Commit 9f7de827 authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds

idr: make idr_get_next() good for rcu_read_lock()

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: default avatarHugh Dickins <hughd@google.com>
Acked-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: default avatarLi Zefan <lizf@cn.fujitsu.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 0e79dedd
...@@ -595,8 +595,10 @@ EXPORT_SYMBOL(idr_for_each); ...@@ -595,8 +595,10 @@ EXPORT_SYMBOL(idr_for_each);
* Returns pointer to registered object with id, which is next number to * 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 * given id. After being looked up, *@nextidp will be updated for the next
* iteration. * 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) void *idr_get_next(struct idr *idp, int *nextidp)
{ {
struct idr_layer *p, *pa[MAX_LEVEL]; struct idr_layer *p, *pa[MAX_LEVEL];
...@@ -605,11 +607,11 @@ void *idr_get_next(struct idr *idp, int *nextidp) ...@@ -605,11 +607,11 @@ void *idr_get_next(struct idr *idp, int *nextidp)
int n, max; int n, max;
/* find first ent */ /* find first ent */
n = idp->layers * IDR_BITS;
max = 1 << n;
p = rcu_dereference_raw(idp->top); p = rcu_dereference_raw(idp->top);
if (!p) if (!p)
return NULL; return NULL;
n = (p->layer + 1) * IDR_BITS;
max = 1 << n;
while (id < max) { while (id < max) {
while (n > 0 && p) { while (n > 0 && p) {
......
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