diff options
| author | Wu Fengguang <fengguang.wu@intel.com> | 2011-08-08 15:22:00 -0600 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2013-04-25 20:25:43 +0100 |
| commit | 40e5c2b17933a25380494548391126affae73c58 (patch) | |
| tree | 7dfb82319c4b1955d3b74b09fdd9050f193420cd /mm | |
| parent | 2f0500f50b8ee7b33407d74f00f5f17ac1d1473e (diff) | |
writeback: fix dirtied pages accounting on redirty
commit 2f800fbd777b792de54187088df19a7df0251254 upstream.
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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/page-writeback.c | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 50f08241f98..ea3f83b2119 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -1801,6 +1801,24 @@ 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 @@ -1808,6 +1826,7 @@ 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); |