Message-ID: <1359963564.1366.0.camel@kernel.cn.ibm.com>
Date:	Mon, 04 Feb 2013 01:39:24 -0600
From:	Ric Mason <ric.masonn@...il.com>
To:	Minchan Kim <minchan@...nel.org>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Nitin Gupta <ngupta@...are.org>,
	Seth Jennings <sjenning@...ux.vnet.ibm.com>,
	Konrad Rzeszutek Wilk <konrad@...nok.org>,
	Dan Magenheimer <dan.magenheimer@...cle.com>,
	Pekka Enberg <penberg@...helsinki.fi>, jmarchan@...hat.com,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v7 4/4] zram: get rid of lockdep warning

On Mon, 2013-02-04 at 08:46 +0900, Minchan Kim wrote:
> Lockdep complains about recursive deadlock of zram->init_lock.
> [1] made it false positive because we can't request IO to zram
> before setting disksize. Anyway, we should shut lockdep up to
> avoid many reporting from user.
> 
> [1] : zram: force disksize setting before using zram
> 
> Acked-by: Jerome Marchand <jmarchan@...hat.com>
> Signed-off-by: Minchan Kim <minchan@...nel.org>
> ---
>  drivers/staging/zram/zram_drv.c   |  189 +++++++++++++++++++------------------
>  drivers/staging/zram/zram_drv.h   |   12 ++-
>  drivers/staging/zram/zram_sysfs.c |   11 ++-
>  3 files changed, 116 insertions(+), 96 deletions(-)
> 
> diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c
> index 85055c4..56e3203 100644
> --- a/drivers/staging/zram/zram_drv.c
> +++ b/drivers/staging/zram/zram_drv.c
> @@ -61,22 +61,22 @@ static void zram_stat64_inc(struct zram *zram, u64 *v)
>  	zram_stat64_add(zram, v, 1);
>  }
>  
> -static int zram_test_flag(struct zram *zram, u32 index,
> +static int zram_test_flag(struct zram_meta *meta, u32 index,
>  			enum zram_pageflags flag)
>  {
> -	return zram->table[index].flags & BIT(flag);
> +	return meta->table[index].flags & BIT(flag);
>  }
>  
> -static void zram_set_flag(struct zram *zram, u32 index,
> +static void zram_set_flag(struct zram_meta *meta, u32 index,
>  			enum zram_pageflags flag)
>  {
> -	zram->table[index].flags |= BIT(flag);
> +	meta->table[index].flags |= BIT(flag);
>  }
>  
> -static void zram_clear_flag(struct zram *zram, u32 index,
> +static void zram_clear_flag(struct zram_meta *meta, u32 index,
>  			enum zram_pageflags flag)
>  {
> -	zram->table[index].flags &= ~BIT(flag);
> +	meta->table[index].flags &= ~BIT(flag);
>  }
>  
>  static int page_zero_filled(void *ptr)
> @@ -96,16 +96,17 @@ static int page_zero_filled(void *ptr)
>  
>  static void zram_free_page(struct zram *zram, size_t index)
>  {
> -	unsigned long handle = zram->table[index].handle;
> -	u16 size = zram->table[index].size;
> +	struct zram_meta *meta = zram->meta;
> +	unsigned long handle = meta->table[index].handle;
> +	u16 size = meta->table[index].size;
>  
>  	if (unlikely(!handle)) {
>  		/*
>  		 * No memory is allocated for zero filled pages.
>  		 * Simply clear zero page flag.
