* Re: Why page w/o buffers can not be released?
[not found] <871uig906i.fsf@openvz.org>
@ 2012-09-05 12:28 ` Jan Kara
0 siblings, 0 replies; only message in thread
From: Jan Kara @ 2012-09-05 12:28 UTC (permalink / raw)
To: Dmitry Monakhov; +Cc: linux-ext4, linux-fsdevel, jack
On Wed 05-09-12 15:30:29, Dmitry Monakhov wrote:
>
> ext3, ext4 and ocfs2 do not allow to release page w/o buffers.
> Can some one please explain me why?
>
> ext4_releasepage(struct page *page, gfp_t wait)
> {
> if (!page_has_buffers(page))
> return 0;
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^( zero means fail to release)
> if (journal)
> return jbd2_journal_try_to_free_buffers(journal, page, wait);
> else
> return try_to_free_buffers(page);
> }
>
> This is looks very strange because if page has not buffers then
> it has no fs-specific data associated with it. Am I right?
> IMHO code should looks like follows:
> xxx_releasepage() {
>
> if(PageWriteback(page))
> return 0;
> if (!page_has_buffers(page))
> return 1;
>
> return do_fs_specific_stuff()
> }
Yeah, I agree. Although this is mostly a harmless thing because all call
sites test for page_has_private(page) before calling try_to_release_page(page)
so !page_has_buffers(page) is impossible. But a cleanup (remove the test) would
be nice.
Also PageWriteback() is checked in try_to_release_page() so filesystems
don't have to care...
Honza
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR
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