diff options
| -rw-r--r-- | fs/file_table.c | 50 | ||||
| -rw-r--r-- | fs/internal.h | 5 | ||||
| -rw-r--r-- | fs/open.c | 45 | ||||
| -rw-r--r-- | fs/overlayfs/file.c | 4 | ||||
| -rw-r--r-- | include/linux/fs.h | 33 |
5 files changed, 114 insertions, 23 deletions
diff --git a/fs/file_table.c b/fs/file_table.c index 4bc713865212..e06c68e2d757 100644 --- a/fs/file_table.c +++ b/fs/file_table.c @@ -44,18 +44,40 @@ static struct kmem_cache *filp_cachep __read_mostly; static struct percpu_counter nr_files __cacheline_aligned_in_smp; +/* Container for backing file with optional real path */ +struct backing_file { + struct file file; + struct path real_path; +}; + +static inline struct backing_file *backing_file(struct file *f) +{ + return container_of(f, struct backing_file, file); +} + +struct path *backing_file_real_path(struct file *f) +{ + return &backing_file(f)->real_path; +} +EXPORT_SYMBOL_GPL(backing_file_real_path); + static void file_free_rcu(struct rcu_head *head) { struct file *f = container_of(head, struct file, f_rcuhead); put_cred(f->f_cred); - kmem_cache_free(filp_cachep, f); + if (unlikely(f->f_mode & FMODE_BACKING)) + kfree(backing_file(f)); + else + kmem_cache_free(filp_cachep, f); } static inline void file_free(struct file *f) { security_file_free(f); - if (!(f->f_mode & FMODE_NOACCOUNT)) + if (unlikely(f->f_mode & FMODE_BACKING)) + path_put(backing_file_real_path(f)); + if (likely(!(f->f_mode & FMODE_NOACCOUNT))) percpu_counter_dec(&nr_files); call_rcu(&f->f_rcuhead, file_free_rcu); } @@ -226,6 +248,30 @@ struct file *alloc_empty_file_noaccount(int flags, const struct cred *cred) return f; } +/* + * Variant of alloc_empty_file() that allocates a backing_file container + * and doesn't check and modify nr_files. + * + * This is only for kernel internal use, and the allocate file must not be + * installed into file tables or such. + */ +struct file *alloc_empty_backing_file(int flags, const struct cred *cred) +{ + struct backing_file *ff; + int error; + + ff = kzalloc(sizeof(struct backing_file), GFP_KERNEL); + if (unlikely(!ff)) + return ERR_PTR(-ENOMEM); + + error = init_file(&ff->file, flags, cred); + if (unlikely(error)) + return ERR_PTR(error); + + ff->file.f_mode |= FMODE_BACKING | FMODE_NOACCOUNT; + return &ff->file; +} + /** * alloc_file - allocate and initialize a 'struct file' * diff --git a/fs/internal.h b/fs/internal.h index bd3b2810a36b..9c31078e0d16 100644 --- a/fs/internal.h +++ b/fs/internal.h @@ -97,8 +97,9 @@ extern void chroot_fs_refs(const struct path *, const struct path *); /* * file_table.c */ -extern struct file *alloc_empty_file(int, const struct cred *); -extern struct file *alloc_empty_file_noaccount(int, const struct cred *); +struct file *alloc_empty_file(int flags, const struct cred *cred); +struct file *alloc_empty_file_noaccount(int flags, const struct cred *cred); +struct file *alloc_empty_backing_file(int flags, const struct cred *cred); static inline void put_file_access(struct file *file) { diff --git a/fs/open.c b/fs/open.c index 322e017bf480..81186b277815 100644 --- a/fs/open.c +++ b/fs/open.c @@ -1149,23 +1149,44 @@ struct file *kernel_file_open(const struct path *path, int flags, } EXPORT_SYMBOL_GPL(kernel_file_open); -struct file *open_with_fake_path(const struct path *path, int flags, - struct inode *inode, const struct cred *cred) +/** + * backing_file_open - open a backing file for kernel internal use + * @path: path of the file to open + * @flags: open flags + * @path: path of the backing file + * @cred: credentials for open + * + * Open a backing file for a stackable filesystem (e.g., overlayfs). + * @path may be on