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Date: Thu, 13 Feb 2014 14:04:39 +0900
From: Minchan Kim <minchan@...nel.org>
To: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc: Jerome Marchand <jmarchan@...hat.com>,
Nitin Gupta <ngupta@...are.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv4 2/4] zram: use zcomp compressing backends
On Wed, Feb 12, 2014 at 10:39:34PM +0300, Sergey Senozhatsky wrote:
> Do not perform direct LZO compress/decompress calls,
> initialise and use zcomp LZO backend instead.
>
> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
> ---
> drivers/block/zram/Makefile | 2 +-
> drivers/block/zram/zram_drv.c | 62 +++++++++++++++++++------------------------
> drivers/block/zram/zram_drv.h | 8 +++---
> 3 files changed, 33 insertions(+), 39 deletions(-)
>
> diff --git a/drivers/block/zram/Makefile b/drivers/block/zram/Makefile
> index cb0f9ce..757c6a5 100644
> --- a/drivers/block/zram/Makefile
> +++ b/drivers/block/zram/Makefile
> @@ -1,3 +1,3 @@
> -zram-y := zram_drv.o
> +zram-y := zcomp_lzo.o zcomp.o zram_drv.o
>
> obj-$(CONFIG_ZRAM) += zram.o
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index 9baac5b..d0d7254 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -29,15 +29,14 @@
> #include <linux/genhd.h>
> #include <linux/highmem.h>
> #include <linux/slab.h>
> -#include <linux/lzo.h>
> #include <linux/string.h>
> -#include <linux/vmalloc.h>
>
> #include "zram_drv.h"
>
> /* Globals */
> static int zram_major;
> static struct zram *zram_devices;
> +static const char *default_compressor = "lzo";
>
> /* Module params (documentation at end) */
> static unsigned int num_devices = 1;
> @@ -160,8 +159,6 @@ static inline int valid_io_request(struct zram *zram, struct bio *bio)
> static void zram_meta_free(struct zram_meta *meta)
> {
> zs_destroy_pool(meta->mem_pool);
> - kfree(meta->compress_workmem);
> - free_pages((unsigned long)meta->compress_buffer, 1);
> vfree(meta->table);
> kfree(meta);
> }
> @@ -173,22 +170,11 @@ static struct zram_meta *zram_meta_alloc(u64 disksize)
> if (!meta)
> goto out;
>
> - meta->compress_workmem = kzalloc(LZO1X_MEM_COMPRESS, GFP_KERNEL);
> - if (!meta->compress_workmem)
> - goto free_meta;
> -
> - meta->compress_buffer =
> - (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, 1);
> - if (!meta->compress_buffer) {
> - pr_err("Error allocating compressor buffer space\n");
> - goto free_workmem;
> - }
> -
> num_pages = disksize >> PAGE_SHIFT;
> meta->table = vzalloc(num_pages * sizeof(*meta->table));
> if (!meta->table) {
> pr_err("Error allocating zram address table\n");
> - goto free_buffer;
> + goto free_meta;
> }
>
> meta->mem_pool = zs_create_pool(GFP_NOIO | __GFP_HIGHMEM);
> @@ -198,15 +184,10 @@ static struct zram_meta *zram_meta_alloc(u64 disksize)
> }
>
> rwlock_init(&meta->tb_lock);
> - mutex_init(&meta->buffer_lock);
> return meta;
>
> free_table:
> vfree(meta->table);
> -free_buffer:
> - free_pages((unsigned long)meta->compress_buffer, 1);
> -free_workmem:
> - kfree(meta->compress_workmem);
> free_meta:
> kfree(meta);
> meta = NULL;
> @@ -280,7 +261,7 @@ static void zram_free_page(struct zram *zram, size_t index)
>
> static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
> {
> - int ret = LZO_E_OK;
> + int ret = 0;
> size_t clen = PAGE_SIZE;
> unsigned char *cmem;
> struct zram_meta *meta = zram->meta;
> @@ -301,12 +282,12 @@ static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
> if (size == PAGE_SIZE)
> copy_page(mem, cmem);
> else
> - ret = lzo1x_decompress_safe(cmem, size, mem, &clen);
> + ret = zcomp_decompress(zram->comp, cmem, size, mem, &clen);
> zs_unmap_object(meta->mem_pool, handle);
> read_unlock(&meta->tb_lock);
>
> /* Should NEVER happen. Return bio error if it does. */
> - if (unlikely(ret != LZO_E_OK)) {
Hmm this code depends on that "LZO_E_OK 0" but it could be changed in future
so it ends up break. Perhaps, we should handle it in backend.
