Re: [PATCH v2] generic/465: just check the actual read data under dio read/write

[Eryu Guan <eguan@redhat.com>]

On Mon, Nov 27, 2017 at 10:34:27AM +0800, Xiao Yang wrote:
> I got the following message when running generic/465 in ext4 data=journal mode
> ---------------------------------------------------------------
> QA output created by 465
> non-aio dio test
> encounter an error: block 0 offset 4096, content 62
> encounter an error: block 0 offset 122880, content 62
> encounter an error: block 0 offset 274432, content 62
> encounter an error: block 0 offset 86016, content 62
> aio-dio test
> encounter an error: block 0 offset 28672, content 62
> encounter an error: block 0 offset 12288, content 62
> encounter an error: block 2 offset 16384, content 62
> encounter an error: block 1 offset 565248, content 62
> ---------------------------------------------------------------
> 
> In ext4 data=journal mode, direct read will fall back to buffer read, and buffer
> read doesn't take inode lock, so it doesn't need to wait for the writer to finish
> first and sees the intermediate inode size and returns data less than 1M.
> 
> We can just check the actual read data instead of the whole read buffer.
> 
> Signed-off-by: Xiao Yang <yangx.jy@cn.fujitsu.com>
> ---
>  src/aio-dio-regress/aio-dio-append-write-read-race.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/src/aio-dio-regress/aio-dio-append-write-read-race.c b/src/aio-dio-regress/aio-dio-append-write-read-race.c
> index 8f94d50..eaec784 100644
> --- a/src/aio-dio-regress/aio-dio-append-write-read-race.c
> +++ b/src/aio-dio-regress/aio-dio-append-write-read-race.c
> @@ -43,6 +43,7 @@ struct io_data {
>  	off_t offset;
>  	char *buf;
>  	int use_aio;
> +	size_t act_sz;

I think this should be a signed value, as pread returns ssize_t. And
maybe rename the variable to read_sz? Otherwise looks fine to me. And I
can do the updates on commit, if there's no further review comments.

Thanks,
Eryu

>  };
>  
>  int reader_ready = 0;
> @@ -57,15 +58,14 @@ static void usage(const char *prog)
>  static void *reader(void *arg)
>  {
>  	struct io_data *data = (struct io_data *)arg;
> -	int ret;
>  
>  	memset(data->buf, 'b', data->blksize);
>  	reader_ready = 1;
>  	do {
> -		ret = pread(data->fd, data->buf, data->blksize, data->offset);
> -		if (ret < 0)
> +		data->act_sz = pread(data->fd, data->buf, data->blksize, data->offset);
> +		if (data->act_sz < 0)
>  			perror("read file");
> -	} while (ret <= 0);
> +	} while (data->act_sz <= 0);
>  
>  	return NULL;
>  }
> @@ -203,7 +203,7 @@ int main(int argc, char *argv[])
>  			goto err;
>  		}
>  
> -		for (j = 0; j < blksize; j++) {
> +		for (j = 0; j < rdata.act_sz; j++) {
>  			if (rdata.buf[j] != 'a') {
>  				fail("encounter an error: "
>  					"block %d offset %d, content %x\n",
> -- 
> 1.8.3.1
> 
> 
> 
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