fuse: add support for mandatory locking

For mandatory locking the userspace filesystem needs to know the lock
ownership for read, write and truncate operations.

This patch adds the necessary fields to the protocol.
Signed-off-by: NMiklos Szeredi <mszeredi@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fs/fuse/dir.c

@@ -1108,6 +1108,11 @@ static int fuse_do_setattr(struct dentry *entry, struct iattr *attr,
 		inarg.valid |= FATTR_FH;
 		inarg.fh = ff->fh;
 	}
+	if (attr->ia_valid & ATTR_SIZE) {
+		/* For mandatory locking in truncate */
+		inarg.valid |= FATTR_LOCKOWNER;
+		inarg.lock_owner = fuse_lock_owner_id(fc, current->files);
+	}
 	req->in.h.opcode = FUSE_SETATTR;
 	req->in.h.nodeid = get_node_id(inode);
 	req->in.numargs = 1;

fs/fuse/file.c

@@ -189,7 +189,7 @@ static int fuse_release(struct inode *inode, struct file *file)
  * Scramble the ID space with XTEA, so that the value of the files_struct
  * pointer is not exposed to userspace.
  */
-static u64 fuse_lock_owner_id(struct fuse_conn *fc, fl_owner_t id)
+u64 fuse_lock_owner_id(struct fuse_conn *fc, fl_owner_t id)
 {
 	u32 *k = fc->scramble_key;
 	u64 v = (unsigned long) id;
@@ -308,11 +308,19 @@ void fuse_read_fill(struct fuse_req *req, struct fuse_file *ff,
 }
 
 static size_t fuse_send_read(struct fuse_req *req, struct file *file,
-			     struct inode *inode, loff_t pos, size_t count)
+			     struct inode *inode, loff_t pos, size_t count,
+			     fl_owner_t owner)
 {
 	struct fuse_conn *fc = get_fuse_conn(inode);
 	struct fuse_file *ff = file->private_data;
+
 	fuse_read_fill(req, ff, inode, pos, count, FUSE_READ);
+	if (owner != NULL) {
+		struct fuse_read_in *inarg = &req->misc.read_in;
+
+		inarg->read_flags |= FUSE_READ_LOCKOWNER;
+		inarg->lock_owner = fuse_lock_owner_id(fc, owner);
+	}
 	request_send(fc, req);
 	return req->out.args[0].size;
 }
@@ -336,7 +344,8 @@ static int fuse_readpage(struct file *file, struct page *page)
 	req->out.page_zeroing = 1;
 	req->num_pages = 1;
 	req->pages[0] = page;
-	fuse_send_read(req, file, inode, page_offset(page), PAGE_CACHE_SIZE);
+	fuse_send_read(req, file, inode, page_offset(page), PAGE_CACHE_SIZE,
+		       NULL);
 	err = req->out.h.error;
 	fuse_put_request(fc, req);
 	if (!err)
@@ -447,6 +456,7 @@ static void fuse_write_fill(struct fuse_req *req, struct fuse_file *ff,
 			    struct inode *inode, loff_t pos, size_t count,
 			    int writepage)
 {
+	struct fuse_conn *fc = get_fuse_conn(inode);
 	struct fuse_write_in *inarg = &req->misc.write.in;
 	struct fuse_write_out *outarg = &req->misc.write.out;
 
@@ -459,7 +469,10 @@ static void fuse_write_fill(struct fuse_req *req, struct fuse_file *ff,
 	req->in.h.nodeid = get_node_id(inode);
 	req->in.argpages = 1;
 	req->in.numargs = 2;
-	req->in.args[0].size = sizeof(struct fuse_write_in);
+	if (fc->minor < 9)
+		req->in.args[0].size = FUSE_COMPAT_WRITE_IN_SIZE;
+	else
+		req->in.args[0].size = sizeof(struct fuse_write_in);
 	req->in.args[0].value = inarg;
 	req->in.args[1].size = count;
 	req->out.numargs = 1;
@@ -468,10 +481,16 @@ static void fuse_write_fill(struct fuse_req *req, struct fuse_file *ff,
 }
 
