// SPDX-License-Identifier: GPL-2.0-only/* * Common helpers for stackable filesystems and backing files. * * Forked from fs/overlayfs/file.c. * * Copyright (C) 2017 Red Hat, Inc. * Copyright (C) 2023 CTERA Networks. */ #include <linux/fs.h>#include <linux/backing-file.h>#include <linux/splice.h>#include <linux/mm.h>#include <linux/security.h> #include "internal.h" /** * backing_file_open - open a backing file for kernel internal use * @user_file:  file the user requested 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_file->f_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 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 file *user_file, int flags,			       const struct path *real_path,			       const struct cred *cred){	const struct path *user_path = file_user_path(user_file);	struct file *f;	int error; 	f = alloc_empty_backing_file(flags, cred, user_file);	if (IS_ERR(f))		return f; 	path_get(user_path);	backing_file_set_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); struct file *backing_tmpfile_open(const struct file *user_file, int flags,				  const struct path *real_parentpath,				  umode_t mode, const struct cred *cred){	struct mnt_idmap *real_idmap = mnt_idmap(real_parentpath->mnt);	const struct path *user_path = &user_file->f_path;	struct file *f;	int error; 	f = alloc_empty_backing_file(flags, cred, user_file);	if (IS_ERR(f))		return f; 	path_get(user_path);	backing_file_set_user_path(f, user_path);	error = vfs_tmpfile(real_idmap, real_parentpath, f, mode);	if (error) {		fput(f);		f = ERR_PTR(error);	}	return f;}EXPORT_SYMBOL(backing_tmpfile_open); struct backing_aio {	struct kiocb iocb;	refcount_t ref;	struct kiocb *orig_iocb;	/* used for aio completion */	void (*end_write)(struct kiocb *iocb, ssize_t);	struct work_struct work;	long res;}; static struct kmem_cache *backing_aio_cachep; #define BACKING_IOCB_MASK \	(IOCB_NOWAIT | IOCB_HIPRI | IOCB_DSYNC | IOCB_SYNC | IOCB_APPEND) static rwf_t iocb_to_rw_flags(int flags){	return (__force rwf_t)(flags & BACKING_IOCB_MASK);} static void backing_aio_put(struct backing_aio *aio){	if (refcount_dec_and_test(&aio->ref)) {		fput(aio->iocb.ki_filp);		kmem_cache_free(backing_aio_cachep, aio);	}} static void backing_aio_cleanup(struct backing_aio *aio, long res){	struct kiocb *iocb = &aio->iocb;	struct kiocb *orig_iocb = aio->orig_iocb; 	orig_iocb->ki_pos = iocb->ki_pos;	if (aio->end_write)		aio->end_write(orig_iocb, res); 	backing_aio_put(aio);} static void backing_aio_rw_complete(struct kiocb *iocb, long res){	struct backing_aio *aio = container_of(iocb, struct backing_aio, iocb);	struct kiocb *orig_iocb = aio->orig_iocb; 	if (iocb->ki_flags & IOCB_WRITE)		kiocb_end_write(iocb); 	backing_aio_cleanup(aio, res);	orig_iocb->ki_complete(orig_iocb, res);} static void backing_aio_complete_work(struct work_struct *work){	struct backing_aio *aio = container_of(work, struct backing_aio, work); 	backing_aio_rw_complete(&aio->iocb, aio->res);} static void backing_aio_queue_completion(struct kiocb *iocb, long res){	struct backing_aio *aio = container_of(iocb, struct backing_aio, iocb); 	/*	 * Punt to a work queue to serialize updates of mtime/size.	 */	aio->res = res;	INIT_WORK(&aio->work, backing_aio_complete_work);	queue_work(file_inode(aio->orig_iocb->ki_filp)->i_sb->s_dio_done_wq,		   &aio->work);} static int backing_aio_init_wq(struct kiocb *iocb){	struct super_block *sb = file_inode(iocb->ki_filp)->i_sb; 	if (sb->s_dio_done_wq)		return 0; 	return sb_init_dio_done_wq(sb);} static int do_backing_file_read_iter(struct file *file, struct iov_iter *iter,				     struct kiocb *iocb, int flags){	struct backing_aio *aio = NULL;	int ret; 	if (is_sync_kiocb(iocb)) {		rwf_t rwf = iocb_to_rw_flags(flags); 		return vfs_iter_read(file, iter, &iocb->ki_pos, rwf);	} 	aio = kmem_cache_zalloc(backing_aio_cachep, GFP_KERNEL);	if (!aio)		return -ENOMEM; 	aio->orig_iocb = iocb;	kiocb_clone(&aio->iocb, iocb, get_file(file));	aio->iocb.ki_complete = backing_aio_rw_complete;	refcount_set(&aio->ref, 2);	ret = vfs_iocb_iter_read(file, &aio->iocb, iter);	backing_aio_put(aio);	if (ret != -EIOCBQUEUED)		backing_aio_cleanup(aio, ret);	return ret;} ssize_t backing_file_read_iter(struct file *file, struct iov_iter *iter,			       struct kiocb *iocb, int flags,			       struct backing_file_ctx *ctx){	ssize_t ret; 	if (WARN_ON_ONCE(!