[PATCH 15/15] parallel lookups: actual switch to rwsem

[Al Viro]

From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxxxxxx>
---
 fs/btrfs/ioctl.c       | 16 ++++++++++------
 fs/configfs/inode.c    |  2 +-
 fs/dcache.c            |  9 +++++----
 fs/gfs2/ops_fstype.c   |  2 +-
 fs/inode.c             | 12 ++++++------
 fs/namei.c             |  4 ++--
 fs/ocfs2/inode.c       |  2 +-
 fs/overlayfs/readdir.c |  4 +++-
 fs/readdir.c           |  7 ++++---
 include/linux/fs.h     | 12 ++++++------
 10 files changed, 39 insertions(+), 31 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 053e677..db1e830 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -837,9 +837,11 @@ static noinline int btrfs_mksubvol(struct path *parent,
 	struct dentry *dentry;
 	int error;
 
-	error = mutex_lock_killable_nested(&dir->i_mutex, I_MUTEX_PARENT);
-	if (error == -EINTR)
-		return error;
+	inode_lock_nested(dir, I_MUTEX_PARENT);
+	// XXX: should've been
+	// mutex_lock_killable_nested(&dir->i_mutex, I_MUTEX_PARENT);
+	// if (error == -EINTR)
+	//	return error;
 
 	dentry = lookup_one_len(name, parent->dentry, namelen);
 	error = PTR_ERR(dentry);
@@ -2366,9 +2368,11 @@ static noinline int btrfs_ioctl_snap_destroy(struct file *file,
 		goto out;
 
 
-	err = mutex_lock_killable_nested(&dir->i_mutex, I_MUTEX_PARENT);
-	if (err == -EINTR)
-		goto out_drop_write;
+	inode_lock_nested(dir, I_MUTEX_PARENT);
+	// XXX: should've been
+	// err = mutex_lock_killable_nested(&dir->i_mutex, I_MUTEX_PARENT);
+	// if (err == -EINTR)
+	//	goto out_drop_write;
 	dentry = lookup_one_len(vol_args->name, parent, namelen);
 	if (IS_ERR(dentry)) {
 		err = PTR_ERR(dentry);
diff --git a/fs/configfs/inode.c b/fs/configfs/inode.c
index 03d124a..0387968 100644
--- a/fs/configfs/inode.c
+++ b/fs/configfs/inode.c
@@ -156,7 +156,7 @@ static void configfs_set_inode_lock_class(struct configfs_dirent *sd,
 
 	if (depth > 0) {
 		if (depth <= ARRAY_SIZE(default_group_class)) {
-			lockdep_set_class(&inode->i_mutex,
+			lockdep_set_class(&inode->i_rwsem,
 					  &default_group_class[depth - 1]);
 		} else {
 			/*
diff --git a/fs/dcache.c b/fs/dcache.c
index 5965588..d110040 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2911,7 +2911,8 @@ 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 */
@@ -2922,15 +2923,15 @@ 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 (!down_read_trylock(&alias->d_parent->d_inode->i_rwsem))
 		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;
diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c
index c09c63d..4546360 100644
--- a/fs/gfs2/ops_fstype.c
+++ b/fs/gfs2/ops_fstype.c
@@ -824,7 +824,7 @@ static int init_inodes(struct gfs2_sbd *sdp, int undo)
 	 * i_mutex on quota files is special. Since this inode is hidden system
 	 * file, we are safe to define locking ourselves.
 	 */
-	lockdep_set_class(&sdp->sd_quota_inode->i_mutex,
+	lockdep_set_class(&sdp->sd_quota_inode->i_rwsem,
 			  &gfs2_quota_imutex_key);
 
 	error = gfs2_rindex_update(sdp);
diff --git a/fs/inode.c b/fs/inode.c
index 4b884f7..4ccbc21 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -166,8 +166,8 @@ int inode_init_always(struct super_block *sb, struct inode *inode)
 	spin_lock_init(&inode->i_lock);
 	lockdep_set_class(&inode->i_lock, &sb->s_type->i_lock_key);
 
-	mutex_init(&inode->i_mutex);
-	lockdep_set_class(&inode->i_mutex, &sb->s_type->i_mutex_key);
+	init_rwsem(&inode->i_rwsem);
+	lockdep_set_class(&inode->i_rwsem, &sb->s_type->i_mutex_key);
 
 	atomic_set(&inode->i_dio_count, 0);
 
@@ -925,13 +925,13 @@ void lockdep_annotate_inode_mutex_key(struct inode *inode)
 		struct file_system_type *type = inode->i_sb->s_type;
 
