Re: [Ext2-devel] Ext3 -mm reservations code: is this fix really correct?

[mingming cao <cmm@us.ibm.com>]

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On Fri, 2004-10-15 at 09:40, Stephen C. Tweedie wrote:
> Hi,
> 
> On Fri, 2004-10-15 at 17:01, mingming cao wrote:
> 
> > > Have I misunderstood something?
> > > 
> > You are correct, again:) We should do a search_reserve_window() from the
> > root.
> > 
> > I will post a fix for these two soon.
> 
> Thanks.  I'll be away for a few days so I probably won't be able to look
> at the fix until Wednesday next week.
> 

How about this? Haven't test it, will do it shortly.:)


Thanks,
Mingming


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---

 linux-2.6.9-rc1-mm5-ming/fs/ext3/balloc.c |   21 +++++++++------------
 1 files changed, 9 insertions(+), 12 deletions(-)

diff -puN fs/ext3/balloc.c~ext3_reservation_window_fix_fix fs/ext3/balloc.c
--- linux-2.6.9-rc1-mm5/fs/ext3/balloc.c~ext3_reservation_window_fix_fix	2004-10-15 18:23:42.824158856 -0700
+++ linux-2.6.9-rc1-mm5-ming/fs/ext3/balloc.c	2004-10-15 20:16:06.037034680 -0700
@@ -184,9 +184,10 @@ goal_in_my_reservation(struct reserve_wi
  * if the goal is not in any window.
  * Returns NULL if there are no windows or if all windows start after the goal.
  */
-static struct reserve_window_node *search_reserve_window(struct rb_node *n,
+static struct reserve_window_node *search_reserve_window(struct rb_root *root,
 							 unsigned long goal)
 {
+	struct rb_node *n = root->rb_node;
 	struct reserve_window_node *rsv;
 
 	if (!n)
@@ -822,10 +823,10 @@ static int alloc_new_reservation(struct 
 		start_block = goal + group_first_block;
 
 	size = atomic_read(&my_rsv->rsv_goal_size);
-	/* if we have a old reservation, start the search from the old rsv */
 	if (!rsv_is_empty(&my_rsv->rsv_window)) {
 		/*
 		 * if the old reservation is cross group boundary
+		 * and if the goal is inside the old reservation window,
 		 * we will come here when we just failed to allocate from
 		 * the first part of the window. We still have another part
 		 * that belongs to the next group. In this case, there is no
@@ -838,10 +839,10 @@ static int alloc_new_reservation(struct 
 		 */
 
 		if ((my_rsv->rsv_start <= group_end_block) &&
-				(my_rsv->rsv_end > group_end_block))
+				(my_rsv->rsv_end > group_end_block) &&
+				(start_block <= my_rsv->rsv_start))
 			return -1;
 
-		search_head = search_reserve_window(&my_rsv->rsv_node, start_block);
 		if ((atomic_read(&my_rsv->rsv_alloc_hit) >
 		     (my_rsv->rsv_end - my_rsv->rsv_start + 1) / 2)) {
 			/*
@@ -855,14 +856,10 @@ static int alloc_new_reservation(struct 
 			atomic_set(&my_rsv->rsv_goal_size, size);
 		}
 	}
-	else {
-		/*
-		 * we don't have a reservation,
-		 * we set our goal(start_block) and
-		 * the list head for the search
-		 */
-		search_head = search_reserve_window(fs_rsv_root->rb_node, start_block);
-	}
+	/*
+	 * shift the search start to the window near the goal block
+	 */
+	search_head = search_reserve_window(fs_rsv_root, start_block);
 
 	/*
 	 * find_next_reservable_window() simply finds a reservable window

_