On Tue, Sep 23, 2014 at 11:14 AM, Liu Bo <bo.li....@oracle.com> wrote:
> 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 <fdman...@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.
No, it's always true when the caller is write_one_eb(). If
submit_extent_page() returns an error, we're sure that the page wasn't
added to a bio, because bio_ret is always not NULL (but *bio_ret can
be). Also, if we call submit_one_bio() in submit_extent_page() (first
if statement) , we know that the bio doesn't contain the page.
thanks
>
> 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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--
Filipe David Manana,
"Reasonable men adapt themselves to the world.
Unreasonable men adapt the world to themselves.
That's why all progress depends on unreasonable men."
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