locks: new locks_mandatory_area calling convention

Pass a loff_t end for the last byte instead of the 32-bit count
parameter to allow full file clones even on 32-bit architectures.
While we're at it also simplify the read/write selection.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: J. Bruce Fields <bfields@fieldses.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/locks.c

@@ -1227,20 +1227,16 @@ int locks_mandatory_locked(struct file *file)
 
 /**
  * locks_mandatory_area - Check for a conflicting lock
- * @read_write: %FLOCK_VERIFY_WRITE for exclusive access, %FLOCK_VERIFY_READ
- *		for shared
- * @inode:      the file to check
+ * @inode:	the file to check
  * @filp:       how the file was opened (if it was)
- * @offset:     start of area to check
- * @count:      length of area to check
+ * @start:	first byte in the file to check
+ * @end:	lastbyte in the file to check
+ * @type:	%F_WRLCK for a write lock, else %F_RDLCK
  *
  * Searches the inode's list of locks to find any POSIX locks which conflict.
- * This function is called from rw_verify_area() and
- * locks_verify_truncate().
  */
-int locks_mandatory_area(int read_write, struct inode *inode,
-			 struct file *filp, loff_t offset,
-			 size_t count)
+int locks_mandatory_area(struct inode *inode, struct file *filp, loff_t start,
+			 loff_t end, unsigned char type)
 {
 	struct file_lock fl;
 	int error;
@@ -1252,9 +1248,9 @@ int locks_mandatory_area(int read_write, struct inode *inode,
 	fl.fl_flags = FL_POSIX | FL_ACCESS;
 	if (filp && !(filp->f_flags & O_NONBLOCK))
 		sleep = true;
-	fl.fl_type = (read_write == FLOCK_VERIFY_WRITE) ? F_WRLCK : F_RDLCK;
-	fl.fl_start = offset;
-	fl.fl_end = offset + count - 1;
+	fl.fl_type = type;
+	fl.fl_start = start;
+	fl.fl_end = end;
 
 	for (;;) {
 		if (filp) {

fs/read_write.c

@@ -396,9 +396,8 @@ int rw_verify_area(int read_write, struct file *file, const loff_t *ppos, size_t
 	}
 
 	if (unlikely(inode->i_flctx && mandatory_lock(inode))) {
-		retval = locks_mandatory_area(
-			read_write == READ ? FLOCK_VERIFY_READ : FLOCK_VERIFY_WRITE,
-			inode, file, pos, count);
+		retval = locks_mandatory_area(inode, file, pos, pos + count - 1,
+				read_write == READ ? F_RDLCK : F_WRLCK);
 		if (retval < 0)
 			return retval;
 	}

include/linux/fs.h

@@ -2030,12 +2030,9 @@ extern struct kobject *fs_kobj;
 
 #define MAX_RW_COUNT (INT_MAX & PAGE_CACHE_MASK)
 
-#define FLOCK_VERIFY_READ  1
-#define FLOCK_VERIFY_WRITE 2
-
 #ifdef CONFIG_FILE_LOCKING
 extern int locks_mandatory_locked(struct file *);
-extern int locks_mandatory_area(int, struct inode *, struct file *, loff_t, size_t);
+extern int locks_mandatory_area(struct inode *, struct file *, loff_t, loff_t, unsigned char);
 
 /*
  * Candidates for mandatory locking have the setgid bit set
@@ -2065,17 +2062,19 @@ static inline int locks_verify_locked(struct file *file)
 }
 
 static inline int locks_verify_truncate(struct inode *inode,
-				    struct file *filp,
+				    struct file *f,
 				    loff_t size)
 {
-	if (inode->i_flctx && mandatory_lock(inode))
-		return locks_mandatory_area(
-			FLOCK_VERIFY_WRITE, inode, filp,
-			size < inode->i_size ? size : inode->i_size,
-			(size < inode->i_size ? inode->i_size - size
-			 : size - inode->i_size)
-		);
-	return 0;
+	if (!inode->i_flctx || !mandatory_lock(inode))
+		return 0;
+
+	if (size < inode->i_size) {
+		return locks_mandatory_area(inode, f, size, inode->i_size - 1,
+				F_WRLCK);
+	} else {
+		return locks_mandatory_area(inode, f, inode->i_size, size - 1,
+				F_WRLCK);
+	}
 }
 
 static inline int break_lease(struct inode *inode, unsigned int mode)
@@ -2144,9 +2143,8 @@ static inline int locks_mandatory_locked(struct file *file)
 	return 0;
 }
 
-static inline int locks_mandatory_area(int rw, struct inode *inode,
-				       struct file *filp, loff_t offset,
-				       size_t count)
+static inline int locks_mandatory_area(struct inode *inode, struct file *filp,
+		loff_t start, loff_t end, unsigned char type)
 {
 	return 0;
 }