The patch titled
Subject: zram: add dictionary support to zstd backend
has been added to the -mm mm-unstable branch. Its filename is
zram-add-dictionary-support-to-zstd-backend.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/zram-add-dictionary-support-to-zstd-backend.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Subject: zram: add dictionary support to zstd backend
Date: Mon, 2 Sep 2024 19:56:10 +0900
This adds support for pre-trained zstd dictionaries [1] Dictionary is
setup in params once (per-comp) and loaded to Cctx and Dctx by reference,
so we don't allocate extra memory.
TEST
====
*** zstd
/sys/block/zram0/mm_stat
1750654976 504565092 514203648 0 514203648 1 0 34204 34204
*** zstd dict=/etc/zstd-dict-amd64
/sys/block/zram0/mm_stat
1750638592 465851259 475373568 0 475373568 1 0 34185 34185
*** zstd level=8 dict=/etc/zstd-dict-amd64
/sys/block/zram0/mm_stat
1750642688 430765171 439955456 0 439955456 1 0 34185 34185
[1] https://github.com/facebook/zstd/blob/dev/programs/zstd.1.md#dictionary-builder
Link: https://lkml.kernel.org/r/20240902105656.1383858-23-senozhatsky@xxxxxxxxxxxx
Signed-off-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Nick Terrell <terrelln@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/block/zram/backend_zstd.c | 150 +++++++++++++++++++++++-----
1 file changed, 124 insertions(+), 26 deletions(-)
--- a/drivers/block/zram/backend_zstd.c~zram-add-dictionary-support-to-zstd-backend
+++ a/drivers/block/zram/backend_zstd.c
@@ -15,29 +15,87 @@ struct zstd_ctx {
};
struct zstd_params {
+ zstd_custom_mem custom_mem;
+ zstd_cdict *cdict;
+ zstd_ddict *ddict;
zstd_parameters cprm;
};
+/*
+ * For C/D dictionaries we need to provide zstd with zstd_custom_mem,
+ * which zstd uses internally to allocate/free memory when needed.
+ *
+ * This means that allocator.customAlloc() can be called from zcomp_compress()
+ * under local-lock (per-CPU compression stream), in which case we must use
+ * GFP_ATOMIC.
+ *
+ * Another complication here is that we can be configured as a swap device.
+ */
+static void *zstd_custom_alloc(void *opaque, size_t size)
+{
+ if (!preemptible())
+ return kvzalloc(size, GFP_ATOMIC);
+
+ return kvzalloc(size, __GFP_KSWAPD_RECLAIM | __GFP_NOWARN);
+}
+
+static void zstd_custom_free(void *opaque, void *address)
+{
+ kvfree(address);
+}
+
static void zstd_release_params(struct zcomp_params *params)
{
- kfree(params->drv_data);
+ struct zstd_params *zp = params->drv_data;
+
+ params->drv_data = NULL;
+ if (!zp)
+ return;
+
+ zstd_free_cdict(zp->cdict);
+ zstd_free_ddict(zp->ddict);
+ kfree(zp);
}
static int zstd_setup_params(struct zcomp_params *params)
{
+ zstd_compression_parameters prm;
struct zstd_params *zp;
zp = kzalloc(sizeof(*zp), GFP_KERNEL);
if (!zp)
return -ENOMEM;
+ params->drv_data = zp;
if (params->level == ZCOMP_PARAM_NO_LEVEL)
params->level = zstd_default_clevel();
zp->cprm = zstd_get_params(params->level, PAGE_SIZE);
- params->drv_data = zp;
+
+ zp->custom_mem.customAlloc = zstd_custom_alloc;
+ zp->custom_mem.customFree = zstd_custom_free;
+
+ prm = zstd_get_cparams(params->level, PAGE_SIZE,
+ params->dict_sz);
+
+ zp->cdict = zstd_create_cdict_byreference(params->dict,
+ params->dict_sz,
+ prm,
+ zp->custom_mem);
+ if (!zp->cdict)
+ goto error;
+
+ zp->ddict = zstd_create_ddict_byreference(params->dict,
+ params->dict_sz,
+ zp->custom_mem);
+ if (!zp->ddict)
+ goto error;
return 0;
+
+error:
+ zstd_release_params(params);
+ return -EINVAL;
}
static void zstd_destroy(struct zcomp_ctx *ctx)
@@ -47,8 +105,23 @@ static void zstd_destroy(struct zcomp_ct
if (!zctx)
return;
- vfree(zctx->cctx_mem);
- vfree(zctx->dctx_mem);
+ /*
+ * If ->cctx_mem and ->dctx_mem were allocated then we didn't use
+ * C/D dictionary and ->cctx / ->dctx were "embedded" into these
+ * buffers.
+ *
+ * If otherwise then we need to explicitly release ->cctx / ->dctx.
