[XFS] Move the XFS inode to the front of its hash list on a cache hit

SGI Modid: xfs-linux:xfs-kern:21915a

Signed-off-by: Nathan Scott <nathans@sgi.com>
Signed-off-by: Christoph Hellwig <hch@sgi.com>

diff --git a/fs/xfs/xfs_iget.c b/fs/xfs/xfs_iget.c
index 3a0ba1d..d3da000 100644 (file)
--- a/fs/xfs/xfs_iget.c
+++ b/fs/xfs/xfs_iget.c
@@ -135,6 +135,40 @@ xfs_chash_free(xfs_mount_t *mp)
        mp->m_chash = NULL;
 }
 
+/*
+ * Try to move an inode to the front of its hash list if possible
+ * (and if its not there already).  Called right after obtaining
+ * the list version number and then dropping the read_lock on the
+ * hash list in question (which is done right after looking up the
+ * inode in question...).
+ */
+STATIC void
+xfs_ihash_promote(
+       xfs_ihash_t     *ih,
+       xfs_inode_t     *ip,
+       ulong           version)
+{
+       xfs_inode_t     *iq;
+
+       if ((ip->i_prevp != &ih->ih_next) && write_trylock(&ih->ih_lock)) {
+               if (likely(version == ih->ih_version)) {
+                       /* remove from list */
+                       if ((iq = ip->i_next)) {
+                               iq->i_prevp = ip->i_prevp;
+                       }
+                       *ip->i_prevp = iq;
+
+                       /* insert at list head */
+                       iq = ih->ih_next;
+                       iq->i_prevp = &ip->i_next;
+                       ip->i_next = iq;
+                       ip->i_prevp = &ih->ih_next;
+                       ih->ih_next = ip;
+               }
+               write_unlock(&ih->ih_lock);
+       }
+}
+
 /*
  * Look up an inode by number in the given file system.
  * The inode is looked up in the hash table for the file system
@@ -229,7 +263,9 @@ again:
                                XFS_STATS_INC(xs_ig_found);
 
                                ip->i_flags &= ~XFS_IRECLAIMABLE;
+                               version = ih->ih_version;
                                read_unlock(&ih->ih_lock);
+                               xfs_ihash_promote(ih, ip, version);
 
                                XFS_MOUNT_ILOCK(mp);
                                list_del_init(&ip->i_reclaim);
@@ -259,8 +295,15 @@ again:
                                                inode_vp, vp);
                        }
 
+                       /*
+                        * Inode cache hit: if ip is not at the front of
+                        * its hash chain, move it there now.
+                        * Do this with the lock held for update, but
+                        * do statistics after releasing the lock.
+                        */
+                       version = ih->ih_version;
                        read_unlock(&ih->ih_lock);
-
+                       xfs_ihash_promote(ih, ip, version);
                        XFS_STATS_INC(xs_ig_found);
 
 finish_inode:
@@ -547,6 +590,7 @@ xfs_inode_incore(xfs_mount_t        *mp,
 {
        xfs_ihash_t     *ih;
        xfs_inode_t     *ip;
+       ulong           version;
 
        ih = XFS_IHASH(mp, ino);
        read_lock(&ih->ih_lock);
@@ -554,11 +598,15 @@ xfs_inode_incore(xfs_mount_t      *mp,
                if (ip->i_ino == ino) {
                        /*
                         * If we find it and tp matches, return it.
+                        * Also move it to the front of the hash list
+                        * if we find it and it is not already there.
                         * Otherwise break from the loop and return
                         * NULL.
                         */
                        if (ip->i_transp == tp) {
+                               version = ih->ih_version;
                                read_unlock(&ih->ih_lock);
+                               xfs_ihash_promote(ih, ip, version);
                                return (ip);
                        }
                        break;
@@ -685,6 +733,7 @@ xfs_iextract(
                iq->i_prevp = ip->i_prevp;
        }
        *ip->i_prevp = iq;
+       ih->ih_version++;
        write_unlock(&ih->ih_lock);
 
        /*