Linux Kernel Mailing List wrote: > Gitweb: > http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=6e1beb3c22496f6e1f1feba8ae74da16f131684c > Commit: 6e1beb3c22496f6e1f1feba8ae74da16f131684c > Parent: 348e3fd19487534d9d4dd70c3ad0b751afd35792 > Author: Martin Schwidefsky <[EMAIL PROTECTED]> > AuthorDate: Wed Apr 4 14:37:10 2007 +0200 > Committer: Martin Schwidefsky <[EMAIL PROTECTED]> > CommitDate: Wed Apr 4 14:37:39 2007 +0200 > > [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 <[EMAIL PROTECTED]> > --- > mm/rmap.c | 4 ++-- > 1 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/rmap.c b/mm/rmap.c > index 22ed3f7..b82146e 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -498,9 +498,9 @@ 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; > }
This changes generic mm code. Is S390 really the only affected architecture? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
