linux-kernel - Re: [PATCH] [v2] bcache: stop using the deprecated get

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Date:   Sat, 23 Jun 2018 16:12:10 +0800
From:   Coly Li <colyli@...e.de>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Kent Overstreet <kent.overstreet@...il.com>,
        y2038@...ts.linaro.org, Jens Axboe <axboe@...nel.dk>,
        Michael Lyle <mlyle@...e.org>,
        Tang Junhui <tang.junhui@....com.cn>,
        Hannes Reinecke <hare@...e.com>, linux-bcache@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [v2] bcache: stop using the deprecated get_seconds()

On 2018/6/22 9:48 PM, Arnd Bergmann wrote:
> The get_seconds function is deprecated now since it returns a 32-bit
> value that will eventually overflow, and we are replacing it throughout
> the kernel with ktime_get_seconds() or ktime_get_real_seconds() that
> return a time64_t.
> 
> bcache uses get_seconds() to read the current system time and store it in
> the superblock as well as in uuid_entry structures that are user visible.
> 
> Unfortunately, the two structures in are still limited to 32 bits, so this
> won't fix any real problems but will still overflow in year 2106. Let's
> at least document that properly, in case we get an updated format in the
> future it can be fixed. We still have a long time before the overflow
> and checking the tools at https://github.com/koverstreet/bcache-tools
> reveals no access to any of them.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Added to 4.19 for-next.

Thanks.

Coly Li

> ---
>  drivers/md/bcache/super.c   | 12 ++++++------
>  include/uapi/linux/bcache.h |  4 ++--
>  2 files changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
> index fa4058e43202..74746d8ee05e 100644
> --- a/drivers/md/bcache/super.c
> +++ b/drivers/md/bcache/super.c
> @@ -181,7 +181,7 @@ static const char *read_super(struct cache_sb *sb, struct block_device *bdev,
>  		goto err;
>  	}
>  
> -	sb->last_mount = get_seconds();
> +	sb->last_mount = (u32)ktime_get_real_seconds();
>  	err = NULL;
>  
>  	get_page(bh->b_page);
> @@ -701,7 +701,7 @@ static void bcache_device_detach(struct bcache_device *d)
>  
>  		SET_UUID_FLASH_ONLY(u, 0);
>  		memcpy(u->uuid, invalid_uuid, 16);
> -		u->invalidated = cpu_to_le32(get_seconds());
> +		u->invalidated = cpu_to_le32((u32)ktime_get_real_seconds());
>  		bch_uuid_write(d->c);
>  	}
>  
> @@ -1027,7 +1027,7 @@ void bch_cached_dev_detach(struct cached_dev *dc)
>  int bch_cached_dev_attach(struct cached_dev *dc, struct cache_set *c,
>  			  uint8_t *set_uuid)
>  {
> -	uint32_t rtime = cpu_to_le32(get_seconds());
> +	uint32_t rtime = cpu_to_le32((u32)ktime_get_real_seconds());
>  	struct uuid_entry *u;
>  	struct cached_dev *exist_dc, *t;
>  
> @@ -1070,7 +1070,7 @@ int bch_cached_dev_attach(struct cached_dev *dc, struct cache_set *c,
>  	    (BDEV_STATE(&dc->sb) == BDEV_STATE_STALE ||
>  	     BDEV_STATE(&dc->sb) == BDEV_STATE_NONE)) {
>  		memcpy(u->uuid, invalid_uuid, 16);
> -		u->invalidated = cpu_to_le32(get_seconds());
> +		u->invalidated = cpu_to_le32((u32)ktime_get_real_seconds());
>  		u = NULL;
>  	}
>  
> @@ -1390,7 +1390,7 @@ int bch_flash_dev_create(struct cache_set *c, uint64_t size)
>  
>  	get_random_bytes(u->uuid, 16);
>  	memset(u->label, 0, 32);
> -	u->first_reg = u->last_reg = cpu_to_le32(get_seconds());
> +	u->first_reg = u->last_reg = cpu_to_le32((u32)ktime_get_real_seconds());
>  
>  	SET_UUID_FLASH_ONLY(u, 1);
>  	u->sectors = size >> 9;
> @@ -1894,7 +1894,7 @@ static void run_cache_set(struct cache_set *c)
>  		goto err;
>  
>  	closure_sync(&cl);
> -	c->sb.last_mount = get_seconds();
> +	c->sb.last_mount = (u32)ktime_get_real_seconds();
>  	bcache_write_super(c);
>  
>  	list_for_each_entry_safe(dc, t, &uncached_devices, list)
> diff --git a/include/uapi/linux/bcache.h b/include/uapi/linux/bcache.h
> index 821f71a2e48f..8d19e02d752a 100644
> --- a/include/uapi/linux/bcache.h
> +++ b/include/uapi/linux/bcache.h
> @@ -195,7 +195,7 @@ struct cache_sb {
>  	};
>  	};
>  
> -	__u32			last_mount;	/* time_t */
> +	__u32			last_mount;	/* time overflow in y2106 */
>  
>  	__u16			first_bucket;
>  	union {
> @@ -318,7 +318,7 @@ struct uuid_entry {
>  		struct {
>  			__u8	uuid[16];
>  			__u8	label[32];
> -			__u32	first_reg;
> +			__u32	first_reg; /* time overflow in y2106 */
>  			__u32	last_reg;
>  			__u32	invalidated;
>  
>