Overlayfs and cachefiles use open_with_fake_path() to allocate internal
files, where overlayfs also puts a "fake" path in f_path - a path which
is not on the same fs as f_inode.
Allocate a container struct backing_file for those internal files, that
is used to hold the "fake" ovl path along with the real path.
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
fs/cachefiles/namei.c | 4 +--
fs/file_table.c | 74 +++++++++++++++++++++++++++++++++++++------
fs/internal.h | 5 +--
fs/open.c | 30 +++++++++++-------
fs/overlayfs/file.c | 4 +--
include/linux/fs.h | 24 +++++++++++---
6 files changed, 109 insertions(+), 32 deletions(-)
diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
index 82219a8f6084..283534c6bc8d 100644
--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -560,8 +560,8 @@ static bool cachefiles_open_file(struct cachefiles_object *object,
*/
path.mnt = cache->mnt;
path.dentry = dentry;
- file = open_with_fake_path(&path, O_RDWR | O_LARGEFILE | O_DIRECT,
- d_backing_inode(dentry), cache->cache_cred);
+ file = open_backing_file(&path, O_RDWR | O_LARGEFILE | O_DIRECT,
+ &path, cache->cache_cred);
if (IS_ERR(file)) {
trace_cachefiles_vfs_error(object, d_backing_inode(dentry),
PTR_ERR(file),
diff --git a/fs/file_table.c b/fs/file_table.c
index 372653b92617..138d5d405df7 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));
+ else
percpu_counter_dec(&nr_files);
call_rcu(&f->f_rcuhead, file_free_rcu);
}
@@ -131,20 +153,15 @@ static int __init init_fs_stat_sysctls(void)
fs_initcall(init_fs_stat_sysctls);
#endif
-static struct file *__alloc_file(int flags, const struct cred *cred)
+static int init_file(struct file *f, int flags, const struct cred *cred)
{
- struct file *f;
int error;
- f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL);
- if (unlikely(!f))
- return ERR_PTR(-ENOMEM);
-
f->f_cred = get_cred(cred);
error = security_file_alloc(f);
if (unlikely(error)) {
file_free_rcu(&f->f_rcuhead);
- return ERR_PTR(error);
+ return error;
}
atomic_long_set(&f->f_count, 1);
@@ -155,6 +172,22 @@ static struct file *__alloc_file(int flags, const struct cred *cred)
f->f_mode = OPEN_FMODE(flags);
/* f->f_version: 0 */
+ return 0;
+}
+
+static struct file *__alloc_file(int flags, const struct cred *cred)
+{
+ struct file *f;
+ int error;
+
+ f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL);
+ if (unlikely(!f))
+ return ERR_PTR(-ENOMEM);
+
+ error = init_file(f, flags, cred);
+ if (unlikely(error))
+ return ERR_PTR(error);
+
return f;
}
@@ -215,6 +248,29 @@ 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.
+ *
+ * Should not be used unless there's a very good reason to do so.
+ */
+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 005ca91a173b..8f745e07a037 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -1121,23 +1121,29 @@ struct file *dentry_create(const struct path *path, int flags, umode_t mode,
}
EXPORT_SYMBOL(dentry_create);
-struct file *open_with_fake_path(const struct path *path, int flags,
- struct inode *inode, const struct cred *cred)
+struct file *open_backing_file(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(open_backing_file);
#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 39737c2aaa84..8cf099aa97de 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 = open_backing_file(&file->f_path, flags, realpath,
+ current_cred());
}
revert_creds(old_cred);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 21a981680856..8393408b9885 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)
@@ -2349,11 +2352,22 @@ 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 *open_backing_file(const struct path *path, int flags,
+ const struct path *real_path,
+ const struct cred *cred);
+struct path *backing_file_real_path(struct file *f);
+static inline const struct path *f_real_path(struct file *f)
+{
+ if (unlikely(f->f_mode & FMODE_BACKING))
+ return backing_file_real_path(f);
+ else
+ 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);
--
2.34.1
