Commit f91a704f authored by Amir Goldstein's avatar Amir Goldstein
Browse files

fs: prepare for stackable filesystems backing file helpers 



In preparation for factoring out some backing file io helpers from
overlayfs, move backing_file_open() into a new file fs/backing-file.c
and header.

Add a MAINTAINERS entry for stackable filesystems and add a Kconfig
FS_STACK which stackable filesystems need to select.

For now, the backing_file struct, the backing_file alloc/free functions
and the backing_file_real_path() accessor remain internal to file_table.c.
We may change that in the future.

Signed-off-by: default avatarAmir Goldstein <amir73il@gmail.com>
parent d9e5d310

MAINTAINERS

+9 −0
Original line number Diff line number Diff line
@@ -8186,6 +8186,15 @@ S: Supported 
F:	fs/iomap/

F:	include/linux/iomap.h









FILESYSTEMS [STACKABLE]









M:	Miklos Szeredi <miklos@szeredi.hu>









M:	Amir Goldstein <amir73il@gmail.com>









L:	linux-fsdevel@vger.kernel.org









L:	linux-unionfs@vger.kernel.org









S:	Maintained









F:	fs/backing-file.c









F:	include/linux/backing-file.h

















FINTEK F75375S HARDWARE MONITOR AND FAN CONTROLLER DRIVER









M:	Riku Voipio <riku.voipio@iki.fi>









L:	linux-hwmon@vger.kernel.org
































fs/Kconfig



+4
−0






























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Diff line number
Diff line







@@ -18,6 +18,10 @@ config VALIDATE_FS_PARSER







config FS_IOMAP









	bool



















# Stackable filesystems









config FS_STACK









	bool



















config BUFFER_HEAD









	bool










































fs/Makefile



+1
−0






























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Diff line number
Diff line







@@ -39,6 +39,7 @@ obj-$(CONFIG_COMPAT_BINFMT_ELF)	+= compat_binfmt_elf.o







obj-$(CONFIG_BINFMT_ELF_FDPIC)	+= binfmt_elf_fdpic.o









obj-$(CONFIG_BINFMT_FLAT)	+= binfmt_flat.o



















obj-$(CONFIG_FS_STACK)		+= backing-file.o









obj-$(CONFIG_FS_MBCACHE)	+= mbcache.o









obj-$(CONFIG_FS_POSIX_ACL)	+= posix_acl.o









obj-$(CONFIG_NFS_COMMON)	+= nfs_common/
































fs/backing-file.c
0 → 100644



+48
−0






























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Diff line number
Diff line









// SPDX-License-Identifier: GPL-2.0-only









/*









 * Common helpers for stackable filesystems and backing files.









 *









 * Copyright (C) 2023 CTERA Networks.









 */



















#include <linux/fs.h>









#include <linux/backing-file.h>



















#include "internal.h"



















/**









 * backing_file_open - open a backing file for kernel internal use









 * @user_path:	path that the user reuqested to open









 * @flags:	open flags









 * @real_path:	path of the backing file









 * @cred:	credentials for open









 *









 * Open a backing file for a stackable filesystem (e.g., overlayfs).









 * @user_path may be on the stackable filesystem and @real_path on the









 * underlying filesystem.  In this case, we want to be able to return the









 * @user_path of the stackable filesystem. This is done by embedding the









 * returned file into a container structure that also stores the stacked









 * file's path, which can be retrieved using backing_file_user_path().









 */









struct file *backing_file_open(const struct path *user_path, int flags,









			       const struct path *real_path,









			       const struct cred *cred)









{









	struct file *f;









	int error;



















	f = alloc_empty_backing_file(flags, cred);









	if (IS_ERR(f))









		return f;



















	path_get(user_path);









	*backing_file_user_path(f) = *user_path;









	error = vfs_open(real_path, f);









	if (error) {









		fput(f);









		f = ERR_PTR(error);









	}



















	return f;









}









EXPORT_SYMBOL_GPL(backing_file_open);
























fs/open.c



+0
−38






























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@@ -1184,44 +1184,6 @@ struct file *kernel_file_open(const struct path *path, int flags,







}









EXPORT_SYMBOL_GPL(kernel_file_open);



















/**









 * backing_file_open - open a backing file for kernel internal use









 * @user_path:	path that the user reuqested to open









 * @flags:	open flags









 * @real_path:	path of the backing file









 * @cred:	credentials for open









 *









 * Open a backing file for a stackable filesystem (e.g., overlayfs).









 * @user_path may be on the stackable filesystem and @real_path on the









 * underlying filesystem.  In this case, we want to be able to return the









 * @user_path of the stackable filesystem. This is done by embedding the









 * returned file into a container structure that also stores the stacked









 * file's path, which can be retrieved using backing_file_user_path().









 */









struct file *backing_file_open(const struct path *user_path, int flags,









			       const struct path *real_path,









			       const struct cred *cred)









{









	struct file *f;









	int error;



















	f = alloc_empty_backing_file(flags, cred);









	if (IS_ERR(f))









		return f;



















	path_get(user_path);









	*backing_file_user_path(f) = *user_path;









	f->f_path = *real_path;









	error = do_dentry_open(f, d_inode(real_path->dentry), NULL);









	if (error) {









		fput(f);









		f = ERR_PTR(error);









	}



















	return f;









}









EXPORT_SYMBOL_GPL(backing_file_open);



















#define WILL_CREATE(flags)	(flags & (O_CREAT | __O_TMPFILE))









#define O_PATH_FLAGS		(O_DIRECTORY | O_NOFOLLOW | O_PATH | O_CLOEXEC)