From dccaf33fa37a1bc5d651baeb3bfeb6becb86597b Mon Sep 17 00:00:00 2001 From: Jiaying Zhang Date: Fri, 19 Aug 2011 19:13:32 -0400 Subject: [PATCH] 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 Signed-off-by: "Theodore Ts'o" Cc: stable@kernel.org --- Reading git-format-patch failed