Josef Bacik
2013-Jul-02 14:40 UTC
[PATCH] Btrfs: wait ordered range before doing direct io
My recent truncate patch uncovered this bug, but I can reproduce it without the
truncate patch. If you mount with -o compress-force, do a direct write to some
area, do a buffered write to some other area, and then do a direct read you will
get the wrong data for where you did the buffered write. This is because the
generic direct io helpers only call filemap_write_and_wait once, and for
compression we need it twice. So to be safe add the btrfs_wait_ordered_range to
the start of the direct io function to make sure any compressed writes have
truly been written. This patch makes xfstests 130 pass when you mount with -o
compress-force=lzo. Thanks,
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
---
fs/btrfs/inode.c | 10 +++++++++-
1 files changed, 9 insertions(+), 1 deletions(-)
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index b7fa96f..4384c7c 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -7254,8 +7254,16 @@ static ssize_t btrfs_direct_IO(int rw, struct kiocb
*iocb,
atomic_inc(&inode->i_dio_count);
smp_mb__after_atomic_inc();
+ /*
+ * The generic stuff only does filemap_write_and_wait_range, which
isn''t
+ * enough if we''ve written compressed pages to this area, so we need
to
+ * call btrfs_wait_ordered_range to make absolutely sure that any
+ * outstanding dirty pages are on disk.
+ */
+ count = iov_length(iov, nr_segs);
+ btrfs_wait_ordered_range(inode, offset, count);
+
if (rw & WRITE) {
- count = iov_length(iov, nr_segs);
/*
* If the write DIO is beyond the EOF, we need update
* the isize, but it is protected by i_mutex. So we can
--
1.7.7.6
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