@@ -61,6 +61,7 @@ ata *);
int (*removexattr) (struct dentry *, const char *);
void (*truncate_range)(struct inode *, loff_t, loff_t);
int (*fiemap)(struct inode *, struct fiemap_extent_info *, u64 start, u64 len);
+ struct file *(*open)(struct dentry *,struct file *,const struct cred *);
locking rules:
all may block
@@ -88,6 +89,7 @@ listxattr: no
removexattr: yes
truncate_range: yes
fiemap: no
+open: no
Additionally, ->rmdir(), ->unlink() and ->rename() have ->i_mutex on
victim.
cross-directory ->rename() has (per-superblock) ->s_vfs_rename_sem.
@@ -364,6 +364,8 @@ struct inode_operations {
ssize_t (*listxattr) (struct dentry *, char *, size_t);
int (*removexattr) (struct dentry *, const char *);
void (*truncate_range)(struct inode *, loff_t, loff_t);
+ struct file *(*open) (struct dentry *, struct file *,
+ const struct cred *);
};
Again, all methods are called without any locks being held, unless
@@ -475,6 +477,12 @@ otherwise noted.
truncate_range: a method provided by the underlying filesystem to truncate a
range of blocks , i.e. punch a hole somewhere in a file.
+ open: this is an alternative to f_op->open(), the difference is that this
+ method may return any open file, not necessarily originating from the
+ same filesystem as the one i_op->open() was called on. It may be useful
+ for stacking filesystems which want to allow native I/O directly on
+ underlying files.
+
The Address Space Object
========================
@@ -795,7 +795,7 @@ struct file *nameidata_to_filp(struct nameidata *nd)
/* Has the filesystem initialised the file for us? */
if (filp->f_path.dentry == NULL)
- filp = __dentry_open(&nd->path, filp, NULL, cred);
+ filp = vfs_open(&nd->path, filp, cred);
return filp;
}
@@ -820,7 +820,7 @@ struct file *dentry_open(struct dentry *dentry, struct vfsmount *mnt, int flags,
f = get_empty_filp();
if (f != NULL) {
f->f_flags = flags;
- ret = __dentry_open(&path, f, NULL, cred);
+ ret = vfs_open(&path, f, cred);
}
path_put(&path);
@@ -828,6 +828,27 @@ struct file *dentry_open(struct dentry *dentry, struct vfsmount *mnt, int flags,
}
EXPORT_SYMBOL(dentry_open);
+/**
+ * vfs_open - open the file at the given path
+ * @path: path to open
+ * @filp: newly allocated file with f_flag initialized
+ * @cred: credentials to use
+ *
+ * Open the file. If successful, the returned file will have acquired
+ * an additional reference for path.
+ */
+struct file *vfs_open(struct path *path, struct file *filp,
+ const struct cred *cred)
+{
+ struct inode *inode = path->dentry->d_inode;
+
+ if (inode->i_op->open)
+ return inode->i_op->open(path->dentry, filp, cred);
+ else
+ return __dentry_open(path, filp, NULL, cred);
+}
+EXPORT_SYMBOL(vfs_open);
+
static void __put_unused_fd(struct files_struct *files, unsigned int fd)
{
struct fdtable *fdt = files_fdtable(files);
@@ -1618,6 +1618,8 @@ struct inode_operations {
void (*truncate_range)(struct inode *, loff_t, loff_t);
int (*fiemap)(struct inode *, struct fiemap_extent_info *, u64 start,
u64 len);
+ struct file *(*open) (struct dentry *, struct file *,
+ const struct cred *);
} ____cacheline_aligned;
struct seq_file;
@@ -2023,6 +2025,7 @@ extern long do_sys_open(int dfd, const char __user *filename, int flags,
extern struct file *filp_open(const char *, int, int);
extern struct file *file_open_root(struct dentry *, struct vfsmount *,
const char *, int);
+extern struct file *vfs_open(struct path *, struct file *, const struct cred *);
extern struct file * dentry_open(struct dentry *, struct vfsmount *, int,
const struct cred *);
extern int filp_close(struct file *, fl_owner_t id);