(file->f_mode & FMODE_BACKING)))		return -EIO; 	if (!iov_iter_count(iter))		return 0; 	if (iocb->ki_flags & IOCB_DIRECT &&	    !(file->f_mode & FMODE_CAN_ODIRECT))		return -EINVAL; 	scoped_with_creds(ctx->cred)		ret = do_backing_file_read_iter(file, iter, iocb, flags); 	if (ctx->accessed)		ctx->accessed(iocb->ki_filp); 	return ret;}EXPORT_SYMBOL_GPL(backing_file_read_iter); static int do_backing_file_write_iter(struct file *file, struct iov_iter *iter,				      struct kiocb *iocb, int flags,				      void (*end_write)(struct kiocb *, ssize_t)){	struct backing_aio *aio;	int ret; 	if (is_sync_kiocb(iocb)) {		rwf_t rwf = iocb_to_rw_flags(flags); 		ret = vfs_iter_write(file, iter, &iocb->ki_pos, rwf);		if (end_write)			end_write(iocb, ret);		return ret;	} 	ret = backing_aio_init_wq(iocb);	if (ret)		return ret; 	aio = kmem_cache_zalloc(backing_aio_cachep, GFP_KERNEL);	if (!aio)		return -ENOMEM; 	aio->orig_iocb = iocb;	aio->end_write = end_write;	kiocb_clone(&aio->iocb, iocb, get_file(file));	aio->iocb.ki_flags = flags;	aio->iocb.ki_complete = backing_aio_queue_completion;	refcount_set(&aio->ref, 2);	ret = vfs_iocb_iter_write(file, &aio->iocb, iter);	backing_aio_put(aio);	if (ret != -EIOCBQUEUED)		backing_aio_cleanup(aio, ret);	return ret;} ssize_t backing_file_write_iter(struct file *file, struct iov_iter *iter,				struct kiocb *iocb, int flags,				struct backing_file_ctx *ctx){	ssize_t ret; 	if (WARN_ON_ONCE(!(file->f_mode & FMODE_BACKING)))		return -EIO; 	if (!iov_iter_count(iter))		return 0; 	ret = file_remove_privs(iocb->ki_filp);	if (ret)		return ret; 	if (iocb->ki_flags & IOCB_DIRECT &&	    !(file->f_mode & FMODE_CAN_ODIRECT))		return -EINVAL; 	scoped_with_creds(ctx->cred)		return do_backing_file_write_iter(file, iter, iocb, flags, ctx->end_write);}EXPORT_SYMBOL_GPL(backing_file_write_iter); ssize_t backing_file_splice_read(struct file *in, struct kiocb *iocb,				 struct pipe_inode_info *pipe, size_t len,				 unsigned int flags,				 struct backing_file_ctx *ctx){	ssize_t ret; 	if (WARN_ON_ONCE(!(in->f_mode & FMODE_BACKING)))		return -EIO; 	scoped_with_creds(ctx->cred)		ret = vfs_splice_read(in, &iocb->ki_pos, pipe, len, flags); 	if (ctx->accessed)		ctx->accessed(iocb->ki_filp); 	return ret;}EXPORT_SYMBOL_GPL(backing_file_splice_read); ssize_t backing_file_splice_write(struct pipe_inode_info *pipe,				  struct file *out, struct kiocb *iocb,				  size_t len, unsigned int flags,				  struct backing_file_ctx *ctx){	ssize_t ret; 	if (WARN_ON_ONCE(!(out->f_mode & FMODE_BACKING)))		return -EIO; 	if (!out->f_op->splice_write)		return -EINVAL; 	ret = file_remove_privs(iocb->ki_filp);	if (ret)		return ret; 	scoped_with_creds(ctx->cred) {		file_start_write(out);		ret = out->f_op->splice_write(pipe, out, &iocb->ki_pos, len, flags);		file_end_write(out);	} 	if (ctx->end_write)		ctx->end_write(iocb, ret); 	return ret;}EXPORT_SYMBOL_GPL(backing_file_splice_write); int backing_file_mmap(struct file *file, struct vm_area_struct *vma,		      struct backing_file_ctx *ctx){	struct file *user_file = vma->vm_file;	int ret; 	if (WARN_ON_ONCE(!(file->f_mode & FMODE_BACKING)))		return -EIO; 	if (!can_mmap_file(file))		return -ENODEV; 	vma_set_file(vma, file); 	scoped_with_creds(ctx->cred) {		ret = security_mmap_backing_file(vma, file, user_file);		if (ret)			return ret; 		ret = vfs_mmap(vma->vm_file, vma);	} 	if (ctx->accessed)		ctx->accessed(user_file); 	return ret;}EXPORT_SYMBOL_GPL(backing_file_mmap); static int __init backing_aio_init(void){	backing_aio_cachep = KMEM_CACHE(backing_aio, SLAB_HWCACHE_ALIGN);	if (!backing_aio_cachep)		return -ENOMEM; 	return 0;}fs_initcall(backing_aio_init);