diff options
authorMartin Schwidefsky <schwidefsky@de.ibm.com>2007-05-04 21:22:10 +0200
committerChris Wright <chrisw@sous-sol.org>2007-06-11 11:37:10 -0700
commitd65453861b813cf20003c8588883703f477809b1 (patch)
parent915db94028ed4c8e3b11c79991a07cacd8437850 (diff)
[PATCH] s390: page_mkclean data corruption.
The git commit c2fda5fed81eea077363b285b66eafce20dfd45a which added the page_test_and_clear_dirty call to page_mkclean and the git commit 7658cc289288b8ae7dd2c2224549a048431222b3 which fixes the "nasty and subtle race in shared mmap'ed page writeback" problem in clear_page_dirty_for_io cause data corruption on s390. The effect of the two changes is that for every call to clear_page_dirty_for_io a page_test_and_clear_dirty is done. If the per page dirty bit is set set_page_dirty is called. Strangly clear_page_dirty_for_io is called for not-uptodate pages, e.g. over this call-chain: [<000000000007c0f2>] clear_page_dirty_for_io+0x12a/0x130 [<000000000007c494>] generic_writepages+0x258/0x3e0 [<000000000007c692>] do_writepages+0x76/0x7c [<00000000000c7a26>] __writeback_single_inode+0xba/0x3e4 [<00000000000c831a>] sync_sb_inodes+0x23e/0x398 [<00000000000c8802>] writeback_inodes+0x12e/0x140 [<000000000007b9ee>] wb_kupdate+0xd2/0x178 [<000000000007cca2>] pdflush+0x162/0x23c The bad news now is that page_test_and_clear_dirty might claim that a not-uptodate page is dirty since SetPageUptodate which resets the per page dirty bit has not yet been called. The page writeback that follows clobbers the data on disk. The simplest solution to this problem is to move the call to page_test_and_clear_dirty under the "if (page_mapped(page))". If a file backed page is mapped it is uptodate. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> Signed-off-by: Chris Wright <chrisw@sous-sol.org>
1 files changed, 2 insertions, 2 deletions
diff --git a/mm/rmap.c b/mm/rmap.c
index 669acb22b572..7ce69c100143 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -490,9 +490,9 @@ int page_mkclean(struct page *page)
struct address_space *mapping = page_mapping(page);
if (mapping)
ret = page_mkclean_file(mapping, page);
+ if (page_test_and_clear_dirty(page))
+ ret = 1;
- if (page_test_and_clear_dirty(page))
- ret = 1;
return ret;