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authorWu Fengguang <fengguang.wu@intel.com>2009-09-16 11:50:14 +0200
committerAndi Kleen <ak@linux.intel.com>2009-09-16 11:50:14 +0200
commit6746aff74da293b5fd24e5c68b870b721e86cd5f (patch)
tree6d2b9e99d247e788c13665ce5e8a0753538ef641 /mm/page-writeback.c
parent257187362123f15d9d1e09918cf87cebbea4e786 (diff)
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HWPOISON: shmem: call set_page_dirty() with locked page
The dirtying of page and set_page_dirty() can be moved into the page lock. - In shmem_write_end(), the page was dirtied while the page lock was held, but it's being marked dirty just after dropping the page lock. - In shmem_symlink(), both dirtying and marking can be moved into page lock. It's valuable for the hwpoison code to know whether one bad page can be dropped without losing data. It mainly judges by testing the PG_dirty bit after taking the page lock. So it becomes important that the dirtying of page and the marking of dirtiness are both done inside the page lock. Which is a common practice, but sadly not a rule. The noticeable exceptions are - mapped pages - pages with buffer_heads The above pages could go dirty at any time. Fortunately the hwpoison will unmap the page and release the buffer_heads beforehand anyway. Many other types of pages (eg. metadata pages) can also be dirtied at will by their owners, the hwpoison code cannot do meaningful things to them anyway. Only the dirtiness of pagecache pages owned by regular files are interested. v2: AK: Add comment about set_page_dirty rules (suggested by Peter Zijlstra) Acked-by: Hugh Dickins <hugh.dickins@tiscali.co.uk> Reviewed-by: WANG Cong <xiyou.wangcong@gmail.com> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com> Signed-off-by: Andi Kleen <ak@linux.intel.com>
Diffstat (limited to 'mm/page-writeback.c')
-rw-r--r--mm/page-writeback.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index dd73d29c15a8..bba82c414ba8 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1149,6 +1149,13 @@ int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page)
EXPORT_SYMBOL(redirty_page_for_writepage);
/*
+ * Dirty a page.
+ *
+ * For pages with a mapping this should be done under the page lock
+ * for the benefit of asynchronous memory errors who prefer a consistent
+ * dirty state. This rule can be broken in some special cases,
+ * but should be better not to.
+ *
* If the mapping doesn't provide a set_page_dirty a_op, then
* just fall through and assume that it wants buffer_heads.
*/