vfs: take path_get_longterm() out of write_seqcount scope

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 15 insertions, 12 deletions

diff --git a/fs/fs_struct.c b/fs/fs_struct.c
index 27114b41362..6324c427495 100644
--- a/fs/fs_struct.c
+++ b/fs/fs_struct.c
@@ -26,11 +26,11 @@ void set_fs_root(struct fs_struct *fs, struct path *path)
 {
         struct path old_root;
 
+        path_get_longterm(path);
         spin_lock(&fs->lock);
         write_seqcount_begin(&fs->seq);
         old_root = fs->root;
         fs->root = *path;
-        path_get_longterm(path);
         write_seqcount_end(&fs->seq);
         spin_unlock(&fs->lock);
         if (old_root.dentry)
@@ -45,11 +45,11 @@ void set_fs_pwd(struct fs_struct *fs, struct path *path)
 {
         struct path old_pwd;
 
+        path_get_longterm(path);
         spin_lock(&fs->lock);
         write_seqcount_begin(&fs->seq);
         old_pwd = fs->pwd;
         fs->pwd = *path;
-        path_get_longterm(path);
         write_seqcount_end(&fs->seq);
         spin_unlock(&fs->lock);
 
@@ -57,6 +57,14 @@ void set_fs_pwd(struct fs_struct *fs, struct path *path)
                 path_put_longterm(&old_pwd);
 }
 
+static inline int replace_path(struct path *p, const struct path *old, const struct path *new)
+{
+        if (likely(p->dentry != old->dentry || p->mnt != old->mnt))
+                return 0;
+        *p = *new;
+        return 1;
+}
+
 void chroot_fs_refs(struct path *old_root, struct path *new_root)
 {
         struct task_struct *g, *p;
@@ -68,21 +76,16 @@ void chroot_fs_refs(struct path *old_root, struct path *new_root)
                 task_lock(p);
                 fs = p->fs;
                 if (fs) {
+                        int hits = 0;
                         spin_lock(&fs->lock);
                         write_seqcount_begin(&fs->seq);
-                        if (fs->root.dentry == old_root->dentry
-                            && fs->root.mnt == old_root->mnt) {
-                                path_get_longterm(new_root);
-                                fs->root = *new_root;
+                        hits += replace_path(&fs->root, old_root, new_root);
+                        hits += replace_path(&fs->pwd, old_root, new_root);
+                        write_seqcount_end(&fs->seq);
+                        while (hits--) {
                                 count++;
-                        }
-                        if (fs->pwd.dentry == old_root->dentry
-                            && fs->pwd.mnt == old_root->mnt) {
                                 path_get_longterm(new_root);
-                                fs->pwd = *new_root;
-                                count++;
                         }
-                        write_seqcount_end(&fs->seq);
                         spin_unlock(&fs->lock);
                 }
                 task_unlock(p);