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crypto: api - Add more comments to crypto_remove_spawns

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This patch explains the logic behind crypto_remove_spawns and its
underling crypto_more_spawns.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Herbert Xu 2019-12-07 22:33:51 +08:00
parent 4f87ee118d
commit 02244ba44b
1 changed files with 25 additions and 0 deletions
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25
crypto/algapi.c
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@ -82,6 +82,15 @@ static void crypto_destroy_instance(struct crypto_alg *alg)
crypto_tmpl_put(tmpl); crypto_tmpl_put(tmpl);
} }
/*
* This function adds a spawn to the list secondary_spawns which
* will be used at the end of crypto_remove_spawns to unregister
* instances, unless the spawn happens to be one that is depended
* on by the new algorithm (nalg in crypto_remove_spawns).
*
* This function is also responsible for resurrecting any algorithms
* in the dependency chain of nalg by unsetting n->dead.
*/
static struct list_head *crypto_more_spawns(struct crypto_alg *alg, static struct list_head *crypto_more_spawns(struct crypto_alg *alg,
struct list_head *stack, struct list_head *stack,
struct list_head *top, struct list_head *top,
@ -128,6 +137,12 @@ static void crypto_remove_instance(struct crypto_instance *inst,
BUG_ON(!list_empty(&inst->alg.cra_users)); BUG_ON(!list_empty(&inst->alg.cra_users));
} }
/*
* Given an algorithm alg, remove all algorithms that depend on it
* through spawns. If nalg is not null, then exempt any algorithms
* that is depended on by nalg. This is useful when nalg itself
* depends on alg.
*/
void crypto_remove_spawns(struct crypto_alg *alg, struct list_head *list, void crypto_remove_spawns(struct crypto_alg *alg, struct list_head *list,
struct crypto_alg *nalg) struct crypto_alg *nalg)
{ {
@ -146,6 +161,11 @@ void crypto_remove_spawns(struct crypto_alg *alg, struct list_head *list,
list_move(&spawn->list, &top); list_move(&spawn->list, &top);
} }
/*
* Perform a depth-first walk starting from alg through
* the cra_users tree. The list stack records the path
* from alg to the current spawn.
*/
spawns = &top; spawns = &top;
do { do {
while (!list_empty(spawns)) { while (!list_empty(spawns)) {
@ -180,6 +200,11 @@ void crypto_remove_spawns(struct crypto_alg *alg, struct list_head *list,
} while ((spawns = crypto_more_spawns(alg, &stack, &top, } while ((spawns = crypto_more_spawns(alg, &stack, &top,
&secondary_spawns))); &secondary_spawns)));
/*
* Remove all instances that are marked as dead. Also
* complete the resurrection of the others by moving them
* back to the cra_users list.
*/
list_for_each_entry_safe(spawn, n, &secondary_spawns, list) { list_for_each_entry_safe(spawn, n, &secondary_spawns, list) {
if (!spawn->dead) if (!spawn->dead)
list_move(&spawn->list, &spawn->alg->cra_users); list_move(&spawn->list, &spawn->alg->cra_users);