diff options
author | Tejun Heo <tj@kernel.org> | 2015-05-23 00:13:15 +0300 |
---|---|---|
committer | Jens Axboe <axboe@fb.com> | 2015-06-02 17:33:33 +0300 |
commit | 11f81becca04bb7d2826a9b65bb8d27b0a1bb543 (patch) | |
tree | 9f0fd3269c54f6e6bc63cb8d9d7db5976f1a4576 /mm | |
parent | f26cdc8536ad50fb802a0445f836b4f94ca09ae7 (diff) | |
download | linux-11f81becca04bb7d2826a9b65bb8d27b0a1bb543.tar.xz |
page_writeback: revive cancel_dirty_page() in a restricted form
cancel_dirty_page() had some issues and b9ea25152e56 ("page_writeback:
clean up mess around cancel_dirty_page()") replaced it with
account_page_cleaned() which makes the caller responsible for clearing
the dirty bit; unfortunately, the planned changes for cgroup writeback
support requires synchronization between dirty bit manipulation and
stat updates. While we can open-code such synchronization in each
account_page_cleaned() callsite, that's gonna be unnecessarily awkward
and verbose.
This patch revives cancel_dirty_page() but in a more restricted form.
All it does is TestClearPageDirty() followed by account_page_cleaned()
invocation if the page was dirty. This helper covers all
account_page_cleaned() usages except for __delete_from_page_cache()
which is a special case anyway and left alone. As this leaves no
module user for account_page_cleaned(), EXPORT_SYMBOL() is dropped
from it.
This patch just revives cancel_dirty_page() as a trivial wrapper to
replace equivalent usages and doesn't introduce any functional
changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'mm')
-rw-r--r-- | mm/page-writeback.c | 27 | ||||
-rw-r--r-- | mm/truncate.c | 4 |
2 files changed, 21 insertions, 10 deletions
diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 5daf5568b9e1..227b867598e1 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -2112,12 +2112,6 @@ EXPORT_SYMBOL(account_page_dirtied); /* * Helper function for deaccounting dirty page without writeback. - * - * 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"? Thought you could. */ void account_page_cleaned(struct page *page, struct address_space *mapping) { @@ -2127,7 +2121,6 @@ void account_page_cleaned(struct page *page, struct address_space *mapping) task_io_account_cancelled_write(PAGE_CACHE_SIZE); } } -EXPORT_SYMBOL(account_page_cleaned); /* * For address_spaces which do not use buffers. Just tag the page as dirty in @@ -2266,6 +2259,26 @@ int set_page_dirty_lock(struct page *page) EXPORT_SYMBOL(set_page_dirty_lock); /* + * 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"? Thought you could. + */ +void cancel_dirty_page(struct page *page) +{ + if (TestClearPageDirty(page)) + account_page_cleaned(page, page_mapping(page)); +} +EXPORT_SYMBOL(cancel_dirty_page); + +/* * Clear a page's dirty flag, while caring for dirty memory accounting. * Returns true if the page was previously dirty. * diff --git a/mm/truncate.c b/mm/truncate.c index 66af9031fae8..0c360259c085 100644 --- a/mm/truncate.c +++ b/mm/truncate.c @@ -116,9 +116,7 @@ truncate_complete_page(struct address_space *mapping, struct page *page) * the VM has canceled the dirty bit (eg ext3 journaling). * Hence dirty accounting check is placed after invalidation. */ - if (TestClearPageDirty(page)) - account_page_cleaned(page, mapping); - + cancel_dirty_page(page); ClearPageMappedToDisk(page); delete_from_page_cache(page); return 0; |