Re: [PATCH] drop_buffers() shouldn't de-ref page->mapping if its NULL

[OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>]

Badari Pulavarty <pbadari@us.ibm.com> writes:

> Hi,
>
> I answered my own question. It looks like we could have pages
> with buffers without page->mapping. In such cases, we shouldn't
> de-ref page->mapping in drop_buffers(). Here is the trivial
> patch to fix it.
>
> Thanks,
> Badari

[...]

>
> Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com>
> --- linux-2.6.12-rc2.org/fs/buffer.c	2005-04-27 07:19:44.000000000 -0700
> +++ linux-2.6.12-rc2/fs/buffer.c	2005-04-27 07:20:34.000000000 -0700
> @@ -2917,7 +2917,7 @@ drop_buffers(struct page *page, struct b
>  
>  	bh = head;
>  	do {
> -		if (buffer_write_io_error(bh))
> +		if (buffer_write_io_error(bh) && page->mapping)
>  			set_bit(AS_EIO, &page->mapping->flags);
>  		if (buffer_busy(bh))
>  			goto failed;

On my experience, this happened the bh leak case only.

If you are not sure whether this is valid state or not, I worry this
patch hides real bug.  How about adding the warning, not just remove
de-ref?

Thanks.
-- 
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
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