Ted Ts'o wrote:
> On Thu, Oct 28, 2010 at 02:01:18PM -0400, Ted Ts'o wrote:
>> On Thu, Oct 28, 2010 at 07:52:21PM +0200, Markus Trippelsdorf wrote:
>>> The same BUG (inode.c:2721) happend here today running latest vanilla
>>> git. There is nothing in my logs unfortunately, but I shot a photo of
>>> the trace (see attachment).
>> I see, it's the page_buffers() call which is triggering. Looking into
>> it...
>
> Can folks let me know if this fixes the problem?
Ted, any idea what caused the change in behavior here?
-Eric
> In this case I haven't been able to replicate the problem, but I've
> eyeballed the problem and I'm about 90% certain this should fix
> things. But I don't want to push this to Linus until I get
> confirmation from you all that it fixes things. That's just one of
> the ways in which your testing is critically important for ext4, so
> thanks again for your help in the past, present, and future.
> Thanks!!
>
> - Ted
>
> commit 51279fcb9720aa856ad81673886ca2349a373dac
> Author: Theodore Ts'o <tytso@xxxxxxx>
> Date: Thu Oct 28 15:15:21 2010 -0400
>
> ext4: BUG_ON fix: check if page has buffers before calling page_buffers()
>
> We need to make check if a page does not have buffes by checking
> page_has_buffers(page) before calling page_buffers(page) in
> ext4_writepage(). Otherwise page_buffers() could throw a BUG_ON.
>
> Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 2d6c6c8..1916164 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -2718,7 +2718,7 @@ static int ext4_writepage(struct page *page,
> * try to create them using __block_write_begin. If this
> * fails, redirty the page and move on.
> */
> - if (!page_buffers(page)) {
> + if (!page_has_buffers(page)) {
> if (__block_write_begin(page, 0, len,
> noalloc_get_block_write)) {
> redirty_page:
> @@ -2732,12 +2732,10 @@ static int ext4_writepage(struct page *page,
> if (walk_page_buffers(NULL, page_bufs, 0, len, NULL,
> ext4_bh_delay_or_unwritten)) {
> /*
> - * We don't want to do block allocation So redirty the
> - * page and return We may reach here when we do a
> - * journal commit via
> - * journal_submit_inode_data_buffers. If we don't
> - * have mapping block we just ignore them. We can also
> - * reach here via shrink_page_list
> + * We don't want to do block allocation, so redirty
> + * the page and return. We may reach here when we do
> + * a journal commit via journal_submit_inode_data_buffers.
> + * We can also reach here via shrink_page_list
> */
> goto redirty_page;
> }
> --
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