From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1MIA0k-0002dD-8a for qemu-devel@nongnu.org; Sat, 20 Jun 2009 19:30:14 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1MIA0f-0002bu-Lq for qemu-devel@nongnu.org; Sat, 20 Jun 2009 19:30:13 -0400 Received: from [199.232.76.173] (port=58214 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1MIA0f-0002bp-D4 for qemu-devel@nongnu.org; Sat, 20 Jun 2009 19:30:09 -0400 Received: from mail2.shareable.org ([80.68.89.115]:55098) by monty-python.gnu.org with esmtps (TLS-1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1MIA0e-0005U6-5f for qemu-devel@nongnu.org; Sat, 20 Jun 2009 19:30:08 -0400 Date: Sun, 21 Jun 2009 00:30:05 +0100 From: Jamie Lokier Subject: Re: [Qemu-devel] [PATCH] replace O_SYNC with O_FSYNC Message-ID: <20090620233005.GB29958@shareable.org> References: <20f282157f4df2f513fdb51427be26c7@hotpop.com> <20090620191629.GB25835@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090620191629.GB25835@lst.de> List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Christoph Hellwig Cc: m a , qemu-devel@nongnu.org Christoph Hellwig wrote: > On Fri, Jun 19, 2009 at 10:22:07PM -0400, m a wrote: > > This patch replaces O_SYNC with O_FSYNC. These two flags do the same > > thing, but only O_FSYNC is available in Mac OS 10.3 and under. It only > > replaces O_SYNC if it doesn't exist. This patch allows the file > > block-raw-posix.c to compile on Mac OS 10.3. This is my first time > > submitting a patch, so there might have been a few mistakes made. > > But O_SYNC is a standard posix flag, while O_FSYNC appears to be > a BSD extension. Also the actual code uses O_DSYNC anyway, which > also is in Posix but not actually natively supported by some OSes, > e.g. Linux (but still provided in libc there). If O_FSYNC and O_SYNC do the same thing, and O_SYNC is used anywhere, there's no harm in this for portability: #if !defined(O_SYNC) && defined(O_FSYNC) #define O_SYNC O_FSYNC #endif The patch assumes O_FSYNC is defined if O_SYNC isn't, which is wrong. > > /* OS X does not have O_DSYNC */ > > #ifndef O_DSYNC > > #define O_DSYNC O_SYNC > > So if the code here is correct and Darwin is the only supported OS where > O_DSYNC is missing we could just replace the O_SYNC in the last line > with O_FSYNC. I agree, though the comment might be misleading, if there's another supported OS without O_DSYNC. -- Jamie