mm/truncate: avoid pointless cleancache_invalidate_inode() calls.

cleancache_invalidate_inode() called truncate_inode_pages_range() and
invalidate_inode_pages2_range() twice - on entry and on exit.  It's
stupid and waste of time.  It's enough to call it once at exit.

Link: http://lkml.kernel.org/r/20170424164135.22350-5-aryabinin@virtuozzo.comSigned-off-by: NAndrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: NJan Kara <jack@suse.cz>
Acked-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Alexey Kuznetsov <kuznet@virtuozzo.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Nikolay Borisov <n.borisov.lkml@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/truncate.c

@@ -266,9 +266,8 @@ void truncate_inode_pages_range(struct address_space *mapping,
 	pgoff_t		index;
 	int		i;
 
-	cleancache_invalidate_inode(mapping);
 	if (mapping->nrpages == 0 && mapping->nrexceptional == 0)
-		return;
+		goto out;
 
 	/* Offsets within partial pages */
 	partial_start = lstart & (PAGE_SIZE - 1);
@@ -363,7 +362,7 @@ void truncate_inode_pages_range(struct address_space *mapping,
 	 * will be released, just zeroed, so we can bail out now.
 	 */
 	if (start >= end)
-		return;
+		goto out;
 
 	index = start;
 	for ( ; ; ) {
@@ -410,6 +409,8 @@ void truncate_inode_pages_range(struct address_space *mapping,
 		pagevec_release(&pvec);
 		index++;
 	}
+
+out:
 	cleancache_invalidate_inode(mapping);
 }
 EXPORT_SYMBOL(truncate_inode_pages_range);
@@ -623,9 +624,8 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
 	int ret2 = 0;
 	int did_range_unmap = 0;
 
-	cleancache_invalidate_inode(mapping);
 	if (mapping->nrpages == 0 && mapping->nrexceptional == 0)
-		return 0;
+		goto out;
 
 	pagevec_init(&pvec, 0);
 	index = start;
@@ -689,6 +689,8 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
 		cond_resched();
 		index++;
 	}
+
+out:
 	cleancache_invalidate_inode(mapping);
 	return ret;
 }