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Subject: Re: [PATCH 2/4] devcoredump: allow to create several coredump files
 in one device
From:   Johannes Berg <johannes@sipsolutions.net>
To:     Akinobu Mita <akinobu.mita@gmail.com>,
        linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org
Cc:     Keith Busch <keith.busch@intel.com>, Jens Axboe <axboe@fb.com>,
        Christoph Hellwig <hch@lst.de>,
        Sagi Grimberg <sagi@grimberg.me>
Date:   Thu, 02 May 2019 14:47:47 +0200
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On Thu, 2019-05-02 at 17:59 +0900, Akinobu Mita wrote:
> 
>  static void devcd_del(struct work_struct *wk)
>  {
>  	struct devcd_entry *devcd;
> +	int i;
>  
>  	devcd = container_of(wk, struct devcd_entry, del_wk.work);
>  
> +	for (i = 0; i < devcd->num_files; i++) {
> +		device_remove_bin_file(&devcd->devcd_dev,
> +				       &devcd->files[i].bin_attr);
> +	}

Not much value in the braces?

> +static struct devcd_entry *devcd_alloc(struct dev_coredumpm_bulk_data *files,
> +				       int num_files, gfp_t gfp)
> +{
> +	struct devcd_entry *devcd;
> +	int i;
> +
> +	devcd = kzalloc(sizeof(*devcd), gfp);
> +	if (!devcd)
> +		return NULL;
> +
> +	devcd->files = kcalloc(num_files, sizeof(devcd->files[0]), gfp);
> +	if (!devcd->files) {
> +		kfree(devcd);
> +		return NULL;
> +	}
> +	devcd->num_files = num_files;

IMHO it would be nicer to allocate all of this in one struct, i.e. have

struct devcd_entry {
	...
	struct devcd_file files[];
}

(and then use struct_size())

> @@ -309,7 +339,41 @@ void dev_coredumpm(struct device *dev, struct module *owner,
>   put_module:
>  	module_put(owner);
>   free:
> -	free(data);
> +	for (i = 0; i < num_files; i++)
> +		files[i].free(files[i].data);
> +}

and then you don't need to do all this kind of thing to free

Otherwise looks fine. I'd worry a bit that existing userspace will only
capture the 'data' file, rather than a tarball of all files, but I guess
that's something you'd have to work out then when actually desiring to
use multiple files.

johannes