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Date: Mon, 3 Apr 2017 08:52:33 +0300
From: Mika Penttilä <mika.penttila@...tfour.com>
To: Minchan Kim <minchan@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>
CC: <linux-kernel@...r.kernel.org>,
Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
<kernel-team@....com>
Subject: Re: [PATCH 2/5] zram: partial IO refactoring
Hi!
On 04/03/2017 08:17 AM, Minchan Kim wrote:
> For architecture(PAGE_SIZE > 4K), zram have supported partial IO.
> However, the mixed code for handling normal/partial IO is too mess,
> error-prone to modify IO handler functions with upcoming feature
> so this patch aims for cleaning up zram's IO handling functions.
>
> Signed-off-by: Minchan Kim <minchan@...nel.org>
> ---
> drivers/block/zram/zram_drv.c | 333 +++++++++++++++++++++++-------------------
> 1 file changed, 184 insertions(+), 149 deletions(-)
>
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index 28c2836f8c96..7938f4b98b01 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -45,6 +45,8 @@ static const char *default_compressor = "lzo";
> /* Module params (documentation at end) */
> static unsigned int num_devices = 1;
>
> +static void zram_free_page(struct zram *zram, size_t index);
> +
> static inline bool init_done(struct zram *zram)
> {
> return zram->disksize;
> @@ -98,10 +100,17 @@ static void zram_set_obj_size(struct zram_meta *meta,
> meta->table[index].value = (flags << ZRAM_FLAG_SHIFT) | size;
> }
>
> +#if PAGE_SIZE != 4096
> static inline bool is_partial_io(struct bio_vec *bvec)
> {
> return bvec->bv_len != PAGE_SIZE;
> }
> +#else
For page size of 4096 bv_len can still be < 4096 and partial pages should be supported
(uncompress before write etc). ?
> +static inline bool is_partial_io(struct bio_vec *bvec)
> +{
> + return false;
> +}
> +#endif
>
> static void zram_revalidate_disk(struct zram *zram)
> {
> @@ -191,18 +200,6 @@ static bool page_same_filled(void *ptr, unsigned long *element)
> return true;
> }
>
> -static void handle_same_page(struct bio_vec *bvec, unsigned long element)
> -{
> - struct page *page = bvec->bv_page;
> - void *user_mem;
> -
> - user_mem = kmap_atomic(page);
> - zram_fill_page(user_mem + bvec->bv_offset, bvec->bv_len, element);
> - kunmap_atomic(user_mem);
> -
> - flush_dcache_page(page);
> -}
> -
> static ssize_t initstate_show(struct device *dev,
> struct device_attribute *attr, char *buf)
> {
> @@ -418,6 +415,53 @@ static DEVICE_ATTR_RO(io_stat);
> static DEVICE_ATTR_RO(mm_stat);
> static DEVICE_ATTR_RO(debug_stat);
>
> +static bool zram_special_page_read(struct zram *zram, u32 index,
> + struct page *page,
> + unsigned int offset, unsigned int len)
> +{
> + struct zram_meta *meta = zram->meta;
> +
> + bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
> + if (unlikely(!meta->table[index].handle) ||
> + zram_test_flag(meta, index, ZRAM_SAME)) {
> + void *mem;
> +
> + bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
> + mem = kmap_atomic(page);
> + zram_fill_page(mem + offset, len, meta->table[index].element);
> + kunmap_atomic(mem);
> + return true;
> + }
> + bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
> +
> + return false;
> +}
> +
> +static bool zram_special_page_write(struct zram *zram, u32 index,
> + struct page *page)
> +{
> + unsigned long element;
> + void *mem = kmap_atomic(page);
> +
> + if (page_same_filled(mem, &element)) {
> + struct zram_meta *meta = zram->meta;
> +
> + kunmap_atomic(mem);
> + /* Free memory associated with this sector now. */
> + bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
> + zram_free_page(zram, index);
> + zram_set_flag(meta, index, ZRAM_SAME);
> + zram_set_element(meta, index, element);
> + bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
> +
> + atomic64_inc(&zram->stats.same_pages);
> + return true;
> + }
> + kunmap_atomic(mem);
> +
> + return false;
> +}
> +
> static void zram_meta_free(struct zram_meta *meta, u64 disksize)
> {
> size_t num_pages = disksize >> PAGE_SHIFT;
> @@ -504,169 +548,104 @@ static void zram_free_page(struct zram *zram, size_t index)
> zram_set_obj_size(meta, index, 0);
> }
>
> -static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
> +static int zram_decompress_page(struct zram *zram, struct page *page, u32 index)
