Re: [PATCH 1/2] Btrfs: add missing end_page_writeback on submit_extent_page failure

[Liu Bo <bo.li.liu@oracle.com>]

On Mon, Sep 22, 2014 at 05:41:04PM +0100, Filipe Manana wrote:
> If submit_extent_page() fails in write_one_eb(), we end up with the current
> page not marked dirty anymore, unlocked and marked for writeback. But we never
> end up calling end_page_writeback() against the page, which will make calls to
> filemap_fdatawait_range (e.g. at transaction commit time) hang forever waiting
> for the writeback bit to be cleared from the page.
> 
> Signed-off-by: Filipe Manana <fdmanana@suse.com>
> ---
>  fs/btrfs/extent_io.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index 3af4966..91f866c 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -3668,6 +3668,7 @@ static noinline_for_stack int write_one_eb(struct extent_buffer *eb,
>  		if (ret) {
>  			set_bit(EXTENT_BUFFER_IOERR, &eb->bflags);
>  			SetPageError(p);
> +			end_page_writeback(p);

This is not always true, and it depends on the place where we get error in
submit_extent_page(), whether it has built and submitted a bio, if it's true,
case can be different as bio_endio will be called, and calling end_page_writeback()
again will end up with panic.

thanks,
-liubo
 
>  			if (atomic_sub_and_test(num_pages - i, &eb->io_pages))
>  				end_extent_buffer_writeback(eb);
>  			ret = -EIO;
> -- 
> 1.9.1
> 
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