[NFS-Ganesha-Devel] Re: O_TRUNC in open2

The open2() API returns the updated attributes of the file. So, if they changed (for example because of a truncate) then we need a getattrs() to return the new attributes. The actual truncation is taken care of by the actual open call (GPFSFSAL_open() -> fsal_internal_handle2fd() -> OPENHANDLE_OPEN_BY_HANDLE) If a FSAL had an extended open call that returned attributes directly, then it wouldn't need a separate getattrs().

Daniel On 08/07/2018 01:36 PM, Tuan Viet Nguyen wrote: > Thanks Daniel, > > I've just tested it again and confirm that it works, sorry for the > noise. But why in GPFS for example we getattrs in case of truncated > instead of setting attrs with size and new ctime? (open_by_handle) > > Thank you > > On Tue, Aug 7, 2018 at 7:22 PM, Daniel Gryniewicz <dang(a)redhat.com > <mailto:dang@redhat.com>> wrote: > > On 08/07/2018 01:03 PM, ntvietvn(a)gmail.com > <mailto:ntvietvn@gmail.com> wrote: > > Hello, > > Can anyone explain how O_TRUNC is handled (open2)? When I try to > open an existing file with this flag, the FSAL_O_TRUNC in > openflags is not enabled in my FSAL open2 fct. > While capturing with tcpdump, the NFS client actually sends a > OPEN then SETATTR with size = 0 but not ctime. > > By looking at an example in open_by_handle, if IIUC if the flag > O_TRUNC is there, we refresh the attrs by calling getattrs to > attrs_out, I do not understand that, why it does that instead of > calling setattrs ? > > > It should work (and, in fact, passes tests, so it does...) Here's > what happens: > > In nfs4_op_open() It checks the attributes to set for ATTR_SIZE, and > if that's zero, it sets FSAL_O_TRUNC in openflags. This is passed to: > > fsal_open2(), which does the same check, and again sets FSAL_O_TRUNC > in openflags. If there's no name (this is an open-by-handle), > openflags is passed to obj_ops->open2(); if there's a name, it's > passed to open2_by_name(), which passes it to obj_ops->open(). > Either way, it gets to: > > mdcache_open2() which calls mdc_open2_by_name() (if there's a name) > which calls obj_ops->open2(), or directly calls obj_ops->open2(); in > either case, that's calling into the FSAL with FSAL_O_TRUNC set. > Once that returns, if that flag is set, MDCACHE invalidates the > cached attributes for that handle. > > So, it looks like it should be working properly. > > Daniel > > _______________________________________________ > Devel mailing list -- devel(a)lists.nfs-ganesha.org > <mailto:devel@lists.nfs-ganesha.org> > To unsubscribe send an email to devel-leave(a)lists.nfs-ganesha.org > <mailto:devel-leave@lists.nfs-ganesha.org> > > _______________________________________________ Devel mailing list -- devel(a)lists.nfs-ganesha.org To unsubscribe send an email to devel-leave(a)lists.nfs-ganesha.org