From mboxrd@z Thu Jan  1 00:00:00 1970
From: Oleg Nesterov <oleg@redhat.com>
Subject: Re: [RFC PATCH] coredump: fix incomplete core file created when
	dump_skip was used last
Date: Wed, 22 Oct 2014 18:55:30 +0200
Message-ID: <20141022165530.GA30358@redhat.com>
References: <1413932228-27642-1-git-send-email-victor.kamensky@linaro.org> <1413932228-27642-2-git-send-email-victor.kamensky@linaro.org>
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Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
	linux-fsdevel@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	Kees Cook <keescook@chromium.org>, linux-kernel@vger.kernel.org
To: Victor Kamensky <victor.kamensky@linaro.org>
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On 10/21, Victor Kamensky wrote:
>
> +static int dump_write_last_byte(struct coredump_params *cprm)
> +{
> +	char lastbyte = 0;
> +	struct file *file = cprm->file;
> +
> +	if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
> +		if (dump_interrupted() ||
> +		    file->f_op->llseek(file, -1, SEEK_CUR) < 0)
> +			return 0;
> +		if (!dump_emit(cprm, &lastbyte, 1))
> +			return 0;
> +	}
> +	return 1;
> +}

Perhaps do_truncate(cprm.file->f_path.dentry, ->f_pos) makes more sense?

and unless I missed something cprm->last_op_status can be avoided, we can
simply check f_pos != i_size_read() at the end?

Oleg.