linux-ext4 - [patch 229/354] ext4: fix reservation extension

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Message-Id: <200612070438.kB74cJlU029798@shell0.pdx.osdl.net>
Date:	Wed, 06 Dec 2006 20:38:19 -0800
From:	akpm@...l.org
To:	torvalds@...l.org
Cc:	akpm@...l.org, cmm@...ibm.com, hugh@...itas.com,
	linux-ext4@...r.kernel.org
Subject: [patch 229/354] ext4: fix reservation extension

From: Mingming Cao <cmm@...ibm.com>

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@...ibm.com>
Cc: "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Cc: Hugh Dickins <hugh@...itas.com>
Signed-off-by: Andrew Morton <akpm@...l.org>
---

 fs/ext4/balloc.c |   12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff -puN fs/ext4/balloc.c~ext4-fix-reservation-extension fs/ext4/balloc.c
--- a/fs/ext4/balloc.c~ext4-fix-reservation-extension
+++ a/fs/ext4/balloc.c
@@ -1324,10 +1324,14 @@ ext4_try_to_allocate_with_rsv(struct sup
 			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)) {
_
-
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