[PATCH v2 2/5] crypto/pool: Add crypto_pool_reserve_scratch()

[Dmitry Safonov <dima@arista.com>]

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 ba8d4a1f10f9..0614c2acfffa 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -1394,6 +1394,12 @@ 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..0cd9eade7b73 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
+ */
+int crypto_pool_reserve_scratch(unsigned long size)
 {
-	int cpu;
-
-	lockdep_assert_held(&cpool_mutex);
+#define FREE_BATCH_SIZE		64
+	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);
-- 
2.39.0