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ext4: fix ext4_writepage() to achieve data=ordered guarantees 

So far ext4_writepage() skipped writing pages that had any delayed or
unwritten buffers attached. When blocksize < pagesize this breaks
data=ordered mode guarantees as we can have a page with one freshly
allocated buffer whose allocation is part of the committing
transaction and another buffer in the page which is delayed or
unwritten. So fix this problem by calling ext4_bio_writepage()
anyway. It will submit mapped buffers and leave others alone.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Jan Kara 2013-01-28 21:06:42 -05:00 committed by Theodore Ts'o
parent 8a850c3fb8
commit fe386132f6
1 changed files with 18 additions and 12 deletions
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26
fs/ext4/inode.c
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@ -1976,22 +1976,28 @@ static int ext4_writepage(struct page *page,
len = PAGE_CACHE_SIZE;
page_bufs = page_buffers(page);
/*
* We cannot do block allocation or other extent handling in this
* function. If there are buffers needing that, we have to redirty
* the page. But we may reach here when we do a journal commit via
* journal_submit_inode_data_buffers() and in that case we must write
* allocated buffers to achieve data=ordered mode guarantees.
*/
if (ext4_walk_page_buffers(NULL, page_bufs, 0, len, NULL,
ext4_bh_delay_or_unwritten)) {
/*
* We don't want to do block allocation, so redirty
* the page and return. We may reach here when we do
* a journal commit via journal_submit_inode_data_buffers.
* We can also reach here via shrink_page_list but it
* should never be for direct reclaim so warn if that
* happens
*/
WARN_ON_ONCE((current->flags & (PF_MEMALLOC|PF_KSWAPD)) ==
PF_MEMALLOC);
redirty_page_for_writepage(wbc, page);
if (current->flags & PF_MEMALLOC) {
/*
* For memory cleaning there's no point in writing only
* some buffers. So just bail out. Warn if we came here
* from direct reclaim.
*/
WARN_ON_ONCE((current->flags & (PF_MEMALLOC|PF_KSWAPD))
== PF_MEMALLOC);
unlock_page(page);
return 0;
}
}
if (PageChecked(page) && ext4_should_journal_data(inode))
/*