vfs: new d_init method

Allow filesystem to initialize dentry at allocation time.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

4 files changed, 17 insertions, 0 deletions

diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index a38da93865c2..794adbe55399 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -15,6 +15,7 @@ prototypes:
         int (*d_compare)(const struct dentry *, const struct dentry *,
                         unsigned int, const char *, const struct qstr *);
         int (*d_delete)(struct dentry *);
+        int (*d_init)(struct dentry *);
         void (*d_release)(struct dentry *);
         void (*d_iput)(struct dentry *, struct inode *);
         char *(*d_dname)((struct dentry *dentry, char *buffer, int buflen);
@@ -30,6 +31,7 @@ d_weak_revalidate:no		no		yes	 	no
 d_hash          no              no              no              maybe
 d_compare:      yes             no              no              maybe
 d_delete:       no              yes             no              no
+d_init: no              no              yes             no
 d_release:      no              no              yes             no
 d_prune:        no              yes             no              no
 d_iput:         no              no              yes             no
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index 70a056fe51a3..15c3fa7c89cc 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -923,6 +923,7 @@ struct dentry_operations {
         int (*d_compare)(const struct dentry *, const struct dentry *,
                         unsigned int, const char *, const struct qstr *);
         int (*d_delete)(const struct dentry *);
+        int (*d_init)(struct dentry *);
         void (*d_release)(struct dentry *);
         void (*d_iput)(struct dentry *, struct inode *);
         char *(*d_dname)(struct dentry *, char *, int);
@@ -995,6 +996,8 @@ struct dentry_operations {
         always cache a reachable dentry. d_delete must be constant and
         idempotent.
 
+  d_init: called when a dentry is allocated
+
   d_release: called when a dentry is really deallocated
 
   d_iput: called when a dentry loses its inode (just prior to its
diff --git a/fs/dcache.c b/fs/dcache.c
index d5beef01cdfc..6d60a764c848 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1569,6 +1569,7 @@ struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
 {
         struct dentry *dentry;
         char *dname;
+        int err;
 
         dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
         if (!dentry)
@@ -1627,6 +1628,16 @@ struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
         INIT_LIST_HEAD(&dentry->d_child);
         d_set_d_op(dentry, dentry->d_sb->s_d_op);
 
+        if (dentry->d_op && dentry->d_op->d_init) {
+                err = dentry->d_op->d_init(dentry);
+                if (err) {
+                        if (dname_external(dentry))
+                                kfree(external_name(dentry));
+                        kmem_cache_free(dentry_cache, dentry);
+                        return NULL;
+                }
+        }
+
         this_cpu_inc(nr_dentry);
 
         return dentry;
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 14df83609c7f..98044a8d1487 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -133,6 +133,7 @@ struct dentry_operations {
         int (*d_compare)(const struct dentry *, const struct dentry *,
                         unsigned int, const char *, const struct qstr *);
         int (*d_delete)(const struct dentry *);
+        int (*d_init)(struct dentry *);
         void (*d_release)(struct dentry *);
         void (*d_prune)(struct dentry *);
         void (*d_iput)(struct dentry *, struct inode *);