linux-ext4 - [PATCH] ext4: protect bb_first_free in ext4_trim_all

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Date:	Thu, 21 Apr 2011 12:26:36 +0200
From:	Lukas Czerner <lczerner@...hat.com>
To:	linux-ext4@...r.kernel.org
Cc:	tytso@....edu, amir73il@...il.com,
	Lukas Czerner <lczerner@...hat.com>
Subject: [PATCH] ext4: protect bb_first_free in ext4_trim_all_free() with group lock

We should protect reading bd_info->bb_first_free with the group lock
because otherwise we might miss some free blocks. This is not a big deal
at all, but the change to do right thing is really simple, so lets do
that.

Signed-off-by: Lukas Czerner <lczerner@...hat.com>
---
 fs/ext4/mballoc.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 776d7a8..804232a 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4775,11 +4775,11 @@ ext4_trim_all_free(struct super_block *sb, ext4_group_t group,
 				"information for %u", group);
 		return ret;
 	}
-
 	bitmap = e4b.bd_bitmap;
+
+	ext4_lock_group(sb, group);
 	start = (e4b.bd_info->bb_first_free > start) ?
 		e4b.bd_info->bb_first_free : start;
-	ext4_lock_group(sb, group);
 
 	while (start < max) {
 		start = mb_find_next_zero_bit(bitmap, max, start);
-- 
1.7.4.4

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