From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Ross Zwisler To: linux-kernel@vger.kernel.org Cc: Ross Zwisler , Alexander Viro , Andrew Morton , Dan Williams , Dave Chinner , Jan Kara , Matthew Wilcox , linux-fsdevel@vger.kernel.org, linux-nvdimm@lists.01.org Subject: [PATCH 2/5] dax: clear TOWRITE flag after flush is complete Date: Wed, 20 Jan 2016 20:36:45 -0700 Message-Id: <1453347408-22830-3-git-send-email-ross.zwisler@linux.intel.com> In-Reply-To: <1453347408-22830-1-git-send-email-ross.zwisler@linux.intel.com> References: <1453347408-22830-1-git-send-email-ross.zwisler@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: Previously in dax_writeback_one() we cleared the PAGECACHE_TAG_TOWRITE flag before we had actually flushed the tagged radix tree entry to media. This is incorrect because of the following race: Thread 1 Thread 2 -------- -------- dax_writeback_mapping_range() tag entry with PAGECACHE_TAG_TOWRITE dax_writeback_mapping_range() tag entry with PAGECACHE_TAG_TOWRITE dax_writeback_one() radix_tree_tag_clear(TOWRITE) TOWRITE flag is no longer set, find_get_entries_tag() finds no entries, return flush entry to media In this case thread 1 returns before the data for the dirty entry is actually durable on media. Fix this by only clearing the PAGECACHE_TAG_TOWRITE flag after all flushing is complete. Signed-off-by: Ross Zwisler Reported-by: Jan Kara --- fs/dax.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index cee9e1b..d589113 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -407,8 +407,6 @@ static int dax_writeback_one(struct block_device *bdev, if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE)) goto unlock; - radix_tree_tag_clear(page_tree, index, PAGECACHE_TAG_TOWRITE); - if (WARN_ON_ONCE(type != RADIX_DAX_PTE && type != RADIX_DAX_PMD)) { ret = -EIO; goto unlock; @@ -432,6 +430,10 @@ static int dax_writeback_one(struct block_device *bdev, } wb_cache_pmem(dax.addr, dax.size); + + spin_lock_irq(&mapping->tree_lock); + radix_tree_tag_clear(page_tree, index, PAGECACHE_TAG_TOWRITE); + spin_unlock_irq(&mapping->tree_lock); unmap: dax_unmap_atomic(bdev, &dax); return ret; -- 2.5.0