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Date: Sat, 14 May 2016 20:35:42 +0000
From: Alexey Dokuchaev <danfe@FreeBSD.org>
To: Rick Macklem <rmacklem@FreeBSD.org>
Cc: src-committers@freebsd.org, svn-src-all@freebsd.org,
 svn-src-head@freebsd.org
Subject: Re: svn commit: r299753 - head/sys/fs/fuse
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References: <201605142003.u4EK3MwV021470@repo.freebsd.org>
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On Sat, May 14, 2016 at 08:03:22PM +0000, Rick Macklem wrote:
> New Revision: 299753
> URL: https://svnweb.freebsd.org/changeset/base/299753
> 
> Log:
>   Fix fuse to use DIRECT_IO when required.
>   
>   When a file is opened write-only and a partial block was written,
>   buffered I/O would try and read the whole block in. This would
>   result in a hung thread, since there was no open (fuse filehandle)
>   that allowed reading. This patch avoids the problem by forcing
>   DIRECT_IO for this case.
>   It also sets DIRECT_IO when the file system specifies the FN_DIRECTIO
>   flag in its reply to the open.

Since you're at fuse now, perhaps you could also have a look at PR 195000?

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=195000

./danfe