[PATCH] mm/zswap: Fix the compatibility of zsmalloc and zswap

[Tian Tao <tiantao6@hisilicon.com>]

add a flag to zpool, named is "can_sleep_mapped", and have it set true
for zbud/z3fold, set false for zsmalloc. Then zswap could go the current
path if the flag is true; and if it's false, copy data from src to a
temporary buffer, then unmap the handle, take the mutex, process the
buffer instead of src to avoid sleeping function called from atomic
context.

Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
---
 include/linux/zpool.h |  2 ++
 mm/z3fold.c           |  1 +
 mm/zbud.c             |  1 +
 mm/zpool.c            | 13 +++++++++++++
 mm/zsmalloc.c         |  1 +
 mm/zswap.c            | 23 +++++++++++++++++++++--
 6 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/include/linux/zpool.h b/include/linux/zpool.h
index 51bf430..a354f4fe 100644
--- a/include/linux/zpool.h
+++ b/include/linux/zpool.h
@@ -82,6 +82,7 @@ u64 zpool_get_total_size(struct zpool *pool);
  */
 struct zpool_driver {
 	char *type;
+	bool sleep_mapped;
 	struct module *owner;
 	atomic_t refcount;
 	struct list_head list;
@@ -112,5 +113,6 @@ void zpool_register_driver(struct zpool_driver *driver);
 int zpool_unregister_driver(struct zpool_driver *driver);
 
 bool zpool_evictable(struct zpool *pool);
+bool zpool_can_sleep_mapped(struct zpool *pool);
 
 #endif
diff --git a/mm/z3fold.c b/mm/z3fold.c
index dacb0d7..234b46f 100644
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -1778,6 +1778,7 @@ static u64 z3fold_zpool_total_size(void *pool)
 
 static struct zpool_driver z3fold_zpool_driver = {
 	.type =		"z3fold",
+	.sleep_mapped = true,
 	.owner =	THIS_MODULE,
 	.create =	z3fold_zpool_create,
 	.destroy =	z3fold_zpool_destroy,
diff --git a/mm/zbud.c b/mm/zbud.c
index c49966e..7ec5f27 100644
--- a/mm/zbud.c
+++ b/mm/zbud.c
@@ -203,6 +203,7 @@ static u64 zbud_zpool_total_size(void *pool)
 
 static struct zpool_driver zbud_zpool_driver = {
 	.type =		"zbud",
+	.sleep_mapped = true,
 	.owner =	THIS_MODULE,
 	.create =	zbud_zpool_create,
 	.destroy =	zbud_zpool_destroy,
diff --git a/mm/zpool.c b/mm/zpool.c
index 3744a2d..5ed7120 100644
--- a/mm/zpool.c
+++ b/mm/zpool.c
@@ -23,6 +23,7 @@ struct zpool {
 	void *pool;
 	const struct zpool_ops *ops;
 	bool evictable;
+	bool can_sleep_mapped;
 
 	struct list_head list;
 };
@@ -183,6 +184,7 @@ struct zpool *zpool_create_pool(const char *type, const char *name, gfp_t gfp,
 	zpool->pool = driver->create(name, gfp, ops, zpool);
 	zpool->ops = ops;
 	zpool->evictable = driver->shrink && ops && ops->evict;
+	zpool->can_sleep_mapped = driver->sleep_mapped;
 
 	if (!zpool->pool) {
 		pr_err("couldn't create %s pool\n", type);
@@ -393,6 +395,17 @@ bool zpool_evictable(struct zpool *zpool)
 	return zpool->evictable;
 }
 
+/**
+ * zpool_can_sleep_mapped - Test if zpool can sleep when do mapped.
+ * @zpool:	The zpool to test
+ *
+ * Returns: true if zpool can sleep; false otherwise.
+ */
+bool zpool_can_sleep_mapped(struct zpool *zpool)
+{
+	return zpool->can_sleep_mapped;
+}
+
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Dan Streetman <ddstreet@ieee.org>");
 MODULE_DESCRIPTION("Common API for compressed memory storage");
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 7289f50..a991d3c 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -440,6 +440,7 @@ static u64 zs_zpool_total_size(void *pool)
 
 static struct zpool_driver zs_zpool_driver = {
 	.type =			  "zsmalloc",
+	.sleep_mapped =		  false,
 	.owner =		  THIS_MODULE,
 	.create =		  zs_zpool_create,
 	.destroy =		  zs_zpool_destroy,
diff --git a/mm/zswap.c b/mm/zswap.c
index 182f6ad..51b033a 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -1235,7 +1235,7 @@ static int zswap_frontswap_load(unsigned type, pgoff_t offset,
 	struct zswap_entry *entry;
 	struct scatterlist input, output;
 	struct crypto_acomp_ctx *acomp_ctx;
-	u8 *src, *dst;
+	u8 *src, *dst, *tmp;
 	unsigned int dlen;
 	int ret;
 
@@ -1256,12 +1256,27 @@ static int zswap_frontswap_load(unsigned type, pgoff_t offset,
 		goto freeentry;
 	}
 
+	if (!zpool_can_sleep_mapped(entry->pool->zpool)) {
+
+		tmp = kzalloc(entry->length, GFP_KERNEL);
+		if (!tmp)
+			return -ENOMEM;
+	}
+
 	/* decompress */
 	dlen = PAGE_SIZE;
 	src = zpool_map_handle(entry->pool->zpool, entry->handle, ZPOOL_MM_RO);
 	if (zpool_evictable(entry->pool->zpool))
 		src += sizeof(struct zswap_header);
 
+	if (!zpool_can_sleep_mapped(entry->pool->zpool)) {
+
+		memcpy(tmp, src, entry->length);
+		src = tmp;
+
+		zpool_unmap_handle(entry->pool->zpool, entry->handle);
+	}
+
 	acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
 	mutex_lock(acomp_ctx->mutex);
 	sg_init_one(&input, src, entry->length);
@@ -1271,7 +1286,11 @@ static int zswap_frontswap_load(unsigned type, pgoff_t offset,
 	ret = crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req), &acomp_ctx->wait);
 	mutex_unlock(acomp_ctx->mutex);
 
-	zpool_unmap_handle(entry->pool->zpool, entry->handle);
+	if (zpool_can_sleep_mapped(entry->pool->zpool))
+		zpool_unmap_handle(entry->pool->zpool, entry->handle);
+	else
+		kfree(tmp);
+
 	BUG_ON(ret);
 
 freeentry:
-- 
2.7.4