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    SubjectRe: [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@gmail.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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