 		/* Set new key only if filesystem hasn't already changed it */
-		if (lockdep_match_class(&inode->i_mutex, &type->i_mutex_key)) {
+		if (lockdep_match_class(&inode->i_rwsem, &type->i_mutex_key)) {
 			/*
 			 * ensure nobody is actually holding i_mutex
 			 */
-			mutex_destroy(&inode->i_mutex);
-			mutex_init(&inode->i_mutex);
-			lockdep_set_class(&inode->i_mutex,
+			// mutex_destroy(&inode->i_mutex);
+			init_rwsem(&inode->i_rwsem);
+			lockdep_set_class(&inode->i_rwsem,
 					  &type->i_mutex_dir_key);
 		}
 	}
diff --git a/fs/namei.c b/fs/namei.c
index eb879d6..877e9ef 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1607,7 +1607,7 @@ static struct dentry *lookup_slow(const struct qstr *name,
 	struct inode *inode = dir->d_inode;
 	DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
 
-	inode_lock(inode);
+	down_read(&inode->i_rwsem);
 	/* Don't go there if it's already dead */
 	if (unlikely(IS_DEADDIR(inode)))
 		goto out;
@@ -1638,7 +1638,7 @@ again:
 		}
 	}
 out:
-	inode_unlock(inode);
+	up_read(&inode->i_rwsem);
 	return dentry;
 }
 
diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c
index 12f4a9e..0748777 100644
--- a/fs/ocfs2/inode.c
+++ b/fs/ocfs2/inode.c
@@ -262,7 +262,7 @@ static int ocfs2_init_locked_inode(struct inode *inode, void *opaque)
 	inode->i_ino = args->fi_ino;
 	OCFS2_I(inode)->ip_blkno = args->fi_blkno;
 	if (args->fi_sysfile_type != 0)
-		lockdep_set_class(&inode->i_mutex,
+		lockdep_set_class(&inode->i_rwsem,
 			&ocfs2_sysfile_lock_key[args->fi_sysfile_type]);
 	if (args->fi_sysfile_type == USER_QUOTA_SYSTEM_INODE ||
 	    args->fi_sysfile_type == GROUP_QUOTA_SYSTEM_INODE ||
diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
index 6ec1e43..da186ee 100644
--- a/fs/overlayfs/readdir.c
+++ b/fs/overlayfs/readdir.c
@@ -218,7 +218,9 @@ static int ovl_check_whiteouts(struct dentry *dir, struct ovl_readdir_data *rdd)
 	cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
 	old_cred = override_creds(override_cred);
 
-	err = mutex_lock_killable(&dir->d_inode->i_mutex);
+	inode_lock(dir->d_inode);
+	err = 0;
+	// XXX: err = mutex_lock_killable(&dir->d_inode->i_mutex);
 	if (!err) {
 		while (rdd->first_maybe_whiteout) {
 			p = rdd->first_maybe_whiteout;
diff --git a/fs/readdir.c b/fs/readdir.c
index e69ef3b..bf583e8 100644
--- a/fs/readdir.c
+++ b/fs/readdir.c
@@ -32,9 +32,10 @@ int iterate_dir(struct file *file, struct dir_context *ctx)
 	if (res)
 		goto out;
 
-	res = mutex_lock_killable(&inode->i_mutex);
-	if (res)
-		goto out;
+	inode_lock(inode);
+	// res = mutex_lock_killable(&inode->i_mutex);
+	// if (res)
+	//	goto out;
 
 	res = -ENOENT;
 	if (!IS_DEADDIR(inode)) {
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 0a32045..313ad28 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -647,7 +647,7 @@ struct inode {
 
 	/* Misc */
 	unsigned long		i_state;
-	struct mutex		i_mutex;
+	struct rw_semaphore	i_rwsem;
 
 	unsigned long		dirtied_when;	/* jiffies of first dirtying */
 	unsigned long		dirtied_time_when;
@@ -734,27 +734,27 @@ enum inode_i_mutex_lock_class
 
 static inline void inode_lock(struct inode *inode)
 {
-	mutex_lock(&inode->i_mutex);
+	down_write(&inode->i_rwsem);
 }
 
 static inline void inode_unlock(struct inode *inode)
 {
-	mutex_unlock(&inode->i_mutex);
+	up_write(&inode->i_rwsem);
 }
 
 static inline int inode_trylock(struct inode *inode)
 {
-	return mutex_trylock(&inode->i_mutex);
+	return down_write_trylock(&inode->i_rwsem);
 }
 
 static inline int inode_is_locked(struct inode *inode)
 {
-	return mutex_is_locked(&inode->i_mutex);
+	return rwsem_is_locked(&inode->i_rwsem);
 }
 
 static inline void inode_lock_nested(struct inode *inode, unsigned subclass)
 {
-	mutex_lock_nested(&inode->i_mutex, subclass);
+	down_write_nested(&inode->i_rwsem, subclass);
 }
 
 void lock_two_nondirectories(struct inode *, struct inode*);
-- 
2.8.0.rc3