fs: dcache rationalise dget variants

dget_locked was a shortcut to avoid the lazy lru manipulation when we already
held dcache_lock (lru manipulation was relatively cheap at that point).
However, how that the lru lock is an innermost one, we never hold it at any
caller, so the lock cost can now be avoided. We already have well working lazy
dcache LRU, so it should be fine to defer LRU manipulations to scan time.

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

12 files changed, 24 insertions, 47 deletions

diff --git a/arch/powerpc/platforms/cell/spufs/inode.c b/arch/powerpc/platforms/cell/spufs/inode.c
index 2662b50ea8d4..03185de7cd4a 100644
--- a/arch/powerpc/platforms/cell/spufs/inode.c
+++ b/arch/powerpc/platforms/cell/spufs/inode.c
@@ -161,7 +161,7 @@ static void spufs_prune_dir(struct dentry *dir)
         list_for_each_entry_safe(dentry, tmp, &dir->d_subdirs, d_u.d_child) {
                 spin_lock(&dentry->d_lock);
                 if (!(d_unhashed(dentry)) && dentry->d_inode) {
-                        dget_locked_dlock(dentry);
+                        dget_dlock(dentry);
                         __d_drop(dentry);
                         spin_unlock(&dentry->d_lock);
                         simple_unlink(dir->d_inode, dentry);
diff --git a/drivers/infiniband/hw/ipath/ipath_fs.c b/drivers/infiniband/hw/ipath/ipath_fs.c
index 925e88227ded..31ae1b108aea 100644
--- a/drivers/infiniband/hw/ipath/ipath_fs.c
+++ b/drivers/infiniband/hw/ipath/ipath_fs.c
@@ -279,7 +279,7 @@ static int remove_file(struct dentry *parent, char *name)
 
         spin_lock(&tmp->d_lock);
         if (!(d_unhashed(tmp) && tmp->d_inode)) {
-                dget_locked_dlock(tmp);
+                dget_dlock(tmp);
                 __d_drop(tmp);
                 spin_unlock(&tmp->d_lock);
                 simple_unlink(parent->d_inode, tmp);
diff --git a/drivers/infiniband/hw/qib/qib_fs.c b/drivers/infiniband/hw/qib/qib_fs.c
index 49af4a6538ba..df7fa251dcdc 100644
--- a/drivers/infiniband/hw/qib/qib_fs.c
+++ b/drivers/infiniband/hw/qib/qib_fs.c
@@ -455,7 +455,7 @@ static int remove_file(struct dentry *parent, char *name)
 
         spin_lock(&tmp->d_lock);
         if (!(d_unhashed(tmp) && tmp->d_inode)) {
-                dget_locked_dlock(tmp);
+                dget_dlock(tmp);
                 __d_drop(tmp);
                 spin_unlock(&tmp->d_lock);
                 simple_unlink(parent->d_inode, tmp);
diff --git a/drivers/staging/smbfs/cache.c b/drivers/staging/smbfs/cache.c
index 75dfd403fb90..f2a1323ca827 100644
--- a/drivers/staging/smbfs/cache.c
+++ b/drivers/staging/smbfs/cache.c
@@ -102,7 +102,7 @@ smb_dget_fpos(struct dentry *dentry, struct dentry *parent, unsigned long fpos)
                 dent = list_entry(next, struct dentry, d_u.d_child);
                 if ((unsigned long)dent->d_fsdata == fpos) {
                         if (dent->d_inode)
-                                dget_locked(dent);
+                                dget(dent);
                         else
                                 dent = NULL;
                         goto out_unlock;
diff --git a/fs/configfs/inode.c b/fs/configfs/inode.c
index fb3a55fff82a..c83f4768eeaa 100644
--- a/fs/configfs/inode.c
+++ b/fs/configfs/inode.c
@@ -252,7 +252,7 @@ void configfs_drop_dentry(struct configfs_dirent * sd, struct dentry * parent)
         if (dentry) {
                 spin_lock(&dentry->d_lock);
                 if (!(d_unhashed(dentry) && dentry->d_inode)) {
-                        dget_locked_dlock(dentry);
+                        dget_dlock(dentry);
                         __d_drop(dentry);
                         spin_unlock(&dentry->d_lock);
                         simple_unlink(parent->d_inode, dentry);
diff --git a/fs/dcache.c b/fs/dcache.c
index 01f016799fd4..b4d2e28eef5b 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -429,32 +429,17 @@ int d_invalidate(struct dentry * dentry)
 EXPORT_SYMBOL(d_invalidate);
 
