[dm-devel] [PATCH] kpartx: Add -P option for partition scanning

[Benjamin Marzinski]

On Fri, Feb 11, 2022 at 12:41:48PM -0800, Ritika Srivastava wrote:
> Add -P, partition scanning option to kpartx which would set
> LO_FLAGS_PARTSCAN flag during loop device creation.
> This option is same as losetup -P option.

I'm confused here. What's the benefit of doing this? Doesn't this create
partition devices, just like kpartx would?

-Ben

> 
> Signed-off-by: Ritika Srivastava <ritika.srivastava at oracle.com>
> ---
>  kpartx/kpartx.c | 17 +++++++++++++----
>  kpartx/lopart.c |  5 ++++-
>  kpartx/lopart.h |  2 +-
>  3 files changed, 18 insertions(+), 6 deletions(-)
> 
> diff --git a/kpartx/kpartx.c b/kpartx/kpartx.c
> index 3c49999..a26d0a2 100644
> --- a/kpartx/kpartx.c
> +++ b/kpartx/kpartx.c
> @@ -87,7 +87,7 @@ initpts(void)
>  	addpts("ps3", read_ps3_pt);
>  }
>  
> -static char short_opts[] = "rladfgvp:t:snu";
> +static char short_opts[] = "rladfPgvp:t:snu";
>  
>  /* Used in gpt.c */
>  int force_gpt=0;
> @@ -98,7 +98,7 @@ static int
>  usage(void) {
>  	printf(VERSION_STRING);
>  	printf("Usage:\n");
> -	printf("  kpartx [-a|-d|-u|-l] [-r] [-p] [-f] [-g] [-s|-n] [-v] wholedisk\n");
> +	printf("  kpartx [-a|-d|-u|-l] [-r] [-p] [-f] [-g] [-s|-n] [-v] [-P] wholedisk\n");
>  	printf("\t-a add partition devmappings\n");
>  	printf("\t-r devmappings will be readonly\n");
>  	printf("\t-d del partition devmappings\n");
> @@ -110,6 +110,7 @@ usage(void) {
>  	printf("\t-v verbose\n");
>  	printf("\t-n nosync mode. Return before the partitions are created\n");
>  	printf("\t-s sync mode (Default). Don't return until the partitions are created\n");
> +	printf("\t-P create partitioned loop device\n");
>  	return 1;
>  }
>  
> @@ -228,7 +229,7 @@ xmalloc (size_t size) {
>  
>  int
>  main(int argc, char **argv){
> -	int i, j, m, n, op, off, arg, c, d, ro=0;
> +	int i, j, m, n, op, off, arg, c, d, ro=0, partscan = 0;
>  	int fd = -1;
>  	struct slice all;
>  	struct pt *ptp;
> @@ -311,6 +312,9 @@ main(int argc, char **argv){
>  		case 'u':
>  			what = UPDATE;
>  			break;
> +		case 'P':
> +			partscan = 1;
> +			break;
>  		default:
>  			usage();
>  			exit(1);
> @@ -328,6 +332,11 @@ main(int argc, char **argv){
>  		exit(1);
>  	}
>  
> +	if (what != ADD && partscan == 1)       {
> +		printf("-P option is allowed only during loop device setup\n");
> +		exit(1);
> +	}
> +
>  	if (hotplug) {
>  		/* already got [disk]device */
>  	} else if (optind == argc-2) {
> @@ -359,7 +368,7 @@ main(int argc, char **argv){
>  			exit (0);
>  
>  		if (!loopdev) {
> -			if (set_loop(&loopdev, rpath, 0, &ro)) {
> +			if (set_loop(&loopdev, rpath, 0, &ro, partscan)) {
>  				fprintf(stderr, "can't set up loop\n");
>  				exit (1);
>  			}
> diff --git a/kpartx/lopart.c b/kpartx/lopart.c
> index 512a59f..9a1ce48 100644
> --- a/kpartx/lopart.c
> +++ b/kpartx/lopart.c
> @@ -233,7 +233,8 @@ no_loop_fd:
>  	return NULL;
>  }
>  
> -int set_loop(char **device, const char *file, int offset, int *loopro)
> +int set_loop(char **device, const char *file, int offset, int *loopro,
> +	     int partscan)
>  {
>  	struct loop_info loopinfo;
>  	int fd = -1, ret = 1, ffd, mode;
> @@ -264,6 +265,8 @@ int set_loop(char **device, const char *file, int offset, int *loopro)
>  	loopinfo.lo_offset = offset;
>  	loopinfo.lo_encrypt_type = LO_CRYPT_NONE;
>  	loopinfo.lo_encrypt_key_size = 0;
> +	if (partscan == 1)
> +		loopinfo.lo_flags |= LO_FLAGS_PARTSCAN;
>  
>  	if (ioctl(fd, LOOP_SET_FD, (void*)(uintptr_t)(ffd)) < 0) {
>  		perror ("ioctl: LOOP_SET_FD");
> diff --git a/kpartx/lopart.h b/kpartx/lopart.h
> index c73ab23..81534e2 100644
> --- a/kpartx/lopart.h
> +++ b/kpartx/lopart.h
> @@ -1,4 +1,4 @@
>  extern int verbose;
> -extern int set_loop (char **, const char *, int, int *);
> +extern int set_loop (char **, const char *, int, int *, int);
>  extern int del_loop (const char *);
>  extern char * find_loop_by_file (const char *);
> -- 
> 2.27.0
> 
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