Re: [PATCH 4/4] ext4: call blkdev_issue_flush on fsync

From: Eric Sandeen
Date: Tue May 20 2008 - 11:53:23 EST

Jamie Lokier wrote:
> Theodore Tso wrote:
>> On Fri, May 16, 2008 at 02:09:56PM -0500, Eric Sandeen wrote:
>>> To ensure that bits are truly on-disk after an fsync,
>>> we should call blkdev_issue_flush if barriers are supported.
>> This patch isn't necessary, and in fact will cause a double flush.
>> When you call fsync(), it calls ext4_force_commit(), and we do a the
>> equivalent of a blkdev_issue_flush() today (which is what happenes
>> when you do a submit_bh(WRITE_BARRIER, bh), which is what setting
>> set_ordered_mode(bh) ends up causing.
> ISTR fsync() on ext3 did not always force a commit, if in-place data
> writes did not change any metadata.

I think that might still be true, but I'm still looking through it (in
the background...)

I tried blktrace to see what was going on but I'm not sure what an "NB"
in the RWBS field means, anyone know?


To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at