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SubjectRe: Kernel 3.3.8 breaks accidental ext3 mount of extended partition
Date
"Richard W.M. Jones" <rjones@redhat.com> writes:

> On Mon, Jun 18, 2012 at 07:59:30AM +0200, Torsten Hilbrich wrote:
>> Hello,
>>
>> a software that tries to mount each existing partition as ext3 file system started to fail when updating from v3.3.7 to v3.3.8.
>>
>> The applications then hangs-up in the mount syscall, here is a snapshot of its stack at this moment:
>
> We just ran into what we think is the same problem.
>
> Note that ext4 fails like this for any 1024 byte sized filesystem (of
> zeroes) that you try to mount. It's really nothing to do with
> extended partitions.
>
> Here is a very simple reproducer + stack trace:
>
> https://bugzilla.redhat.com/show_bug.cgi?id=835019#c4
>
> I will try out the patch suggested later on in this thread.

Please try the attached patch instead. The patch I had originally
posted for this allowed marking the first buffer beyond EOD as
uptodate. This isn't correct. The patch I've attached below fixes the
infinite loop in __getblk_slow.

Cheers,
Jeff

diff --git a/fs/buffer.c b/fs/buffer.c
index 838a9cf..c7062c8 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1036,6 +1036,9 @@ grow_buffers(struct block_device *bdev, sector_t block, int size)
static struct buffer_head *
__getblk_slow(struct block_device *bdev, sector_t block, int size)
{
+ int ret;
+ struct buffer_head *bh;
+
/* Size must be multiple of hard sectorsize */
if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
(size < 512 || size > PAGE_SIZE))) {
@@ -1048,20 +1051,21 @@ __getblk_slow(struct block_device *bdev, sector_t block, int size)
return NULL;
}

- for (;;) {
- struct buffer_head * bh;
- int ret;
+retry:
+ bh = __find_get_block(bdev, block, size);
+ if (bh)
+ return bh;

+ ret = grow_buffers(bdev, block, size);
+ if (ret == 0) {
+ free_more_memory();
+ goto retry;
+ } else if (ret > 0) {
bh = __find_get_block(bdev, block, size);
if (bh)
return bh;
-
- ret = grow_buffers(bdev, block, size);
- if (ret < 0)
- return NULL;
- if (ret == 0)
- free_more_memory();
}
+ return NULL;
}

/*

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