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Message-ID: <20101223224309.GH18264@dastard> Date: Fri, 24 Dec 2010 09:43:09 +1100 From: Dave Chinner <david@...morbit.com> To: Olaf van der Spek <olafvdspek@...il.com> Cc: linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org Subject: Re: Atomic non-durable file write API On Thu, Dec 23, 2010 at 04:49:53PM +0100, Olaf van der Spek wrote: > On Sun, Dec 19, 2010 at 5:39 PM, Olaf van der Spek <olafvdspek@...il.com> wrote: > > On Sat, Dec 18, 2010 at 11:15 PM, Calvin Walton <calvin.walton@...il.com> wrote: > >> Hmm. I’m doing a little interpretation of what Olaf said here; but I > >> think you may have misunderstood the question? > >> > >> He doesn’t care about whether or not the file is securely written to > >> disk (durable); however he doesn’t want to see any partially written > >> files. In other words, something like > >> > >> 1. Write to temp file > >> 2. Rename temp file over original file > > > > Meta data, including file owner, should be preserved. > > Ideally, no temp files should be visible either. > > > >> Where the rename is only committed to disk once the entire contents of > >> the file have been written securely – whenever that may eventually > >> happen. > >> > >> He doesn’t want to synchronously wait for the file to be written, > >> because the new data isn’t particularly important. The only important > >> thing is that the file either contains the old or new data after a > >> filesystem crash; not incomplete data. So, it’s more of an ordering > >> problem, I think? (Analogous to putting some sort of barrier between the > >> file write/close and the file rename to maintain ordering.) > >> > >> Hopefully I’ve interpreted the original question correctly, because this > >> is something I would find interesting as well. > > > > Yes, you did. > > Somebody? So you are looking for something like: http://developer.apple.com/library/mac/#DOCUMENTATION/Darwin/Reference/ManPages/man2/exchangedata.2.html ? Cheers, Dave. -- Dave Chinner david@...morbit.com -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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