12:22 p.m.
On 08/07/2018 01:03 PM, ntvietvn(a)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