hostfs: simplify locking

Remove dcache_lock locking from hostfs filesystem, and move it into dcache
helpers. All that is required is a coherent path name. Protection from
concurrent modification of the namespace after path name generation is not
provided in current code, because dcache_lock is dropped before the path is
used.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>

3 files changed, 24 insertions, 17 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index 6f59f375ed9d..61beb40dd6bf 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2171,7 +2171,7 @@ char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen,
 /*
  * Write full pathname from the root of the filesystem into the buffer.
  */
-char *__dentry_path(struct dentry *dentry, char *buf, int buflen)
+static char *__dentry_path(struct dentry *dentry, char *buf, int buflen)
 {
         char *end = buf + buflen;
         char *retval;
@@ -2198,7 +2198,18 @@ char *__dentry_path(struct dentry *dentry, char *buf, int buflen)
 Elong:
         return ERR_PTR(-ENAMETOOLONG);
 }
-EXPORT_SYMBOL(__dentry_path);
+
+char *dentry_path_raw(struct dentry *dentry, char *buf, int buflen)
+{
+        char *retval;
+
+        spin_lock(&dcache_lock);
+        retval = __dentry_path(dentry, buf, buflen);
+        spin_unlock(&dcache_lock);
+
+        return retval;
+}
+EXPORT_SYMBOL(dentry_path_raw);
 
 char *dentry_path(struct dentry *dentry, char *buf, int buflen)
 {
diff --git a/fs/hostfs/hostfs_kern.c b/fs/hostfs/hostfs_kern.c
index cfe8bc7de511..39dc505ed273 100644
--- a/fs/hostfs/hostfs_kern.c
+++ b/fs/hostfs/hostfs_kern.c
@@ -92,12 +92,10 @@ __uml_setup("hostfs=", hostfs_args,
 
 static char *__dentry_name(struct dentry *dentry, char *name)
 {
-        char *p = __dentry_path(dentry, name, PATH_MAX);
+        char *p = dentry_path_raw(dentry, name, PATH_MAX);
         char *root;
         size_t len;
 
-        spin_unlock(&dcache_lock);
-
         root = dentry->d_sb->s_fs_info;
         len = strlen(root);
         if (IS_ERR(p)) {
@@ -123,25 +121,23 @@ static char *dentry_name(struct dentry *dentry)
         if (!name)
                 return NULL;
 
-        spin_lock(&dcache_lock);
         return __dentry_name(dentry, name); /* will unlock */
 }
 
 static char *inode_name(struct inode *ino)
 {
         struct dentry *dentry;
-        char *name = __getname();
-        if (!name)
-                return NULL;
+        char *name;
 
-        spin_lock(&dcache_lock);
-        if (list_empty(&ino->i_dentry)) {
-                spin_unlock(&dcache_lock);
-                __putname(name);
+        dentry = d_find_alias(ino);
+        if (!dentry)
                 return NULL;
-        }
-        dentry = list_first_entry(&ino->i_dentry, struct dentry, d_alias);
-        return __dentry_name(dentry, name); /* will unlock */
+
+        name = dentry_name(dentry);
+
+        dput(dentry);
+
+        return name;
 }
 
 static char *follow_link(char *link)
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 1149e706f04d..cea27dfca532 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -311,7 +311,7 @@ extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
 extern char *__d_path(const struct path *path, struct path *root, char *, int);
 extern char *d_path(const struct path *, char *, int);
 extern char *d_path_with_unreachable(const struct path *, char *, int);
-extern char *__dentry_path(struct dentry *, char *, int);
+extern char *dentry_path_raw(struct dentry *, char *, int);
 extern char *dentry_path(struct dentry *, char *, int);
 
 /* Allocation counts.. */