mm: filemap: move radix tree hole searching here

The radix tree hole searching code is only used for page cache, for
example the readahead code trying to get a a picture of the area
surrounding a fault.

It sufficed to rely on the radix tree definition of holes, which is
"empty tree slot".  But this is about to change, though, as shadow page
descriptors will be stored in the page cache after the actual pages get
evicted from memory.

Move the functions over to mm/filemap.c and make them native page cache
operations, where they can later be adapted to handle the new definition
of "page cache hole".

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Minchan Kim <minchan@kernel.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Bob Liu <bob.liu@oracle.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Luigi Semenzato <semenzato@google.com>
Cc: Metin Doslu <metin@citusdata.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Ozgun Erdogan <ozgun@citusdata.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roman Gushchin <klamm@yandex-team.ru>
Cc: Ryan Mallon <rmallon@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 0 insertions, 75 deletions

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index d832117..7e30d2a 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -946,81 +946,6 @@ next:
 }
 EXPORT_SYMBOL(radix_tree_range_tag_if_tagged);
 
-
-/**
- *	radix_tree_next_hole    -    find the next hole (not-present entry)
- *	@root:		tree root
- *	@index:		index key
- *	@max_scan:	maximum range to search
- *
- *	Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the lowest
- *	indexed hole.
- *
- *	Returns: the index of the hole if found, otherwise returns an index
- *	outside of the set specified (in which case 'return - index >= max_scan'
- *	will be true). In rare cases of index wrap-around, 0 will be returned.
- *
- *	radix_tree_next_hole may be called under rcu_read_lock. However, like
- *	radix_tree_gang_lookup, this will not atomically search a snapshot of
- *	the tree at a single point in time. For example, if a hole is created
- *	at index 5, then subsequently a hole is created at index 10,
- *	radix_tree_next_hole covering both indexes may return 10 if called
- *	under rcu_read_lock.
- */
-unsigned long radix_tree_next_hole(struct radix_tree_root *root,
-				unsigned long index, unsigned long max_scan)
-{
-	unsigned long i;
-
-	for (i = 0; i < max_scan; i++) {
-		if (!radix_tree_lookup(root, index))
-			break;
-		index++;
-		if (index == 0)
-			break;
-	}
-
-	return index;
-}
-EXPORT_SYMBOL(radix_tree_next_hole);
-
-/**
- *	radix_tree_prev_hole    -    find the prev hole (not-present entry)
- *	@root:		tree root
- *	@index:		index key
- *	@max_scan:	maximum range to search
- *
- *	Search backwards in the range [max(index-max_scan+1, 0), index]
- *	for the first hole.
- *
- *	Returns: the index of the hole if found, otherwise returns an index
- *	outside of the set specified (in which case 'index - return >= max_scan'
- *	will be true). In rare cases of wrap-around, ULONG_MAX will be returned.
- *
- *	radix_tree_next_hole may be called under rcu_read_lock. However, like
- *	radix_tree_gang_lookup, this will not atomically search a snapshot of
- *	the tree at a single point in time. For example, if a hole is created
- *	at index 10, then subsequently a hole is created at index 5,
- *	radix_tree_prev_hole covering both indexes may return 5 if called under
- *	rcu_read_lock.
- */
-unsigned long radix_tree_prev_hole(struct radix_tree_root *root,
-				   unsigned long index, unsigned long max_scan)
-{
-	unsigned long i;
-
-	for (i = 0; i < max_scan; i++) {
-		if (!radix_tree_lookup(root, index))
-			break;
-		index--;
-		if (index == ULONG_MAX)
-			break;
-	}
-
-	return index;
-}
-EXPORT_SYMBOL(radix_tree_prev_hole);
-
 /**
  *	radix_tree_gang_lookup - perform multiple lookup on a radix tree
  *	@root:		radix tree root