[PATCH] Turn do_sync_file_range() into do_sync_mapping_range()

do_sync_file_range() accepts a file * from which it takes an address_space to
sync.  Abstract out the bulk of the function into do_sync_mapping_range()
which takes the address_space directly.  This way callers who want to sync an
address_space directly can take advantage of the functionality provided.

do_sync_file_range() is preserved as a small wrapper around
do_sync_mapping_range().

Ocfs2 in particular would like to use this to initiate a sync of a specific
inode range during truncate, where a file * may not be available.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/sync.c

@@ -239,13 +239,11 @@ asmlinkage long sys_sync_file_range(int fd, loff_t offset, loff_t nbytes,
 /*
  * `endbyte' is inclusive
  */
-int do_sync_file_range(struct file *file, loff_t offset, loff_t endbyte,
-			unsigned int flags)
+int do_sync_mapping_range(struct address_space *mapping, loff_t offset,
+			  loff_t endbyte, unsigned int flags)
 {
 	int ret;
-	struct address_space *mapping;
 
-	mapping = file->f_mapping;
 	if (!mapping) {
 		ret = -EINVAL;
 		goto out;
@@ -275,4 +273,4 @@ int do_sync_file_range(struct file *file, loff_t offset, loff_t endbyte,
 out:
 	return ret;
 }
-EXPORT_SYMBOL_GPL(do_sync_file_range);
+EXPORT_SYMBOL_GPL(do_sync_mapping_range);

include/linux/fs.h

@@ -843,8 +843,13 @@ extern int fcntl_setlease(unsigned int fd, struct file *filp, long arg);
 extern int fcntl_getlease(struct file *filp);
 
 /* fs/sync.c */
-extern int do_sync_file_range(struct file *file, loff_t offset, loff_t endbyte,
-			unsigned int flags);
+extern int do_sync_mapping_range(struct address_space *mapping, loff_t offset,
+			loff_t endbyte, unsigned int flags);
+static inline int do_sync_file_range(struct file *file, loff_t offset,
+			loff_t endbyte, unsigned int flags)
+{
+	return do_sync_mapping_range(file->f_mapping, offset, endbyte, flags);
+}
 
 /* fs/locks.c */
 extern void locks_init_lock(struct file_lock *);