[PATCH v3 02/36] crypto_pool: Add crypto_pool_reserve_scratch()

Dmitry Safonov
2022-10-27T20:44:14Z

Instead of having build-time hardcoded constant, reallocate scratch
area, if needed by user. Different algos, different users may need
different size of temp per-CPU buffer. Only up-sizing supported for
simplicity.

Signed-off-by: Dmitry Safonov <dima@arista.com>
---
crypto/Kconfig | 6 ++++
crypto/crypto_pool.c | 77 ++++++++++++++++++++++++++++++++++---------
include/crypto/pool.h | 3 +-
3 files changed, 69 insertions(+), 17 deletions(-)

diff --git a/crypto/Kconfig b/crypto/Kconfig
index 768d331e626b..e002cd321e79 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -1397,6 +1397,12 @@ config CRYPTO_POOL
help
Per-CPU pool of crypto requests ready for usage in atomic contexts.

+config CRYPTO_POOL_DEFAULT_SCRATCH_SIZE
+ hex "Per-CPU default scratch area size"
+ depends on CRYPTO_POOL
+ default 0x100
+ range 0x100 0x10000
+
if !KMSAN # avoid false positives from assembly
if ARM
source "arch/arm/crypto/Kconfig"
diff --git a/crypto/crypto_pool.c b/crypto/crypto_pool.c
index 37131952c5a7..2f1deb3f5218 100644
--- a/crypto/crypto_pool.c
+++ b/crypto/crypto_pool.c
@@ -1,13 +1,14 @@
// SPDX-License-Identifier: GPL-2.0-or-later

#include <crypto/pool.h>
+#include <linux/cpu.h>
#include <linux/kref.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/percpu.h>
#include <linux/workqueue.h>

-static unsigned long scratch_size = DEFAULT_CRYPTO_POOL_SCRATCH_SZ;
+static unsigned long scratch_size = CONFIG_CRYPTO_POOL_DEFAULT_SCRATCH_SIZE;
static DEFINE_PER_CPU(void *, crypto_pool_scratch);

struct crypto_pool_entry {
@@ -22,26 +23,69 @@ static struct crypto_pool_entry cpool[CPOOL_SIZE];
static unsigned int cpool_populated;
static DEFINE_MUTEX(cpool_mutex);

-static int crypto_pool_scratch_alloc(void)
+/* Slow-path */
+/**
+ * crypto_pool_reserve_scratch - re-allocates scratch buffer, slow-path
+ * @size: request size for the scratch/temp buffer
+ */
+#define FREE_BATCH_SIZE 64
+int crypto_pool_reserve_scratch(unsigned long size)
{
- int cpu;
-
- lockdep_assert_held(&cpool_mutex);
+ void *free_batch[FREE_BATCH_SIZE];
+ int cpu, err = 0;
+ unsigned int i = 0;

+ mutex_lock(&cpool_mutex);
+ if (size == scratch_size) {
+ for_each_possible_cpu(cpu) {
+ if (per_cpu(crypto_pool_scratch, cpu))
+ continue;
+ goto allocate_scratch;
+ }
+ mutex_unlock(&cpool_mutex);
+ return 0;
+ }
+allocate_scratch:
+ size = max(size, scratch_size);
+ cpus_read_lock();
for_each_possible_cpu(cpu) {
- void *scratch = per_cpu(crypto_pool_scratch, cpu);
+ void *scratch, *old_scratch;

- if (scratch)
+ scratch = kmalloc_node(size, GFP_KERNEL, cpu_to_node(cpu));
+ if (!scratch) {
+ err = -ENOMEM;
+ break;
+ }
+
+ old_scratch = per_cpu(crypto_pool_scratch, cpu);
+ /* Pairs with crypto_pool_get() */
+ WRITE_ONCE(*per_cpu_ptr(&crypto_pool_scratch, cpu), scratch);
+ if (!cpu_online(cpu)) {
+ kfree(old_scratch);
continue;
+ }
+ free_batch[i++] = old_scratch;
+ if (i == FREE_BATCH_SIZE) {
+ cpus_read_unlock();
+ synchronize_rcu();
+ while (i > 0)
+ kfree(free_batch[--i]);
+ cpus_read_lock();
+ }
+ }
+ cpus_read_unlock();
+ if (!err)
+ scratch_size = size;
+ mutex_unlock(&cpool_mutex);

- scratch = kmalloc_node(scratch_size, GFP_KERNEL,
- cpu_to_node(cpu));
- if (!scratch)
- return -ENOMEM;
- per_cpu(crypto_pool_scratch, cpu) = scratch;
+ if (i > 0) {
+ synchronize_rcu();
+ while (i > 0)
+ kfree(free_batch[--i]);
}
- return 0;
+ return err;
}
+EXPORT_SYMBOL_GPL(crypto_pool_reserve_scratch);

static void crypto_pool_scratch_free(void)
{
@@ -138,7 +182,6 @@ int crypto_pool_alloc_ahash(const char *alg)

/* slow-path */
mutex_lock(&cpool_mutex);
-
for (i = 0; i < cpool_populated; i++) {
if (cpool[i].alg && !strcmp(cpool[i].alg, alg)) {
if (kref_read(&cpool[i].kref) > 0) {
@@ -263,7 +306,11 @@ int crypto_pool_get(unsigned int id, struct crypto_pool *c)
return -EINVAL;
}
ret->req = *this_cpu_ptr(cpool[id].req);
- ret->base.scratch = this_cpu_read(crypto_pool_scratch);
+ /*
+ * Pairs with crypto_pool_reserve_scratch(), scartch area is
+ * valid (allocated) until crypto_pool_put().
+ */
+ ret->base.scratch = READ_ONCE(*this_cpu_ptr(&crypto_pool_scratch));
return 0;
}
EXPORT_SYMBOL_GPL(crypto_pool_get);
diff --git a/include/crypto/pool.h b/include/crypto/pool.h
index 2c61aa45faff..c7d817860cc3 100644
--- a/include/crypto/pool.h
+++ b/include/crypto/pool.h
@@ -4,8 +4,6 @@

#include <crypto/hash.h>

-#define DEFAULT_CRYPTO_POOL_SCRATCH_SZ 128
-
struct crypto_pool {
void *scratch;
};
@@ -20,6 +18,7 @@ struct crypto_pool_ahash {
struct ahash_request *req;
};

+int crypto_pool_reserve_scratch(unsigned long size);
int crypto_pool_alloc_ahash(const char *alg);
void crypto_pool_add(unsigned int id);
void crypto_pool_release(unsigned int id);
--
2.38.1