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Diffstat (limited to 'ipc')
-rw-r--r--ipc/util.c44
-rw-r--r--ipc/util.h3
2 files changed, 42 insertions, 5 deletions
diff --git a/ipc/util.c b/ipc/util.c
index cfa0045e748d..0027e47626b7 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -64,6 +64,7 @@
#include <linux/memory.h>
#include <linux/ipc_namespace.h>
#include <linux/rhashtable.h>
+#include <linux/log2.h>
#include <asm/unistd.h>
@@ -451,6 +452,41 @@ static void ipc_kht_remove(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
}
/**
+ * ipc_search_maxidx - search for the highest assigned index
+ * @ids: ipc identifier set
+ * @limit: known upper limit for highest assigned index
+ *
+ * The function determines the highest assigned index in @ids. It is intended
+ * to be called when ids->max_idx needs to be updated.
+ * Updating ids->max_idx is necessary when the current highest index ipc
+ * object is deleted.
+ * If no ipc object is allocated, then -1 is returned.
+ *
+ * ipc_ids.rwsem needs to be held by the caller.
+ */
+static int ipc_search_maxidx(struct ipc_ids *ids, int limit)
+{
+ int tmpidx;
+ int i;
+ int retval;
+
+ i = ilog2(limit+1);
+
+ retval = 0;
+ for (; i >= 0; i--) {
+ tmpidx = retval | (1<<i);
+ /*
+ * "0" is a possible index value, thus search using
+ * e.g. 15,7,3,1,0 instead of 16,8,4,2,1.
+ */
+ tmpidx = tmpidx-1;
+ if (idr_get_next(&ids->ipcs_idr, &tmpidx))
+ retval |= (1<<i);
+ }
+ return retval - 1;
+}
+
+/**
* ipc_rmid - remove an ipc identifier
* @ids: ipc identifier set
* @ipcp: ipc perm structure containing the identifier to remove
@@ -468,11 +504,9 @@ void ipc_rmid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
ipcp->deleted = true;
if (unlikely(idx == ids->max_idx)) {
- do {
- idx--;
- if (idx == -1)
- break;
- } while (!idr_find(&ids->ipcs_idr, idx));
+ idx = ids->max_idx-1;
+ if (idx >= 0)
+ idx = ipc_search_maxidx(ids, idx);
ids->max_idx = idx;
}
}
diff --git a/ipc/util.h b/ipc/util.h
index 5766c61aed0e..2dd7ce0416d8 100644
--- a/ipc/util.h
+++ b/ipc/util.h
@@ -145,6 +145,9 @@ int ipcperms(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp, short flg);
* ipc_get_maxidx - get the highest assigned index
* @ids: ipc identifier set
*
+ * The function returns the highest assigned index for @ids. The function
+ * doesn't scan the idr tree, it uses a cached value.
+ *
* Called with ipc_ids.rwsem held for reading.
*/
static inline int ipc_get_maxidx(struct ipc_ids *ids)