linux-ext4 - Re: [PATCH 1/7] ext4: Mark superblock writes synchronous for nobarrier mounts

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Date:   Thu, 4 May 2017 11:00:17 -0400
From:   Theodore Ts'o <tytso@....edu>
To:     Jan Kara <jack@...e.cz>
Cc:     linux-fsdevel@...r.kernel.org,
        Christoph Hellwig <hch@...radead.org>,
        linux-ext4@...r.kernel.org
Subject: Re: [PATCH 1/7] ext4: Mark superblock writes synchronous for
 nobarrier mounts

On Tue, May 02, 2017 at 05:03:45PM +0200, Jan Kara wrote:
> Commit b685d3d65ac7 "block: treat REQ_FUA and REQ_PREFLUSH as
> synchronous" removed REQ_SYNC flag from WRITE_FUA implementation.
> generic_make_request_checks() however strips REQ_FUA flag from a bio
> when the storage doesn't report volatile write cache and thus write
> effectively becomes asynchronous which can lead to performance
> regressions. This affects superblock writes for ext4. Fix the problem
> by marking superblock writes always as synchronous.
> 
> Fixes: b685d3d65ac791406e0dfd8779cc9b3707fea5a3
> CC: linux-ext4@...r.kernel.org
> CC: "Theodore Ts'o" <tytso@....edu>
> Signed-off-by: Jan Kara <jack@...e.cz>

Thanks, applied.

						- Ted