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vfs: document ->d_real() 

Add missing documentation for the d_op->d_real() method and d_real()
helper.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Miklos Szeredi 2016-06-30 08:53:27 +02:00
parent 2d902671ce
commit e698b8a436
3 changed files with 36 additions and 1 deletions
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3
Documentation/filesystems/Locking
View File

@ -20,6 +20,8 @@ prototypes:
char *(*d_dname)((struct dentry *dentry, char *buffer, int buflen);
struct vfsmount *(*d_automount)(struct path *path);
int (*d_manage)(struct dentry *, bool);
struct dentry *(*d_real)(struct dentry *, const struct inode *,
unsigned int);
locking rules:
rename_lock ->d_lock may block rcu-walk
@ -34,6 +36,7 @@ d_iput: no no yes no
d_dname: no no no no
d_automount: no no yes no
d_manage: no no yes (ref-walk) maybe
d_real no no yes no
--------------------------- inode_operations ---------------------------
prototypes:

20
Documentation/filesystems/vfs.txt
View File

@ -938,6 +938,8 @@ struct dentry_operations {
char *(*d_dname)(struct dentry *, char *, int);
struct vfsmount *(*d_automount)(struct path *);
int (*d_manage)(struct dentry *, bool);
struct dentry *(*d_real)(struct dentry *, const struct inode *,
unsigned int);
};
d_revalidate: called when the VFS needs to revalidate a dentry. This
@ -1060,6 +1062,24 @@ struct dentry_operations {
This function is only used if DCACHE_MANAGE_TRANSIT is set on the
dentry being transited from.
d_real: overlay/union type filesystems implement this method to return one of
the underlying dentries hidden by the overlay. It is used in three
different modes:
Called from open it may need to copy-up the file depending on the
supplied open flags. This mode is selected with a non-zero flags
argument. In this mode the d_real method can return an error.
Called from file_dentry() it returns the real dentry matching the inode
argument. The real dentry may be from a lower layer already copied up,
but still referenced from the file. This mode is selected with a
non-NULL inode argument. This will always succeed.
With NULL inode and zero flags the topmost real underlying dentry is
returned. This will always succeed.
This method is never called with both non-NULL inode and non-zero flags.
Example :
static char *pipefs_dname(struct dentry *dent, char *buffer, int buflen)

14
include/linux/dcache.h
View File

@ -139,7 +139,8 @@ struct dentry_operations {
char *(*d_dname)(struct dentry *, char *, int);
struct vfsmount *(*d_automount)(struct path *);
int (*d_manage)(struct dentry *, bool);
struct dentry *(*d_real)(struct dentry *, const struct inode *, unsigned int);
struct dentry *(*d_real)(struct dentry *, const struct inode *,
unsigned int);
} ____cacheline_aligned;
/*
@ -554,6 +555,17 @@ static inline struct dentry *d_backing_dentry(struct dentry *upper)
return upper;
}
/**
* d_real - Return the real dentry
* @dentry: the dentry to query
* @inode: inode to select the dentry from multiple layers (can be NULL)
* @flags: open flags to control copy-up behavior
*
* If dentry is on an union/overlay, then return the underlying, real dentry.
* Otherwise return the dentry itself.
*
* See also: Documentation/filesystems/vfs.txt
*/
static inline struct dentry *d_real(struct dentry *dentry,
const struct inode *inode,
unsigned int flags)