fuse: use d_materialise_unique()

Use d_materialise_unique() instead of d_splice_alias().  This allows dentry
subtrees to be moved to a new place if there moved, even if something is
referencing a dentry in the subtree (open fd, cwd, etc..).

This will also allow us to drop a subtree if it is found to be replaced by
something else.  In this case the disconnected subtree can later be
reconnected to its new location.

d_materialise_unique() ensures that a directory entry only ever has one
alias.  We keep fc->inst_mutex around the calls for d_materialise_unique()
on directories to prevent a race with mkdir "stealing" the inode.

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

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 72a5d5b04494ded2468bc4a2f5f30e30c9ca12f7..131d14b604ef79bb94d100ded46b7ea36cd999b0 100644 (file)
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -267,26 +267,6 @@ int fuse_valid_type(int m)
                S_ISBLK(m) || S_ISFIFO(m) || S_ISSOCK(m);
 }
 
-/*
- * Add a directory inode to a dentry, ensuring that no other dentry
- * refers to this inode.  Called with fc->inst_mutex.
- */
-static struct dentry *fuse_d_add_directory(struct dentry *entry,
-                                          struct inode *inode)
-{
-       struct dentry *alias = d_find_alias(inode);
-       if (alias && !(alias->d_flags & DCACHE_DISCONNECTED)) {
-               /* This tries to shrink the subtree below alias */
-               fuse_invalidate_entry(alias);
-               dput(alias);
-               if (!hlist_empty(&inode->i_dentry))
-                       return ERR_PTR(-EBUSY);
-       } else {
-               dput(alias);
-       }
-       return d_splice_alias(inode, entry);
-}
-
 int fuse_lookup_name(struct super_block *sb, u64 nodeid, struct qstr *name,
                     struct fuse_entry_out *outarg, struct inode **inode)
 {
@@ -345,6 +325,24 @@ int fuse_lookup_name(struct super_block *sb, u64 nodeid, struct qstr *name,
        return err;
 }
 
+static struct dentry *fuse_materialise_dentry(struct dentry *dentry,
+                                             struct inode *inode)
+{
+       struct dentry *newent;
+
+       if (inode && S_ISDIR(inode->i_mode)) {
+               struct fuse_conn *fc = get_fuse_conn(inode);
+
+               mutex_lock(&fc->inst_mutex);
+               newent = d_materialise_unique(dentry, inode);
+               mutex_unlock(&fc->inst_mutex);
+       } else {
+               newent = d_materialise_unique(dentry, inode);
+       }
+
+       return newent;
+}
+
 static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry,
                                  unsigned int flags)
 {
@@ -352,7 +350,6 @@ static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry,
        struct fuse_entry_out outarg;
        struct inode *inode;
        struct dentry *newent;
-       struct fuse_conn *fc = get_fuse_conn(dir);
        bool outarg_valid = true;
 
        err = fuse_lookup_name(dir->i_sb, get_node_id(dir), &entry->d_name,
@@ -368,16 +365,10 @@ static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry,
        if (inode && get_node_id(inode) == FUSE_ROOT_ID)
                goto out_iput;
 
-       if (inode && S_ISDIR(inode->i_mode)) {
-               mutex_lock(&fc->inst_mutex);
-               newent = fuse_d_add_directory(entry, inode);
-               mutex_unlock(&fc->inst_mutex);
-               err = PTR_ERR(newent);
-               if (IS_ERR(newent))
-                       goto out_iput;
-       } else {
-               newent = d_splice_alias(inode, entry);
-       }
+       newent = fuse_materialise_dentry(entry, inode);
+       err = PTR_ERR(newent);
+       if (IS_ERR(newent))
+               goto out_err;
 
        entry = newent ? newent : entry;
        if (outarg_valid)
@@ -1275,18 +1266,10 @@ static int fuse_direntplus_link(struct file *file,
        if (!inode)
                goto out;
 
-       if (S_ISDIR(inode->i_mode)) {
-               mutex_lock(&fc->inst_mutex);
-               alias = fuse_d_add_directory(dentry, inode);
-               mutex_unlock(&fc->inst_mutex);
-               err = PTR_ERR(alias);
-               if (IS_ERR(alias)) {
-                       iput(inode);
-                       goto out;
-               }
-       } else {
-               alias = d_splice_alias(inode, dentry);
-       }
+       alias = fuse_materialise_dentry(dentry, inode);
+       err = PTR_ERR(alias);
+       if (IS_ERR(alias))
+               goto out;
 
        if (alias) {
                dput(dentry);