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aio_fsync() a directory ?
- From: Xavier Roche <xavier dot roche at 3ds dot com>
- To: libc-alpha at sourceware dot org
- Date: Tue, 12 Mar 2013 10:01:59 +0100
- Subject: aio_fsync() a directory ?
As a followup to a discussion
regarding synchronization of file operations (file creation, renaming,
symlink, etc.), it seems that the only way to "commit" a filename change
is to open() the containing directory in O_RDONLY, and fsync() the given
This behavior seems to work with fsync() [even if it is not really
documented], and appears to have the expected side effects.
However, aio_fsync() [as tested in glibc 2.17) refuses to operate on a
file descriptor not opened in write mode:
Extract from the glibc-2.17 sysdeps/pthread/aio_fsync.c:
aio_fsync (int op, struct aiocb *aiocbp)
flags = fcntl (aiocbp->aio_fildes, F_GETFL);
if (__builtin_expect (flags == -1, 0)
|| __builtin_expect ((flags & O_ACCMODE) == O_RDONLY, 0))
This behavior is inconsistent with fsync() ; but OTOH it is consistent
with the standard ; aio_fsync() "shall fail if the aio_fildes member of
the aiocb structure referenced by the aiocbp argument is not a valid
file descriptor open for writing"
Strangely, fsync() does not have this restriction (neither in the
standard nor on the implementation) - was it on purpose ?
At last, is fsync'ing a directory the right way to commit operations on
files entries ? If so, isn't it inconsistent not to accept this on the
aio side ?