Messages in this thread | | | Subject | Re: [PATCH] vfs: new O_NODE open flag | From | Miklos Szeredi <> | Date | Mon, 28 Sep 2009 12:25:26 +0200 |
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On Fri, 25 Sep 2009, Valdis.Kletnieks wrote: > On Fri, 25 Sep 2009 19:35:23 BST, "Dr. David Alan Gilbert" said: > > > I know it's not possible without this flag, my interest is whether > > it would be possible WITH this flag to promote an fd opened with the > > O_NODE to a normal fd, guaranteeing that it's still operating on the > > same object. > > Well, maybe the question is if we should treat "promote" differently than > "re-open"? > > (And now I'm wondering what happens if you dup() one of these beasts....)
dup() only duplicates _references_ to an open file, it does not create a new file. The same applies to fork().
BTW I just checked, and it is possible to re-open or promote an fd opened with O_NODE like this:
char tmp[64];
fd = open(filename, O_NODE | O_NOACCESS); /* ... */ sprintf(tmp, "/proc/self/fd/%i", fd); fd_rw = open(tmp, O_RDWR);
Now fd_rw is guaranteed to refer to the same inode as fd.
Thanks, Miklos
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