> {
> - int ret = 0;
> - unsigned char *cmem;
> - struct zram_meta *meta = zram->meta;
> + int ret;
> unsigned long handle;
> unsigned int size;
> + void *src, *dst;
> + struct zram_meta *meta = zram->meta;
> +
> + if (zram_special_page_read(zram, index, page, 0, PAGE_SIZE))
> + return 0;
>
> bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
> handle = meta->table[index].handle;
> size = zram_get_obj_size(meta, index);
>
> - if (!handle || zram_test_flag(meta, index, ZRAM_SAME)) {
> - bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
> - zram_fill_page(mem, PAGE_SIZE, meta->table[index].element);
> - return 0;
> - }
> -
> - cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_RO);
> + src = zs_map_object(meta->mem_pool, handle, ZS_MM_RO);
> if (size == PAGE_SIZE) {
> - copy_page(mem, cmem);
> + dst = kmap_atomic(page);
> + copy_page(dst, src);
> + kunmap_atomic(dst);
> + ret = 0;
> } else {
> struct zcomp_strm *zstrm = zcomp_stream_get(zram->comp);
>
> - ret = zcomp_decompress(zstrm, cmem, size, mem);
> + dst = kmap_atomic(page);
> + ret = zcomp_decompress(zstrm, src, size, dst);
> + kunmap_atomic(dst);
> zcomp_stream_put(zram->comp);
> }
> zs_unmap_object(meta->mem_pool, handle);
> bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
>
> /* Should NEVER happen. Return bio error if it does. */
> - if (unlikely(ret)) {
> + if (unlikely(ret))
> pr_err("Decompression failed! err=%d, page=%u\n", ret, index);
> - return ret;
> - }
>
> - return 0;
> + return ret;
> }
>
> static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
> - u32 index, int offset)
> + u32 index, int offset)
> {
> int ret;
> struct page *page;
> - unsigned char *user_mem, *uncmem = NULL;
> - struct zram_meta *meta = zram->meta;
> - page = bvec->bv_page;
>
> - bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
> - if (unlikely(!meta->table[index].handle) ||
> - zram_test_flag(meta, index, ZRAM_SAME)) {
> - bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
> - handle_same_page(bvec, meta->table[index].element);
> + page = bvec->bv_page;
> + if (zram_special_page_read(zram, index, page, bvec->bv_offset,
> + bvec->bv_len))
> return 0;
> - }
> - bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
> -
> - if (is_partial_io(bvec))
> - /* Use a temporary buffer to decompress the page */
> - uncmem = kmalloc(PAGE_SIZE, GFP_NOIO);
> -
> - user_mem = kmap_atomic(page);
> - if (!is_partial_io(bvec))
> - uncmem = user_mem;
>
> - if (!uncmem) {
> - pr_err("Unable to allocate temp memory\n");
> - ret = -ENOMEM;
> - goto out_cleanup;
> + if (is_partial_io(bvec)) {
> + /* Use a temporary buffer to decompress the page */
> + page = alloc_page(GFP_NOIO|__GFP_HIGHMEM);
> + if (!page)
> + return -ENOMEM;
> }
>
> - ret = zram_decompress_page(zram, uncmem, index);
> - /* Should NEVER happen. Return bio error if it does. */
> + ret = zram_decompress_page(zram, page, index);
> if (unlikely(ret))
> - goto out_cleanup;
> + goto out;
>
> - if (is_partial_io(bvec))
> - memcpy(user_mem + bvec->bv_offset, uncmem + offset,
> - bvec->bv_len);
> + if (is_partial_io(bvec)) {
> + void *dst = kmap_atomic(bvec->bv_page);
> + void *src = kmap_atomic(page);
>
> - flush_dcache_page(page);
> - ret = 0;
> -out_cleanup:
> - kunmap_atomic(user_mem);
> + memcpy(dst + bvec->bv_offset, src + offset, bvec->bv_len);
> + kunmap_atomic(src);
> + kunmap_atomic(dst);
> + }
> +out:
> if (is_partial_io(bvec))
> - kfree(uncmem);
> + __free_page(page);
> +
> return ret;
> }
>
> -static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> - int offset)
> +static int zram_compress(struct zram *zram, struct zcomp_strm **zstrm,
> + struct page *page,
> + unsigned long *out_handle, unsigned int *out_comp_len)
> {
> - int ret = 0;
> - unsigned int clen;
> + int ret;
> + unsigned int comp_len;
> + void *src;
> unsigned long handle = 0;
> - struct page *page;
> - unsigned char *user_mem, *cmem, *src, *uncmem = NULL;
> struct zram_meta *meta = zram->meta;
> - struct zcomp_strm *zstrm = NULL;
> - unsigned long alloced_pages;
> - unsigned long element;
> -
> - page = bvec->bv_page;
> - if (is_partial_io(bvec)) {
> - /*
> - * This is a partial IO. We need to read the full page
> - * before to write the changes.
