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| author | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-01-26 12:47:06 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-01-26 12:47:06 -0800 |
| commit | ecdfc9787fe527491baefc22dce8b2dbd5b2908d (patch) | |
| tree | 31e7ddac0339498095c40444f81c0b03751434ae /mm | |
| parent | 5ad0d383ddbf0d2fce43b8aac267a6c299fd2dff (diff) | |
| download | linux-stable-ecdfc9787fe527491baefc22dce8b2dbd5b2908d.tar.gz linux-stable-ecdfc9787fe527491baefc22dce8b2dbd5b2908d.tar.bz2 linux-stable-ecdfc9787fe527491baefc22dce8b2dbd5b2908d.zip | |
Resurrect 'try_to_free_buffers()' VM hackery
It's not pretty, but it appears that ext3 with data=journal will clean
pages without ever actually telling the VM that they are clean. This,
in turn, will result in the VM (and balance_dirty_pages() in particular)
to never realize that the pages got cleaned, and wait forever for an
event that already happened.
Technically, this seems to be a problem with ext3 itself, but it used to
be hidden by 'try_to_free_buffers()' noticing this situation on its own,
and just working around the filesystem problem.
This commit re-instates that hack, in order to avoid a regression for
the 2.6.20 release. This fixes bugzilla 7844:
http://bugzilla.kernel.org/show_bug.cgi?id=7844
Peter Zijlstra points out that we should probably retain the debugging
code that this removes from cancel_dirty_page(), and I agree, but for
the imminent release we might as well just silence the warning too
(since it's not a new bug: anything that triggers that warning has been
around forever).
Acked-by: Randy Dunlap <rdunlap@xenotime.net>
Acked-by: Jens Axboe <jens.axboe@oracle.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/truncate.c | 21 |
1 files changed, 14 insertions, 7 deletions
diff --git a/mm/truncate.c b/mm/truncate.c index 6c79ca4a1ca7..3262740aa059 100644 --- a/mm/truncate.c +++ b/mm/truncate.c @@ -51,15 +51,22 @@ static inline void truncate_partial_page(struct page *page, unsigned partial) do_invalidatepage(page, partial); } +/* + * This cancels just the dirty bit on the kernel page itself, it + * does NOT actually remove dirty bits on any mmap's that may be + * around. It also leaves the page tagged dirty, so any sync + * activity will still find it on the dirty lists, and in particular, + * clear_page_dirty_for_io() will still look at the dirty bits in + * the VM. + * + * Doing this should *normally* only ever be done when a page + * is truncated, and is not actually mapped anywhere at all. However, + * fs/buffer.c does this when it notices that somebody has cleaned + * out all the buffers on a page without actually doing it through + * the VM. Can you say "ext3 is horribly ugly"? Tought you could. + */ void cancel_dirty_page(struct page *page, unsigned int account_size) { - /* If we're cancelling the page, it had better not be mapped any more */ - if (page_mapped(page)) { - static unsigned int warncount; - - WARN_ON(++warncount < 5); - } - if (TestClearPageDirty(page)) { struct address_space *mapping = page->mapping; if (mapping && mapping_cap_account_dirty(mapping)) { |