diff --git a/mm/readahead.c b/mm/readahead.c
index 6a9d99229bd6..096cf9020648 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -156,7 +156,7 @@ static void read_pages(struct readahead_control *rac, struct list_head *pages,
  * We really don't want to intermingle reads and writes like that.
  */
 void __do_page_cache_readahead(struct address_space *mapping,
-		struct file *filp, pgoff_t offset, unsigned long nr_to_read,
+		struct file *filp, pgoff_t index, unsigned long nr_to_read,
 		unsigned long lookahead_size)
 {
 	struct inode *inode = mapping->host;
@@ -181,7 +181,7 @@ 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 = offset + page_idx;
+		pgoff_t page_offset = index + page_idx;
 
 		if (page_offset > end_index)
 			break;
@@ -220,7 +220,7 @@ void __do_page_cache_readahead(struct address_space *mapping,
  * memory at once.
  */
 void force_page_cache_readahead(struct address_space *mapping,
-		struct file *filp, pgoff_t offset, unsigned long nr_to_read)
+		struct file *filp, pgoff_t index, unsigned long nr_to_read)
 {
 	struct backing_dev_info *bdi = inode_to_bdi(mapping->host);
 	struct file_ra_state *ra = &filp->f_ra;
@@ -240,9 +240,9 @@ void force_page_cache_readahead(struct address_space *mapping,
 
 		if (this_chunk > nr_to_read)
 			this_chunk = nr_to_read;
-		__do_page_cache_readahead(mapping, filp, offset, this_chunk, 0);
+		__do_page_cache_readahead(mapping, filp, index, this_chunk, 0);
 
-		offset += this_chunk;
+		index += this_chunk;
 		nr_to_read -= this_chunk;
 	}
 }
@@ -323,21 +323,21 @@ static unsigned long get_next_ra_size(struct file_ra_state *ra,
  */
 
 /*
- * Count contiguously cached pages from @offset-1 to @offset-@max,
+ * Count contiguously cached pages from @index-1 to @index-@max,
  * this count is a conservative estimation of
  * 	- length of the sequential read sequence, or
  * 	- thrashing threshold in memory tight systems
  */
 static pgoff_t count_history_pages(struct address_space *mapping,
-				   pgoff_t offset, unsigned long max)
+				   pgoff_t index, unsigned long max)
 {
 	pgoff_t head;
 
 	rcu_read_lock();
-	head = page_cache_prev_miss(mapping, offset - 1, max);
+	head = page_cache_prev_miss(mapping, index - 1, max);
 	rcu_read_unlock();
 
-	return offset - 1 - head;
+	return index - 1 - head;
 }
 
 /*
@@ -345,13 +345,13 @@ static pgoff_t count_history_pages(struct address_space *mapping,
  */
 static int try_context_readahead(struct address_space *mapping,
 				 struct file_ra_state *ra,
-				 pgoff_t offset,
+				 pgoff_t index,
 				 unsigned long req_size,
 				 unsigned long max)
 {
 	pgoff_t size;
 
-	size = count_history_pages(mapping, offset, max);
+	size = count_history_pages(mapping, index, max);
 
 	/*
 	 * not enough history pages:
@@ -364,10 +364,10 @@ static int try_context_readahead(struct address_space *mapping,
 	 * starts from beginning of file:
 	 * it is a strong indication of long-run stream (or whole-file-read)
 	 */
-	if (size >= offset)
+	if (size >= index)
 		size *= 2;
 
-	ra->start = offset;
+	ra->start = index;
 	ra->size = min(size + req_size, max);
 	ra->async_size = 1;
 
@@ -379,13 +379,13 @@ static int try_context_readahead(struct address_space *mapping,
  */
 static void ondemand_readahead(struct address_space *mapping,
 		struct file_ra_state *ra, struct file *filp,
-		bool hit_readahead_marker, pgoff_t offset,
+		bool hit_readahead_marker, pgoff_t index,
 		unsigned long req_size)
 {
 	struct backing_dev_info *bdi = inode_to_bdi(mapping->host);
 	unsigned long max_pages = ra->ra_pages;
 	unsigned long add_pages;
-	pgoff_t prev_offset;
+	pgoff_t prev_index;
 
 	/*
 	 * If the request exceeds the readahead window, allow the read to
@@ -397,15 +397,15 @@ static void ondemand_readahead(struct address_space *mapping,
 	/*
 	 * start of file
 	 */
-	if (!offset)
+	if (!index)
 		goto initial_readahead;
 
 	/*
-	 * It's the expected callback offset, assume sequential access.
+	 * It's the expected callback index, assume sequential access.
 	 * Ramp up sizes, and push forward the readahead window.
 	 */
-	if ((offset == (ra->start + ra->size - ra->async_size) ||
-	     offset == (ra->start + ra->size))) {
+	if ((index == (ra->start + ra->size - ra->async_size) ||
+	     index == (ra->start + ra->size))) {
 		ra->start += ra->size;
 		ra->size = get_next_ra_size(ra, max_pages);
 		ra->async_size = ra->size;
@@ -422,14 +422,14 @@ static void ondemand_readahead(struct address_space *mapping,
 		pgoff_t start;
 
 		rcu_read_lock();
-		start = page_cache_next_miss(mapping, offset + 1, max_pages);
+		start = page_cache_next_miss(mapping, index + 1, max_pages);
 		rcu_read_unlock();
 
