fuse: prepare for failing open response

In preparation for inode io modes, a server open response could fail due to
conflicting inode io modes.

Allow returning an error from fuse_finish_open() and handle the error in
the callers.

fuse_finish_open() is used as the callback of finish_open(), so that
FMODE_OPENED will not be set if fuse_finish_open() fails.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fs/fuse/dir.c

@@ -692,13 +692,15 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry,
 	d_instantiate(entry, inode);
 	fuse_change_entry_timeout(entry, &outentry);
 	fuse_dir_changed(dir);
-	err = finish_open(file, entry, generic_file_open);
+	err = generic_file_open(inode, file);
+	if (!err) {
+		file->private_data = ff;
+		err = finish_open(file, entry, fuse_finish_open);
+	}
 	if (err) {
 		fi = get_fuse_inode(inode);
 		fuse_sync_release(fi, ff, flags);
 	} else {
-		file->private_data = ff;
-		fuse_finish_open(inode, file);
 		if (fm->fc->atomic_o_trunc && trunc)
 			truncate_pagecache(inode, 0);
 		else if (!(ff->open_flags & FOPEN_KEEP_CACHE))

fs/fuse/file.c

@@ -200,7 +200,7 @@ static void fuse_link_write_file(struct file *file)
 	spin_unlock(&fi->lock);
 }
 
-void fuse_finish_open(struct inode *inode, struct file *file)
+int fuse_finish_open(struct inode *inode, struct file *file)
 {
 	struct fuse_file *ff = file->private_data;
 	struct fuse_conn *fc = get_fuse_conn(inode);
@@ -212,6 +212,8 @@ void fuse_finish_open(struct inode *inode, struct file *file)
 
 	if ((file->f_mode & FMODE_WRITE) && fc->writeback_cache)
 		fuse_link_write_file(file);
+
+	return 0;
 }
 
 static void fuse_truncate_update_attr(struct inode *inode, struct file *file)
@@ -230,7 +232,9 @@ static void fuse_truncate_update_attr(struct inode *inode, struct file *file)
 static int fuse_open(struct inode *inode, struct file *file)
 {
 	struct fuse_mount *fm = get_fuse_mount(inode);
+	struct fuse_inode *fi = get_fuse_inode(inode);
 	struct fuse_conn *fc = fm->fc;
+	struct fuse_file *ff;
 	int err;
 	bool is_truncate = (file->f_flags & O_TRUNC) && fc->atomic_o_trunc;
 	bool is_wb_truncate = is_truncate && fc->writeback_cache;
@@ -258,16 +262,17 @@ static int fuse_open(struct inode *inode, struct file *file)
 
 	err = fuse_do_open(fm, get_node_id(inode), file, false);
 	if (!err) {
-		fuse_finish_open(inode, file);
-		if (is_truncate)
+		ff = file->private_data;
+		err = fuse_finish_open(inode, file);
+		if (err)
+			fuse_sync_release(fi, ff, file->f_flags);
+		else if (is_truncate)
 			fuse_truncate_update_attr(inode, file);
 	}
 
 	if (is_wb_truncate || dax_truncate)
 		fuse_release_nowrite(inode);
 	if (!err) {
-		struct fuse_file *ff = file->private_data;
-
 		if (is_truncate)
 			truncate_pagecache(inode, 0);
 		else if (!(ff->open_flags & FOPEN_KEEP_CACHE))

fs/fuse/fuse_i.h

@@ -1033,7 +1033,7 @@ void fuse_read_args_fill(struct fuse_io_args *ia, struct file *file, loff_t pos,
 
 struct fuse_file *fuse_file_alloc(struct fuse_mount *fm, bool release);
 void fuse_file_free(struct fuse_file *ff);
-void fuse_finish_open(struct inode *inode, struct file *file);
+int fuse_finish_open(struct inode *inode, struct file *file);
 
 void fuse_sync_release(struct fuse_inode *fi, struct fuse_file *ff,
 		       unsigned int flags);