>  		 */
> -		if (zram_test_flag(zram, index, ZRAM_ZERO)) {
> -			zram_clear_flag(zram, index, ZRAM_ZERO);
> +		if (zram_test_flag(meta, index, ZRAM_ZERO)) {
> +			zram_clear_flag(meta, index, ZRAM_ZERO);
>  			zram->stats.pages_zero--;
>  		}
>  		return;
> @@ -114,17 +115,17 @@ static void zram_free_page(struct zram *zram, size_t index)
>  	if (unlikely(size > max_zpage_size))
>  		zram->stats.bad_compress--;
>  
> -	zs_free(zram->mem_pool, handle);
> +	zs_free(meta->mem_pool, handle);
>  
>  	if (size <= PAGE_SIZE / 2)
>  		zram->stats.good_compress--;
>  
>  	zram_stat64_sub(zram, &zram->stats.compr_size,
> -			zram->table[index].size);
> +			meta->table[index].size);
>  	zram->stats.pages_stored--;
>  
> -	zram->table[index].handle = 0;
> -	zram->table[index].size = 0;
> +	meta->table[index].handle = 0;
> +	meta->table[index].size = 0;
>  }
>  
>  static void handle_zero_page(struct bio_vec *bvec)
> @@ -149,20 +150,21 @@ static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
>  	int ret = LZO_E_OK;
>  	size_t clen = PAGE_SIZE;
>  	unsigned char *cmem;
> -	unsigned long handle = zram->table[index].handle;
> +	struct zram_meta *meta = zram->meta;
> +	unsigned long handle = meta->table[index].handle;
>  
> -	if (!handle || zram_test_flag(zram, index, ZRAM_ZERO)) {
> +	if (!handle || zram_test_flag(meta, index, ZRAM_ZERO)) {
>  		memset(mem, 0, PAGE_SIZE);
>  		return 0;
>  	}
>  
> -	cmem = zs_map_object(zram->mem_pool, handle, ZS_MM_RO);
> -	if (zram->table[index].size == PAGE_SIZE)
> +	cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_RO);
> +	if (meta->table[index].size == PAGE_SIZE)
>  		memcpy(mem, cmem, PAGE_SIZE);
>  	else
> -		ret = lzo1x_decompress_safe(cmem, zram->table[index].size,
> +		ret = lzo1x_decompress_safe(cmem, meta->table[index].size,
>  						mem, &clen);
> -	zs_unmap_object(zram->mem_pool, handle);
> +	zs_unmap_object(meta->mem_pool, handle);
>  
>  	/* Should NEVER happen. Return bio error if it does. */
>  	if (unlikely(ret != LZO_E_OK)) {
> @@ -180,11 +182,11 @@ static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
>  	int ret;
>  	struct page *page;
>  	unsigned char *user_mem, *uncmem = NULL;
> -
> +	struct zram_meta *meta = zram->meta;
>  	page = bvec->bv_page;
>  
> -	if (unlikely(!zram->table[index].handle) ||
> -			zram_test_flag(zram, index, ZRAM_ZERO)) {
> +	if (unlikely(!meta->table[index].handle) ||
> +			zram_test_flag(meta, index, ZRAM_ZERO)) {
>  		handle_zero_page(bvec);
>  		return 0;
>  	}
> @@ -232,9 +234,10 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
>  	unsigned long handle;
>  	struct page *page;
>  	unsigned char *user_mem, *cmem, *src, *uncmem = NULL;
> +	struct zram_meta *meta = zram->meta;
>  
>  	page = bvec->bv_page;
> -	src = zram->compress_buffer;
> +	src = meta->compress_buffer;

Could you explain compress_buffer is used for what? Thanks for your
clarify! 

>  
>  	if (is_partial_io(bvec)) {
>  		/*
> @@ -256,8 +259,8 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
>  	 * System overwrites unused sectors. Free memory associated
>  	 * with this sector now.