 static size_t fuse_send_write(struct fuse_req *req, struct file *file,
-			      struct inode *inode, loff_t pos, size_t count)
+			      struct inode *inode, loff_t pos, size_t count,
+			      fl_owner_t owner)
 {
 	struct fuse_conn *fc = get_fuse_conn(inode);
 	fuse_write_fill(req, file->private_data, inode, pos, count, 0);
+	if (owner != NULL) {
+		struct fuse_write_in *inarg = &req->misc.write.in;
+		inarg->write_flags |= FUSE_WRITE_LOCKOWNER;
+		inarg->lock_owner = fuse_lock_owner_id(fc, owner);
+	}
 	request_send(fc, req);
 	return req->misc.write.out.size;
 }
@@ -508,7 +527,7 @@ static int fuse_buffered_write(struct file *file, struct inode *inode,
 	req->num_pages = 1;
 	req->pages[0] = page;
 	req->page_offset = offset;
-	nres = fuse_send_write(req, file, inode, pos, count);
+	nres = fuse_send_write(req, file, inode, pos, count, NULL);
 	err = req->out.h.error;
 	fuse_put_request(fc, req);
 	if (!err && !nres)
@@ -609,9 +628,11 @@ static ssize_t fuse_direct_io(struct file *file, const char __user *buf,
 		nbytes = (req->num_pages << PAGE_SHIFT) - req->page_offset;
 		nbytes = min(count, nbytes);
 		if (write)
-			nres = fuse_send_write(req, file, inode, pos, nbytes);
+			nres = fuse_send_write(req, file, inode, pos, nbytes,
+					       current->files);
 		else
-			nres = fuse_send_read(req, file, inode, pos, nbytes);
+			nres = fuse_send_read(req, file, inode, pos, nbytes,
+					      current->files);
 		fuse_release_user_pages(req, !write);
 		if (req->out.h.error) {
 			if (!res)

fs/fuse/fuse_i.h

@@ -591,3 +591,5 @@ int fuse_valid_type(int m);
  * Is task allowed to perform filesystem operation?
  */
 int fuse_allow_task(struct fuse_conn *fc, struct task_struct *task);
+
+u64 fuse_lock_owner_id(struct fuse_conn *fc, fl_owner_t id);

include/linux/fuse.h

@@ -14,6 +14,7 @@
  * 7.9:
  *  - new fuse_getattr_in input argument of GETATTR
  *  - add lk_flags in fuse_lk_in
+ *  - add lock_owner field to fuse_setattr_in, fuse_read_in and fuse_write_in
  */
 
 #include <asm/types.h>
@@ -86,6 +87,7 @@ struct fuse_file_lock {
 #define FATTR_FH	(1 << 6)
 #define FATTR_ATIME_NOW	(1 << 7)
 #define FATTR_MTIME_NOW	(1 << 8)
+#define FATTR_LOCKOWNER	(1 << 9)
 
 /**
  * Flags returned by the OPEN request
@@ -123,8 +125,15 @@ struct fuse_file_lock {
  * WRITE flags
  *
  * FUSE_WRITE_CACHE: delayed write from page cache, file handle is guessed
+ * FUSE_WRITE_LOCKOWNER: lock_owner field is valid
  */
 #define FUSE_WRITE_CACHE	(1 << 0)
+#define FUSE_WRITE_LOCKOWNER	(1 << 1)
+
+/**
+ * Read flags
+ */
+#define FUSE_READ_LOCKOWNER	(1 << 1)
 
 enum fuse_opcode {
 	FUSE_LOOKUP	   = 1,
@@ -219,7 +228,7 @@ struct fuse_setattr_in {
 	__u32	padding;
 	__u64	fh;
 	__u64	size;
-	__u64	unused1;
+	__u64	lock_owner;
 	__u64	atime;
 	__u64	mtime;
 	__u64	unused2;
@@ -262,14 +271,18 @@ struct fuse_read_in {
 	__u64	fh;
 	__u64	offset;
 	__u32	size;
-	__u32	padding;
+	__u32	read_flags;
+	__u64	lock_owner;
 };
 
+#define FUSE_COMPAT_WRITE_IN_SIZE 24
+
 struct fuse_write_in {
 	__u64	fh;
 	__u64	offset;
 	__u32	size;
 	__u32	write_flags;
+	__u64	lock_owner;
 };
 
 struct fuse_write_out {