diff options
author | Jiaying Zhang <jiayingz@google.com> | 2011-08-19 19:13:32 -0400 |
---|---|---|
committer | Theodore Ts'o <tytso@mit.edu> | 2011-08-19 19:13:32 -0400 |
commit | dccaf33fa37a1bc5d651baeb3bfeb6becb86597b (patch) | |
tree | ff41c9c0208589fded8176089380e316dd5c7965 | |
parent | 9dd75f1f1a02d656a11a7b9b9e6c2759b9c1e946 (diff) |
ext4: flush any pending end_io requests before DIO reads w/dioread_nolock
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: stable@kernel.org
-rw-r--r-- | fs/ext4/indirect.c | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c index b8602cde5b5..0962642119c 100644 --- a/fs/ext4/indirect.c +++ b/fs/ext4/indirect.c @@ -800,12 +800,17 @@ 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, iov, offset, nr_segs, ext4_get_block); |