From mboxrd@z Thu Jan  1 00:00:00 1970
From: tytso@mit.edu
Subject: Re: [Bug 15910] zero-length files and performance degradation
Date: Mon, 10 May 2010 10:34:33 -0400
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References: <bug-15910-13602@https.bugzilla.kernel.org/>
 <201005091819.o49IJCQG017276@demeter.kernel.org>
 <20100510025612.GM18762@thunk.org>
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To: Peng Tao <bergwolf@gmail.com>
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On Mon, May 10, 2010 at 10:22:47PM +0800, Peng Tao wrote:
> What about letting fsync() on dir recursively fsync() all
> files/sub-dirs in the dir?
> Then apps can unpack package in a temp dir, fsync(), and rename.

There are programs to do who execute fsync() on a directory, and they
do not expect a recursive fsync() on all files/subdirectories in a
directory.

At least for Linux, sync() is synchronous and will do what you want.
There is unfortunately not a portable way to do what you want short of
fsync'ing all of the files after they are written.  This case is
mostly optimized under ext3/4 (we could do a bit better for ext4, but
the performance shouldn't be disastrous --- certainly much better than
write a file, fsync, rename a file, repeat).

					- Ted