parallel lookups: actual switch to rwsem

ta-da!

The main issue is the lack of down_write_killable(), so the places
like readdir.c switched to plain inode_lock(); once killable
variants of rwsem primitives appear, that'll be dealt with.

lockdep side also might need more work

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

1 files changed, 5 insertions, 4 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index 59fcffcbf096..e49ba7d1b957 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2932,7 +2932,8 @@ struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
 static int __d_unalias(struct inode *inode,
                 struct dentry *dentry, struct dentry *alias)
 {
-        struct mutex *m1 = NULL, *m2 = NULL;
+        struct mutex *m1 = NULL;
+        struct rw_semaphore *m2 = NULL;
         int ret = -ESTALE;
 
         /* If alias and dentry share a parent, then no extra locks required */
@@ -2943,15 +2944,15 @@ static int __d_unalias(struct inode *inode,
         if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
                 goto out_err;
         m1 = &dentry->d_sb->s_vfs_rename_mutex;
-        if (!inode_trylock(alias->d_parent->d_inode))
+        if (!inode_trylock_shared(alias->d_parent->d_inode))
                 goto out_err;
-        m2 = &alias->d_parent->d_inode->i_mutex;
+        m2 = &alias->d_parent->d_inode->i_rwsem;
 out_unalias:
         __d_move(alias, dentry, false);
         ret = 0;
 out_err:
         if (m2)
-                mutex_unlock(m2);
+                up_read(m2);
         if (m1)
                 mutex_unlock(m1);
         return ret;