The patch titled
Subject: dax: clear TOWRITE flag after flush is complete
has been added to the -mm tree. Its filename is
dax-add-support-for-fsync-msync-v8-fix.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/dax-add-support-for-fsync-msync-v8-fix.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/dax-add-support-for-fsync-msync-v8-fix.patch
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------------------------------------------------------
From: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Subject: dax: clear TOWRITE flag after flush is complete
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 <ross.zwisler@xxxxxxxxxxxxxxx>
Reported-by: Jan Kara <jack@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/dax.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff -puN fs/dax.c~dax-add-support-for-fsync-msync-v8-fix fs/dax.c
--- a/fs/dax.c~dax-add-support-for-fsync-msync-v8-fix
+++ a/fs/dax.c
@@ -406,8 +406,6 @@ static int dax_writeback_one(struct bloc
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;
@@ -431,6 +429,10 @@ static int dax_writeback_one(struct bloc
}
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;
_
Patches currently in -mm which might be from ross.zwisler@xxxxxxxxxxxxxxx are
dax-fix-null-pointer-dereference-in-__dax_dbg.patch
dax-fix-conversion-of-holes-to-pmds.patch
pmem-add-wb_cache_pmem-to-the-pmem-api.patch
pmem-add-wb_cache_pmem-to-the-pmem-api-v6.patch
dax-support-dirty-dax-entries-in-radix-tree.patch
dax-support-dirty-dax-entries-in-radix-tree-v6.patch
mm-add-find_get_entries_tag.patch
dax-add-support-for-fsync-sync.patch
dax-add-support-for-fsync-sync-v6.patch
dax-add-support-for-fsync-msync-v7.patch
dax-add-support-for-fsync-msync-v8.patch
dax-add-support-for-fsync-msync-v8-fix.patch
dax-add-support-for-fsync-msync-v8-fix-2.patch
dax-add-support-for-fsync-msync-v8-fix-3.patch
dax-add-support-for-fsync-sync-v8-fix-4.patch
ext2-call-dax_pfn_mkwrite-for-dax-fsync-msync.patch
ext4-call-dax_pfn_mkwrite-for-dax-fsync-msync.patch
xfs-call-dax_pfn_mkwrite-for-dax-fsync-msync.patch
dax-never-rely-on-bhb_dev-being-set-by-get_block.patch
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