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

From: Jens Axboe
Date: Tue May 20 2008 - 15:54:58 EST

On Tue, May 20 2008, Jamie Lokier wrote:
> Does WRITE_BARRIER always cause a flush? It does not have to
> according to Documentation/block/barrier.txt. There are caveats about
> tagged queuing "not yet implemented" in the text, but can we rely on
> that? The documentation is older than the current implementation;
> those caveats might no longer apply.

It does, if you use ordered tags then that assumes write through
caching (or ordered tag + drain + flush after completion).

Jens Axboe

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