Commit 6df8ba4f authored by Fengguang Wu's avatar Fengguang Wu Committed by Linus Torvalds
Browse files

radixtree: introduce radix_tree_next_hole() 



Introduce radix_tree_next_hole(root, index, max_scan) to scan radix tree for
the first hole.  It will be used in interleaved readahead.

The implementation is dumb and obviously correct.  It can help debug(and
document) the possible smart one in future.

Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: default avatarFengguang Wu <wfg@mail.ustc.edu.cn>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f4e6b498

include/linux/radix-tree.h

+2 −0
Original line number Diff line number Diff line
@@ -155,6 +155,8 @@ void *radix_tree_delete(struct radix_tree_root *, unsigned long); 
unsigned int

radix_tree_gang_lookup(struct radix_tree_root *root, void **results,

			unsigned long first_index, unsigned int max_items);

unsigned long radix_tree_next_hole(struct radix_tree_root *root,

				unsigned long index, unsigned long max_scan);

int radix_tree_preload(gfp_t gfp_mask);

void radix_tree_init(void);

void *radix_tree_tag_set(struct radix_tree_root *root,

lib/radix-tree.c

+36 −0
Original line number Diff line number Diff line
@@ -599,6 +599,42 @@ int radix_tree_tag_get(struct radix_tree_root *root, 
EXPORT_SYMBOL(radix_tree_tag_get);

#endif



/**

 *	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).

 *

 *	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);



static unsigned int

__lookup(struct radix_tree_node *slot, void **results, unsigned long index,

	unsigned int max_items, unsigned long *next_index)

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