Messages in this thread | | | From | David Howells <> | Subject | Re: [RFC][PATCH 0/4] Enhanced file stat system call | Date | Thu, 17 Nov 2016 16:45:45 +0000 |
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One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> wrote:
> > (2) Lightweight stat (AT_STATX_DONT_SYNC): Ask for just those details of > > interest, and allow a network fs to approximate anything not of > > interest, without going to the server. > > > > (3) Heavyweight stat (AT_STATX_FORCE_SYNC): Force a network fs to flush > > buffers and go to the server, even if it thinks its cached attributes > > are up to date. > > That seems an odd way to do it. Wouldn't it be cleaner and more flexible > to give a timestamp of the oldest time you consider acceptable (and > obviously passing 0 indicates whatever you have)
Perhaps, though adding 6-argument syscalls is apparently frowned upon.
> > Note that no lstat() equivalent is required as that can be implemented > > through statx() with atflag == 0. There is also no fstat() equivalent as > > that can be implemented through statx() with filename == NULL and the > > relevant fd passed as dfd. > > and dfd + a name gives you fstatat() ?
Yes.
> The cover note could be clearer on this.
Fixed.
> Should the fields really be split the way they are for times rather than > a struct for each one so you can write code generically to handle one of > those rather than having to have a 4 way switch statement all the time.
It depends. Doing so leaves 16 bytes of hole in the structure. I could ameliorate the wastage by using a union to overlay useful fields in the gaps, but that's pretty icky and might be compiler dependent.
> Another attribute that would be nice (but migt need some trivial device > layer tweaking) would be STATX_ATTR_VOLATILE for filesystems that will > probably evaporate on a reboot. That's useful information for tools like > installers and also for sanity checking things like backup paths.
There's a FILE_ATTRIBUTE_TEMPORARY that I could map for windows filesystems that could be used with this.
> Remote needs to have clear semantics: is ext4fs over nbd 'remote' for > example ?
Hmmm... Interesting question. Probably should. But you could be insane and RAID an nbd and a local disk. Further, does NFS over a loopback device to nfsd on the same machine qualify as root? What if that's exposing a local fs on NBD? Perhaps I should drop 'REMOTE' for now. It sounds like something that a GUI filemanager might find interesting, though.
David
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