[PATCH] fuse: add POSIX file locking support

This patch adds POSIX file locking support to the fuse interface.

This implementation doesn't keep any locking state in kernel.  Unlocking on
close() is handled by the FLUSH message, which now contains the lock owner id.

Mandatory locking is not supported.  The filesystem may enfoce mandatory
locking in userspace if needed.

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 154 insertions, 2 deletions

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 1d59af306b28..d9a8289297c0 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -160,6 +160,18 @@ static int fuse_release(struct inode *inode, struct file *file)
 	return fuse_release_common(inode, file, 0);
 }
 
+/*
+ * It would be nice to scramble the ID space, so that the value of the
+ * files_struct pointer is not exposed to userspace.  Symmetric crypto
+ * functions are overkill, since the inverse function doesn't need to
+ * be implemented (though it does have to exist).  Is there something
+ * simpler?
+ */
+static inline u64 fuse_lock_owner_id(fl_owner_t id)
+{
+	return (unsigned long) id;
+}
+
 static int fuse_flush(struct file *file, fl_owner_t id)
 {
 	struct inode *inode = file->f_dentry->d_inode;
@@ -181,11 +193,13 @@ static int fuse_flush(struct file *file, fl_owner_t id)
 
 	memset(&inarg, 0, sizeof(inarg));
 	inarg.fh = ff->fh;
+	inarg.lock_owner = fuse_lock_owner_id(id);
 	req->in.h.opcode = FUSE_FLUSH;
 	req->in.h.nodeid = get_node_id(inode);
 	req->in.numargs = 1;
 	req->in.args[0].size = sizeof(inarg);
 	req->in.args[0].value = &inarg;
+	req->force = 1;
 	request_send(fc, req);
 	err = req->out.h.error;
 	fuse_put_request(fc, req);
@@ -604,6 +618,122 @@ static int fuse_set_page_dirty(struct page *page)
 	return 0;
 }
 
+static int convert_fuse_file_lock(const struct fuse_file_lock *ffl,
+				  struct file_lock *fl)
+{
+	switch (ffl->type) {
+	case F_UNLCK:
+		break;
+
+	case F_RDLCK:
+	case F_WRLCK:
+		if (ffl->start > OFFSET_MAX || ffl->end > OFFSET_MAX ||
+		    ffl->end < ffl->start)
+			return -EIO;
+
+		fl->fl_start = ffl->start;
+		fl->fl_end = ffl->end;
+		fl->fl_pid = ffl->pid;
+		break;
+
+	default:
+		return -EIO;
+	}
+	fl->fl_type = ffl->type;
+	return 0;
+}
+
+static void fuse_lk_fill(struct fuse_req *req, struct file *file,
+			 const struct file_lock *fl, int opcode, pid_t pid)
+{
+	struct inode *inode = file->f_dentry->d_inode;
+	struct fuse_file *ff = file->private_data;
+	struct fuse_lk_in *arg = &req->misc.lk_in;
+
+	arg->fh = ff->fh;
+	arg->owner = fuse_lock_owner_id(fl->fl_owner);
+	arg->lk.start = fl->fl_start;
+	arg->lk.end = fl->fl_end;
+	arg->lk.type = fl->fl_type;
+	arg->lk.pid = pid;
+	req->in.h.opcode = opcode;
+	req->in.h.nodeid = get_node_id(inode);
+	req->in.numargs = 1;
+	req->in.args[0].size = sizeof(*arg);
+	req->in.args[0].value = arg;
+}
+
+static int fuse_getlk(struct file *file, struct file_lock *fl)
+{
+	struct inode *inode = file->f_dentry->d_inode;
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_req *req;
+	struct fuse_lk_out outarg;
+	int err;
+
+	req = fuse_get_req(fc);
+	if (IS_ERR(req))
+		return PTR_ERR(req);
+
+	fuse_lk_fill(req, file, fl, FUSE_GETLK, 0);
+	req->out.numargs = 1;
+	req->out.args[0].size = sizeof(outarg);
+	req->out.args[0].value = &outarg;
+	request_send(fc, req);
+	err = req->out.h.error;
+	fuse_put_request(fc, req);
+	if (!err)
+		err = convert_fuse_file_lock(&outarg.lk, fl);
+
+	return err;
+}
+
+static int fuse_setlk(struct file *file, struct file_lock *fl)
+{
+	struct inode *inode = file->f_dentry->d_inode;
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_req *req;
+	int opcode = (fl->fl_flags & FL_SLEEP) ? FUSE_SETLKW : FUSE_SETLK;
+	pid_t pid = fl->fl_type != F_UNLCK ? current->tgid : 0;
+	int err;
+
+	/* Unlock on close is handled by the flush method */
+	if (fl->fl_flags & FL_CLOSE)
+		return 0;
+
+	req = fuse_get_req(fc);
+	if (IS_ERR(req))
+		return PTR_ERR(req);
+
+	fuse_lk_fill(req, file, fl, opcode, pid);
+	request_send(fc, req);
+	err = req->out.h.error;
+	fuse_put_request(fc, req);
+	return err;
+}
+
+static int fuse_file_lock(struct file *file, int cmd, struct file_lock *fl)
+{
+	struct inode *inode = file->f_dentry->d_inode;
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	int err;
+
+	if (cmd == F_GETLK) {
+		if (fc->no_lock) {
+			if (!posix_test_lock(file, fl, fl))
+				fl->fl_type = F_UNLCK;
+			err = 0;
+		} else
+			err = fuse_getlk(file, fl);
+	} else {
+		if (fc->no_lock)
+			err = posix_lock_file_wait(file, fl);
+		else
+			err = fuse_setlk(file, fl);
+	}
+	return err;
+}
+
 static const struct file_operations fuse_file_operations = {
 	.llseek		= generic_file_llseek,
 	.read		= generic_file_read,
@@ -613,6 +743,7 @@ static const struct file_operations fuse_file_operations = {
 	.flush		= fuse_flush,
 	.release	= fuse_release,
 	.fsync		= fuse_fsync,
+	.lock		= fuse_file_lock,
 	.sendfile	= generic_file_sendfile,
 };
 
