3.2-stable review patch. If anyone has any objections, please let me know.
------------------
From: Hugh Dickins <hughd@xxxxxxxxxx>
commit 9f7de8275b46d9d11b1505adbfe6c2bb48df4741 upstream.
Make one small adjustment to idr_get_next(): take the height from the top
layer (stable under RCU) instead of from the root (unprotected by RCU), as
idr_find() does: so that it can be used with RCU locking. Copied comment
on RCU locking from idr_find().
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Acked-by: Li Zefan <lizf@xxxxxxxxxxxxxx>
Cc: Eric Dumazet <eric.dumazet@xxxxxxxxx>
Acked-by: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
lib/idr.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -595,8 +595,10 @@ EXPORT_SYMBOL(idr_for_each);
* Returns pointer to registered object with id, which is next number to
* given id. After being looked up, *@nextidp will be updated for the next
* iteration.
+ *
+ * This function can be called under rcu_read_lock(), given that the leaf
+ * pointers lifetimes are correctly managed.
*/
-
void *idr_get_next(struct idr *idp, int *nextidp)
{
struct idr_layer *p, *pa[MAX_LEVEL];
@@ -605,11 +607,11 @@ void *idr_get_next(struct idr *idp, int
int n, max;
/* find first ent */
- n = idp->layers * IDR_BITS;
- max = 1 << n;
p = rcu_dereference_raw(idp->top);
if (!p)
return NULL;
+ n = (p->layer + 1) * IDR_BITS;
+ max = 1 << n;
while (id < max) {
while (n > 0 && p) {
--
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