zcomp_lzo.c:
int lzo_decompress()
{
int ret = lzo1x_decompress_safe(xxx);
if (ret != LZO_E_OK)
return ret;
}
> + if (unlikely(ret)) {
> pr_err("Decompression failed! err=%d, page=%u\n", ret, index);
> atomic64_inc(&zram->stats.failed_reads);
> return ret;
> @@ -349,7 +330,7 @@ static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
>
> ret = zram_decompress_page(zram, uncmem, index);
> /* Should NEVER happen. Return bio error if it does. */
> - if (unlikely(ret != LZO_E_OK))
> + if (unlikely(ret))
> goto out_cleanup;
>
> if (is_partial_io(bvec))
> @@ -374,11 +355,10 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> struct page *page;
> unsigned char *user_mem, *cmem, *src, *uncmem = NULL;
> struct zram_meta *meta = zram->meta;
> + struct zcomp_strm *zstrm;
> bool locked = false;
>
> page = bvec->bv_page;
> - src = meta->compress_buffer;
> -
> if (is_partial_io(bvec)) {
> /*
> * This is a partial IO. We need to read the full page
> @@ -394,7 +374,7 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> goto out;
> }
>
> - mutex_lock(&meta->buffer_lock);
> + zstrm = zcomp_strm_get(zram->comp);
> locked = true;
> user_mem = kmap_atomic(page);
>
> @@ -420,19 +400,18 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> goto out;
> }
>
> - ret = lzo1x_1_compress(uncmem, PAGE_SIZE, src, &clen,
> - meta->compress_workmem);
> + ret = zcomp_compress(zram->comp, zstrm, uncmem, bvec->bv_len, &clen);
> if (!is_partial_io(bvec)) {
> kunmap_atomic(user_mem);
> user_mem = NULL;
> uncmem = NULL;
> }
>
> - if (unlikely(ret != LZO_E_OK)) {
> + if (unlikely(ret)) {
> pr_err("Compression failed! err=%d\n", ret);
> goto out;
> }
> -
> + src = zstrm->buffer;
> if (unlikely(clen > max_zpage_size)) {
> clen = PAGE_SIZE;
> src = NULL;
> @@ -457,6 +436,8 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> memcpy(cmem, src, clen);
> }
>
> + zcomp_strm_put(zram->comp, zstrm);
> + locked = false;
> zs_unmap_object(meta->mem_pool, handle);
>
> /*
> @@ -475,10 +456,9 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> atomic64_inc(&zram->stats.pages_stored);
> out:
> if (locked)
> - mutex_unlock(&meta->buffer_lock);
> + zcomp_strm_put(zram->comp, zstrm);
> if (is_partial_io(bvec))
> kfree(uncmem);
> -
> if (ret)
> atomic64_inc(&zram->stats.failed_writes);
> return ret;
> @@ -522,6 +502,10 @@ static void zram_reset_device(struct zram *zram, bool reset_capacity)
> zs_free(meta->mem_pool, handle);
> }
>
> + if (zram->comp)
> + zcomp_destroy(zram->comp);
> + zram->comp = NULL;
Why we need to reset NULL?
> +
> zram_meta_free(zram->meta);
> zram->meta = NULL;
> /* Reset stats */
> @@ -550,9 +534,18 @@ static ssize_t disksize_store(struct device *dev,
> return -EBUSY;
> }
>
> + zram->comp = zcomp_create(default_compressor);
> + if (!zram->comp) {
> + up_write(&zram->init_lock);
> + pr_info("Cannot initialise compressing backend\n");
> + return -EINVAL;
> + }
> +
> disksize = PAGE_ALIGN(disksize);
> zram->meta = zram_meta_alloc(disksize);
> if (!zram->meta) {
> + zcomp_destroy(zram->comp);
> + zram->comp = NULL;
> up_write(&zram->init_lock);
> return -ENOMEM;
> }
> @@ -790,6 +783,7 @@ static int create_device(struct zram *zram, int device_id)
> }
>
> zram->meta = NULL;
> + zram->comp = NULL;
> return 0;
>
> out_free_disk:
> diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
> index 1d5b1f5..45e04f7 100644
> --- a/drivers/block/zram/zram_drv.h
> +++ b/drivers/block/zram/zram_drv.h
> @@ -16,9 +16,10 @@
> #define _ZRAM_DRV_H_
>
> #include <linux/spinlock.h>
> -#include <linux/mutex.h>
> #include <linux/zsmalloc.h>
>
> +#include "zcomp.h"
> +
> /*
> * Some arbitrary value. This is just to catch
> * invalid value for num_devices module parameter.
> @@ -81,17 +82,16 @@ struct zram_stats {
>
> struct zram_meta {
> rwlock_t tb_lock; /* protect table */
> - void *compress_workmem;
> - void *compress_buffer;
> struct table *table;
> struct zs_pool *mem_pool;
> - struct mutex buffer_lock; /* protect compress buffers */
> };
>
> struct zram {
> struct zram_meta *meta;
> struct request_queue *queue;
> struct gendisk *disk;
> + struct zcomp *comp;
> +
> /* Prevent concurrent execution of device init, reset and R/W request */
> struct rw_semaphore init_lock;
> /*
> --
> 1.9.0.rc3.256.g4af3ebd
>
> --
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--
Kind regards,
Minchan Kim
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