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Message-ID: <20231221150558.2740823-5-libaokun1@huawei.com>
Date: Thu, 21 Dec 2023 23:05:54 +0800
From: Baokun Li <libaokun1@...wei.com>
To: <linux-ext4@...r.kernel.org>
CC: <tytso@....edu>, <adilger.kernel@...ger.ca>, <jack@...e.cz>,
<ritesh.list@...il.com>, <linux-kernel@...r.kernel.org>,
<yi.zhang@...wei.com>, <yangerkun@...wei.com>, <yukuai3@...wei.com>,
<libaokun1@...wei.com>, <stable@...r.kernel.org>
Subject: [PATCH v2 4/8] ext4: avoid bb_free and bb_fragments inconsistency in mb_free_blocks()
After updating bb_free in mb_free_blocks, it is possible to return without
updating bb_fragments because the block being freed is found to have
already been freed, which leads to inconsistency between bb_free and
bb_fragments.
Since the group may be unlocked in ext4_grp_locked_error(), this can lead
to problems such as dividing by zero when calculating the average fragment
length. Hence move the update of bb_free to after the block double-free
check guarantees that the corresponding statistics are updated only after
the core block bitmap is modified.
Fixes: eabe0444df90 ("ext4: speed-up releasing blocks on commit")
CC: stable@...r.kernel.org # 3.10
Signed-off-by: Baokun Li <libaokun1@...wei.com>
---
fs/ext4/mballoc.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index f6131ba514c8..1f15774971d7 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -1910,11 +1910,6 @@ static void mb_free_blocks(struct inode *inode, struct ext4_buddy *e4b,
mb_check_buddy(e4b);
mb_free_blocks_double(inode, e4b, first, count);
- this_cpu_inc(discard_pa_seq);
- e4b->bd_info->bb_free += count;
- if (first < e4b->bd_info->bb_first_free)
- e4b->bd_info->bb_first_free = first;
-
/* access memory sequentially: check left neighbour,
* clear range and then check right neighbour
*/
@@ -1941,10 +1936,16 @@ static void mb_free_blocks(struct inode *inode, struct ext4_buddy *e4b,
EXT4_GROUP_INFO_BBITMAP_CORRUPT);
} else {
mb_regenerate_buddy(e4b);
+ goto check;
}
- goto done;
+ return;
}
+ this_cpu_inc(discard_pa_seq);
+ e4b->bd_info->bb_free += count;
+ if (first < e4b->bd_info->bb_first_free)
+ e4b->bd_info->bb_first_free = first;
+
/* let's maintain fragments counter */
if (left_is_free && right_is_free)
e4b->bd_info->bb_fragments--;
@@ -1969,9 +1970,9 @@ static void mb_free_blocks(struct inode *inode, struct ext4_buddy *e4b,
if (first <= last)
mb_buddy_mark_free(e4b, first >> 1, last >> 1);
-done:
mb_set_largest_free_order(sb, e4b->bd_info);
mb_update_avg_fragment_size(sb, e4b->bd_info);
+check:
mb_check_buddy(e4b);
}
--
2.31.1
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