zram: add dictionary support to lz4

Support pre-trained dictionary param.  lz4 doesn't mandate specific format
of the dictionary and even zstd --train can be used to train a dictionary
for lz4, according to [1].

TEST
====

*** lz4
/sys/block/zram0/mm_stat
1750654976 664188565 676864000        0 676864000        1        0    34288    34288

*** lz4 dict=/etc/lz4-dict-amd64
/sys/block/zram0/mm_stat
1750638592 619891141 632053760        0 632053760        1        0    34278    34278

*** lz4 level=5 dict=/etc/lz4-dict-amd64
/sys/block/zram0/mm_stat
1750638592 727174243 740810752        0 740810752        1        0    34437    34437

[1] https://github.com/lz4/lz4/issues/557

Link: https://lkml.kernel.org/r/20240902105656.1383858-21-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nick Terrell <terrelln@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/drivers/block/zram/backend_lz4.c b/drivers/block/zram/backend_lz4.c
index cf3c029bd5ad27d3ea59218d7ed53fffdc10c988..847f3334eb38248674976361cd425fc795ef9d80 100644 (file)
--- a/drivers/block/zram/backend_lz4.c
+++ b/drivers/block/zram/backend_lz4.c
@@ -5,6 +5,13 @@
 
 #include "backend_lz4.h"
 
+struct lz4_ctx {
+       void *mem;
+
+       LZ4_streamDecode_t *dstrm;
+       LZ4_stream_t *cstrm;
+};
+
 static void lz4_release_params(struct zcomp_params *params)
 {
 }
@@ -19,25 +26,66 @@ static int lz4_setup_params(struct zcomp_params *params)
 
 static void lz4_destroy(struct zcomp_ctx *ctx)
 {
-       vfree(ctx->context);
+       struct lz4_ctx *zctx = ctx->context;
+
+       if (!zctx)
+               return;
+
+       vfree(zctx->mem);
+       kfree(zctx->dstrm);
+       kfree(zctx->cstrm);
+       kfree(zctx);
 }
 
 static int lz4_create(struct zcomp_params *params, struct zcomp_ctx *ctx)
 {
-       ctx->context = vmalloc(LZ4_MEM_COMPRESS);
-       if (!ctx->context)
+       struct lz4_ctx *zctx;
+
+       zctx = kzalloc(sizeof(*zctx), GFP_KERNEL);
+       if (!zctx)
                return -ENOMEM;
 
+       ctx->context = zctx;
+       if (params->dict_sz == 0) {
+               zctx->mem = vmalloc(LZ4_MEM_COMPRESS);
+               if (!zctx->mem)
+                       goto error;
+       } else {
+               zctx->dstrm = kzalloc(sizeof(*zctx->dstrm), GFP_KERNEL);
+               if (!zctx->dstrm)
+                       goto error;
+
+               zctx->cstrm = kzalloc(sizeof(*zctx->cstrm), GFP_KERNEL);
+               if (!zctx->cstrm)
+                       goto error;
+       }
+
        return 0;
+
+error:
+       lz4_destroy(ctx);
+       return -ENOMEM;
 }
 
 static int lz4_compress(struct zcomp_params *params, struct zcomp_ctx *ctx,
                        struct zcomp_req *req)
 {
+       struct lz4_ctx *zctx = ctx->context;
        int ret;
 
-       ret = LZ4_compress_fast(req->src, req->dst, req->src_len,
-                               req->dst_len, params->level, ctx->context);
+       if (!zctx->cstrm) {
+               ret = LZ4_compress_fast(req->src, req->dst, req->src_len,
+                                       req->dst_len, params->level,
+                                       zctx->mem);
+       } else {
+               /* Cstrm needs to be reset */
+               ret = LZ4_loadDict(zctx->cstrm, params->dict, params->dict_sz);
+               if (ret != params->dict_sz)
+                       return -EINVAL;
+               ret = LZ4_compress_fast_continue(zctx->cstrm, req->src,
+                                                req->dst, req->src_len,
+                                                req->dst_len, params->level);
+       }
        if (!ret)
                return -EINVAL;
        req->dst_len = ret;
@@ -47,10 +95,22 @@ static int lz4_compress(struct zcomp_params *params, struct zcomp_ctx *ctx,
 static int lz4_decompress(struct zcomp_params *params, struct zcomp_ctx *ctx,
                          struct zcomp_req *req)
 {
+       struct lz4_ctx *zctx = ctx->context;
        int ret;
 
-       ret = LZ4_decompress_safe(req->src, req->dst, req->src_len,
-                                 req->dst_len);
+       if (!zctx->dstrm) {
+               ret = LZ4_decompress_safe(req->src, req->dst, req->src_len,
+                                         req->dst_len);
+       } else {
+               /* Dstrm needs to be reset */
+               ret = LZ4_setStreamDecode(zctx->dstrm, params->dict,
+                                         params->dict_sz);
+               if (!ret)
+                       return -EINVAL;
+               ret = LZ4_decompress_safe_continue(zctx->dstrm, req->src,
+                                                  req->dst, req->src_len,
+                                                  req->dst_len);
+       }
        if (ret < 0)
                return -EINVAL;
        return 0;