From: Martin Wilck <mwilck@xxxxxxxx>
If we can assume that the bindings array is totally ordered for every
prefix, which the previous patch guarantees, the search for a free ID can be
simplified.
Signed-off-by: Martin Wilck <mwilck@xxxxxxxx>
---
libmultipath/alias.c | 87 ++++++++++----------------------------------
1 file changed, 19 insertions(+), 68 deletions(-)
diff --git a/libmultipath/alias.c b/libmultipath/alias.c
index af6565b..66e34e3 100644
--- a/libmultipath/alias.c
+++ b/libmultipath/alias.c
@@ -356,83 +356,34 @@ int get_free_id(const Bindings *bindings, const char *prefix, const char *map_ww
{
const struct binding *bdg;
int i, id = 1;
- int biggest_id = 1;
- int smallest_bigger_id = INT_MAX;
vector_foreach_slot(bindings, bdg, i) {
int curr_id = scan_devname(bdg->alias, prefix);
- /*
- * Find an unused index - explanation of the algorithm
- *
- * ID: 1 = mpatha, 2 = mpathb, ...
- *
- * We assume the bindings are unsorted. The only constraint
- * is that no ID occurs more than once. IDs that occur in the
- * bindings are called "used".
- *
- * We call the list 1,2,3,..., exactly in this order, the list
- * of "expected" IDs. The variable "id" always holds the next
- * "expected" ID, IOW the last "expected" ID encountered plus 1.
- * Thus all IDs below "id" are known to be used. However, at the
- * end of the loop, the value of "id" isn't necessarily unused.
- *
- * "smallest_bigger_id" is the smallest used ID that was
- * encountered while it was larger than the next "expected" ID
- * at that iteration. Let X be some used ID. If all IDs below X
- * are used and encountered in the right sequence before X, "id"
- * will be > X when the loop ends. Otherwise, X was encountered
- * "out of order", the condition (X > id) holds when X is
- * encountered, and "smallest_bigger_id" will be set to X; i.e.
- * it will be less or equal than X when the loop ends.
- *
- * At the end of the loop, (id < smallest_bigger_id) means that
- * the value of "id" had been encountered neither in order nor
- * out of order, and is thus unused. (id >= smallest_bigger_id)
- * means that "id"'s value is in use. In this case, we play safe
- * and use "biggest_id + 1" as the next value to try.
- *
- * biggest_id is always > smallest_bigger_id, except in the
- * "perfectly ordered" case.
- */
- if (curr_id == id) {
- if (id < INT_MAX)
- id++;
- else {
- id = -1;
- break;
- }
+ if (curr_id == -1)
+ continue;
+ if (id > curr_id) {
+ condlog(0, "%s: ERROR: bindings are not sorted", __func__);
+ return -1;
}
- if (curr_id > biggest_id)
- biggest_id = curr_id;
-
- if (curr_id > id && curr_id < smallest_bigger_id)
- smallest_bigger_id = curr_id;
- }
-
- if (id >= smallest_bigger_id)
- id = biggest_id < INT_MAX ? biggest_id + 1 : -1;
-
- if (id > 0) {
- while(id_already_taken(id, prefix, map_wwid)) {
- if (id == INT_MAX) {
- id = -1;
- break;
- }
+ while (id < curr_id && id_already_taken(id, prefix, map_wwid))
id++;
- if (id == smallest_bigger_id) {
- if (biggest_id == INT_MAX) {
- id = -1;
- break;
- }
- if (biggest_id >= smallest_bigger_id)
- id = biggest_id + 1;
- }
- }
+ if (id < curr_id)
+ return id;
+ id++;
+ if (id <= 0)
+ break;
}
- if (id < 0)
+ for (; id > 0; id++) {
+ if (!id_already_taken(id, prefix, map_wwid))
+ break;
+ }
+
+ if (id <= 0) {
+ id = -1;
condlog(0, "no more available user_friendly_names");
+ }
return id;
}
--
2.42.0
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