[PATCH v2 15/21] fuse: add passthrough support for create+open

[Joanne Koong <joannelkoong@gmail.com>]

Use the extended fuse_entry2_out reply for FUSE_CREATE and FUSE_TMPFILE
when FUSE_PASSTHROUGH_INO is enabled. If the server returns a backing
id, the newly created inode is associated with the backing file for
passthrough operations before the dentry is instantiated.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
---
 fs/fuse/dir.c | 43 +++++++++++++++++++++++++++++++++++--------
 1 file changed, 35 insertions(+), 8 deletions(-)

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index a11f9e4c1999..4c7e3e1604af 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -934,9 +934,12 @@ static int fuse_create_open(struct mnt_idmap *idmap, struct inode *dir,
 	struct fuse_create_in inarg;
 	struct fuse_open_out *outopenp;
 	struct fuse_entry_out outentry;
+	struct fuse_entry2_out outentry2;
+	struct fuse_statx *sx = NULL;
 	struct fuse_inode *fi;
 	struct fuse_file *ff;
 	int epoch, err;
+	int backing_id;
 	bool trunc = flags & O_TRUNC;
 
 	/* Userspace expects S_IFREG in create mode */
@@ -957,7 +960,6 @@ static int fuse_create_open(struct mnt_idmap *idmap, struct inode *dir,
 
 	flags &= ~O_NOCTTY;
 	memset(&inarg, 0, sizeof(inarg));
-	memset(&outentry, 0, sizeof(outentry));
 	inarg.flags = flags;
 	inarg.mode = mode;
 	inarg.umask = current_umask();
@@ -975,8 +977,15 @@ static int fuse_create_open(struct mnt_idmap *idmap, struct inode *dir,
 	args.in_args[1].size = entry->d_name.len + 1;
 	args.in_args[1].value = entry->d_name.name;
 	args.out_numargs = 2;
-	args.out_args[0].size = sizeof(outentry);
-	args.out_args[0].value = &outentry;
+	if (fuse_use_entry2(fm->fc)) {
+		memset(&outentry2, 0, sizeof(outentry2));
+		args.out_args[0].size = sizeof(outentry2);
+		args.out_args[0].value = &outentry2;
+	} else {
+		memset(&outentry, 0, sizeof(outentry));
+		args.out_args[0].size = sizeof(outentry);
+		args.out_args[0].value = &outentry;
+	}
 	/* Store outarg for fuse_finish_open() */
 	outopenp = &ff->args->open_outarg;
 	args.out_args[1].size = sizeof(*outopenp);
@@ -991,6 +1000,8 @@ static int fuse_create_open(struct mnt_idmap *idmap, struct inode *dir,
 	if (err)
 		goto out_free_ff;
 
+	backing_id = fuse_process_entry2(fm->fc, &outentry2, &outentry, &sx);
+
 	err = -EIO;
 	if (!S_ISREG(outentry.attr.mode) || invalid_nodeid(outentry.nodeid) ||
 	    fuse_invalid_attr(&outentry.attr))
@@ -999,16 +1010,26 @@ static int fuse_create_open(struct mnt_idmap *idmap, struct inode *dir,
 	ff->fh = outopenp->fh;
 	ff->nodeid = outentry.nodeid;
 	ff->open_flags = outopenp->open_flags;
+
+	if (backing_id < 0) {
+		err = backing_id;
+		goto out_queue_forget;
+	}
+
 	inode = fuse_iget(dir->i_sb, outentry.nodeid, outentry.generation,
-			  &outentry.attr, NULL, ATTR_TIMEOUT(&outentry), 0, 0);
+			  &outentry.attr, sx, ATTR_TIMEOUT(&outentry), 0, 0);
 	if (!inode) {
-		flags &= ~(O_CREAT | O_EXCL | O_TRUNC);
-		fuse_sync_release(NULL, ff, flags, false);
-		fuse_chan_queue_forget(fm->fc->chan, forget, outentry.nodeid, 1);
 		err = -ENOMEM;
-		goto out_err;
+		goto out_queue_forget;
 	}
 	kfree(forget);
+	if (backing_id) {
+		err = fuse_inode_set_passthrough(inode, backing_id);
+		if (err) {
+			iput(inode);
+			goto out_sync_release;
+		}
+	}
 	d_instantiate(entry, inode);
 	entry->d_time = epoch;
 	fuse_change_entry_timeout(entry, &outentry);
@@ -1035,6 +1056,12 @@ static int fuse_create_open(struct mnt_idmap *idmap, struct inode *dir,
 	kfree(forget);
 out_err:
 	return err;
+out_queue_forget:
+	fuse_chan_queue_forget(fm->fc->chan, forget, outentry.nodeid, 1);
+out_sync_release:
+	flags &= ~(O_CREAT | O_EXCL | O_TRUNC);
+	fuse_sync_release(NULL, ff, flags, false);
+	return err;
 }
 
 static int fuse_mknod(struct mnt_idmap *, struct inode *, struct dentry *,
-- 
2.52.0