> - */
> - uncmem = kmalloc(PAGE_SIZE, GFP_NOIO);
> - if (!uncmem) {
> - ret = -ENOMEM;
> - goto out;
> - }
> - ret = zram_decompress_page(zram, uncmem, index);
> - if (ret)
> - goto out;
> - }
>
> compress_again:
> - user_mem = kmap_atomic(page);
> - if (is_partial_io(bvec)) {
> - memcpy(uncmem + offset, user_mem + bvec->bv_offset,
> - bvec->bv_len);
> - kunmap_atomic(user_mem);
> - user_mem = NULL;
> - } else {
> - uncmem = user_mem;
> - }
> -
> - if (page_same_filled(uncmem, &element)) {
> - if (user_mem)
> - kunmap_atomic(user_mem);
> - /* Free memory associated with this sector now. */
> - bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
> - zram_free_page(zram, index);
> - zram_set_flag(meta, index, ZRAM_SAME);
> - zram_set_element(meta, index, element);
> - bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
> -
> - atomic64_inc(&zram->stats.same_pages);
> - ret = 0;
> - goto out;
> - }
> -
> - zstrm = zcomp_stream_get(zram->comp);
> - ret = zcomp_compress(zstrm, uncmem, &clen);
> - if (!is_partial_io(bvec)) {
> - kunmap_atomic(user_mem);
> - user_mem = NULL;
> - uncmem = NULL;
> - }
> + src = kmap_atomic(page);
> + ret = zcomp_compress(*zstrm, src, &comp_len);
> + kunmap_atomic(src);
>
> if (unlikely(ret)) {
> pr_err("Compression failed! err=%d\n", ret);
> - goto out;
> + return ret;
> }
>
> - src = zstrm->buffer;
> - if (unlikely(clen > max_zpage_size)) {
> - clen = PAGE_SIZE;
> - if (is_partial_io(bvec))
> - src = uncmem;
> - }
> + if (unlikely(comp_len > max_zpage_size))
> + comp_len = PAGE_SIZE;
>
> /*
> * handle allocation has 2 paths:
> @@ -682,50 +661,70 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> * from the slow path and handle has already been allocated.
