On Monday 30 March 2009, Fernando Luis Vázquez Cao wrote:This patch adds a helper function that should be used by filesystems that need
to flush the underlying block device on fsync()/fdatasync().
Signed-off-by: Fernando Luis Vazquez Cao <fernando@xxxxxxxxxxxxx>
---
diff -urNp linux-2.6.29-orig/fs/buffer.c linux-2.6.29/fs/buffer.c
--- linux-2.6.29-orig/fs/buffer.c 2009-03-24 08:12:14.000000000 +0900
+++ linux-2.6.29/fs/buffer.c 2009-03-30 15:27:04.000000000 +0900
@@ -165,6 +165,17 @@ void end_buffer_write_sync(struct buffer
put_bh(bh);
}
+/* Issue flush of write caches on the block device */
+int block_flush_device(struct block_device *bdev)
I don't consider this an improvement over using blkdev_issue_flush().
+{
+ int ret = 0;
+
+ ret = blkdev_issue_flush(bdev, NULL);
The problem lies in using NULL for error_sector argument which shows
a subtle deficiency of the current implementation/usage of barriers
based on a write cache flushing.
I intend to document the issue with adding the FIXME to the current
users of blkdev_issue_flush() so the problem is at least known and not
forgotten (fixing it would require some work from both block and fs
sides and unfortunately there wasn't even a willingness to discuss
possible solutions few years back when the original code was added).
Thanks,
Bart