 /* This must be called with d_lock held */
-static inline struct dentry * __dget_locked_dlock(struct dentry *dentry)
+static inline void __dget_dlock(struct dentry *dentry)
 {
         dentry->d_count++;
-        dentry_lru_del(dentry);
-        return dentry;
 }
 
-/* This must be called with d_lock held */
-static inline struct dentry * __dget_locked(struct dentry *dentry)
+static inline void __dget(struct dentry *dentry)
 {
         spin_lock(&dentry->d_lock);
-        __dget_locked_dlock(dentry);
+        __dget_dlock(dentry);
         spin_unlock(&dentry->d_lock);
-        return dentry;
-}
-
-struct dentry * dget_locked_dlock(struct dentry *dentry)
-{
-        return __dget_locked_dlock(dentry);
-}
-
-struct dentry * dget_locked(struct dentry *dentry)
-{
-        return __dget_locked(dentry);
 }
-EXPORT_SYMBOL(dget_locked);
 
 struct dentry *dget_parent(struct dentry *dentry)
 {
@@ -512,7 +497,7 @@ again:
                             (alias->d_flags & DCACHE_DISCONNECTED)) {
                                 discon_alias = alias;
                         } else if (!want_discon) {
-                                __dget_locked_dlock(alias);
+                                __dget_dlock(alias);
                                 spin_unlock(&alias->d_lock);
                                 return alias;
                         }
@@ -525,7 +510,7 @@ again:
                 if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
                         if (IS_ROOT(alias) &&
                             (alias->d_flags & DCACHE_DISCONNECTED)) {
-                                __dget_locked_dlock(alias);
+                                __dget_dlock(alias);
                                 spin_unlock(&alias->d_lock);
                                 return alias;
                         }
@@ -561,7 +546,7 @@ restart:
         list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
                 spin_lock(&dentry->d_lock);
                 if (!dentry->d_count) {
-                        __dget_locked_dlock(dentry);
+                        __dget_dlock(dentry);
                         __d_drop(dentry);
                         spin_unlock(&dentry->d_lock);
                         spin_unlock(&dcache_inode_lock);
@@ -1257,7 +1242,8 @@ struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
                  * don't need child lock because it is not subject
                  * to concurrency here
                  */
-                dentry->d_parent = dget_dlock(parent);
+                __dget_dlock(parent);
+                dentry->d_parent = parent;
                 dentry->d_sb = parent->d_sb;
                 list_add(&dentry->d_u.d_child, &parent->d_subdirs);
                 spin_unlock(&parent->d_lock);
@@ -1360,7 +1346,7 @@ static struct dentry *__d_instantiate_unique(struct dentry *entry,
                         continue;
                 if (memcmp(qstr->name, name, len))
                         continue;
-                dget_locked(alias);
+                __dget(alias);
                 return alias;
         }
 
@@ -1613,7 +1599,7 @@ struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
          * reference to it, move it in place and use it.
          */
         new = list_entry(inode->i_dentry.next, struct dentry, d_alias);
-        dget_locked(new);
+        __dget(new);
         spin_unlock(&dcache_inode_lock);
         security_d_instantiate(found, inode);
         d_move(new, found);
@@ -1789,7 +1775,7 @@ int d_validate(struct dentry *dentry, struct dentry *dparent)
         list_for_each_entry(child, &dparent->d_subdirs, d_u.d_child) {
                 if (dentry == child) {
                         spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
-                        __dget_locked_dlock(dentry);
+                        __dget_dlock(dentry);
                         spin_unlock(&dentry->d_lock);
                         spin_unlock(&dparent->d_lock);
                         return 1;
diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
index 53a5c08fb63c..f06a940065f6 100644
--- a/fs/exportfs/expfs.c
+++ b/fs/exportfs/expfs.c
@@ -49,7 +49,7 @@ find_acceptable_alias(struct dentry *result,
 
