Re: fallocate vs O_(D)SYNC

[Zheng Liu <gnehzuil.liu@gmail.com>]

On Wed, Nov 16, 2011 at 03:42:56AM -0500, Christoph Hellwig wrote:
> It seems all filesystems but XFS ignore O_SYNC for fallocate, and never
> make sure the size update transaction made it to disk.
> 
> Given that a fallocate without FALLOC_FL_KEEP_SIZE very much is a data
> operation (it adds new blocks that return zeroes) that seems like a
> fairly nasty surprise for O_SYNC users.

Hi all,

This patch should be fix this problem in ext4.

From: Zheng Liu <wenqing.lz@taobao.com>

Make sure the transaction to be commited if O_(D)SYNC flag is set in
ext4_fallocate().

Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
---
 fs/ext4/extents.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 61fa9e1..f47e3ad 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4356,6 +4356,8 @@ retry:
                        ret = PTR_ERR(handle);
                        break;
                }
+               if (file->f_flags & O_SYNC)
+                       ext4_handle_sync(handle);
                ret = ext4_map_blocks(handle, inode, &map, flags);
                if (ret <= 0) {
 #ifdef EXT4FS_DEBUG
-- 
1.7.4.1


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