parallel lookups: actual switch to rwsem (9902af79) · Commits · e / devices / android_kernel_teracube_emerald

Documentation/filesystems/porting

+18 −0

Original line number	Original line	Diff line number	Diff line
	@@ -539,3 +539,21 @@ in your dentry operations instead.
	it's a symlink. Checking ->i_mode is really needed now. In-tree we had		it's a symlink. Checking ->i_mode is really needed now. In-tree we had
	to fix shmem_destroy_callback() that used to take that kind of shortcut;		to fix shmem_destroy_callback() that used to take that kind of shortcut;
	watch out, since that shortcut is no longer valid.		watch out, since that shortcut is no longer valid.
			--
			[mandatory]
			->i_mutex is replaced with ->i_rwsem now. inode_lock() et.al. work as
			they used to - they just take it exclusive. However, ->lookup() may be
			called with parent locked shared. Its instances must not
			* use d_instantiate) and d_rehash() separately - use d_add() or
			d_splice_alias() instead.
			* use d_rehash() alone - call d_add(new_dentry, NULL) instead.
			* in the unlikely case when (read-only) access to filesystem
			data structures needs exclusion for some reason, arrange it
			yourself. None of the in-tree filesystems needed that.
			* rely on ->d_parent and ->d_name not changing after dentry has
			been fed to d_add() or d_splice_alias(). Again, none of the
			in-tree instances relied upon that.
			We are guaranteed that lookups of the same name in the same directory
			will not happen in parallel ("same" in the sense of your ->d_compare()).
			Lookups on different names in the same directory can and do happen in
			parallel now.

+11 −7

Original line number	Original line	Diff line number	Diff line
	@@ -837,9 +837,11 @@ static noinline int btrfs_mksubvol(struct path *parent,
	struct dentry *dentry;		struct dentry *dentry;
	int error;		int error;

	error = mutex_lock_killable_nested(&dir->i_mutex, I_MUTEX_PARENT);		inode_lock_nested(dir, I_MUTEX_PARENT);
	if (error == -EINTR)		// XXX: should've been
	return error;		// mutex_lock_killable_nested(&dir->i_mutex, I_MUTEX_PARENT);
			// if (error == -EINTR)
			// return error;

	dentry = lookup_one_len(name, parent->dentry, namelen);		dentry = lookup_one_len(name, parent->dentry, namelen);
	error = PTR_ERR(dentry);		error = PTR_ERR(dentry);
	@@ -2366,9 +2368,11 @@ static noinline int btrfs_ioctl_snap_destroy(struct file *file,
	goto out;		goto out;


	err = mutex_lock_killable_nested(&dir->i_mutex, I_MUTEX_PARENT);		inode_lock_nested(dir, I_MUTEX_PARENT);
	if (err == -EINTR)		// XXX: should've been
	goto out_drop_write;		// 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);		dentry = lookup_one_len(vol_args->name, parent, namelen);
	if (IS_ERR(dentry)) {		if (IS_ERR(dentry)) {
	err = PTR_ERR(dentry);		err = PTR_ERR(dentry);
	@@ -2558,7 +2562,7 @@ static noinline int btrfs_ioctl_snap_destroy(struct file *file,
	dput(dentry);		dput(dentry);
	out_unlock_dir:		out_unlock_dir:
	inode_unlock(dir);		inode_unlock(dir);
	out_drop_write:		//out_drop_write:
	mnt_drop_write_file(file);		mnt_drop_write_file(file);
	out:		out:
	kfree(vol_args);		kfree(vol_args);

+1 −1

Original line number	Original line	Diff line number	Diff line
	@@ -156,7 +156,7 @@ static void configfs_set_inode_lock_class(struct configfs_dirent *sd,

	if (depth > 0) {		if (depth > 0) {
	if (depth <= ARRAY_SIZE(default_group_class)) {		if (depth <= ARRAY_SIZE(default_group_class)) {
	lockdep_set_class(&inode->i_mutex,		lockdep_set_class(&inode->i_rwsem,
	&default_group_class[depth - 1]);		&default_group_class[depth - 1]);
	} else {		} else {
	/*		/*

+5 −4

Original line number	Original line	Diff line number	Diff line
	@@ -2932,7 +2932,8 @@ struct dentry d_ancestor(struct dentry p1, struct dentry *p2)
	static int __d_unalias(struct inode *inode,		static int __d_unalias(struct inode *inode,
	struct dentry dentry, struct dentry alias)		struct dentry dentry, struct dentry alias)
	{		{
	struct mutex m1 = NULL, m2 = NULL;		struct mutex *m1 = NULL;
			struct rw_semaphore *m2 = NULL;
	int ret = -ESTALE;		int ret = -ESTALE;

	/* If alias and dentry share a parent, then no extra locks required */		/* 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))		if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
	goto out_err;		goto out_err;
	m1 = &dentry->d_sb->s_vfs_rename_mutex;		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;		goto out_err;
	m2 = &alias->d_parent->d_inode->i_mutex;		m2 = &alias->d_parent->d_inode->i_rwsem;
	out_unalias:		out_unalias:
	__d_move(alias, dentry, false);		__d_move(alias, dentry, false);
	ret = 0;		ret = 0;
	out_err:		out_err:
	if (m2)		if (m2)
	mutex_unlock(m2);		up_read(m2);
	if (m1)		if (m1)
	mutex_unlock(m1);		mutex_unlock(m1);
	return ret;		return ret;

+1 −1

Original line number	Original line	Diff line number	Diff line
	@@ -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		* i_mutex on quota files is special. Since this inode is hidden system
	* file, we are safe to define locking ourselves.		* 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);		&gfs2_quota_imutex_key);

	error = gfs2_rindex_update(sdp);		error = gfs2_rindex_update(sdp);