libfs: add stashed_dentry_prune()

[linux-2.6-block.git] / fs / libfs.c

diff --git a/fs/libfs.c b/fs/libfs.c
index 7617e1bc6e5ba9f71f0dd9b27e5dfcc7f983a587..472f21bd032549c5531ed8054f49aac5648f223b 100644 (file)
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -1988,7 +1988,8 @@ static inline struct dentry *get_stashed_dentry(struct dentry *stashed)
        return dentry;
 }
 
-static struct dentry *prepare_anon_dentry(unsigned long ino,
+static struct dentry *prepare_anon_dentry(struct dentry **stashed,
+                                         unsigned long ino,
                                          struct super_block *sb,
                                          const struct file_operations *fops,
                                          const struct inode_operations *iops,
@@ -2019,6 +2020,9 @@ static struct dentry *prepare_anon_dentry(unsigned long ino,
        inode->i_private = data;
        simple_inode_init_ts(inode);
 
+       /* Store address of location where dentry's supposed to be stashed. */
+       dentry->d_fsdata = stashed;
+
        /* @data is now owned by the fs */
        d_instantiate(dentry, inode);
        return dentry;
@@ -2081,7 +2085,7 @@ int path_from_stashed(struct dentry **stashed, unsigned long ino,
                goto out_path;
 
        /* Allocate a new dentry. */
-       dentry = prepare_anon_dentry(ino, mnt->mnt_sb, fops, iops, data);
+       dentry = prepare_anon_dentry(stashed, ino, mnt->mnt_sb, fops, iops, data);
        if (IS_ERR(dentry))
                return PTR_ERR(dentry);
 
@@ -2092,6 +2096,27 @@ int path_from_stashed(struct dentry **stashed, unsigned long ino,
        ret = 1;
 
 out_path:
+       WARN_ON_ONCE(path->dentry->d_fsdata != stashed);
+       WARN_ON_ONCE(d_inode(path->dentry)->i_private != data);
        path->mnt = mntget(mnt);
        return ret;
 }
+
+void stashed_dentry_prune(struct dentry *dentry)
+{
+       struct dentry **stashed = dentry->d_fsdata;
+       struct inode *inode = d_inode(dentry);
+
+       if (WARN_ON_ONCE(!stashed))
+               return;
+
+       if (!inode)
+               return;
+
+       /*
+        * Only replace our own @dentry as someone else might've
+        * already cleared out @dentry and stashed their own
+        * dentry in there.
+        */
+       cmpxchg(stashed, dentry, NULL);
+}