mm/fadvise: use LLONG_MAX instead of -1 for eof

generic_fadvise() sets endbyte = -1 to specify end of file (i.e.  if
length == 0 is passed from userspace).  Most other callers to
filemap_fdatawrite_range() use LLONG_MAX for this purpose, particularly if
they also call fdatawait_range() (which requires end >= start).  For
example, sync_file_range(), vfs_fsync() (where the range is passed down
through per-fs ->fsync() callbacks), filemap_flush(), etc. 
generic_fadvise() does not currently wait on writeback, but fix the call
up to be consistent with other callers.

Link: https://lkml.kernel.org/r/20221128155632.3950447-3-bfoster@redhat.comSigned-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/fadvise.c

@@ -72,7 +72,7 @@ int generic_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
 	 */
 	endbyte = (u64)offset + (u64)len;
 	if (!len || endbyte < len)
-		endbyte = -1;
+		endbyte = LLONG_MAX;
 	else
 		endbyte--;		/* inclusive */