On 03/03/2011 06:01 PM, Lukas Czerner wrote:
On Thu, 3 Mar 2011, Tao Ma wrote:
From: Tao Ma<boyu.mt@xxxxxxxxxx>
In a bs=4096 volume, if we call FITRIM with the following parameter as
fstrim_range(start = 102400, len = 134144000, minlen = 10240),
we will trigger a BUG_ON.
BUG_ON(start + len> (e4b->bd_sb->s_blocksize<< 3));
Mar 4 00:55:52 boyu-tm kernel: ------------[ cut here ]------------
Mar 4 00:55:52 boyu-tm kernel: kernel BUG at fs/ext4/mballoc.c:1506!
Mar 4 01:21:09 boyu-tm kernel: Code: d4 00 00 00 00 49 89 fe 8b 56 0c 44 8b 7e 04 89 55 c4 48 8b 4f 28 89 d6 44 01 fe 48 63 d6 48 8b 41 18 48 c1 e0 03 48 39 c2 76 04<0f> 0b eb fe 48 8b 55 b0 8b 47 34 3b 42 08 74 04 0f 0b eb fe 48
Mar 4 01:21:09 boyu-tm kernel: RIP [<ffffffffa053eb42>] mb_mark_used+0x47/0x26c [ext4]
Mar 4 01:21:09 boyu-tm kernel: RSP<ffff880121e45c38>
Mar 4 01:21:09 boyu-tm kernel: ---[ end trace 9f461696f6a9dcf2 ]---
The reason is that in ext4_trim_fs, the last_block is checked wrongly.
if (len>= EXT4_BLOCKS_PER_GROUP(sb))
len -= (EXT4_BLOCKS_PER_GROUP(sb) - first_block);
else
last_block = first_block + len;
So if len< EXT4_BLOCKS_PER_GROUP while first_block + len> EXT4_BLOCKS_PER_GROUP,
last_block will be set to a overflow value which exceeds EXT4_BLOCKS_PER_GROUP.
This patch fixes it and adjusts len accordingly.
Oh, thanks for spotting this. One comment though.
Cc: "Theodore Ts'o"<tytso@xxxxxxx>
Signed-off-by: Tao Ma<boyu.mt@xxxxxxxxxx>
---
fs/ext4/mballoc.c | 5 +++--
1 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 29d7d17..ed63c3e 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4889,10 +4889,11 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range)
break;
}
- if (len>= EXT4_BLOCKS_PER_GROUP(sb))
- len -= (EXT4_BLOCKS_PER_GROUP(sb) - first_block);
+ if (first_block + len>= EXT4_BLOCKS_PER_GROUP(sb))
+ last_block = EXT4_BLOCKS_PER_GROUP(sb);
else
last_block = first_block + len;
Since last_block would not change until the last group, can we simplify
the condition ?
if (first_block + len< EXT4_BLOCKS_PER_GROUP(sb))
last_block = first_block + len;
yes, it should work. But it is a bit tricky. And I guess we need a
comment here
to describe the situation. Otherwise, the people who read the code would
consider
why last_block won't be reset in case first _block + len >=
EXT4_BLOCKS_PER_GROUP
every time. Agree?
+ len -= last_block - first_block;
if (e4b.bd_info->bb_free>= minlen) {
cnt = ext4_trim_all_free(sb,&e4b, first_block,
Thanks!
-Lukas
Regards,
Tao
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