xfs: add a short cut to xfs_dialloc for the non-NULL agbp case

In this case we already have selected an AG and know it has free space
beause the buffer lock never got released.  Jump directly into xfs_dialloc_ag
and short cut the AG selection loop.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

1 files changed, 26 insertions, 21 deletions

diff --git a/fs/xfs/xfs_ialloc.c b/fs/xfs/xfs_ialloc.c
index 2b70952c9d8c..7aa8a02b7937 100644
--- a/fs/xfs/xfs_ialloc.c
+++ b/fs/xfs/xfs_ialloc.c
@@ -634,6 +634,10 @@ xfs_dialloc_ag(
 
         pag = xfs_perag_get(mp, agno);
 
+        ASSERT(pag->pagi_init);
+        ASSERT(pag->pagi_inodeok);
+        ASSERT(pag->pagi_freecount > 0);
+
  restart_pagno:
         cur = xfs_inobt_init_cursor(mp, tp, agbp, agno);
         /*
@@ -907,32 +911,32 @@ xfs_dialloc(
         xfs_agnumber_t          tagno;
         struct xfs_perag        *pag;
 
-        if (*IO_agbp == NULL) {
-                /*
-                 * We do not have an agbp, so select an initial allocation
-                 * group for inode allocation.
-                 */
-                agbp = xfs_ialloc_ag_select(tp, parent, mode, okalloc);
+        if (*IO_agbp) {
                 /*
-                 * Couldn't find an allocation group satisfying the
-                 * criteria, give up.
-                 */
-                if (!agbp) {
-                        *inop = NULLFSINO;
-                        return 0;
-                }
-                agi = XFS_BUF_TO_AGI(agbp);
-                ASSERT(agi->agi_magicnum == cpu_to_be32(XFS_AGI_MAGIC));
-        } else {
-                /*
-                 * Continue where we left off before.  In this case, we
+                 * If the caller passes in a pointer to the AGI buffer,
+                 * continue where we left off before.  In this case, we
                  * know that the allocation group has free inodes.
                  */
                 agbp = *IO_agbp;
-                agi = XFS_BUF_TO_AGI(agbp);
-                ASSERT(agi->agi_magicnum == cpu_to_be32(XFS_AGI_MAGIC));
-                ASSERT(be32_to_cpu(agi->agi_freecount) > 0);
+                goto out_alloc;
         }
+
+        /*
+         * We do not have an agbp, so select an initial allocation
+         * group for inode allocation.
+         */
+        agbp = xfs_ialloc_ag_select(tp, parent, mode, okalloc);
+
+        /*
+         * Couldn't find an allocation group satisfying the
+         * criteria, give up.
+         */
+        if (!agbp) {
+                *inop = NULLFSINO;
+                return 0;
+        }
+        agi = XFS_BUF_TO_AGI(agbp);
+
         mp = tp->t_mountp;
         agno = be32_to_cpu(agi->agi_seqno);
         tagno = agno;
@@ -1012,6 +1016,7 @@ nextag:
                 ASSERT(agi->agi_magicnum == cpu_to_be32(XFS_AGI_MAGIC));
         }
 
+out_alloc:
         *IO_agbp = NULL;
         return xfs_dialloc_ag(tp, agbp, parent, inop);
 }