Re: [PATCH blktests] loop/004: Need to wait for drop caches if block_size is changed

[Omar Sandoval <osandov@osandov.com>]

On Wed, Feb 20, 2019 at 05:38:06PM +0800, zhengbin wrote:
> When i test blktests, loop/004 will be fail. The Key test steps
> are as follows:
> 1. losetup -f --show  /dev/sda
> 2. src/loblksize /dev/loop0 4096
> 
> step 1 will create /dev/loop0. after that, daemon systemd-udevd
> will visit and close /dev/loop0 who will add and delete
> i_mapping->nrpages.
> PS: the operation of systemd-udevd is in the background.
> 
> step 2 will set /dev/loop0 block size, linux kernel function
> loop_set_block_size has been changed since commit 5db470e229e2
> ("loop: drop caches if offset or block_size are changed")
> + if (lo->lo_queue->limits.logical_block_size != arg &&
> +     lo->lo_device->bd_inode->i_mapping->nrpages) {
> +               err = -EAGAIN;
> +               pr_warn("%s: loop%d (%s) has still dirty pages\n",
> +                       __func__, lo->lo_number, lo->lo_file_name,
> +                       lo->lo_device->bd_inode->i_mapping->nrpages);
> +               goto out_unfreeze;
> +       }
> --->maybe systemd-udevd just visited /dev/loop0, this leads to failure
> 
> Add a step between 1 and 2.
> 
> Signed-off-by: zhengbin <zhengbin13@huawei.com>
> ---
>  tests/loop/004 | 1 +
>  1 file changed, 1 insertion(+)

Applied, thanks!