From: "Besogonov, Aleksei" <cyberax@amazon.com>
To: Dave Chinner <david@fromorbit.com>,
"Darrick J. Wong" <darrick.wong@oracle.com>
Cc: "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
xfs <linux-xfs@vger.kernel.org>
Subject: Re: fallocate on XFS for swap
Date: Mon, 12 Mar 2018 22:01:54 +0000 [thread overview]
Message-ID: <A59B9E63-29A2-4C40-960B-E09809DE501F@amazon.com> (raw)
In-Reply-To: <20180310013646.GX18129@dastard>
[snip unrelated]
So I'm looking at the XFS code and it appears that the iomap is limited to 1024*PAGE_SIZE blocks at a time, which is too small for most of swap use-cases. I can of course just loop through the file in 4Mb increments and, just like the bmap() code does today. But this just doesn't look right and it's not atomic. And it looks like iomap in ext2 doesn't have this limitation.
The stated rationale for the XFS limit is:
>/*
> * We cap the maximum length we map here to MAX_WRITEBACK_PAGES pages
> * to keep the chunks of work done where somewhat symmetric with the
> * work writeback does. This is a completely arbitrary number pulled
> * out of thin air as a best guess for initial testing.
> *
> * Note that the values needs to be less than 32-bits wide until
> * the lower level functions are updated.
> */
So can it be lifted today?
next prev parent reply other threads:[~2018-03-12 22:01 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-09 22:05 Besogonov, Aleksei
2018-03-09 23:44 ` Darrick J. Wong
2018-03-10 0:58 ` Dave Chinner
2018-03-10 1:17 ` Darrick J. Wong
2018-03-10 1:36 ` Dave Chinner
2018-03-12 22:01 ` Besogonov, Aleksei [this message]
2018-03-13 1:31 ` Dave Chinner
2018-03-10 9:38 ` Christoph Hellwig
2018-03-12 21:46 ` Dave Chinner
2018-03-13 7:14 ` Christoph Hellwig
2018-03-12 18:40 ` Besogonov, Aleksei
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