From: Andreas Dilger <email@example.com> To: "J. Bruce Fields" <firstname.lastname@example.org> Cc: David Howells <email@example.com>, One Thousand Gnomes <firstname.lastname@example.org>, email@example.com, firstname.lastname@example.org Subject: Re: [RFC][PATCH 0/4] Enhanced file stat system call Date: Thu, 17 Nov 2016 19:30:25 -0700 [thread overview] Message-ID: <3852DE26-42A6-4AFF-AA9C-08C4E9837511@dilger.ca> (raw) In-Reply-To: <20161117200026.GE20937@fieldses.org> [-- Attachment #1: Type: text/plain, Size: 3696 bytes --] > On Nov 17, 2016, at 1:00 PM, J. Bruce Fields <email@example.com> wrote: > > On Thu, Nov 17, 2016 at 04:45:45PM +0000, David Howells wrote: >> One Thousand Gnomes <firstname.lastname@example.org> 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. > > Sorry, I haven't been paying attention, just popping up for this, but: > "shared" might be a more useful term than "remote". > > A filesystem that may be mounted from more than one system is "shared". > Caching performance and semantics of such a filesystem are more > complicated since the filesystem may change out from under us. This is > what makes e.g. the lightweight/heavyweight stat difference more > interesting in the shared case. > > The filesystem should be able to make that shared/unshared distinction > without knowledge of the storage it's sitting on top of. > > Answering your questions by that criterion: > > - ext4/nbd: not shared > - nfs/lo: shared > > But, it's fine with me to drop any features for now as long as we can > always add them later. Please, please, please, let's get the syscall and basic functionality landed first, and then nit-pick about extensions later. This has been dragging on for _years_ and bike shedded to death. Cheers, Andreas [-- Attachment #2: Message signed with OpenPGP using GPGMail --] [-- Type: application/pgp-signature, Size: 833 bytes --]
next prev parent reply other threads:[~2016-11-18 2:46 UTC|newest] Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-11-17 13:34 David Howells 2016-11-17 13:35 ` [PATCH 1/4] statx: Add a system call to make enhanced file info available David Howells 2016-11-17 18:39 ` Jeff Layton 2016-11-18 2:32 ` Andreas Dilger 2016-11-18 8:59 ` David Howells 2016-11-18 8:59 ` David Howells 2016-11-18 9:25 ` Andreas Dilger 2016-11-18 9:25 ` Andreas Dilger 2016-11-17 23:40 ` Dave Chinner 2016-11-18 3:28 ` Andreas Dilger 2016-11-18 22:07 ` Dave Chinner 2016-11-18 22:54 ` David Howells 2016-11-19 22:43 ` Dave Chinner 2016-11-21 14:30 ` One Thousand Gnomes 2016-11-21 20:43 ` Dave Chinner 2016-11-22 10:39 ` David Howells 2016-11-22 13:55 ` Jeff Layton 2016-11-22 20:58 ` Dave Chinner 2016-11-18 9:53 ` David Howells 2016-11-18 8:48 ` David Howells 2016-11-18 12:01 ` Jeff Layton 2016-11-18 9:36 ` David Howells 2016-11-18 17:17 ` Jeff Layton 2016-11-18 18:04 ` David Howells 2016-11-18 18:54 ` Jeff Layton 2016-11-18 19:08 ` David Howells 2016-11-18 9:43 ` David Howells 2016-11-18 21:41 ` Dave Chinner 2016-11-18 22:24 ` David Howells 2016-11-18 10:29 ` David Howells 2016-11-18 10:29 ` David Howells 2016-11-18 21:27 ` Dave Chinner 2016-11-18 21:48 ` David Howells 2016-11-18 21:48 ` David Howells 2016-11-18 22:17 ` Dave Chinner 2016-11-18 22:17 ` Dave Chinner 2016-11-19 10:21 ` Michael Kerrisk (man-pages) 2016-11-17 13:35 ` [PATCH 2/4] statx: Ext4: Return enhanced file attributes David Howells 2016-11-18 3:30 ` Andreas Dilger 2016-11-17 13:35 ` [PATCH 3/4] statx: NFS: " David Howells 2016-11-17 13:35 ` [PATCH 4/4] statx: AFS: " David Howells 2016-11-18 3:34 ` Andreas Dilger 2016-11-18 8:47 ` David Howells 2016-11-17 14:39 ` [RFC][PATCH 0/4] Enhanced file stat system call One Thousand Gnomes 2016-11-17 15:10 ` Michael Kerrisk 2016-11-17 16:33 ` David Howells 2016-11-17 16:45 ` David Howells 2016-11-17 20:00 ` J. Bruce Fields 2016-11-18 2:30 ` Andreas Dilger [this message] 2016-11-18 4:29 ` NeilBrown 2016-11-18 13:41 ` One Thousand Gnomes 2016-11-18 13:49 ` David Howells
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