From 6ccfa806a9cfbbf1cd43d5b6aa47ef2c0eb518fd Mon Sep 17 00:00:00 2001 From: Hisashi Hifumi Date: Tue, 2 Sep 2008 14:35:40 -0700 Subject: [PATCH] VFS: fix dio write returning EIO when try_to_release_page fails Dio write returns EIO when try_to_release_page fails because bh is still referenced. The patch commit 3f31fddfa26b7594b44ff2b34f9a04ba409e0f91 Author: Mingming Cao Date: Fri Jul 25 01:46:22 2008 -0700 jbd: fix race between free buffer and commit transaction was merged into 2.6.27-rc1, but I noticed that this patch is not enough to fix the race. I did fsstress test heavily to 2.6.27-rc1, and found that dio write still sometimes got EIO through this test. The patch above fixed race between freeing buffer(dio) and committing transaction(jbd) but I discovered that there is another race, freeing buffer(dio) and ext3/4_ordered_writepage. : background_writeout() ->write_cache_pages() ->ext3_ordered_writepage() walk_page_buffers() -> take a bh ref block_write_full_page() -> unlock_page : <- end_page_writeback : <- race! (dio write->try_to_release_page fails) walk_page_buffers() ->release a bh ref ext3_ordered_writepage holds bh ref and does unlock_page remaining taking a bh ref, so this causes the race and failure of try_to_release_page. To fix this race, I used the approach of falling back to buffered writes if try_to_release_page() fails on a page. [akpm@linux-foundation.org: cleanups] Signed-off-by: Hisashi Hifumi Cc: Chris Mason Cc: Jan Kara Cc: Mingming Cao Cc: Zach Brown Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/filemap.c | 11 +++++++++-- mm/truncate.c | 4 ++-- 2 files changed, 11 insertions(+), 4 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index 54e9686..876bc59 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2129,13 +2129,20 @@ generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov, * After a write we want buffered reads to be sure to go to disk to get * the new data. We invalidate clean cached page from the region we're * about to write. We do this *before* the write so that we can return - * -EIO without clobbering -EIOCBQUEUED from ->direct_IO(). + * without clobbering -EIOCBQUEUED from ->direct_IO(). */ if (mapping->nrpages) { written = invalidate_inode_pages2_range(mapping, pos >> PAGE_CACHE_SHIFT, end); - if (written) + /* + * If a page can not be invalidated, return 0 to fall back + * to buffered write. + */ + if (written) { + if (written == -EBUSY) + return 0; goto out; + } } written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs); diff --git a/mm/truncate.c b/mm/truncate.c index 2505050..6650c1d 100644 --- a/mm/truncate.c +++ b/mm/truncate.c @@ -380,7 +380,7 @@ static int do_launder_page(struct address_space *mapping, struct page *page) * Any pages which are found to be mapped into pagetables are unmapped prior to * invalidation. * - * Returns -EIO if any pages could not be invalidated. + * Returns -EBUSY if any pages could not be invalidated. */ int invalidate_inode_pages2_range(struct address_space *mapping, pgoff_t start, pgoff_t end) @@ -440,7 +440,7 @@ int invalidate_inode_pages2_range(struct address_space *mapping, ret2 = do_launder_page(mapping, page); if (ret2 == 0) { if (!invalidate_complete_page2(mapping, page)) - ret2 = -EIO; + ret2 = -EBUSY; } if (ret2 < 0) ret = ret2; -- 1.8.2.3