fs: Preserve error code in get_empty_filp(), part 2

Allocating a file structure in function get_empty_filp() might fail because
of several reasons:
 - not enough memory for file structures
 - operation is not allowed
 - user is over its limit

Currently the function returns NULL in all cases and we loose the exact
reason of the error. All callers of get_empty_filp() assume that the function
can fail with ENFILE only.

Return error through pointer. Change all callers to preserve this error code.

[AV: cleaned up a bit, carved the get_empty_filp() part out into a separate commit
(things remaining here deal with alloc_file()), removed pipe(2) behaviour change]

Signed-off-by: Anatol Pomozov <anatol.pomozov@gmail.com>
Reviewed-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/anon_inodes.c

@@ -131,7 +131,6 @@ struct file *anon_inode_getfile(const char *name,
 	struct qstr this;
 	struct path path;
 	struct file *file;
-	int error;
 
 	if (IS_ERR(anon_inode_inode))
 		return ERR_PTR(-ENODEV);
@@ -143,7 +142,7 @@ struct file *anon_inode_getfile(const char *name,
 	 * Link the inode to a directory entry by creating a unique name
 	 * using the inode sequence number.
 	 */
-	error = -ENOMEM;
+	file = ERR_PTR(-ENOMEM);
 	this.name = name;
 	this.len = strlen(name);
 	this.hash = 0;
@@ -160,9 +159,8 @@ struct file *anon_inode_getfile(const char *name,
 
 	d_instantiate(path.dentry, anon_inode_inode);
 
-	error = -ENFILE;
 	file = alloc_file(&path, OPEN_FMODE(flags), fops);
-	if (!file)
+	if (IS_ERR(file))
 		goto err_dput;
 	file->f_mapping = anon_inode_inode->i_mapping;
 
@@ -177,7 +175,7 @@ err_dput:
 	path_put(&path);
 err_module:
 	module_put(fops->owner);
-	return ERR_PTR(error);
+	return file;
 }
 EXPORT_SYMBOL_GPL(anon_inode_getfile);
 

fs/file_table.c

@@ -173,7 +173,7 @@ struct file *alloc_file(struct path *path, fmode_t mode,
 
 	file = get_empty_filp();
 	if (IS_ERR(file))
-		return NULL;
+		return file;
 
 	file->f_path = *path;
 	file->f_mapping = path->dentry->d_inode->i_mapping;

fs/hugetlbfs/inode.c

@@ -923,8 +923,7 @@ struct file *hugetlb_file_setup(const char *name, unsigned long addr,
 				struct user_struct **user,
 				int creat_flags, int page_size_log)
 {
-	int error = -ENOMEM;
-	struct file *file;
+	struct file *file = ERR_PTR(-ENOMEM);
 	struct inode *inode;
 	struct path path;
 	struct dentry *root;
@@ -964,7 +963,7 @@ struct file *hugetlb_file_setup(const char *name, unsigned long addr,
 		goto out_shm_unlock;
 
 	path.mnt = mntget(hugetlbfs_vfsmount[hstate_idx]);
-	error = -ENOSPC;
+	file = ERR_PTR(-ENOSPC);
 	inode = hugetlbfs_get_inode(root->d_sb, NULL, S_IFREG | S_IRWXUGO, 0);
 	if (!inode)
 		goto out_dentry;
@@ -973,7 +972,7 @@ struct file *hugetlb_file_setup(const char *name, unsigned long addr,
 	size += addr & ~huge_page_mask(hstate);
 	num_pages = ALIGN(size, huge_page_size(hstate)) >>
 			huge_page_shift(hstate);
-	error = -ENOMEM;
+	file = ERR_PTR(-ENOMEM);
 	if (hugetlb_reserve_pages(inode, 0, num_pages, NULL, acctflag))
 		goto out_inode;
 
@@ -981,10 +980,9 @@ struct file *hugetlb_file_setup(const char *name, unsigned long addr,
 	inode->i_size = size;
 	clear_nlink(inode);
 
-	error = -ENFILE;
 	file = alloc_file(&path, FMODE_WRITE | FMODE_READ,
 			&hugetlbfs_file_operations);
-	if (!file)
+	if (IS_ERR(file))
 		goto out_dentry; /* inode is already attached */
 
 	return file;
@@ -998,7 +996,7 @@ out_shm_unlock:
 		user_shm_unlock(size, *user);
 		*user = NULL;
 	}
-	return ERR_PTR(error);
+	return file;
 }
 
 static int __init init_hugetlbfs_fs(void)

fs/pipe.c

@@ -1037,13 +1037,13 @@ int create_pipe_files(struct file **res, int flags)
 
 	err = -ENFILE;
 	f = alloc_file(&path, FMODE_WRITE, &write_pipefifo_fops);
-	if (!f)
+	if (IS_ERR(f))
 		goto err_dentry;
 
 	f->f_flags = O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT));
 
 	res[0] = alloc_file(&path, FMODE_READ, &read_pipefifo_fops);
-	if (!res[0])
+	if (IS_ERR(res[0]))
 		goto err_file;
 
 	path_get(&path);