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authorMiklos Szeredi <mszeredi@suse.cz>2014-10-24 00:14:35 +0200
committerMiklos Szeredi <mszeredi@suse.cz>2014-10-24 00:14:35 +0200
commit4aa7c6346be395bdf776f82bbb2e3e2bc60bdd2b (patch)
treea2135754a04370e7fcf7b867b0f4fbeaa58b3521
parentf114040e3ea6e07372334ade75d1ee0775c355e1 (diff)
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>
-rw-r--r--Documentation/filesystems/Locking2
-rw-r--r--Documentation/filesystems/vfs.txt7
-rw-r--r--fs/namei.c9
-rw-r--r--fs/open.c23
-rw-r--r--include/linux/fs.h4
5 files changed, 40 insertions, 5 deletions
diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index 94d93b1f8b53..b30753cbf431 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -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.
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index fceff7c00a3c..20bf204426ca 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -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
diff --git a/fs/namei.c b/fs/namei.c
index 43927d14db67..75306b3c9526 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -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;
diff --git a/fs/open.c b/fs/open.c
index d6fd3acde134..de92c13b58be 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -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;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index a957d4366c24..5cf7f6759679 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -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);