diff options
| author | Wu Fengguang <fengguang.wu@intel.com> | 2011-08-08 15:22:00 -0600 |
|---|---|---|
| committer | Wu Fengguang <fengguang.wu@intel.com> | 2011-12-18 14:20:23 +0800 |
| commit | 2f800fbd777b792de54187088df19a7df0251254 (patch) | |
| tree | 2dc813b41da42d647468dafcf49a0b9e673df8b5 | |
| parent | d3bc1fef9389e409a772ea174a5e41a6f93d9b7b (diff) | |
writeback: fix dirtied pages accounting on redirty
De-account the accumulative dirty counters on page redirty.
Page redirties (very common in ext4) will introduce mismatch between
counters (a) and (b)
a) NR_DIRTIED, BDI_DIRTIED, tsk->nr_dirtied
b) NR_WRITTEN, BDI_WRITTEN
This will introduce systematic errors in balanced_rate and result in
dirty page position errors (ie. the dirty pages are no longer balanced
around the global/bdi setpoints).
Acked-by: Jan Kara <jack@suse.cz>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
| -rw-r--r-- | include/linux/writeback.h | 2 | ||||
| -rw-r--r-- | mm/page-writeback.c | 19 |
2 files changed, 21 insertions, 0 deletions
diff --git a/include/linux/writeback.h b/include/linux/writeback.h index 05eaf5e3aad..b30419cd425 100644 --- a/include/linux/writeback.h +++ b/include/linux/writeback.h @@ -197,6 +197,8 @@ void writeback_set_ratelimit(void); void tag_pages_for_writeback(struct address_space *mapping, pgoff_t start, pgoff_t end); +void account_page_redirty(struct page *page); + /* pdflush.c */ extern int nr_pdflush_threads; /* Global so it can be exported to sysctl read-only. */ diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 5d1ef5d8613..96b3e7aa705 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -1825,6 +1825,24 @@ int __set_page_dirty_nobuffers(struct page *page) EXPORT_SYMBOL(__set_page_dirty_nobuffers); /* + * Call this whenever redirtying a page, to de-account the dirty counters + * (NR_DIRTIED, BDI_DIRTIED, tsk->nr_dirtied), so that they match the written + * counters (NR_WRITTEN, BDI_WRITTEN) in long term. The mismatches will lead to + * systematic errors in balanced_dirty_ratelimit and the dirty pages position + * control. + */ +void account_page_redirty(struct page *page) +{ + struct address_space *mapping = page->mapping; + if (mapping && mapping_cap_account_dirty(mapping)) { + current->nr_dirtied--; + dec_zone_page_state(page, NR_DIRTIED); + dec_bdi_stat(mapping->backing_dev_info, BDI_DIRTIED); + } +} +EXPORT_SYMBOL(account_page_redirty); + +/* * When a writepage implementation decides that it doesn't want to write this * page for some reason, it should redirty the locked page via * redirty_page_for_writepage() and it should then unlock the page and return 0 @@ -1832,6 +1850,7 @@ EXPORT_SYMBOL(__set_page_dirty_nobuffers); int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page) { wbc->pages_skipped++; + account_page_redirty(page); return __set_page_dirty_nobuffers(page); } EXPORT_SYMBOL(redirty_page_for_writepage); |