Date:   Mon, 3 Apr 2017 14:12:50 +0900
From:   Minchan Kim <minchan@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     sergey.senozhatsky@...il.com, mm-commits@...r.kernel.org
Subject: Re: + zram-factor-out-partial-io-routine.patch added to -mm tree

Hi Andrew,

Could you drop this patchset because I will send new patchset to replace
this.

Thanks.

On Wed, Mar 29, 2017 at 03:25:32PM -0700, akpm@...ux-foundation.org wrote:
> 
> The patch titled
>      Subject: zram: factor out partial IO routine
> has been added to the -mm tree.  Its filename is
>      zram-factor-out-partial-io-routine.patch
> 
> This patch should soon appear at
>     http://ozlabs.org/~akpm/mmots/broken-out/zram-factor-out-partial-io-routine.patch
> and later at
>     http://ozlabs.org/~akpm/mmotm/broken-out/zram-factor-out-partial-io-routine.patch
> 
> 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/SubmitChecklist when testing your code ***
> 
> The -mm tree is included into linux-next and is updated
> there every 3-4 working days
> 
> ------------------------------------------------------
> From: Minchan Kim <minchan@...nel.org>
> Subject: zram: factor out partial IO routine
> 
> For architecture(PAGE_SIZE > 4K), zram have supported partial IO. 
> However, the mixed code for handling normal/partial IO is too messy,
> error-prone to modify IO handler functions with upcoming feature so this
> patch aims for cleaning up via factoring out partial IO routines to
> zram_bvec_partial_[read|write] which will be disabled for most 4K page
> architecures.
> 
> x86(4K architecure)
> add/remove: 0/1 grow/shrink: 0/1 up/down: 0/-664 (-664)
> function                                     old     new   delta
> zram_bvec_rw                                2301    2039    -262
> zram_decompress_page.isra                    402       -    -402
> 
> So, we will save 662 bytes.
> 
> However, as side effect, it will increase binary size in non-4K
> architecure but it's not major for zram so I believe benefit(maintainance,
> binary size for most architecture) is bigger.
> 
> Link: http://lkml.kernel.org/r/1490773683-10701-1-git-send-email-minchan@kernel.org
> Signed-off-by: Minchan Kim <minchan@...nel.org>
> Cc: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> ---
> 
>  drivers/block/zram/zram_drv.c |  259 ++++++++++++++++++++++----------
>  1 file changed, 186 insertions(+), 73 deletions(-)
> 
> diff -puN drivers/block/zram/zram_drv.c~zram-factor-out-partial-io-routine drivers/block/zram/zram_drv.c
> --- a/drivers/block/zram/zram_drv.c~zram-factor-out-partial-io-routine
> +++ a/drivers/block/zram/zram_drv.c
> @@ -98,10 +98,17 @@ static void zram_set_obj_size(struct zra
>  	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
> +static inline bool is_partial_io(struct bio_vec *bvec)
> +{
> +	return false;
> +}
> +#endif
>  
>  static void zram_revalidate_disk(struct zram *zram)
>  {
> @@ -544,8 +551,8 @@ static int zram_decompress_page(struct z
>  	return 0;
>  }
>  
> -static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
> -			  u32 index, int offset)
> +static int zram_bvec_partial_read(struct zram *zram, struct bio_vec *bvec,
> +				u32 index, int offset)
>  {
>  	int ret;
>  	struct page *page;
> @@ -562,81 +569,87 @@ static int zram_bvec_read(struct zram *z
>  	}
>  	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;
> -
> +	/* Use  a temporary buffer to decompress the page */
> +	uncmem = kmalloc(PAGE_SIZE, GFP_NOIO);
>  	if (!uncmem) {
>  		pr_err("Unable to allocate temp memory\n");
> -		ret = -ENOMEM;
> -		goto out_cleanup;
> +		return -ENOMEM;
>  	}
>  
> +	user_mem = kmap_atomic(page);
>  	ret = zram_decompress_page(zram, uncmem, index);
> -	/* Should NEVER happen. Return bio error if it does. */
>  	if (unlikely(ret))
>  		goto out_cleanup;
>  
> -	if (is_partial_io(bvec))
> -		memcpy(user_mem + bvec->bv_offset, uncmem + offset,
> +	memcpy(user_mem + bvec->bv_offset, uncmem + offset,
>  				bvec->bv_len);
> -
>  	flush_dcache_page(page);
>  	ret = 0;
>  out_cleanup:
>  	kunmap_atomic(user_mem);
> -	if (is_partial_io(bvec))
> -		kfree(uncmem);
> +	kfree(uncmem);
>  	return ret;
>  }
>  
> -static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> -			   int offset)
