dead/wrong code in ext3/4_releasepage()

Andrew Perepechko
2012-06-29T16:59:16Z

Hello!

The implementation of ext4_releasepage() for many kernel versions
(as well as current git) is the following:

static int ext4_releasepage(struct page *page, gfp_t wait)
{
journal_t *journal = EXT4_JOURNAL(page->mapping->host);

trace_ext4_releasepage(page);

WARN_ON(PageChecked(page));
if (!page_has_buffers(page))
return 0;
if (journal)
return jbd2_journal_try_to_free_buffers(journal, page,
wait);
else
return try_to_free_buffers(page);
}

The "if (!page_has_buffers(page))" check seems to be attempting to
handle the "nobh" case. However, the correct return value for this case
seems to be 1 (success), not 0 (failure).

This does not lead to oom or any similar issue since calls to
try_to_release_page()
are accompanied by page_has_private() checks.

If ->release_page() can be called without a prior check, then
the return code is wrong. Otherwise, the check is dead code.

What do you think?

Thank you,
Andrew