>  	 */
> -	if (zram->table[index].handle ||
> -	    zram_test_flag(zram, index, ZRAM_ZERO))
> +	if (meta->table[index].handle ||
> +	    zram_test_flag(meta, index, ZRAM_ZERO))
>  		zram_free_page(zram, index);
>  
>  	user_mem = kmap_atomic(page);
> @@ -276,13 +279,13 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
>  		if (is_partial_io(bvec))
>  			kfree(uncmem);
>  		zram->stats.pages_zero++;
> -		zram_set_flag(zram, index, ZRAM_ZERO);
> +		zram_set_flag(meta, index, ZRAM_ZERO);
>  		ret = 0;
>  		goto out;
>  	}
>  
>  	ret = lzo1x_1_compress(uncmem, PAGE_SIZE, src, &clen,
> -			       zram->compress_workmem);
> +			       meta->compress_workmem);
>  
>  	if (!is_partial_io(bvec)) {
>  		kunmap_atomic(user_mem);
> @@ -303,14 +306,14 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
>  			src = uncmem;
>  	}
>  
> -	handle = zs_malloc(zram->mem_pool, clen);
> +	handle = zs_malloc(meta->mem_pool, clen);
>  	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, ZS_MM_WO);
> +	cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_WO);
>  
>  	if ((clen == PAGE_SIZE) && !is_partial_io(bvec))
>  		src = kmap_atomic(page);
> @@ -318,10 +321,10 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
>  	if ((clen == PAGE_SIZE) && !is_partial_io(bvec))
>  		kunmap_atomic(src);
>  
> -	zs_unmap_object(zram->mem_pool, handle);
> +	zs_unmap_object(meta->mem_pool, handle);
>  
> -	zram->table[index].handle = handle;
> -	zram->table[index].size = clen;
> +	meta->table[index].handle = handle;
> +	meta->table[index].size = clen;
>  
>  	/* Update stats */
>  	zram_stat64_add(zram, &zram->stats.compr_size, clen);
> @@ -464,34 +467,25 @@ error:
>  void __zram_reset_device(struct zram *zram)
>  {
>  	size_t index;
> +	struct zram_meta *meta;
>  
>  	if (!zram->init_done)
>  		return;
>  
> +	meta = zram->meta;
>  	zram->init_done = 0;
>  
> -	/* Free various per-device buffers */
> -	kfree(zram->compress_workmem);
> -	free_pages((unsigned long)zram->compress_buffer, 1);
> -
> -	zram->compress_workmem = NULL;
> -	zram->compress_buffer = NULL;
> -
>  	/* 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;
> +		unsigned long handle = meta->table[index].handle;
>  		if (!handle)
>  			continue;
>  
> -		zs_free(zram->mem_pool, handle);
> +		zs_free(meta->mem_pool, handle);
>  	}
>  
> -	vfree(zram->table);
> -	zram->table = NULL;
> -
> -	zs_destroy_pool(zram->mem_pool);
> -	zram->mem_pool = NULL;
> -
> +	zram_meta_free(zram->meta);
> +	zram->meta = NULL;
>  	/* Reset stats */
>  	memset(&zram->stats, 0, sizeof(zram->stats));
>  
> @@ -506,12 +500,65 @@ void zram_reset_device(struct zram *zram)
>  	up_write(&zram->init_lock);
>  }
>  
> -/* zram->init_lock should be held */
> -int zram_init_device(struct zram *zram)
> +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);
> +}
> +
> +struct zram_meta *zram_meta_alloc(u64 disksize)
>  {
> -	int ret;
>  	size_t num_pages;
> +	struct zram_meta *meta = kmalloc(sizeof(*meta), GFP_KERNEL);
> +	if (!meta)
> +		goto out;
> +
> +	meta->compress_workmem = kzalloc(LZO1X_MEM_COMPRESS, GFP_KERNEL);
> +	if (!meta->compress_workmem) {
> +		pr_err("Error allocating compressor working memory!\n");
> +		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;
> +	}
> +
> +	meta->mem_pool = zs_create_pool(GFP_NOIO | __GFP_HIGHMEM);
> +	if (!meta->mem_pool) {
> +		pr_err("Error creating memory pool\n");
> +		goto free_table;
> +	}
> +
> +	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;
> +out:
> +	return meta;
> +}
>  
> +void zram_init_device(struct zram *zram, struct zram_meta *meta)
> +{
>  	if (zram->disksize > 2 * (totalram_pages << PAGE_SHIFT)) {
>  		pr_info(
>  		"There is little point creating a zram of greater than "
> @@ -526,51 +573,13 @@ int zram_init_device(struct zram *zram)
>  		);
>  	}
>  
> -	zram->compress_workmem = kzalloc(LZO1X_MEM_COMPRESS, GFP_KERNEL);
> -	if (!zram->compress_workmem) {
> -		pr_err("Error allocating compressor working memory!\n");
