2011-03-11 14:39:01

by Jens Axboe

Subject: [GIT PULL] Single important block patch for 2.6.38

Hi Linus,

This fixes a regression introduced early in the 2.6.38 series, where
blkdev_issue_zeroout() has a nasty race that causes a panic. Thanks to
Lukas Czerner for finding and fixing this one. Please pull!

git://git.kernel.dk/linux-2.6-block.git for-linus

Lukas Czerner (1):
block: fix mis-synchronisation in blkdev_issue_zeroout()

block/blk-lib.c | 19 +++++++------------
1 files changed, 7 insertions(+), 12 deletions(-)

diff --git a/block/blk-lib.c b/block/blk-lib.c
index eec78be..bd3e8df 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -109,7 +109,6 @@ struct bio_batch
atomic_t done;
unsigned long flags;
struct completion *wait;
- bio_end_io_t *end_io;
};

static void bio_batch_end_io(struct bio *bio, int err)
@@ -122,12 +121,9 @@ static void bio_batch_end_io(struct bio *bio, int err)
else
clear_bit(BIO_UPTODATE, &bb->flags);
}
- if (bb) {
- if (bb->end_io)
- bb->end_io(bio, err);
- atomic_inc(&bb->done);
- complete(bb->wait);
- }
+ if (bb)
+ if (atomic_dec_and_test(&bb->done))
+ complete(bb->wait);
bio_put(bio);
}

@@ -150,13 +146,12 @@ int blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
int ret;
struct bio *bio;
struct bio_batch bb;
- unsigned int sz, issued = 0;
+ unsigned int sz;
DECLARE_COMPLETION_ONSTACK(wait);

- atomic_set(&bb.done, 0);
+ atomic_set(&bb.done, 1);
bb.flags = 1 << BIO_UPTODATE;
bb.wait = &wait;
- bb.end_io = NULL;

submit:
ret = 0;
@@ -185,12 +180,12 @@ submit:
break;
}
ret = 0;
- issued++;
+ atomic_inc(&bb.done);
submit_bio(WRITE, bio);
}

/* Wait for bios in-flight */
- while (issued != atomic_read(&bb.done))
+ if (!atomic_dec_and_test(&bb.done))
wait_for_completion(&wait);

if (!test_bit(BIO_UPTODATE, &bb.flags))

--
Jens Axboe

2011-03-13 22:52:48

by Linus Torvalds

Subject: Re: [GIT PULL] Single important block patch for 2.6.38

On Fri, Mar 11, 2011 at 6:38 AM, Jens Axboe <[email protected]> wrote:
>
> This fixes a regression introduced early in the 2.6.38 series, where
> blkdev_issue_zeroout() has a nasty race that causes a panic. Thanks to
> Lukas Czerner for finding and fixing this one. Please pull!

What about the "Null pointer OOPS in sync_inodes_sb" issue due to the
broken sb->s_bdi setting to NULL?

Linus

2011-03-14 08:20:08

by Jens Axboe

Subject: Re: [GIT PULL] Single important block patch for 2.6.38

On 2011-03-13 23:51, Linus Torvalds wrote:
> On Fri, Mar 11, 2011 at 6:38 AM, Jens Axboe <[email protected]> wrote:
>>
>> This fixes a regression introduced early in the 2.6.38 series, where
>> blkdev_issue_zeroout() has a nasty race that causes a panic. Thanks to
>> Lukas Czerner for finding and fixing this one. Please pull!
>
> What about the "Null pointer OOPS in sync_inodes_sb" issue due to the
> broken sb->s_bdi setting to NULL?

Sent something out to George to test, hopefully we can close this one
for 2.6.38 in a simple fashion.

--
Jens Axboe