diff options
| author | Jiaying Zhang <jiayingz@google.com> | 2011-08-19 19:13:32 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-04-02 09:27:18 -0700 |
| commit | fb9ea4df52f6114571e1e03f13f38d4bfc4b3587 (patch) | |
| tree | 07e91444a339e9f4f04951892ce1bc2fda1b1692 | |
| parent | 65554407a7dbc5ebcc42d53b6a1dfcd18ca7685d (diff) | |
ext4: flush any pending end_io requests before DIO reads w/dioread_nolock
commit dccaf33fa37a1bc5d651baeb3bfeb6becb86597b upstream.
(backported to 3.0 by mjt)
There is a race between ext4 buffer write and direct_IO read with
dioread_nolock mount option enabled. The problem is that we clear
PageWriteback flag during end_io time but will do
uninitialized-to-initialized extent conversion later with dioread_nolock.
If an O_direct read request comes in during this period, ext4 will return
zero instead of the recently written data.
This patch checks whether there are any pending uninitialized-to-initialized
extent conversion requests before doing O_direct read to close the race.
Note that this is just a bandaid fix. The fundamental issue is that we
clear PageWriteback flag before we really complete an IO, which is
problem-prone. To fix the fundamental issue, we may need to implement an
extent tree cache that we can use to look up pending to-be-converted extents.
Signed-off-by: Jiaying Zhang <jiayingz@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | fs/ext4/inode.c | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index af0906080fd..792e6a9fdc5 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -3510,12 +3510,17 @@ static ssize_t ext4_ind_direct_IO(int rw, struct kiocb *iocb, } retry: - if (rw == READ && ext4_should_dioread_nolock(inode)) + if (rw == READ && ext4_should_dioread_nolock(inode)) { + if (unlikely(!list_empty(&ei->i_completed_io_list))) { + mutex_lock(&inode->i_mutex); + ext4_flush_completed_IO(inode); + mutex_unlock(&inode->i_mutex); + } ret = __blockdev_direct_IO(rw, iocb, inode, inode->i_sb->s_bdev, iov, offset, nr_segs, ext4_get_block, NULL, NULL, 0); - else { + } else { ret = blockdev_direct_IO(rw, iocb, inode, inode->i_sb->s_bdev, iov, offset, nr_segs, |