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Subject[RFC PATCH 02/35] vfs: add path_open()
Date
Currently opening an overlay file results in:

- the real file on the underlying layer being opened
- f_path being set to the overlay {mount, dentry} pair

This patch adds a new helper that allows the above to be explicitly
performed. I.e. it's the same as dentry_open(), except the underlying
inode to open is given as a separate argument.

This is in preparation for stacking I/O operations on overlay files.

Later, when implicit opening is removed, dentry_open() can be implemented
by just calling path_open().

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
---
fs/open.c | 27 +++++++++++++++++++++++++++
include/linux/fs.h | 2 ++
2 files changed, 29 insertions(+)

diff --git a/fs/open.c b/fs/open.c
index 7ea118471dce..8c315f9ec2f6 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -866,6 +866,33 @@ int vfs_open(const struct path *path, struct file *file,
return do_dentry_open(file, d_backing_inode(dentry), NULL, cred);
}

+struct file *path_open(const struct path *path, int flags, struct inode *inode,
+ const struct cred *cred)
+{
+ struct file *file;
+ int retval;
+
+ file = get_empty_filp();
+ if (!IS_ERR(file)) {
+ file->f_flags = flags;
+ file->f_path = *path;
+ retval = do_dentry_open(file, inode, NULL, cred);
+ if (retval) {
+ put_filp(file);
+ file = ERR_PTR(retval);
+ } else {
+ retval = open_check_o_direct(file);
+ if (retval) {
+ fput(file);
+ file = ERR_PTR(retval);
+ }
+ }
+ }
+
+ return file;
+}
+EXPORT_SYMBOL(path_open);
+
struct file *dentry_open(const struct path *path, int flags,
const struct cred *cred)
{
diff --git a/include/linux/fs.h b/include/linux/fs.h
index f0f87f2beb79..c6d7e3b00163 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2401,6 +2401,8 @@ extern struct file *filp_open(const char *, int, umode_t);
extern struct file *file_open_root(struct dentry *, struct vfsmount *,
const char *, int, umode_t);
extern struct file * dentry_open(const struct path *, int, const struct cred *);
+extern struct file *path_open(const struct path *, int, struct inode *,
+ const struct cred *);
extern int filp_close(struct file *, fl_owner_t id);

extern struct filename *getname_flags(const char __user *, int, int *);
--
2.14.3
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