the stackable filesystem and backing inode on the + * underlying filesystem. In this case, we want to be able to return + * the @real_path of the backing inode. This is done by embedding the + * returned file into a container structure that also stores the path of + * the backing inode on the underlying filesystem, which can be + * retrieved using backing_file_real_path(). + */ +struct file *backing_file_open(const struct path *path, int flags, + const struct path *real_path, + const struct cred *cred) { - struct file *f = alloc_empty_file_noaccount(flags, cred); - if (!IS_ERR(f)) { - int error; + struct file *f; + int error; - f->f_path = *path; - error = do_dentry_open(f, inode, NULL); - if (error) { - fput(f); - f = ERR_PTR(error); - } + f = alloc_empty_backing_file(flags, cred); + if (IS_ERR(f)) + return f; + + f->f_path = *path; + path_get(real_path); + *backing_file_real_path(f) = *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(open_with_fake_path); +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) diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c index 7c04f033aadd..71fa6c83f093 100644 --- a/fs/overlayfs/file.c +++ b/fs/overlayfs/file.c @@ -61,8 +61,8 @@ static struct file *ovl_open_realfile(const struct file *file, if (!inode_owner_or_capable(real_idmap, realinode)) flags &= ~O_NOATIME; - realfile = open_with_fake_path(&file->f_path, flags, realinode, - current_cred()); + realfile = backing_file_open(&file->f_path, flags, realpath, + current_cred()); } revert_creds(old_cred); diff --git a/include/linux/fs.h b/include/linux/fs.h index 1f8486e773af..24e1be1c13ca 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -171,6 +171,9 @@ typedef int (dio_iodone_t)(struct kiocb *iocb, loff_t offset, /* File supports non-exclusive O_DIRECT writes from multiple threads */ #define FMODE_DIO_PARALLEL_WRITE ((__force fmode_t)0x1000000) +/* File is embedded in backing_file object */ +#define FMODE_BACKING ((__force fmode_t)0x2000000) + /* File was opened by fanotify and shouldn't generate fanotify events */ #define FMODE_NONOTIFY ((__force fmode_t)0x4000000) @@ -2352,11 +2355,31 @@ static inline struct file *file_open_root_mnt(struct vfsmount *mnt, return file_open_root(&(struct path){.mnt = mnt, .dentry = mnt->mnt_root}, name, flags, mode); } -extern struct file * dentry_open(const struct path *, int, const struct cred *); -extern struct file *dentry_create(const struct path *path, int flags, - umode_t mode, const struct cred *cred); -extern struct file * open_with_fake_path(const struct path *, int, - struct inode*, const struct cred *); +struct file *dentry_open(const struct path *path, int flags, + const struct cred *creds); +struct file *dentry_create(const struct path *path, int flags, umode_t mode, + const struct cred *cred); +struct file *backing_file_open(const struct path *path, int flags, + const struct path *real_path, + const struct cred *cred); +struct path *backing_file_real_path(struct file *f); + +/* + * file_real_path - get the path corresponding to f_inode + * + * When opening a backing file for a stackable filesystem (e.g., + * overlayfs) f_path may be on the stackable filesystem and f_inode on + * the underlying filesystem. When the path associated with f_inode is + * needed, this helper should be used instead of accessing f_path + * directly. +*/ +static inline const struct path *file_real_path(struct file *f) +{ + if (unlikely(f->f_mode & FMODE_BACKING)) + return backing_file_real_path(f); + return &f->f_path; +} + static inline struct file *file_clone_open(struct file *file) { return dentry_open(&file->f_path, file->f_flags, file->f_cred); |