On 09.08.21 21:08, Vivek Goyal wrote:
On Fri, Jul 30, 2021 at 05:01:34PM +0200, Max Reitz wrote:
lo_find() right now takes two lookup keys for two maps, namely the file
handle for inodes_by_handle and the statx information for inodes_by_ids.
However, we only need the statx information if looking up the inode by
the file handle failed.
There are two callers of lo_find(): The first one, lo_do_lookup(), has
both keys anyway, so passing them does not incur any additional cost.
The second one, lookup_name(), though, needs to explicitly invoke
name_to_handle_at() (through get_file_handle()) and statx() (through
do_statx()). We need to try to get a file handle as the primary key, so
we cannot get rid of get_file_handle(), but we only need the statx
information if looking up an inode by handle failed; so we can defer
that until the lookup has indeed failed.
So IIUC, this patch seems to be all about avoiding do_statx()
call in lookup_name() if file handle could be successfully
generated.
So can't we just not modify lookup_name() to not call statx()
if file handle could be generated. And also modfiy lo_find()
to use st/mnt_id only if fhandle==NULL.
That probably is much simpler change as compared to passing function
pointers around.
Definitely, but I don’t know whether it’s correct.
Or, we can just drop this patch and say that we don’t need to
over-optimize C virtiofsd.
Hanna
