On Wed, 3 Feb 2021 11:37:18 +0000
Stefan Hajnoczi <stefa...@redhat.com> wrote:
> lo_do_lookup() finds an existing inode or allocates a new one. It
> increments nlookup so that the inode stays alive until the client
> releases it.
>
> Existing callers don't need the struct lo_inode so the function doesn't
> return it. Extend the function to optionally return the inode. The next
> commit will need it.
>
> Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
> ---
> tools/virtiofsd/passthrough_ll.c | 29 +++++++++++++++++++++--------
> 1 file changed, 21 insertions(+), 8 deletions(-)
>
> diff --git a/tools/virtiofsd/passthrough_ll.c
> b/tools/virtiofsd/passthrough_ll.c
> index e63cbd3fb7..c87a1f3d72 100644
> --- a/tools/virtiofsd/passthrough_ll.c
> +++ b/tools/virtiofsd/passthrough_ll.c
> @@ -831,11 +831,13 @@ static int do_statx(struct lo_data *lo, int dirfd,
> const char *pathname,
> }
>
> /*
> - * Increments nlookup and caller must release refcount using
> - * lo_inode_put(&parent).
> + * Increments nlookup on the inode on success. unref_inode_lolocked() must be
> + * called eventually to decrement nlookup again. If inodep is non-NULL, the
> + * inode pointer is stored and the caller must call lo_inode_put().
> */
> static int lo_do_lookup(fuse_req_t req, fuse_ino_t parent, const char *name,
> - struct fuse_entry_param *e)
> + struct fuse_entry_param *e,
> + struct lo_inode **inodep)
> {
> int newfd;
> int res;
> @@ -845,6 +847,10 @@ static int lo_do_lookup(fuse_req_t req, fuse_ino_t
> parent, const char *name,
> struct lo_inode *inode = NULL;
> struct lo_inode *dir = lo_inode(req, parent);
>
> + if (inodep) {
> + *inodep = NULL;
> + }
> +
Is this side-effect needed ? If lo_do_lookup() returns an error, it
rather seems that the caller shouldn't expect anything to be written
here, i.e. the content of *inodep still belongs to the caller and
whatever value it previously put in there (as patch 3/3 does) should
be preserved IMHO.
Apart from that LGTM.
> /*
> * name_to_handle_at() and open_by_handle_at() can reach here with fuse
> * mount point in guest, but we don't have its inode info in the
> @@ -913,7 +919,14 @@ static int lo_do_lookup(fuse_req_t req, fuse_ino_t
> parent, const char *name,
> pthread_mutex_unlock(&lo->mutex);
> }
> e->ino = inode->fuse_ino;
> - lo_inode_put(lo, &inode);
> +
> + /* Transfer ownership of inode pointer to caller or drop it */
> + if (inodep) {
> + *inodep = inode;
> + } else {
> + lo_inode_put(lo, &inode);
> + }
> +
> lo_inode_put(lo, &dir);
>
> fuse_log(FUSE_LOG_DEBUG, " %lli/%s -> %lli\n", (unsigned long
> long)parent,
> @@ -948,7 +961,7 @@ static void lo_lookup(fuse_req_t req, fuse_ino_t parent,
> const char *name)
> return;
> }
>
> - err = lo_do_lookup(req, parent, name, &e);
> + err = lo_do_lookup(req, parent, name, &e, NULL);
> if (err) {
> fuse_reply_err(req, err);
> } else {
> @@ -1056,7 +1069,7 @@ static void lo_mknod_symlink(fuse_req_t req, fuse_ino_t
> parent,
> goto out;
> }
>
> - saverr = lo_do_lookup(req, parent, name, &e);
> + saverr = lo_do_lookup(req, parent, name, &e, NULL);
> if (saverr) {
> goto out;
> }
> @@ -1534,7 +1547,7 @@ static void lo_do_readdir(fuse_req_t req, fuse_ino_t
> ino, size_t size,
>
> if (plus) {
> if (!is_dot_or_dotdot(name)) {
> - err = lo_do_lookup(req, ino, name, &e);
> + err = lo_do_lookup(req, ino, name, &e, NULL);
> if (err) {
> goto error;
> }
> @@ -1732,7 +1745,7 @@ static void lo_create(fuse_req_t req, fuse_ino_t
> parent, const char *name,
> }
>
> fi->fh = fh;
> - err = lo_do_lookup(req, parent, name, &e);
> + err = lo_do_lookup(req, parent, name, &e, NULL);
> }
> if (lo->cache == CACHE_NONE) {
> fi->direct_io = 1;
