Re: [PATCH v3] fs: ratelimit __find_get_block_slow() failure message.

[Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>]

Hello, Jens. Can we apply this patch?

On 2019/01/21 22:49, Tetsuo Handa wrote:
> When something let __find_get_block_slow() hit all_mapped path, it calls
> printk() for 100+ times per a second. But there is no need to print same
> message with such high frequency; it is just asking for stall warning, or
> at least bloating log files.
> 
>   [  399.866302][T15342] __find_get_block_slow() failed. block=1, b_blocknr=8
>   [  399.873324][T15342] b_state=0x00000029, b_size=512
>   [  399.878403][T15342] device loop0 blocksize: 4096
>   [  399.883296][T15342] __find_get_block_slow() failed. block=1, b_blocknr=8
>   [  399.890400][T15342] b_state=0x00000029, b_size=512
>   [  399.895595][T15342] device loop0 blocksize: 4096
>   [  399.900556][T15342] __find_get_block_slow() failed. block=1, b_blocknr=8
>   [  399.907471][T15342] b_state=0x00000029, b_size=512
>   [  399.912506][T15342] device loop0 blocksize: 4096
> 
> This patch reduces frequency to up to once per a second, in addition to
> concatenating three lines into one.
> 
>   [  399.866302][T15342] __find_get_block_slow() failed. block=1, b_blocknr=8, b_state=0x00000029, b_size=512, device loop0 blocksize: 4096
> 
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> Reviewed-by: Jan Kara <jack@suse.cz>
> Cc: Dmitry Vyukov <dvyukov@google.com>
> ---
>  fs/buffer.c | 19 ++++++++++---------
>  1 file changed, 10 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/buffer.c b/fs/buffer.c
> index 52d024b..48318fb 100644
> --- a/fs/buffer.c
> +++ b/fs/buffer.c
> @@ -200,6 +200,7 @@ void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
>  	struct buffer_head *head;
>  	struct page *page;
>  	int all_mapped = 1;
> +	static DEFINE_RATELIMIT_STATE(last_warned, HZ, 1);
>  
>  	index = block >> (PAGE_SHIFT - bd_inode->i_blkbits);
>  	page = find_get_page_flags(bd_mapping, index, FGP_ACCESSED);
> @@ -227,15 +228,15 @@ void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
>  	 * file io on the block device and getblk.  It gets dealt with
>  	 * elsewhere, don't buffer_error if we had some unmapped buffers
>  	 */
> -	if (all_mapped) {
> -		printk("__find_get_block_slow() failed. "
> -			"block=%llu, b_blocknr=%llu\n",
> -			(unsigned long long)block,
> -			(unsigned long long)bh->b_blocknr);
> -		printk("b_state=0x%08lx, b_size=%zu\n",
> -			bh->b_state, bh->b_size);
> -		printk("device %pg blocksize: %d\n", bdev,
> -			1 << bd_inode->i_blkbits);
> +	ratelimit_set_flags(&last_warned, RATELIMIT_MSG_ON_RELEASE);
> +	if (all_mapped && __ratelimit(&last_warned)) {
> +		printk("__find_get_block_slow() failed. block=%llu, "
> +		       "b_blocknr=%llu, b_state=0x%08lx, b_size=%zu, "
> +		       "device %pg blocksize: %d\n",
> +		       (unsigned long long)block,
> +		       (unsigned long long)bh->b_blocknr,
> +		       bh->b_state, bh->b_size, bdev,
> +		       1 << bd_inode->i_blkbits);
>  	}
>  out_unlock:
>  	spin_unlock(&bd_mapping->private_lock);
>