[PATCH 2/2] zram: lz4/lz4hc: accept dictionaries of more than 64 KiB

[Sergey Senozhatsky]

From: Josef Bacik <josef@xxxxxxxxxxxxxx>

From: Josef Bacik <josef@xxxxxxxxxxxxxx>

LZ4_loadDict() and LZ4_loadDictHC() only use the last 64KiB of a
dictionary and return how much they used, which the zram backends
take for an error.  Expect that instead.

Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
Signed-off-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
---
 drivers/block/zram/backend_lz4.c   | 4 +++-
 drivers/block/zram/backend_lz4hc.c | 4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/block/zram/backend_lz4.c b/drivers/block/zram/backend_lz4.c
index 9767482a2fea..bad648c158da 100644
--- a/drivers/block/zram/backend_lz4.c
+++ b/drivers/block/zram/backend_lz4.c
@@ -4,6 +4,7 @@
 
 #include <linux/kernel.h>
 #include <linux/lz4.h>
+#include <linux/sizes.h>
 #include <linux/vmalloc.h>
 
 #include "backend_lz4.h"
@@ -39,7 +40,8 @@ static int lz4_setup_params(struct zcomp_params *params)
 		return -ENOMEM;
 
 	ret = LZ4_loadDict(dict_stream, params->dict, params->dict_sz);
-	if (ret != params->dict_sz) {
+	/* Only the last 64 KiB of a dictionary are of use */
+	if (ret != min_t(size_t, params->dict_sz, SZ_64K)) {
 		vfree(dict_stream);
 		return -EINVAL;
 	}
diff --git a/drivers/block/zram/backend_lz4hc.c b/drivers/block/zram/backend_lz4hc.c
index 2d1364a29b27..5825c8ba78da 100644
--- a/drivers/block/zram/backend_lz4hc.c
+++ b/drivers/block/zram/backend_lz4hc.c
@@ -4,6 +4,7 @@
 
 #include <linux/kernel.h>
 #include <linux/lz4.h>
+#include <linux/sizes.h>
 #include <linux/vmalloc.h>
 
 #include "backend_lz4hc.h"
@@ -46,7 +47,8 @@ static int lz4hc_setup_params(struct zcomp_params *params)
 
 	LZ4_resetStreamHC(dict_stream, params->level);
 	ret = LZ4_loadDictHC(dict_stream, params->dict, params->dict_sz);
-	if (ret != params->dict_sz) {
+	/* Only the last 64 KiB of a dictionary are of use */
+	if (ret != min_t(size_t, params->dict_sz, SZ_64K)) {
 		vfree(dict_stream);
 		return -EINVAL;
 	}
-- 
2.56.0.317.g454f8302e1-goog