From 11f81becca04bb7d2826a9b65bb8d27b0a1bb543 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Fri, 22 May 2015 17:13:15 -0400 Subject: [PATCH] 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 Cc: Konstantin Khlebnikov Signed-off-by: Jens Axboe --- .../include/linux/lustre_patchless_compat.h | 4 +-- fs/buffer.c | 4 +-- include/linux/mm.h | 1 + mm/page-writeback.c | 27 ++++++++++++++----- mm/truncate.c | 4 +-- 5 files changed, 25 insertions(+), 15 deletions(-) diff --git a/drivers/staging/lustre/lustre/include/linux/lustre_patchless_compat.h b/drivers/staging/lustre/lustre/include/linux/lustre_patchless_compat.h index d72605864b0a..14562788e4e0 100644 --- a/drivers/staging/lustre/lustre/include/linux/lustre_patchless_compat.h +++ b/drivers/staging/lustre/lustre/include/linux/lustre_patchless_compat.h @@ -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); } diff --git a/fs/buffer.c b/fs/buffer.c index f96173ad62d9..f21327d1f673 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -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) { diff --git a/include/linux/mm.h b/include/linux/mm.h index 0755b9fd03a7..a83cf3a6f78e 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -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); 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 @@ -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. 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;