vfs: add i_op->dentry_open()

Add a new inode operation i_op->dentry_open().  This is for stacked filesystems
that want to return a struct file from a different filesystem.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
This commit is contained in:
Miklos Szeredi 2014-10-24 00:14:35 +02:00
parent f114040e3e
commit 4aa7c6346b
5 changed files with 40 additions and 5 deletions

View file

@ -67,6 +67,7 @@ prototypes:
struct file *, unsigned open_flag,
umode_t create_mode, int *opened);
int (*tmpfile) (struct inode *, struct dentry *, umode_t);
int (*dentry_open)(struct dentry *, struct file *, const struct cred *);
locking rules:
all may block
@ -96,6 +97,7 @@ fiemap: no
update_time: no
atomic_open: yes
tmpfile: no
dentry_open: no
Additionally, ->rmdir(), ->unlink() and ->rename() have ->i_mutex on
victim.

View file

@ -364,6 +364,7 @@ struct inode_operations {
int (*atomic_open)(struct inode *, struct dentry *, struct file *,
unsigned open_flag, umode_t create_mode, int *opened);
int (*tmpfile) (struct inode *, struct dentry *, umode_t);
int (*dentry_open)(struct dentry *, struct file *, const struct cred *);
};
Again, all methods are called without any locks being held, unless
@ -696,6 +697,12 @@ struct address_space_operations {
but instead uses bmap to find out where the blocks in the file
are and uses those addresses directly.
dentry_open: *WARNING: probably going away soon, do not use!* This is an
alternative to f_op->open(), the difference is that this method may open
a 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.
invalidatepage: If a page has PagePrivate set, then invalidatepage
will be called when part or all of the page is to be removed

View file

@ -3064,9 +3064,12 @@ finish_open_created:
error = may_open(&nd->path, acc_mode, open_flag);
if (error)
goto out;
file->f_path.mnt = nd->path.mnt;
error = finish_open(file, nd->path.dentry, NULL, opened);
if (error) {
BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */
error = vfs_open(&nd->path, file, current_cred());
if (!error) {
*opened |= FILE_OPENED;
} else {
if (error == -EOPENSTALE)
goto stale_open;
goto out;

View file

@ -823,8 +823,7 @@ struct file *dentry_open(const struct path *path, int flags,
f = get_empty_filp();
if (!IS_ERR(f)) {
f->f_flags = flags;
f->f_path = *path;
error = do_dentry_open(f, NULL, cred);
error = vfs_open(path, f, cred);
if (!error) {
/* from now on we need fput() to dispose of f */
error = open_check_o_direct(f);
@ -841,6 +840,26 @@ struct file *dentry_open(const struct path *path, 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
*/
int vfs_open(const struct path *path, struct file *filp,
const struct cred *cred)
{
struct inode *inode = path->dentry->d_inode;
if (inode->i_op->dentry_open)
return inode->i_op->dentry_open(path->dentry, filp, cred);
else {
filp->f_path = *path;
return do_dentry_open(filp, NULL, cred);
}
}
EXPORT_SYMBOL(vfs_open);
static inline int build_open_flags(int flags, umode_t mode, struct open_flags *op)
{
int lookup_flags = 0;

View file

@ -1528,6 +1528,9 @@ struct inode_operations {
umode_t create_mode, int *opened);
int (*tmpfile) (struct inode *, struct dentry *, umode_t);
int (*set_acl)(struct inode *, struct posix_acl *, int);
/* WARNING: probably going away soon, do not use! */
int (*dentry_open)(struct dentry *, struct file *, const struct cred *);
} ____cacheline_aligned;
ssize_t rw_copy_check_uvector(int type, const struct iovec __user * uvector,
@ -2040,6 +2043,7 @@ extern struct file *file_open_name(struct filename *, int, umode_t);
extern struct file *filp_open(const char *, int, umode_t);
extern struct file *file_open_root(struct dentry *, struct vfsmount *,
const char *, int);
extern int vfs_open(const struct path *, struct file *, const struct cred *);
extern struct file * dentry_open(const struct path *, int, const struct cred *);
extern int filp_close(struct file *, fl_owner_t id);