linux-kernel - Re: [PATCH v2 02/18] earlycpio.c: Fix the confusing comment of find_cpio

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Date:	Thu, 01 Aug 2013 15:57:51 -0600
From:	Toshi Kani <toshi.kani@...com>
To:	Tang Chen <tangchen@...fujitsu.com>
Cc:	rjw@...k.pl, lenb@...nel.org, tglx@...utronix.de, mingo@...e.hu,
	hpa@...or.com, akpm@...ux-foundation.org, tj@...nel.org,
	trenn@...e.de, yinghai@...nel.org, jiang.liu@...wei.com,
	wency@...fujitsu.com, laijs@...fujitsu.com,
	isimatu.yasuaki@...fujitsu.com, izumi.taku@...fujitsu.com,
	mgorman@...e.de, minchan@...nel.org, mina86@...a86.com,
	gong.chen@...ux.intel.com, vasilis.liaskovitis@...fitbricks.com,
	lwoodman@...hat.com, riel@...hat.com, jweiner@...hat.com,
	prarit@...hat.com, zhangyanfei@...fujitsu.com,
	yanghy@...fujitsu.com, x86@...nel.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linux-acpi@...r.kernel.org
Subject: Re: [PATCH v2 02/18] earlycpio.c: Fix the confusing comment of
 find_cpio_data().

On Thu, 2013-08-01 at 15:06 +0800, Tang Chen wrote:
> The comments of find_cpio_data() says:
> 
>   * @offset: When a matching file is found, this is the offset to the
>   *          beginning of the cpio. ......
> 
> But according to the code,
> 
>   dptr = PTR_ALIGN(p + ch[C_NAMESIZE], 4);
>   nptr = PTR_ALIGN(dptr + ch[C_FILESIZE], 4);
>   ....
>   *offset = (long)nptr - (long)data;	/* data is the cpio file */
> 
> @offset is the offset of the next file, not the matching file itself.
> This is confused and may cause unnecessary waste of time to debug.
> So fix it.
> 
> v1 -> v2:
> As tj suggested, rename @offset to @nextoff which is more clear to
> users. And also adjust the new comments.
> 
> Signed-off-by: Tang Chen <tangchen@...fujitsu.com>
> Reviewed-by: Zhang Yanfei <zhangyanfei@...fujitsu.com>
> ---
>  lib/earlycpio.c |   27 ++++++++++++++-------------
>  1 files changed, 14 insertions(+), 13 deletions(-)
> 
> diff --git a/lib/earlycpio.c b/lib/earlycpio.c
> index 8078ef4..7affac0 100644
> --- a/lib/earlycpio.c
> +++ b/lib/earlycpio.c
> @@ -49,22 +49,23 @@ enum cpio_fields {
>  
>  /**
>   * cpio_data find_cpio_data - Search for files in an uncompressed cpio
> - * @path:   The directory to search for, including a slash at the end
> - * @data:   Pointer to the the cpio archive or a header inside
> - * @len:    Remaining length of the cpio based on data pointer
> - * @offset: When a matching file is found, this is the offset to the
> - *          beginning of the cpio. It can be used to iterate through
> - *          the cpio to find all files inside of a directory path
> + * @path:       The directory to search for, including a slash at the end
> + * @data:       Pointer to the the cpio archive or a header inside
> + * @len:        Remaining length of the cpio based on data pointer
> + * @nextoff:    When a matching file is found, this is the offset from the
> + *              beginning of the cpio to the beginning of the next file, not the
> + *              matching file itself. It can be used to iterate through the cpio
> + *              to find all files inside of a directory path
>   *
> - * @return: struct cpio_data containing the address, length and
> - *          filename (with the directory path cut off) of the found file.
> - *          If you search for a filename and not for files in a directory,
> - *          pass the absolute path of the filename in the cpio and make sure
> - *          the match returned an empty filename string.
> + * @return:     struct cpio_data containing the address, length and
> + *              filename (with the directory path cut off) of the found file.
> + *              If you search for a filename and not for files in a directory,
> + *              pass the absolute path of the filename in the cpio and make sure
> + *              the match returned an empty filename string.
>   */
>  
>  struct cpio_data __cpuinit find_cpio_data(const char *path, void *data,

This patch does not apply cleanly.  It seems that your branch does not
have 0db0628d90125193280eabb501c94feaf48fa9ab.

Thanks,
-Toshi


> -					  size_t len,  long *offset)
> +					  size_t len,  long *nextoff)
>  {
>  	const size_t cpio_header_len = 8*C_NFIELDS - 2;
>  	struct cpio_data cd = { NULL, 0, "" };
> @@ -124,7 +125,7 @@ struct cpio_data __cpuinit find_cpio_data(const char *path, void *data,
>  		if ((ch[C_MODE] & 0170000) == 0100000 &&
>  		    ch[C_NAMESIZE] >= mypathsize &&
>  		    !memcmp(p, path, mypathsize)) {
> -			*offset = (long)nptr - (long)data;
> +			*nextoff = (long)nptr - (long)data;
>  			if (ch[C_NAMESIZE] - mypathsize >= MAX_CPIO_FILE_NAME) {
>  				pr_warn(
>  				"File %s exceeding MAX_CPIO_FILE_NAME [%d]\n",


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