Add ->flock() operation to low and high level interfaces

This fixes problems with emulating flock() with POSIX locking.
Reported by Sebastian Pipping.

As with lock/setlk/getlk most filesystems don't need to implement
this, as the kernel takes care of file locking.  The only reason to
implement locking operations is for network filesystems which want
file locking to work between clients.

4 files changed, 59 insertions, 3 deletions

diff --git a/include/fuse.h b/include/fuse.h
index 7e52719..b05152d 100644
--- a/include/fuse.h
+++ b/include/fuse.h
@@ -548,6 +548,27 @@ struct fuse_operations {
 	 */
 	int (*read_buf) (const char *, struct fuse_bufvec **bufp,
 			 size_t size, off_t off, struct fuse_file_info *);
+	/**
+	 * Perform BSD file locking operation
+	 *
+	 * The op argument will be either LOCK_SH, LOCK_EX or LOCK_UN
+	 *
+	 * Nonblocking requests will be indicated by ORing LOCK_NB to
+	 * the above operations
+	 *
+	 * For more information see the flock(2) manual page.
+	 *
+	 * Additionally fi->owner will be set to a value unique to
+	 * this open file.  This same value will be supplied to
+	 * ->release() when the file is released.
+	 *
+	 * Note: if this method is not implemented, the kernel will still
+	 * allow file locking to work locally.  Hence it is only
+	 * interesting for network filesystems and similar.
+	 *
+	 * Introduced in version 2.9
+	 */
+	int (*flock) (const char *, struct fuse_file_info *, int op);
 };
 
 /** Extra context that may be needed by some filesystems
@@ -813,6 +834,8 @@ int fuse_fs_create(struct fuse_fs *fs, const char *path, mode_t mode,
 		   struct fuse_file_info *fi);
 int fuse_fs_lock(struct fuse_fs *fs, const char *path,
 		 struct fuse_file_info *fi, int cmd, struct flock *lock);
+int fuse_fs_flock(struct fuse_fs *fs, const char *path,
+		  struct fuse_file_info *fi, int op);
 int fuse_fs_chmod(struct fuse_fs *fs, const char *path, mode_t mode);
 int fuse_fs_chown(struct fuse_fs *fs, const char *path, uid_t uid, gid_t gid);
 int fuse_fs_truncate(struct fuse_fs *fs, const char *path, off_t size);
diff --git a/include/fuse_common.h b/include/fuse_common.h
index db17fa6..76f7200 100644
--- a/include/fuse_common.h
+++ b/include/fuse_common.h
@@ -70,8 +70,14 @@ struct fuse_file_info {
 	    seekable.  Introduced in version 2.8 */
 	unsigned int nonseekable : 1;
 
+	/* Indicates that flock locks for this file should be
+	   released.  If set, lock_owner shall contain a valid value.
+	   May only be set in ->release().  Introduced in version
+	   2.9 */
+	unsigned int flock_release : 1;
+
 	/** Padding.  Do not use*/
-	unsigned int padding : 28;
+	unsigned int padding : 27;
 
 	/** File handle.  May be filled in by filesystem in open().
 	    Available in all other file operations */
@@ -103,6 +109,7 @@ struct fuse_file_info {
 #define FUSE_CAP_SPLICE_WRITE	(1 << 7)
 #define FUSE_CAP_SPLICE_MOVE	(1 << 8)
 #define FUSE_CAP_SPLICE_READ	(1 << 9)
+#define FUSE_CAP_FLOCK_LOCKS	(1 << 10)
 
 /**
  * Ioctl flags
diff --git a/include/fuse_kernel.h b/include/fuse_kernel.h
index ab8b94e..8b65f46 100644
--- a/include/fuse_kernel.h
+++ b/include/fuse_kernel.h
@@ -73,6 +73,9 @@
  *  - FUSE_IOCTL_UNRESTRICTED shall now return with array of 'struct
  *    fuse_ioctl_iovec' instead of ambiguous 'struct iovec'
  *  - add FUSE_IOCTL_32BIT flag
+ *
+ * 7.17
+ *  - add FUSE_FLOCK_LOCKS and FUSE_RELEASE_FLOCK_UNLOCK
  */
 
 #ifndef _LINUX_FUSE_H
@@ -109,7 +112,7 @@
 #define FUSE_KERNEL_VERSION 7
 
 /** Minor version number of this interface */
-#define FUSE_KERNEL_MINOR_VERSION 16
+#define FUSE_KERNEL_MINOR_VERSION 17
 
 /** The node ID of the root inode */
 #define FUSE_ROOT_ID 1
@@ -184,8 +187,10 @@ struct fuse_file_lock {
 /**
  * INIT request/reply flags
  *
+ * FUSE_POSIX_LOCKS: remote locking for POSIX file locks
  * FUSE_EXPORT_SUPPORT: filesystem handles lookups of "." and ".."
  * FUSE_DONT_MASK: don't apply umask to file mode on create operations
+ * FUSE_FLOCK_LOCKS: remote locking for BSD style file locks
  */
 #define FUSE_ASYNC_READ		(1 << 0)
 #define FUSE_POSIX_LOCKS	(1 << 1)
@@ -194,6 +199,7 @@ struct fuse_file_lock {
 #define FUSE_EXPORT_SUPPORT	(1 << 4)
 #define FUSE_BIG_WRITES		(1 << 5)
 #define FUSE_DONT_MASK		(1 << 6)
+#define FUSE_FLOCK_LOCKS	(1 << 10)
 
 /**
  * CUSE INIT request/reply flags
@@ -206,6 +212,7 @@ struct fuse_file_lock {
  * Release flags
  */
 #define FUSE_RELEASE_FLUSH	(1 << 0)
+#define FUSE_RELEASE_FLOCK_UNLOCK	(1 << 1)
 
 /**
  * Getattr flags
diff --git a/include/fuse_lowlevel.h b/include/fuse_lowlevel.h
index e38fe92..7c00f76 100644
--- a/include/fuse_lowlevel.h
+++ b/include/fuse_lowlevel.h
@@ -796,7 +796,7 @@ struct fuse_lowlevel_ops {
 	 * @param req request handle
 	 * @param ino the inode number
 	 * @param fi file information
-	 * @param lock the region/type to test
+	 * @param lock the region/type to set
 	 * @param sleep locking operation may sleep
 	 */
 	void (*setlk) (fuse_req_t req, fuse_ino_t ino,
@@ -932,6 +932,25 @@ struct fuse_lowlevel_ops {
 	void (*forget_multi) (fuse_req_t req, size_t count,
 			      struct fuse_forget_data *forgets);
 
+	/**
+	 * Acquire, modify or release a BSD file lock
+	 *
+	 * Note: if the locking methods are not implemented, the kernel
+	 * will still allow file locking to work locally.  Hence these are
+	 * only interesting for network filesystems and similar.
+	 *
+	 * Introduced in version 2.9
+	 *
+	 * Valid replies:
+	 *   fuse_reply_err
+	 *
+	 * @param req request handle
+	 * @param ino the inode number
+	 * @param fi file information
+	 * @param op the locking operation, see flock(2)
+	 */
+	void (*flock) (fuse_req_t req, fuse_ino_t ino,
+		       struct fuse_file_info *fi, int op);
 };
 
 /**