-		if (!start || start - offset > max_pages)
+		if (!start || start - index > max_pages)
 			return;
 
 		ra->start = start;
-		ra->size = start - offset;	/* old async_size */
+		ra->size = start - index;	/* old async_size */
 		ra->size += req_size;
 		ra->size = get_next_ra_size(ra, max_pages);
 		ra->async_size = ra->size;
@@ -444,29 +444,29 @@ static void ondemand_readahead(struct address_space *mapping,
 
 	/*
 	 * sequential cache miss
-	 * trivial case: (offset - prev_offset) == 1
-	 * unaligned reads: (offset - prev_offset) == 0
+	 * trivial case: (index - prev_index) == 1
+	 * unaligned reads: (index - prev_index) == 0
 	 */
-	prev_offset = (unsigned long long)ra->prev_pos >> PAGE_SHIFT;
-	if (offset - prev_offset <= 1UL)
+	prev_index = (unsigned long long)ra->prev_pos >> PAGE_SHIFT;
+	if (index - prev_index <= 1UL)
 		goto initial_readahead;
 
 	/*
 	 * Query the page cache and look for the traces(cached history pages)
 	 * that a sequential stream would leave behind.
 	 */
-	if (try_context_readahead(mapping, ra, offset, req_size, max_pages))
+	if (try_context_readahead(mapping, ra, index, req_size, max_pages))
 		goto readit;
 
 	/*
 	 * standalone, small random read
 	 * Read as is, and do not pollute the readahead state.
 	 */
-	__do_page_cache_readahead(mapping, filp, offset, req_size, 0);
+	__do_page_cache_readahead(mapping, filp, index, req_size, 0);
 	return;
 
 initial_readahead:
-	ra->start = offset;
+	ra->start = index;
 	ra->size = get_init_ra_size(req_size, max_pages);
 	ra->async_size = ra->size > req_size ? ra->size - req_size : ra->size;
 
@@ -477,7 +477,7 @@ static void ondemand_readahead(struct address_space *mapping,
 	 * the resulted next readahead window into the current one.
 	 * Take care of maximum IO pages as above.
 	 */
-	if (offset == ra->start && ra->size == ra->async_size) {
+	if (index == ra->start && ra->size == ra->async_size) {
 		add_pages = get_next_ra_size(ra, max_pages);
 		if (ra->size + add_pages <= max_pages) {
 			ra->async_size = add_pages;
@@ -496,9 +496,8 @@ static void ondemand_readahead(struct address_space *mapping,
  * @mapping: address_space which holds the pagecache and I/O vectors
  * @ra: file_ra_state which holds the readahead state
  * @filp: passed on to ->readpage() and ->readpages()
- * @offset: start offset into @mapping, in pagecache page-sized units
- * @req_size: hint: total size of the read which the caller is performing in
- *            pagecache pages
+ * @index: Index of first page to be read.
+ * @req_count: Total number of pages being read by the caller.
  *
  * page_cache_sync_readahead() should be called when a cache miss happened:
  * it will submit the read.  The readahead logic may decide to piggyback more
@@ -507,7 +506,7 @@ static void ondemand_readahead(struct address_space *mapping,
  */
 void page_cache_sync_readahead(struct address_space *mapping,
 			       struct file_ra_state *ra, struct file *filp,
-			       pgoff_t offset, unsigned long req_size)
+			       pgoff_t index, unsigned long req_count)
 {
 	/* no read-ahead */
 	if (!ra->ra_pages)
@@ -518,12 +517,12 @@ void page_cache_sync_readahead(struct address_space *mapping,
 
 	/* be dumb */
 	if (filp && (filp->f_mode & FMODE_RANDOM)) {
-		force_page_cache_readahead(mapping, filp, offset, req_size);
+		force_page_cache_readahead(mapping, filp, index, req_count);
 		return;
 	}
 
 	/* do read-ahead */
-	ondemand_readahead(mapping, ra, filp, false, offset, req_size);
+	ondemand_readahead(mapping, ra, filp, false, index, req_count);
 }
 EXPORT_SYMBOL_GPL(page_cache_sync_readahead);
 
@@ -532,21 +531,20 @@ EXPORT_SYMBOL_GPL(page_cache_sync_readahead);
  * @mapping: address_space which holds the pagecache and I/O vectors
  * @ra: file_ra_state which holds the readahead state
  * @filp: passed on to ->readpage() and ->readpages()
- * @page: the page at @offset which has the PG_readahead flag set
- * @offset: start offset into @mapping, in pagecache page-sized units
- * @req_size: hint: total size of the read which the caller is performing in
- *            pagecache pages
+ * @page: The page at @index which triggered the readahead call.
+ * @index: Index of first page to be read.
+ * @req_count: Total number of pages being read by the caller.
  *
  * page_cache_async_readahead() should be called when a page is used which
- * has the PG_readahead flag; this is a marker to suggest that the application
+ * is marked as PageReadahead; this is a marker to suggest that the application
  * has used up enough of the readahead window that we should start pulling in
  * more pages.
  */
 void
 page_cache_async_readahead(struct address_space *mapping,
 			   struct file_ra_state *ra, struct file *filp,
-			   struct page *page, pgoff_t offset,
-			   unsigned long req_size)
+			   struct page *page, pgoff_t index,
+			   unsigned long req_count)
 {
 	/* no read-ahead */
 	if (!ra->ra_pages)
@@ -570,7 +568,7 @@ page_cache_async_readahead(struct address_space *mapping,
 		return;
 
 	/* do read-ahead */
-	ondemand_readahead(mapping, ra, filp, true, offset, req_size);
+	ondemand_readahead(mapping, ra, filp, true, index, req_count);
 }
 EXPORT_SYMBOL_GPL(page_cache_async_readahead);
 
