This is a note to let you know that I've just added the patch titled
ext4: flush any pending end_io requests before DIO reads w/dioread_nolock
to the 3.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ext4-flush-any-pending-end_io-requests-before-dio-reads-w-dioread_nolock.patch
and it can be found in the queue-3.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From dccaf33fa37a1bc5d651baeb3bfeb6becb86597b Mon Sep 17 00:00:00 2001
From: Jiaying Zhang <[email protected]>
Date: Fri, 19 Aug 2011 19:13:32 -0400
Subject: ext4: flush any pending end_io requests before DIO reads
w/dioread_nolock
From: Jiaying Zhang <[email protected]>
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 <[email protected]>
Signed-off-by: "Theodore Ts'o" <[email protected]>
Cc: Jan Kara <[email protected]>
Signed-off-by: Michael Tokarev <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
fs/ext4/inode.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3510,12 +3510,17 @@ static ssize_t ext4_ind_direct_IO(int rw
}
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,
Patches currently in stable-queue which might be from [email protected] are
queue-3.0/ext4-flush-any-pending-end_io-requests-before-dio-reads-w-dioread_nolock.patch
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