[PATCH] ext4: 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>

1 files changed, 8 insertions, 4 deletions

diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index 5d45582f9517..6bd0bd5bbdc8 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -1324,10 +1324,14 @@ ext4_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)) {