radix-tree: add radix_tree_prev_hole()
The counterpart of radix_tree_next_hole(). To be used by context readahead. Signed-off-by: Wu Fengguang <fengguang.wu@intel.com> Cc: Vladislav Bolkhovitin <vst@vlnb.net> Cc: Jens Axboe <jens.axboe@oracle.com> Cc: Jeff Moyer <jmoyer@redhat.com> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: Ying Han <yinghan@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
parent
d30a11004e
commit
dc566127dd
@ -167,6 +167,8 @@ radix_tree_gang_lookup_slot(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);
|
||||
unsigned long radix_tree_prev_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,
|
||||
|
@ -666,6 +666,43 @@ unsigned long radix_tree_next_hole(struct radix_tree_root *root,
|
||||
}
|
||||
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, LONG_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 == LONG_MAX)
|
||||
break;
|
||||
}
|
||||
|
||||
return index;
|
||||
}
|
||||
EXPORT_SYMBOL(radix_tree_prev_hole);
|
||||
|
||||
static unsigned int
|
||||
__lookup(struct radix_tree_node *slot, void ***results, unsigned long index,
|
||||
unsigned int max_items, unsigned long *next_index)
|
||||
|
Loading…
Reference in New Issue
Block a user