[PATCH] ext3: fix reservation extension

Hugh Dickins wrote:
> Not found anything relevant, but I keep noticing these lines
> in ext2_try_to_allocate_with_rsv(), ext3 and ext4 similar:
>
> 		} else if (grp_goal > 0 &&
> 				(my_rsv->rsv_end - grp_goal + 1) < *count)
> 			try_to_extend_reservation(my_rsv, sb,
> 					*count-my_rsv->rsv_end + grp_goal - 1);
>
> They're wrong, a no-op in most groups, aren't they?  rsv_end is an
> absolute block number, whereas grp_goal is group-relative, so the
> calculation ought to bring in group_first_block?  Or I'm confused.
>

Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Cc: "linux-ext4@vger.kernel.org" <linux-ext4@vger.kernel.org>
Cc: Hugh Dickins <hugh@veritas.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 b41a7d7e20f006bc7e85a6e4b2315cf38ee2fdc9..f96c40a90e2e7441df9613894283429ed89330f6 100644 (file)
--- a/fs/ext3/balloc.c
+++ b/fs/ext3/balloc.c
@@ -1307,10 +1307,14 @@ ext3_try_to_allocate_with_rsv(struct super_block *sb, handle_t *handle,
                        if (!goal_in_my_reservation(&my_rsv->rsv_window,
                                                        grp_goal, group, sb))
                                grp_goal = -1;
-               } else if (grp_goal > 0 &&
-                         (my_rsv->rsv_end-grp_goal+1) < *count)
-                       try_to_extend_reservation(my_rsv, sb,
-                                       *count-my_rsv->rsv_end + grp_goal - 1);
+               } else if (grp_goal > 0) {
+                       int curr = my_rsv->rsv_end -
+                                       (grp_goal + group_first_block) + 1;
+
+                       if (curr < *count)
+                               try_to_extend_reservation(my_rsv, sb,
+                                                       *count - curr);
+               }
 
                if ((my_rsv->rsv_start > group_last_block) ||
                                (my_rsv->rsv_end < group_first_block)) {