Commit 11f81bec authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
Browse files

page_writeback: revive cancel_dirty_page() in a restricted form

cancel_dirty_page() had some issues and b9ea2515

 ("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: default avatarTejun Heo <tj@kernel.org>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent f26cdc85
......@@ -55,9 +55,7 @@ truncate_complete_page(struct address_space *mapping, struct page *page)
if (PagePrivate(page))
page->mapping->a_ops->invalidatepage(page, 0, PAGE_CACHE_SIZE);
if (TestClearPageDirty(page))
account_page_cleaned(page, mapping);
cancel_dirty_page(page);
ClearPageMappedToDisk(page);
ll_delete_from_page_cache(page);
}
......
......@@ -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) {
......
......@@ -1215,6 +1215,7 @@ void account_page_dirtied(struct page *page, struct address_space *mapping);
void account_page_cleaned(struct page *page, struct address_space *mapping);
int set_page_dirty(struct page *page);
int set_page_dirty_lock(struct page *page);
void cancel_dirty_page(struct page *page);
int clear_page_dirty_for_io(struct page *page);
int get_cmdline(struct task_struct *task, char *buffer, int buflen);
......
......@@ -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
......@@ -2265,6 +2258,26 @@ 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.
......
......@@ -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;
......
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