1 files changed, 16 insertions, 3 deletions

diff --git a/mm/zswap.c b/mm/zswap.c
index f6316b66fb23..5a27af8d86ea 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -880,6 +880,18 @@ static int zswap_cpu_comp_dead(unsigned int cpu, struct hlist_node *node)
 	return 0;
 }
 
+/* Prevent CPU hotplug from freeing up the per-CPU acomp_ctx resources */
+static struct crypto_acomp_ctx *acomp_ctx_get_cpu(struct crypto_acomp_ctx __percpu *acomp_ctx)
+{
+	cpus_read_lock();
+	return raw_cpu_ptr(acomp_ctx);
+}
+
+static void acomp_ctx_put_cpu(void)
+{
+	cpus_read_unlock();
+}
+
 static bool zswap_compress(struct page *page, struct zswap_entry *entry,
 			   struct zswap_pool *pool)
 {
@@ -893,8 +905,7 @@ static bool zswap_compress(struct page *page, struct zswap_entry *entry,
 	gfp_t gfp;
 	u8 *dst;
 
-	acomp_ctx = raw_cpu_ptr(pool->acomp_ctx);
-
+	acomp_ctx = acomp_ctx_get_cpu(pool->acomp_ctx);
 	mutex_lock(&acomp_ctx->mutex);
 
 	dst = acomp_ctx->buffer;
@@ -950,6 +961,7 @@ unlock:
 		zswap_reject_alloc_fail++;
 
 	mutex_unlock(&acomp_ctx->mutex);
+	acomp_ctx_put_cpu();
 	return comp_ret == 0 && alloc_ret == 0;
 }
 
@@ -960,7 +972,7 @@ static void zswap_decompress(struct zswap_entry *entry, struct folio *folio)
 	struct crypto_acomp_ctx *acomp_ctx;
 	u8 *src;
 
-	acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
+	acomp_ctx = acomp_ctx_get_cpu(entry->pool->acomp_ctx);
 	mutex_lock(&acomp_ctx->mutex);
 
 	src = zpool_map_handle(zpool, entry->handle, ZPOOL_MM_RO);
@@ -990,6 +1002,7 @@ static void zswap_decompress(struct zswap_entry *entry, struct folio *folio)
 
 	if (src != acomp_ctx->buffer)
 		zpool_unmap_handle(zpool, entry->handle);
+	acomp_ctx_put_cpu();
 }
 
 /*********************************