> -		ret = -ENOMEM;
> -		goto fail_no_table;
> -	}
> -
> -	zram->compress_buffer =
> -		(void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, 1);
> -	if (!zram->compress_buffer) {
> -		pr_err("Error allocating compressor buffer space\n");
> -		ret = -ENOMEM;
> -		goto fail_no_table;
> -	}
> -
> -	num_pages = zram->disksize >> PAGE_SHIFT;
> -	zram->table = vzalloc(num_pages * sizeof(*zram->table));
> -	if (!zram->table) {
> -		pr_err("Error allocating zram address table\n");
> -		ret = -ENOMEM;
> -		goto fail_no_table;
> -	}
> -
>  	/* zram devices sort of resembles non-rotational disks */
>  	queue_flag_set_unlocked(QUEUE_FLAG_NONROT, zram->disk->queue);
>  
> -	zram->mem_pool = zs_create_pool(GFP_NOIO | __GFP_HIGHMEM);
> -	if (!zram->mem_pool) {
> -		pr_err("Error creating memory pool\n");
> -		ret = -ENOMEM;
> -		goto fail;
> -	}
> -
> +	zram->meta = meta;
>  	zram->init_done = 1;
>  
>  	pr_debug("Initialization done!\n");
> -	return 0;
> -
> -fail_no_table:
> -	/* To prevent accessing table entries during cleanup */
> -	zram->disksize = 0;
> -fail:
> -	__zram_reset_device(zram);
> -	pr_err("Initialization failed: err=%d\n", ret);
> -	return ret;
>  }
>  
>  static void zram_slot_free_notify(struct block_device *bdev,
> diff --git a/drivers/staging/zram/zram_drv.h b/drivers/staging/zram/zram_drv.h
> index 5b671d1..2d1a3f1 100644
> --- a/drivers/staging/zram/zram_drv.h
> +++ b/drivers/staging/zram/zram_drv.h
> @@ -83,11 +83,15 @@ struct zram_stats {
>  	u32 bad_compress;	/* % of pages with compression ratio>=75% */
>  };
>  
> -struct zram {
> -	struct zs_pool *mem_pool;
> +struct zram_meta {
>  	void *compress_workmem;
>  	void *compress_buffer;
>  	struct table *table;
> +	struct zs_pool *mem_pool;
> +};
> +
> +struct zram {
> +	struct zram_meta *meta;
>  	spinlock_t stat64_lock;	/* protect 64-bit stats */
>  	struct rw_semaphore lock; /* protect compression buffers and table
>  				   * against concurrent read and writes */
> @@ -111,7 +115,9 @@ unsigned int zram_get_num_devices(void);
>  extern struct attribute_group zram_disk_attr_group;
>  #endif
>  
> -extern int zram_init_device(struct zram *zram);
>  extern void zram_reset_device(struct zram *zram);
> +extern struct zram_meta *zram_meta_alloc(u64 disksize);
> +extern void zram_meta_free(struct zram_meta *meta);
> +extern void zram_init_device(struct zram *zram, struct zram_meta *meta);
>  
>  #endif
> diff --git a/drivers/staging/zram/zram_sysfs.c b/drivers/staging/zram/zram_sysfs.c
> index 369db12..e6a929d 100644
> --- a/drivers/staging/zram/zram_sysfs.c
> +++ b/drivers/staging/zram/zram_sysfs.c
> @@ -56,22 +56,26 @@ static ssize_t disksize_store(struct device *dev,
>  		struct device_attribute *attr, const char *buf, size_t len)
>  {
>  	u64 disksize;
> +	struct zram_meta *meta;
>  	struct zram *zram = dev_to_zram(dev);
>  
>  	disksize = memparse(buf, NULL);
>  	if (!disksize)
>  		return -EINVAL;
>  
> +	disksize = PAGE_ALIGN(disksize);
> +	meta = zram_meta_alloc(disksize);
>  	down_write(&zram->init_lock);
>  	if (zram->init_done) {
>  		up_write(&zram->init_lock);
> +		zram_meta_free(meta);
>  		pr_info("Cannot change disksize for initialized device\n");
>  		return -EBUSY;
>  	}
>  
> -	zram->disksize = PAGE_ALIGN(disksize);
> +	zram->disksize = disksize;
>  	set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT);
> -	zram_init_device(zram);
> +	zram_init_device(zram, meta);
>  	up_write(&zram->init_lock);
>  
>  	return len;
> @@ -182,9 +186,10 @@ static ssize_t mem_used_total_show(struct device *dev,
>  {
>  	u64 val = 0;
>  	struct zram *zram = dev_to_zram(dev);
> +	struct zram_meta *meta = zram->meta;
>  
>  	if (zram->init_done)
> -		val = zs_get_total_size_bytes(zram->mem_pool);
> +		val = zs_get_total_size_bytes(meta->mem_pool);
>  
>  	return sprintf(buf, "%llu\n", val);
>  }


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Powered by blists - more mailing lists