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| author | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-01-26 23:47:06 +0300 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-01-26 23:47:06 +0300 |
| commit | ecdfc9787fe527491baefc22dce8b2dbd5b2908d (patch) | |
| tree | 31e7ddac0339498095c40444f81c0b03751434ae /fs | |
| parent | 5ad0d383ddbf0d2fce43b8aac267a6c299fd2dff (diff) | |
| download | linux-ecdfc9787fe527491baefc22dce8b2dbd5b2908d.tar.xz | |
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 'fs')
| -rw-r--r-- | fs/buffer.c | 15 |
1 files changed, 14 insertions, 1 deletions
diff --git a/fs/buffer.c b/fs/buffer.c index 3b116078b4c3..460f1c43238e 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -2834,7 +2834,7 @@ int try_to_free_buffers(struct page *page) int ret = 0; BUG_ON(!PageLocked(page)); - if (PageDirty(page) || PageWriteback(page)) + if (PageWriteback(page)) return 0; if (mapping == NULL) { /* can this still happen? */ @@ -2845,6 +2845,19 @@ int try_to_free_buffers(struct page *page) spin_lock(&mapping->private_lock); ret = drop_buffers(page, &buffers_to_free); spin_unlock(&mapping->private_lock); + + /* + * If the filesystem writes its buffers by hand (eg ext3) + * then we can have clean buffers against a dirty page. We + * clean the page here; otherwise the VM will never notice + * that the filesystem did any IO at all. + * + * Also, during truncate, discard_buffer will have marked all + * the page's buffers clean. We discover that here and clean + * the page also. + */ + if (ret) + cancel_dirty_page(page, PAGE_CACHE_SIZE); out: if (buffers_to_free) { struct buffer_head *bh = buffers_to_free; |