[PATCH] ext3_get_blocks: Adjust reservation window size for mblocks

Optimize the block reservation and the multiple block allocation: with the
knowledge of the total number of blocks ahead, set or adjust the reservation
window size properly (based on the number of blocks needed) before block
allocation happens: if there isn't any reservation yet, make sure the
reservation window equals to or greater than the number of blocks needed,
before create an reservation window; if a reservation window is already
exists, try to extends the window size to match the number of blocks to
allocate.  This could increase the possibility of completing multiple blocks
allocation in a single request, as blocks are only allocated in the range of
the inode's reservation window.

Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/fs/ext3/balloc.c b/fs/ext3/balloc.c
index 7a2c719..77927d6 100644 (file)
--- a/fs/ext3/balloc.c
+++ b/fs/ext3/balloc.c
@@ -1011,6 +1011,31 @@ retry:
        goto retry;
 }
 
+static void try_to_extend_reservation(struct ext3_reserve_window_node *my_rsv,
+                       struct super_block *sb, int size)
+{
+       struct ext3_reserve_window_node *next_rsv;
+       struct rb_node *next;
+       spinlock_t *rsv_lock = &EXT3_SB(sb)->s_rsv_window_lock;
+
+       if (!spin_trylock(rsv_lock))
+               return;
+
+       next = rb_next(&my_rsv->rsv_node);
+
+       if (!next)
+               my_rsv->rsv_end += size;
+       else {
+               next_rsv = list_entry(next, struct ext3_reserve_window_node, rsv_node);
+
+               if ((next_rsv->rsv_start - my_rsv->rsv_end - 1) >= size)
+                       my_rsv->rsv_end += size;
+               else
+                       my_rsv->rsv_end = next_rsv->rsv_start - 1;
+       }
+       spin_unlock(rsv_lock);
+}
+
 /*
  * This is the main function used to allocate a new block and its reservation
  * window.
@@ -1095,6 +1120,8 @@ ext3_try_to_allocate_with_rsv(struct super_block *sb, handle_t *handle,
        while (1) {
                if (rsv_is_empty(&my_rsv->rsv_window) || (ret < 0) ||
                        !goal_in_my_reservation(&my_rsv->rsv_window, goal, group, sb)) {
+                       if (my_rsv->rsv_goal_size < *count)
+                               my_rsv->rsv_goal_size = *count;
                        ret = alloc_new_reservation(my_rsv, goal, sb,
                                                        group, bitmap_bh);
                        if (ret < 0)
@@ -1102,7 +1129,10 @@ ext3_try_to_allocate_with_rsv(struct super_block *sb, handle_t *handle,
 
                        if (!goal_in_my_reservation(&my_rsv->rsv_window, goal, group, sb))
                                goal = -1;
-               }
+               } else if (goal > 0 && (my_rsv->rsv_end-goal+1) < *count)
+                       try_to_extend_reservation(my_rsv, sb,
+                                       *count-my_rsv->rsv_end + goal - 1);
+
                if ((my_rsv->rsv_start >= group_first_block + EXT3_BLOCKS_PER_GROUP(sb))
                    || (my_rsv->rsv_end < group_first_block))
                        BUG();