount->m_sb.sb_dblocks);
-       if (cmap.bm_bn < 0 || cmap.bm_bn >= eofs) {
-               xfs_alert(btp->bt_mount,
-                         "%s: daddr 0x%llx out of range, EOFS 0x%llx",
-                         __func__, cmap.bm_bn, eofs);
-               WARN_ON(1);
-               return -EFSCORRUPTED;
-       }
+       error = xfs_buf_map_verify(btp, &cmap);
+       if (error)
+               return error;
 
        pag = xfs_perag_get(btp->bt_mount,
                            xfs_daddr_to_agno(btp->bt_mount, cmap.bm_bn));
 
        spin_lock(&pag->pag_buf_lock);
-       bp = rhashtable_lookup_fast(&pag->pag_buf_hash, &cmap,
-                                   xfs_buf_hash_params);
-       if (bp) {
-               atomic_inc(&bp->b_hold);
+       bp = xfs_buf_lookup(pag, &cmap);
+       if (bp)
                goto found;
-       }
-
-       /* No match found */
-       if (!new_bp) {
-               XFS_STATS_INC(btp->bt_mount, xb_miss_locked);
-               spin_unlock(&pag->pag_buf_lock);
-               xfs_perag_put(pag);
-               return -ENOENT;
-       }
 
-       /* the buffer keeps the perag reference until it is freed */
-       new_bp->b_pag = pag;
-       rhashtable_insert_fast(&pag->pag_buf_hash, &new_bp->b_rhash_head,
-                              xfs_buf_hash_params);
+       error = xfs_buf_find_insert(btp, pag, new_bp);
        spin_unlock(&pag->pag_buf_lock);
+       if (error)
+               return error;
        *found_bp = new_bp;
        return 0;
 
@@ -589,26 +656,9 @@ found:
        spin_unlock(&pag->pag_buf_lock);
        xfs_perag_put(pag);
 
-       if (!xfs_buf_trylock(bp)) {
-               if (flags & XBF_TRYLOCK) {
-                       xfs_buf_rele(bp);
-                       XFS_STATS_INC(btp->bt_mount, xb_busy_locked);
-                       return -EAGAIN;
-               }
-               xfs_buf_lock(bp);
-               XFS_STATS_INC(btp->bt_mount, xb_get_locked_waited);
-       }
-
-       /*
-        * if the buffer is stale, clear all the external state associated with
-        * it. We need to keep flags such as how we allocated the buffer memory
-        * intact here.
-        */
-       if (bp->b_flags & XBF_STALE) {
-               ASSERT((bp->b_flags & _XBF_DELWRI_Q) == 0);
-               bp->b_flags &= _XBF_KMEM | _XBF_PAGES;
-               bp->b_ops = NULL;
-       }
+       error = xfs_buf_find_lock(bp, flags);
+       if (error)
+               return error;
 
        trace_xfs_buf_find(bp, flags, _RET_IP_);
        XFS_STATS_INC(btp->bt_mount, xb_get_locked);