> */
> if (!handle)
> - handle = zs_malloc(meta->mem_pool, clen,
> + handle = zs_malloc(meta->mem_pool, comp_len,
> __GFP_KSWAPD_RECLAIM |
> __GFP_NOWARN |
> __GFP_HIGHMEM |
> __GFP_MOVABLE);
> if (!handle) {
> zcomp_stream_put(zram->comp);
> - zstrm = NULL;
> -
> atomic64_inc(&zram->stats.writestall);
> -
> - handle = zs_malloc(meta->mem_pool, clen,
> + handle = zs_malloc(meta->mem_pool, comp_len,
> GFP_NOIO | __GFP_HIGHMEM |
> __GFP_MOVABLE);
> + *zstrm = zcomp_stream_get(zram->comp);
> if (handle)
> goto compress_again;
> + return -ENOMEM;
> + }
>
> - pr_err("Error allocating memory for compressed page: %u, size=%u\n",
> - index, clen);
> - ret = -ENOMEM;
> - goto out;
> + *out_handle = handle;
> + *out_comp_len = comp_len;
> + return 0;
> +}
> +
> +static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
> + u32 index, int offset)
> +{
> + int ret;
> + unsigned long handle;
> + unsigned int comp_len;
> + void *src, *dst;
> + struct zcomp_strm *zstrm;
> + unsigned long alloced_pages;
> + struct zram_meta *meta = zram->meta;
> + struct page *page = bvec->bv_page;
> +
> + if (zram_special_page_write(zram, index, page))
> + return 0;
> +
> + zstrm = zcomp_stream_get(zram->comp);
> + ret = zram_compress(zram, &zstrm, page, &handle, &comp_len);
> + if (ret) {
> + zcomp_stream_put(zram->comp);
> + return ret;
> }
>
> alloced_pages = zs_get_total_pages(meta->mem_pool);
> update_used_max(zram, alloced_pages);
>
> if (zram->limit_pages && alloced_pages > zram->limit_pages) {
> + zcomp_stream_put(zram->comp);
> zs_free(meta->mem_pool, handle);
> - ret = -ENOMEM;
> - goto out;
> + return -ENOMEM;
> }
>
> - cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_WO);
> + dst = zs_map_object(meta->mem_pool, handle, ZS_MM_WO);
>
> - if ((clen == PAGE_SIZE) && !is_partial_io(bvec)) {
> + if (comp_len == PAGE_SIZE) {
> src = kmap_atomic(page);
> - copy_page(cmem, src);
> + copy_page(dst, src);
> kunmap_atomic(src);
> } else {
> - memcpy(cmem, src, clen);
> + memcpy(dst, zstrm->buffer, comp_len);
> }
>
> zcomp_stream_put(zram->comp);
> - zstrm = NULL;
> zs_unmap_object(meta->mem_pool, handle);
>
> /*
> @@ -734,19 +733,54 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> */
> bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
> zram_free_page(zram, index);
> -
> meta->table[index].handle = handle;
> - zram_set_obj_size(meta, index, clen);
> + zram_set_obj_size(meta, index, comp_len);
> bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
>
> /* Update stats */
> - atomic64_add(clen, &zram->stats.compr_data_size);
> + atomic64_add(comp_len, &zram->stats.compr_data_size);
> atomic64_inc(&zram->stats.pages_stored);
> + return 0;
> +}
> +
> +static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
> + u32 index, int offset)
> +{
> + int ret;
> + struct page *page = NULL;
> + void *src;
> + struct bio_vec vec;
> +
> + vec = *bvec;
> + if (is_partial_io(bvec)) {
> + void *dst;
> + /*
> + * This is a partial IO. We need to read the full page
> + * before to write the changes.
> + */
> + page = alloc_page(GFP_NOIO|__GFP_HIGHMEM);
> + if (!page)
> + return -ENOMEM;
> +
> + ret = zram_decompress_page(zram, page, index);
> + if (ret)
> + goto out;
> +
> + src = kmap_atomic(bvec->bv_page);
> + dst = kmap_atomic(page);
> + memcpy(dst + offset, src + bvec->bv_offset, bvec->bv_len);
> + kunmap_atomic(dst);
> + kunmap_atomic(src);
> +
> + vec.bv_page = page;
> + vec.bv_len = PAGE_SIZE;
> + vec.bv_offset = 0;
> + }
> +
> + ret = __zram_bvec_write(zram, &vec, index, offset);
> out:
> - if (zstrm)
> - zcomp_stream_put(zram->comp);
> if (is_partial_io(bvec))
> - kfree(uncmem);
> + __free_page(page);
> return ret;
> }
>
> @@ -802,6 +836,7 @@ static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
> if (!is_write) {
> atomic64_inc(&zram->stats.num_reads);
> ret = zram_bvec_read(zram, bvec, index, offset);
> + flush_dcache_page(bvec->bv_page);
> } else {
> atomic64_inc(&zram->stats.num_writes);
> ret = zram_bvec_write(zram, bvec, index, offset);
>
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