From: Jamie Lokier <jamie@shareable.org>
To: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH] add file: migration support (r2)
Date: Thu, 13 Nov 2008 18:39:53 +0000 [thread overview]
Message-ID: <20081113183953.GA29026@shareable.org> (raw)
In-Reply-To: <gfhq8c$pjm$1@ger.gmane.org>
Charles Duffy wrote:
> documents the limitations of O_NONBLOCK on Linux with local
> filesystem access.
That's not a Linux limitation.
All OSes ignore O_NONBLOCK for filesystem accesses, including remote
filesystems. This is a POSIX thing.
The reason is that there's no way to select() on a file. (You'd need
to select() on readiness to read/write a specific byte range anyway,
so the interface doesn't work.)
The nearest equivalent to select() on file I/O is AIO, which is
probably what should be used if migration file I/O is blocking QEMU.
-- Jamie
next prev parent reply other threads:[~2008-11-13 18:40 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-11-13 18:04 [Qemu-devel] [PATCH] add file: migration support (r2) Charles Duffy
2008-11-13 18:39 ` Jamie Lokier [this message]
2008-11-13 18:44 ` Paul Brook
2008-11-13 18:49 ` Anthony Liguori
2008-11-14 3:33 ` Jamie Lokier
2008-11-14 3:49 ` Paul Brook
2008-11-18 3:04 ` Jamie Lokier
2008-11-18 12:57 ` Paul Brook
2008-11-18 14:26 ` Anthony Liguori
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