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page_writeback: revive cancel_dirty_page() in a restricted form

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cancel_dirty_page() had some issues and b9ea25152e ("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>
This commit is contained in:
Tejun Heo 2015-05-22 17:13:15 -04:00 • committed by Jens Axboe
parent f26cdc8536
commit 11f81becca
5 changed files with 25 additions and 15 deletions
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4
fs/buffer.c
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@ -3232,8 +3232,8 @@ int try_to_free_buffers(struct page *page)
* to synchronise against __set_page_dirty_buffers and prevent the
* dirty bit from being lost.
*/
if (ret && TestClearPageDirty(page))
account_page_cleaned(page, mapping);
if (ret)
cancel_dirty_page(page);
spin_unlock(&mapping->private_lock);
out:
if (buffers_to_free) {