         spin_lock(&dcache_inode_lock);
         list_for_each_entry(dentry, &result->d_inode->i_dentry, d_alias) {
-                dget_locked(dentry);
+                dget(dentry);
                 spin_unlock(&dcache_inode_lock);
                 if (toput)
                         dput(toput);
diff --git a/fs/ncpfs/dir.c b/fs/ncpfs/dir.c
index de15c533311c..0ba3cdc95a44 100644
--- a/fs/ncpfs/dir.c
+++ b/fs/ncpfs/dir.c
@@ -397,7 +397,7 @@ ncp_dget_fpos(struct dentry *dentry, struct dentry *parent, unsigned long fpos)
                 dent = list_entry(next, struct dentry, d_u.d_child);
                 if ((unsigned long)dent->d_fsdata == fpos) {
                         if (dent->d_inode)
-                                dget_locked(dent);
+                                dget(dent);
                         else
                                 dent = NULL;
                         spin_unlock(&parent->d_lock);
diff --git a/fs/ocfs2/dcache.c b/fs/ocfs2/dcache.c
index b7de749bdd12..4d54c60ceee4 100644
--- a/fs/ocfs2/dcache.c
+++ b/fs/ocfs2/dcache.c
@@ -178,7 +178,7 @@ struct dentry *ocfs2_find_local_alias(struct inode *inode,
                         mlog(0, "dentry found: %.*s\n",
                              dentry->d_name.len, dentry->d_name.name);
 
-                        dget_locked_dlock(dentry);
+                        dget_dlock(dentry);
                         spin_unlock(&dentry->d_lock);
                         break;
                 }
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index a2ceb94b0e38..ca648685f0cc 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -287,23 +287,17 @@ extern char *dentry_path(struct dentry *, char *, int);
 /* Allocation counts.. */
 
 /**
- *      dget, dget_locked       -       get a reference to a dentry
+ *      dget, dget_dlock -      get a reference to a dentry
  *      @dentry: dentry to get a reference to
  *
  *      Given a dentry or %NULL pointer increment the reference count
  *      if appropriate and return the dentry. A dentry will not be 
- *      destroyed when it has references. dget() should never be
- *      called for dentries with zero reference counter. For these cases
- *      (preferably none, functions in dcache.c are sufficient for normal
- *      needs and they take necessary precautions) you should hold d_lock
- *      and call dget_dlock() instead of dget().
+ *      destroyed when it has references.
  */
 static inline struct dentry *dget_dlock(struct dentry *dentry)
 {
-        if (dentry) {
-                BUG_ON(!dentry->d_count);
+        if (dentry)
                 dentry->d_count++;
-        }
         return dentry;
 }
 
@@ -317,9 +311,6 @@ static inline struct dentry *dget(struct dentry *dentry)
         return dentry;
 }
 
-extern struct dentry * dget_locked(struct dentry *);
-extern struct dentry * dget_locked_dlock(struct dentry *);
-
 extern struct dentry *dget_parent(struct dentry *dentry);
 
 /**
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 1864cb6a6a59..9f41470c3949 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -887,7 +887,7 @@ static void cgroup_clear_directory(struct dentry *dentry)
                         /* This should never be called on a cgroup
                          * directory with child cgroups */
                         BUG_ON(d->d_inode->i_mode & S_IFDIR);
-                        dget_locked_dlock(d);
+                        dget_dlock(d);
                         spin_unlock(&d->d_lock);
                         spin_unlock(&dentry->d_lock);
                         d_delete(d);
diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index 2285d693f296..43deac219491 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -1154,7 +1154,7 @@ static void sel_remove_entries(struct dentry *de)
                 list_del_init(node);
 
                 if (d->d_inode) {
-                        dget_locked_dlock(d);
+                        dget_dlock(d);
                         spin_unlock(&de->d_lock);
                         spin_unlock(&d->d_lock);
                         d_delete(d);