Messages in this thread | | | Date | Tue, 19 Dec 2006 18:59:43 +1100 | From | Nick Piggin <> | Subject | Re: 2.6.19 file content corruption on ext3 |
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Peter Zijlstra wrote: > On Tue, 2006-12-19 at 15:36 +1100, Nick Piggin wrote: > > >>plain text document attachment (fs-fix.patch) >>Index: linux-2.6/fs/buffer.c >>=================================================================== >>--- linux-2.6.orig/fs/buffer.c 2006-12-19 15:15:46.000000000 +1100 >>+++ linux-2.6/fs/buffer.c 2006-12-19 15:36:01.000000000 +1100 >>@@ -2852,7 +2852,17 @@ int try_to_free_buffers(struct page *pag >> * This only applies in the rare case where try_to_free_buffers >> * succeeds but the page is not freed. >> */ >>- clear_page_dirty(page); >>+ >>+ /* >>+ * If the page has been dirtied via the user mappings, then >>+ * clean buffers does not indicate the page data is actually >>+ * clean! Only clear the page dirty bit if there are no dirty >>+ * ptes either. >>+ * >>+ * If there are dirty ptes, then the page must be uptodate, so >>+ * the above concern does not apply. >>+ */ >>+ clear_page_dirty_sync_ptes(page); >> } >> out: >> if (buffers_to_free) { >>Index: linux-2.6/include/linux/page-flags.h >>=================================================================== >>--- linux-2.6.orig/include/linux/page-flags.h 2006-12-19 15:17:18.000000000 +1100 >>+++ linux-2.6/include/linux/page-flags.h 2006-12-19 15:34:24.000000000 +1100 >>@@ -254,6 +254,7 @@ static inline void SetPageUptodate(struc >> struct page; /* forward declaration */ >> >> int test_clear_page_dirty(struct page *page); >>+int test_clear_page_dirty_sync_ptes(struct page *page); >> int test_clear_page_writeback(struct page *page); >> int test_set_page_writeback(struct page *page); >> >>@@ -262,6 +263,11 @@ static inline void clear_page_dirty(stru >> test_clear_page_dirty(page); >> } >> >>+static inline void clear_page_dirty_sync_ptes(struct page *page) >>+{ >>+ test_clear_page_dirty_sync_ptes(page); >>+} >>+ >> static inline void set_page_writeback(struct page *page) >> { >> test_set_page_writeback(page); >>Index: linux-2.6/mm/page-writeback.c >>=================================================================== >>--- linux-2.6.orig/mm/page-writeback.c 2006-12-19 15:17:53.000000000 +1100 >>+++ linux-2.6/mm/page-writeback.c 2006-12-19 15:33:29.000000000 +1100 >>@@ -844,9 +844,10 @@ EXPORT_SYMBOL(set_page_dirty_lock); >> >> /* >> * Clear a page's dirty flag, while caring for dirty memory accounting. >>+ * Does not clear pte dirty bits. >> * Returns true if the page was previously dirty. >> */ >>-int test_clear_page_dirty(struct page *page) >>+static int test_clear_page_dirty_leave_ptes(struct page *page) >> { >> struct address_space *mapping = page_mapping(page); >> unsigned long flags; >>@@ -862,10 +863,8 @@ int test_clear_page_dirty(struct page *p >> * We can continue to use `mapping' here because the >> * page is locked, which pins the address_space >> */ >>- if (mapping_cap_account_dirty(mapping)) { >>- page_mkclean(page); >>+ if (mapping_cap_account_dirty(mapping)) >> dec_zone_page_state(page, NR_FILE_DIRTY); >>- } >> return 1; >> } >> write_unlock_irqrestore(&mapping->tree_lock, flags); >>@@ -873,9 +872,43 @@ int test_clear_page_dirty(struct page *p >> } >> return TestClearPageDirty(page); >> } >>+ >>+/* >>+ * As above, but does clear dirty bits from ptes >>+ */ >>+int test_clear_page_dirty(struct page *page) >>+{ >>+ struct address_space *mapping = page_mapping(page); >>+ >>+ if (test_clear_page_dirty_leave_ptes(page)) { >>+ if (mapping_cap_account_dirty(mapping)) >>+ page_mkclean(page); >>+ return 1; >>+ } >>+ return 0; >>+} >> EXPORT_SYMBOL(test_clear_page_dirty); >> >> /* >>+ * As above, but redirties page if any dirty ptes are found (and then only >>+ * if the mapping accounts dirty pages, otherwise dirty ptes are left dirty >>+ * but the page is cleaned). >>+ */ >>+int test_clear_page_dirty_sync_ptes(struct page *page) >>+{ >>+ struct address_space *mapping = page_mapping(page); >>+ >>+ if (test_clear_page_dirty_leave_ptes(page)) { >>+ if (mapping_cap_account_dirty(mapping)) { >>+ if (page_mkclean(page)) >>+ set_page_dirty(page); >>+ } >>+ return 1; >>+ } >>+ return 0; >>+} >>+ >>+/* >> * Clear a page's dirty flag, while caring for dirty memory accounting. >> * Returns true if the page was previously dirty. >> * > > > Hmm, not quite; It certainly look better than the extra ,[01] tagged to > test_clear_page_dirty() though. Although I would have expected it the > other way around - test_clear_pages_dirty_sync_ptes to be the default > case and test_clear_pages_dirty_clean_ptes to be used in > clear_page_dirty_for_io(). > > Anyway it has the same issues as the others. See what happens when you > run two test_clear_page_dirty_sync_ptes() consecutively, you still loose > PG_dirty even though the page might actually be dirty.
How can this happen? We'll only test_clear_page_dirty_sync_ptes again after buffers have been reattached, and subsequently cleaned. And in that case if the ptes are still clean at this point then the page really is clean.
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