> +static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
> +			  u32 index, int offset)
>  {
> -	int ret = 0;
> +	int ret;
> +	struct page *page;
> +	unsigned char *user_mem;
> +	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);
> +		return 0;
> +	}
> +	bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
> +
> +	user_mem = kmap_atomic(page);
> +	ret = zram_decompress_page(zram, user_mem, index);
> +	kunmap_atomic(user_mem);
> +
> +	flush_dcache_page(page);
> +	return ret;
> +}
> +
> +static int zram_bvec_partial_write(struct zram *zram, struct bio_vec *bvec,
> +				u32 index, int offset)
> +{
> +	int ret = -ENOMEM;
>  	unsigned int clen;
>  	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;
> +	struct zcomp_strm *zstrm;
>  	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;
> -	}
> +	/*
> +	 * 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)
> +		return ret;
> +
> +	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;
> -	}
> +	memcpy(uncmem + offset, user_mem + bvec->bv_offset,
> +	       bvec->bv_len);
> +	kunmap_atomic(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);
> @@ -651,13 +664,8 @@ compress_again:
>  
>  	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;
> -	}
> -
>  	if (unlikely(ret)) {
> +		zcomp_stream_put(zram->comp);
>  		pr_err("Compression failed! err=%d\n", ret);
>  		goto out;
>  	}
> @@ -665,8 +673,7 @@ compress_again:
>  	src = zstrm->buffer;
>  	if (unlikely(clen > max_zpage_size)) {
>  		clen = PAGE_SIZE;
> -		if (is_partial_io(bvec))
> -			src = uncmem;
> +		src = uncmem;
>  	}
>  
>  	/*
> @@ -690,8 +697,6 @@ compress_again:
>  				__GFP_MOVABLE);
>  	if (!handle) {
>  		zcomp_stream_put(zram->comp);
> -		zstrm = NULL;
> -
>  		atomic64_inc(&zram->stats.writestall);
>  
>  		handle = zs_malloc(meta->mem_pool, clen,
> @@ -702,7 +707,6 @@ compress_again:
>  
>  		pr_err("Error allocating memory for compressed page: %u, size=%u\n",
>  			index, clen);
> -		ret = -ENOMEM;
>  		goto out;
>  	}
>  
> @@ -711,22 +715,131 @@ compress_again:
>  
>  	if (zram->limit_pages && alloced_pages > zram->limit_pages) {
>  		zs_free(meta->mem_pool, handle);
> -		ret = -ENOMEM;
> +		zcomp_stream_put(zram->comp);
>  		goto out;
>  	}
>  
>  	cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_WO);
>  
> -	if ((clen == PAGE_SIZE) && !is_partial_io(bvec)) {
> -		src = kmap_atomic(page);
> -		copy_page(cmem, src);
> -		kunmap_atomic(src);
> +	memcpy(cmem, src, clen);
> +	zcomp_stream_put(zram->comp);
> +	zs_unmap_object(meta->mem_pool, handle);
> +
> +	/*
> +	 * Free memory associated with this sector
> +	 * before overwriting unused sectors.
> +	 */
> +	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);
> +	bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
> +
> +	/* Update stats */
> +	atomic64_add(clen, &zram->stats.compr_data_size);
> +	atomic64_inc(&zram->stats.pages_stored);
> +	ret = 0;
> +out:
> +	kfree(uncmem);
> +	return ret;
> +}
> +
> +static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> +			   int offset)
> +{
> +	int ret;
> +	unsigned int clen;
> +	unsigned long handle = 0;
> +	struct page *page;
> +	void *user_mem, *cmem;
> +	struct zram_meta *meta = zram->meta;
> +	struct zcomp_strm *zstrm;
> +	unsigned long alloced_pages;
> +	unsigned long element;
> +
> +	page = bvec->bv_page;
> +compress_again:
> +	user_mem = kmap_atomic(page);
> +	if (page_same_filled(user_mem, &element)) {
> +		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);
> +		return 0;
> +	}
> +
> +	zstrm = zcomp_stream_get(zram->comp);
> +	ret = zcomp_compress(zstrm, user_mem, &clen);
> +	kunmap_atomic(user_mem);
> +
> +	if (unlikely(ret)) {
> +		pr_err("Compression failed! err=%d\n", ret);
> +		zcomp_stream_put(zram->comp);
> +		return ret;
> +	}
> +
> +	if (unlikely(clen > max_zpage_size))
> +		clen = PAGE_SIZE;
> +
> +	/*
> +	 * handle allocation has 2 paths:
> +	 * a) fast path is executed with preemption disabled (for
> +	 *  per-cpu streams) and has __GFP_DIRECT_RECLAIM bit clear,
> +	 *  since we can't sleep;
> +	 * b) slow path enables preemption and attempts to allocate
> +	 *  the page with __GFP_DIRECT_RECLAIM bit set. we have to
> +	 *  put per-cpu compression stream and, thus, to re-do
> +	 *  the compression once handle is allocated.
