Re: [PATCH 2/2] zram: clean up handle
From: Nitin Gupta
Date: Wed Jun 06 2012 - 01:04:37 EST
On 06/05/2012 12:23 AM, Minchan Kim wrote:
> zram's handle variable can store handle of zsmalloc in case of
> compressing efficiently. Otherwise, it stores point of page descriptor.
> This patch clean up the mess by union struct.
>
> changelog
> * from v1
> - none(new add in v2)
>
> Cc: Nitin Gupta <ngupta@xxxxxxxxxx>
> Acked-by: Seth Jennings <sjenning@xxxxxxxxxxxxxxxxxx>
> Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
> ---
> drivers/staging/zram/zram_drv.c | 77 ++++++++++++++++++++-------------------
> drivers/staging/zram/zram_drv.h | 5 ++-
> 2 files changed, 44 insertions(+), 38 deletions(-)
>
I think page vs handle distinction was added since xvmalloc could not
handle full page allocation. Now that zsmalloc allows full page
allocation, we can just use it for both cases. This would also allow
removing the ZRAM_UNCOMPRESSED flag. The only downside will be slightly
slower code path for full page allocation but this event is anyways
supposed to be rare, so should be fine.
I should have discussed this earlier and saved you a lot of effort!
Thanks,
Nitin
> diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c
> index abd69d1..ceab5ca 100644
> --- a/drivers/staging/zram/zram_drv.c
> +++ b/drivers/staging/zram/zram_drv.c
> @@ -150,7 +150,7 @@ static void zram_free_page(struct zram *zram, size_t index)
> }
>
> if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED))) {
> - __free_page((struct page *)handle);
> + __free_page(zram->table[index].page);
> zram_clear_flag(zram, index, ZRAM_UNCOMPRESSED);
> zram_stat_dec(&zram->stats.pages_expand);
> goto out;
> @@ -189,7 +189,7 @@ static void handle_uncompressed_page(struct zram *zram, struct bio_vec *bvec,
> unsigned char *user_mem, *cmem;
>
> user_mem = kmap_atomic(page);
> - cmem = kmap_atomic((struct page *)zram->table[index].handle);
> + cmem = kmap_atomic(zram->table[index].page);
>
> memcpy(user_mem + bvec->bv_offset, cmem + offset, bvec->bv_len);
> kunmap_atomic(cmem);
> @@ -315,7 +315,6 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> int offset)
> {
> int ret;
> - u32 store_offset;
> size_t clen;
> unsigned long handle;
> struct zobj_header *zheader;
> @@ -396,25 +395,33 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> goto out;
> }
>
> - store_offset = 0;
> - zram_set_flag(zram, index, ZRAM_UNCOMPRESSED);
> - zram_stat_inc(&zram->stats.pages_expand);
> - handle = (unsigned long)page_store;
> src = kmap_atomic(page);
> cmem = kmap_atomic(page_store);
> - goto memstore;
> - }
> + memcpy(cmem, src, clen);
> + kunmap_atomic(cmem);
> + kunmap_atomic(src);
>
> - handle = zs_malloc(zram->mem_pool, clen + sizeof(*zheader));
> - if (!handle) {
> - pr_info("Error allocating memory for compressed "
> - "page: %u, size=%zu\n", index, clen);
> - ret = -ENOMEM;
> - goto out;
> - }
> - cmem = zs_map_object(zram->mem_pool, handle);
> + zram->table[index].page = page_store;
> + zram->table[index].size = PAGE_SIZE;
> +
> + zram_set_flag(zram, index, ZRAM_UNCOMPRESSED);
> + zram_stat_inc(&zram->stats.pages_expand);
> + } else {
> + handle = zs_malloc(zram->mem_pool, clen + sizeof(*zheader));
> + if (!handle) {
> + pr_info("Error allocating memory for "
> + "compressed page: %u, size=%zu\n", index, clen);
> + ret = -ENOMEM;
> + goto out;
> + }
> +
> + zram->table[index].handle = handle;
> + zram->table[index].size = clen;
>
> -memstore:
> + cmem = zs_map_object(zram->mem_pool, handle);
> + memcpy(cmem, src, clen);
> + zs_unmap_object(zram->mem_pool, handle);
> + }
> #if 0
> /* Back-reference needed for memory defragmentation */
> if (!zram_test_flag(zram, index, ZRAM_UNCOMPRESSED)) {
> @@ -424,18 +431,6 @@ memstore:
> }
> #endif
>
> - memcpy(cmem, src, clen);
> -
> - if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED))) {
> - kunmap_atomic(cmem);
> - kunmap_atomic(src);
> - } else {
> - zs_unmap_object(zram->mem_pool, handle);
> - }
> -
> - zram->table[index].handle = handle;
> - zram->table[index].size = clen;
> -
> /* Update stats */
> zram_stat64_add(zram, &zram->stats.compr_size, clen);
> zram_stat_inc(&zram->stats.pages_stored);
> @@ -580,6 +575,8 @@ error:
> void __zram_reset_device(struct zram *zram)
> {
> size_t index;
> + unsigned long handle;
> + struct page *page;
>
> zram->init_done = 0;
>
> @@ -592,14 +589,17 @@ void __zram_reset_device(struct zram *zram)
>
> /* Free all pages that are still in this zram device */
> for (index = 0; index < zram->disksize >> PAGE_SHIFT; index++) {
> - unsigned long handle = zram->table[index].handle;
> - if (!handle)
> - continue;
> -
> - if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED)))
> - __free_page((struct page *)handle);
> - else
> + if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED))) {
> + page = zram->table[index].page;
> + if (!page)
> + continue;
> + __free_page(page);
> + } else {
> + handle = zram->table[index].handle;
> + if (!handle)
> + continue;
> zs_free(zram->mem_pool, handle);
> + }
> }
>
> vfree(zram->table);
> @@ -788,6 +788,9 @@ static int __init zram_init(void)
> {
> int ret, dev_id;
>
> + BUILD_BUG_ON(sizeof(((struct table *)0)->page) !=
> + sizeof(((struct table *)0)->handle));
> +
> if (num_devices > max_num_devices) {
> pr_warning("Invalid value for num_devices: %u\n",
> num_devices);
> diff --git a/drivers/staging/zram/zram_drv.h b/drivers/staging/zram/zram_drv.h
> index 7a7e256..54d082f 100644
> --- a/drivers/staging/zram/zram_drv.h
> +++ b/drivers/staging/zram/zram_drv.h
> @@ -81,7 +81,10 @@ enum zram_pageflags {
>
> /* Allocated for each disk page */
> struct table {
> - unsigned long handle;
> + union {
> + unsigned long handle; /* compressible */
> + struct page *page; /* incompressible */
> + };
> u16 size; /* object size (excluding header) */
> u8 count; /* object ref count (not yet used) */
> u8 flags;
--
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