@@ -624,6 +755,7 @@ static const struct file_operations fuse_direct_io_file_operations = {
 	.flush		= fuse_flush,
 	.release	= fuse_release,
 	.fsync		= fuse_fsync,
+	.lock		= fuse_file_lock,
 	/* no mmap and sendfile */
 };
 
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index ac12b01f4446..eb3166625ca9 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -190,6 +190,7 @@ struct fuse_req {
 		struct fuse_init_in init_in;
 		struct fuse_init_out init_out;
 		struct fuse_read_in read_in;
+		struct fuse_lk_in lk_in;
 	} misc;
 
 	/** page vector */
@@ -307,6 +308,9 @@ struct fuse_conn {
 	/** Is removexattr not implemented by fs? */
 	unsigned no_removexattr : 1;
 
+	/** Are file locking primitives not implemented by fs? */
+	unsigned no_lock : 1;
+
 	/** Is access not implemented by fs? */
 	unsigned no_access : 1;
 
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 13a7e8ab7a78..412892905838 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -98,6 +98,14 @@ static void fuse_clear_inode(struct inode *inode)
 	}
 }
 
+static int fuse_remount_fs(struct super_block *sb, int *flags, char *data)
+{
+	if (*flags & MS_MANDLOCK)
+		return -EINVAL;
+
+	return 0;
+}
+
 void fuse_change_attributes(struct inode *inode, struct fuse_attr *attr)
 {
 	if (S_ISREG(inode->i_mode) && i_size_read(inode) != attr->size)
@@ -409,6 +417,7 @@ static struct super_operations fuse_super_operations = {
 	.destroy_inode  = fuse_destroy_inode,
 	.read_inode	= fuse_read_inode,
 	.clear_inode	= fuse_clear_inode,
+	.remount_fs	= fuse_remount_fs,
 	.put_super	= fuse_put_super,
 	.umount_begin	= fuse_umount_begin,
 	.statfs		= fuse_statfs,
@@ -428,8 +437,12 @@ static void process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
 			ra_pages = arg->max_readahead / PAGE_CACHE_SIZE;
 			if (arg->flags & FUSE_ASYNC_READ)
 				fc->async_read = 1;
-		} else
+			if (!(arg->flags & FUSE_POSIX_LOCKS))
+				fc->no_lock = 1;
+		} else {
 			ra_pages = fc->max_read / PAGE_CACHE_SIZE;
+			fc->no_lock = 1;
+		}
 
 		fc->bdi.ra_pages = min(fc->bdi.ra_pages, ra_pages);
 		fc->minor = arg->minor;
@@ -447,7 +460,7 @@ static void fuse_send_init(struct fuse_conn *fc, struct fuse_req *req)
 	arg->major = FUSE_KERNEL_VERSION;
 	arg->minor = FUSE_KERNEL_MINOR_VERSION;
 	arg->max_readahead = fc->bdi.ra_pages * PAGE_CACHE_SIZE;
-	arg->flags |= FUSE_ASYNC_READ;
+	arg->flags |= FUSE_ASYNC_READ | FUSE_POSIX_LOCKS;
 	req->in.h.opcode = FUSE_INIT;
 	req->in.numargs = 1;
 	req->in.args[0].size = sizeof(*arg);
@@ -479,6 +492,9 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
 	struct fuse_req *init_req;
 	int err;
 
+	if (sb->s_flags & MS_MANDLOCK)
+		return -EINVAL;
+
 	if (!parse_fuse_opt((char *) data, &d))
 		return -EINVAL;