From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Wed, 27 May 2020 11:19:42 +0200
Subject: mm/zswap: Use local lock to protect per-CPU data
Patch-mainline: Queued in subsystem maintainer repository
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-stable-rt.git
Git-commit: 05e50eed2fd330752c9d1805680c622c0f48dbc7
References: SLE Realtime Extension

This is an incremental update of the zswap patch. Addtional spots were
identified, which were lacking proper locking, during the rework of the
patch for upstream.
The complete patch description is available as commit
   79410590ae87e ("mm/zswap: Use local lock to protect per-CPU data")

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: Daniel Wagner <dwagner@suse.de>
---
 mm/zswap.c |   21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -372,6 +372,8 @@ static struct zswap_entry *zswap_entry_f
 * per-cpu code
 **********************************/
 static DEFINE_PER_CPU(u8 *, zswap_dstmem);
+/* Used for zswap_dstmem and tfm */
+static DEFINE_LOCAL_IRQ_LOCK(zswap_cpu_lock);
 
 static int zswap_dstmem_prepare(unsigned int cpu)
 {
@@ -890,10 +892,11 @@ static int zswap_writeback_entry(struct
 		src = (u8 *)zpool_map_handle(entry->pool->zpool, entry->handle,
 				ZPOOL_MM_RO) + sizeof(struct zswap_header);
 		dst = kmap_atomic(page);
-		tfm = *get_cpu_ptr(entry->pool->tfm);
+		local_lock(zswap_cpu_lock);
+		tfm = *this_cpu_ptr(entry->pool->tfm);
 		ret = crypto_comp_decompress(tfm, src, entry->length,
 					     dst, &dlen);
-		put_cpu_ptr(entry->pool->tfm);
+		local_unlock(zswap_cpu_lock);
 		kunmap_atomic(dst);
 		zpool_unmap_handle(entry->pool->zpool, entry->handle);
 		BUG_ON(ret);
@@ -982,8 +985,6 @@ static void zswap_fill_page(void *ptr, u
 	memset_l(page, value, PAGE_SIZE / sizeof(unsigned long));
 }
 
-/* protect zswap_dstmem from concurrency */
-static DEFINE_LOCAL_IRQ_LOCK(zswap_dstmem_lock);
 /*********************************
 * frontswap hooks
 **********************************/
@@ -1060,7 +1061,8 @@ static int zswap_frontswap_store(unsigne
 	}
 
 	/* compress */
-	dst = get_locked_var(zswap_dstmem_lock, zswap_dstmem);
+	local_lock(zswap_cpu_lock);
+	dst = *this_cpu_ptr(&zswap_dstmem);
 	tfm = *this_cpu_ptr(entry->pool->tfm);
 	src = kmap_atomic(page);
 	ret = crypto_comp_compress(tfm, src, PAGE_SIZE, dst, &dlen);
@@ -1087,7 +1089,7 @@ static int zswap_frontswap_store(unsigne
 	memcpy(buf, &zhdr, hlen);
 	memcpy(buf + hlen, dst, dlen);
 	zpool_unmap_handle(entry->pool->zpool, handle);
-	put_locked_var(zswap_dstmem_lock, zswap_dstmem);
+	local_unlock(zswap_cpu_lock);
 
 	/* populate entry */
 	entry->offset = offset;
@@ -1115,7 +1117,7 @@ static int zswap_frontswap_store(unsigne
 	return 0;
 
 put_dstmem:
-	put_locked_var(zswap_dstmem_lock, zswap_dstmem);
+	local_unlock(zswap_cpu_lock);
 	zswap_pool_put(entry->pool);
 freepage:
 	zswap_entry_cache_free(entry);
@@ -1160,9 +1162,10 @@ static int zswap_frontswap_load(unsigned
 	if (zpool_evictable(entry->pool->zpool))
 		src += sizeof(struct zswap_header);
 	dst = kmap_atomic(page);
-	tfm = *get_cpu_ptr(entry->pool->tfm);
+	local_lock(zswap_cpu_lock);
+	tfm = *this_cpu_ptr(entry->pool->tfm);
 	ret = crypto_comp_decompress(tfm, src, entry->length, dst, &dlen);
-	put_cpu_ptr(entry->pool->tfm);
+	local_unlock(zswap_cpu_lock);
 	kunmap_atomic(dst);
 	zpool_unmap_handle(entry->pool->zpool, entry->handle);
 	BUG_ON(ret);