mm: rename readahead loop variable to 'i'

Change the type of page_idx to unsigned long, and rename it -- it's just
a loop counter, not a page index.
Suggested-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Cc: Chao Yu <yuchao0@huawei.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: Eric Biggers <ebiggers@google.com>
Cc: Gao Xiang <gaoxiang25@huawei.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Link: http://lkml.kernel.org/r/20200414150233.24495-9-willy@infradead.orgSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/readahead.c

@@ -163,13 +163,13 @@ void __do_page_cache_readahead(struct address_space *mapping,
 	struct page *page;
 	unsigned long end_index;	/* The last page we want to read */
 	LIST_HEAD(page_pool);
-	int page_idx;
 	loff_t isize = i_size_read(inode);
 	gfp_t gfp_mask = readahead_gfp_mask(mapping);
 	struct readahead_control rac = {
 		.mapping = mapping,
 		.file = filp,
 	};
+	unsigned long i;
 
 	if (isize == 0)
 		return;
@@ -179,8 +179,8 @@ void __do_page_cache_readahead(struct address_space *mapping,
 	/*
 	 * Preallocate as many pages as we will need.
 	 */
-	for (page_idx = 0; page_idx < nr_to_read; page_idx++) {
-		pgoff_t page_offset = index + page_idx;
+	for (i = 0; i < nr_to_read; i++) {
+		pgoff_t page_offset = index + i;
 
 		if (page_offset > end_index)
 			break;
@@ -201,7 +201,7 @@ void __do_page_cache_readahead(struct address_space *mapping,
 			break;
 		page->index = page_offset;
 		list_add(&page->lru, &page_pool);
-		if (page_idx == nr_to_read - lookahead_size)
+		if (i == nr_to_read - lookahead_size)
 			SetPageReadahead(page);
 		rac._nr_pages++;
 	}