> +	 *
> +	 * if we have a 'non-null' handle here then we are coming
> +	 * from the slow path and handle has already been allocated.
> +	 */
> +	if (!handle)
> +		handle = zs_malloc(meta->mem_pool, clen,
> +				__GFP_KSWAPD_RECLAIM |
> +				__GFP_NOWARN |
> +				__GFP_HIGHMEM |
> +				__GFP_MOVABLE);
> +	if (!handle) {
> +		zcomp_stream_put(zram->comp);
> +		atomic64_inc(&zram->stats.writestall);
> +		handle = zs_malloc(meta->mem_pool, clen,
> +				GFP_NOIO | __GFP_HIGHMEM |
> +				__GFP_MOVABLE);
> +		if (handle)
> +			goto compress_again;
> +
> +		pr_err("Error allocating memory for compressed page: %u, size=%u\n",
> +			index, clen);
> +		return -ENOMEM;
> +	}
> +
> +	alloced_pages = zs_get_total_pages(meta->mem_pool);
> +	update_used_max(zram, alloced_pages);
> +
> +	if (zram->limit_pages && alloced_pages > zram->limit_pages) {
> +		zs_free(meta->mem_pool, handle);
> +		zcomp_stream_put(zram->comp);
> +		return -ENOMEM;
> +	}
> +
> +	cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_WO);
> +
> +	if (clen == PAGE_SIZE) {
> +		user_mem = kmap_atomic(page);
> +		copy_page(cmem, user_mem);
> +		kunmap_atomic(user_mem);
>  	} else {
> -		memcpy(cmem, src, clen);
> +		memcpy(cmem, zstrm->buffer, clen);
>  	}
>  
>  	zcomp_stream_put(zram->comp);
> -	zstrm = NULL;
>  	zs_unmap_object(meta->mem_pool, handle);
>  
>  	/*
> @@ -735,7 +848,6 @@ compress_again:
>  	 */
>  	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);
>  	bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
> @@ -743,12 +855,7 @@ compress_again:
>  	/* Update stats */
>  	atomic64_add(clen, &zram->stats.compr_data_size);
>  	atomic64_inc(&zram->stats.pages_stored);
> -out:
> -	if (zstrm)
> -		zcomp_stream_put(zram->comp);
> -	if (is_partial_io(bvec))
> -		kfree(uncmem);
> -	return ret;
> +	return 0;
>  }
>  
>  /*
> @@ -802,10 +909,16 @@ static int zram_bvec_rw(struct zram *zra
>  
>  	if (!is_write) {
>  		atomic64_inc(&zram->stats.num_reads);
> -		ret = zram_bvec_read(zram, bvec, index, offset);
> +		if (!is_partial_io(bvec))
> +			ret = zram_bvec_read(zram, bvec, index, offset);
> +		else
> +			ret = zram_bvec_partial_read(zram, bvec, index, offset);
>  	} else {
>  		atomic64_inc(&zram->stats.num_writes);
> -		ret = zram_bvec_write(zram, bvec, index, offset);
> +		if (!is_partial_io(bvec))
> +			ret = zram_bvec_write(zram, bvec, index, offset);
> +		else
> +			ret = zram_bvec_partial_write(zram, bvec, index, offset);
>  	}
>  
>  	generic_end_io_acct(rw_acct, &zram->disk->part0, start_time);
> _
> 
> Patches currently in -mm which might be from minchan@...nel.org are
> 
> mm-reclaim-madv_free-pages-fix.patch
> mm-fix-lazyfree-bug-on-check-in-try_to_unmap_one.patch
> mm-fix-lazyfree-bug-on-check-in-try_to_unmap_one-fix.patch
> mm-do-not-use-double-negation-for-testing-page-flags.patch
> mm-remove-unncessary-ret-in-page_referenced.patch
> mm-remove-swap_dirty-in-ttu.patch
> mm-remove-swap_mlock-check-for-swap_success-in-ttu.patch
> mm-make-the-try_to_munlock-void-function.patch
> mm-remove-swap_mlock-in-ttu.patch
> mm-remove-swap_again-in-ttu.patch
> mm-make-ttus-return-boolean.patch
> mm-make-rmap_walk-void-function.patch
> mm-make-rmap_one-boolean-function.patch
> mm-remove-swap_.patch
> mm-remove-swap_-fix.patch
> zram-factor-out-partial-io-routine.patch
> 
> --
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