+ */
+ if (zctx->cctx_mem)
+ vfree(zctx->cctx_mem);
+ else
+ zstd_free_cctx(zctx->cctx);
+
+ if (zctx->dctx_mem)
+ vfree(zctx->dctx_mem);
+ else
+ zstd_free_dctx(zctx->dctx);
+
kfree(zctx);
}
@@ -63,28 +136,41 @@ static int zstd_create(struct zcomp_para
return -ENOMEM;
ctx->context = zctx;
- prm = zstd_get_params(params->level, PAGE_SIZE);
- sz = zstd_cctx_workspace_bound(&prm.cParams);
- zctx->cctx_mem = vzalloc(sz);
- if (!zctx->cctx_mem)
- goto error;
-
- zctx->cctx = zstd_init_cctx(zctx->cctx_mem, sz);
- if (!zctx->cctx)
- goto error;
-
- sz = zstd_dctx_workspace_bound();
- zctx->dctx_mem = vzalloc(sz);
- if (!zctx->dctx_mem)
- goto error;
-
- zctx->dctx = zstd_init_dctx(zctx->dctx_mem, sz);
- if (!zctx->dctx)
- goto error;
+ if (params->dict_sz == 0) {
+ prm = zstd_get_params(params->level, PAGE_SIZE);
+ sz = zstd_cctx_workspace_bound(&prm.cParams);
+ zctx->cctx_mem = vzalloc(sz);
+ if (!zctx->cctx_mem)
+ goto error;
+
+ zctx->cctx = zstd_init_cctx(zctx->cctx_mem, sz);
+ if (!zctx->cctx)
+ goto error;
+
+ sz = zstd_dctx_workspace_bound();
+ zctx->dctx_mem = vzalloc(sz);
+ if (!zctx->dctx_mem)
+ goto error;
+
+ zctx->dctx = zstd_init_dctx(zctx->dctx_mem, sz);
+ if (!zctx->dctx)
+ goto error;
+ } else {
+ struct zstd_params *zp = params->drv_data;
+
+ zctx->cctx = zstd_create_cctx_advanced(zp->custom_mem);
+ if (!zctx->cctx)
+ goto error;
+
+ zctx->dctx = zstd_create_dctx_advanced(zp->custom_mem);
+ if (!zctx->dctx)
+ goto error;
+ }
return 0;
error:
+ zstd_release_params(params);
zstd_destroy(ctx);
return -EINVAL;
}
@@ -96,8 +182,14 @@ static int zstd_compress(struct zcomp_pa
struct zstd_ctx *zctx = ctx->context;
size_t ret;
- ret = zstd_compress_cctx(zctx->cctx, req->dst, req->dst_len,
- req->src, req->src_len, &zp->cprm);
+ if (params->dict_sz == 0)
+ ret = zstd_compress_cctx(zctx->cctx, req->dst, req->dst_len,
+ req->src, req->src_len, &zp->cprm);
+ else
+ ret = zstd_compress_using_cdict(zctx->cctx, req->dst,
+ req->dst_len, req->src,
+ req->src_len,
+ zp->cdict);
if (zstd_is_error(ret))
return -EINVAL;
req->dst_len = ret;
@@ -107,11 +199,17 @@ static int zstd_compress(struct zcomp_pa
static int zstd_decompress(struct zcomp_params *params, struct zcomp_ctx *ctx,
struct zcomp_req *req)
{
+ struct zstd_params *zp = params->drv_data;
struct zstd_ctx *zctx = ctx->context;
size_t ret;
- ret = zstd_decompress_dctx(zctx->dctx, req->dst, req->dst_len,
- req->src, req->src_len);
+ if (params->dict_sz == 0)
+ ret = zstd_decompress_dctx(zctx->dctx, req->dst, req->dst_len,
+ req->src, req->src_len);
+ else
+ ret = zstd_decompress_using_ddict(zctx->dctx, req->dst,
+ req->dst_len, req->src,
+ req->src_len, zp->ddict);
if (zstd_is_error(ret))
return -EINVAL;
return 0;
_
Patches currently in -mm which might be from senozhatsky@xxxxxxxxxxxx are
lib-zstd-export-api-needed-for-dictionary-support.patch
lib-lz4hc-export-lz4_resetstreamhc-symbol.patch
lib-zstd-fix-null-deref-in-zstd_createcdict_advanced2.patch
zram-introduce-custom-comp-backends-api.patch
zram-add-lzo-and-lzorle-compression-backends-support.patch
zram-add-lz4-compression-backend-support.patch
zram-add-lz4hc-compression-backend-support.patch
zram-add-zstd-compression-backend-support.patch
zram-pass-estimated-src-size-hint-to-zstd.patch
zram-add-zlib-compression-backend-support.patch
zram-add-842-compression-backend-support.patch
zram-check-that-backends-array-has-at-least-one-backend.patch
zram-introduce-zcomp_params-structure.patch
zram-recalculate-zstd-compression-params-once.patch
zram-introduce-algorithm_params-device-attribute.patch
zram-add-support-for-dict-comp-config.patch
zram-introduce-zcomp_req-structure.patch
zram-introduce-zcomp_ctx-structure.patch
zram-move-immutable-comp-params-away-from-per-cpu-context.patch
zram-add-dictionary-support-to-lz4.patch
zram-add-dictionary-support-to-lz4hc.patch
zram-add-dictionary-support-to-zstd-backend.patch
documentation-zram-add-documentation-for-algorithm-parameters.patch
zram-support-priority-parameter-in-recompression.patch
