On Wed, May 18, 2022 at 01:41:02PM -0400, Vivek Goyal wrote:
> On Tue, May 17, 2022 at 03:37:42PM +0530, Dharmendra Singh wrote:
>
> [..]
> > diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
> > index d6ccee961891..bebe4be3f1cb 100644
> > --- a/include/uapi/linux/fuse.h
> > +++ b/include/uapi/linux/fuse.h
> > @@ -301,6 +301,7 @@ struct fuse_file_lock {
> > * FOPEN_CACHE_DIR: allow caching this directory
> > * FOPEN_STREAM: the file is stream-like (no file position at all)
> > * FOPEN_NOFLUSH: don't flush data cache on close (unless FUSE_WRITEBACK_CACHE)
> > + * FOPEN_FILE_CREATED: the file was actually created
> > */
> > #define FOPEN_DIRECT_IO (1 << 0)
> > #define FOPEN_KEEP_CACHE (1 << 1)
> > @@ -308,6 +309,7 @@ struct fuse_file_lock {
> > #define FOPEN_CACHE_DIR (1 << 3)
> > #define FOPEN_STREAM (1 << 4)
> > #define FOPEN_NOFLUSH (1 << 5)
> > +#define FOPEN_FILE_CREATED (1 << 6)
> >
> > /**
> > * INIT request/reply flags
> > @@ -537,6 +539,7 @@ enum fuse_opcode {
> > FUSE_SETUPMAPPING = 48,
> > FUSE_REMOVEMAPPING = 49,
> > FUSE_SYNCFS = 50,
> > + FUSE_CREATE_EXT = 51,
>
> I am wondering if we really have to introduce a new opcode for this. Both
> FUSE_CREATE and FUSE_CREATE_EXT prepare and send fuse_create_in{} and
> expect fuse_entry_out and fuse_open_out in response. So no new structures
> are being added. Only thing FUSE_CREATE_EXT does extra is that it also
> reports back whether file was actually created or not.
>
> May be instead of adding an new fuse_opcode, we could simply add a
> new flag which we send in fuse_create_in and that reqeusts to report
> if file was created or not. This is along the lines of
> FUSE_OPEN_KILL_SUIDGID.
>
> So say, a new flag FUSE_OPEN_REPORT_CREATE flag. Which we will set in
> fuse_create_in->open_flags. If file server sees this flag is set, it
> knows that it needs to set FOPEN_FILE_CREATED flag in response.
>
> To me creating a new flag FUSE_OPEN_REPORT_CREATE seems better instead
> of adding a new opcode.
Actually I take that back. If we were to use a flag, then we will have to
do feature negotiation in advance at init time and only then we can set
FUSE_OPEN_REPORT_CREATE. But we are relying on no new feature bit instead
-ENOSYS will be returned if server does not support FUSE_CREATE_EXT.
So adding a new opcode is better.
Thanks
Vivek
