Re: [PATCH mdadm v2] super1: report truncated device

[Mariusz Tkaczyk <mariusz.tkaczyk@linux.intel.com>]

Hi Neil,

On Wed, 13 Jul 2022 13:48:11 +1000
"NeilBrown" <neilb@suse.de> wrote:

> When the metadata is at the start of the device, it is possible that it
> describes a device large than the one it is actually stored on.  When
> this happens, report it loudly in --examine.
> 
> ....
>    Unused Space : before=1968 sectors, after=-2047 sectors DEVICE TOO SMALL
>           State : clean TRUNCATED DEVICE
> ....

State : clean TRUNCATED DEVICE is enough. "DEVICE TOO SMALL" seems to be
redundant.
> 
> Also report in --assemble so that the failure which the kernel will
> report will be explained.

Understand but you've added it in load_super1() so it affects all load_super()
calls, is it indented? I assume yes but please confirm. 
> 
> mdadm: Device /dev/sdb is not large enough for data described in superblock
> mdadm: no RAID superblock on /dev/sdb
> mdadm: /dev/sdb has no superblock - assembly aborted
> 
> Scenario can be demonstrated as follows:
> 
> mdadm: Note: this array has metadata at the start and
>     may not be suitable as a boot device.  If you plan to
>     store '/boot' on this device please ensure that
>     your boot-loader understands md/v1.x metadata, or use
>     --metadata=0.90
> mdadm: Defaulting to version 1.2 metadata
> mdadm: array /dev/md/test started.
> mdadm: stopped /dev/md/test
>    Unused Space : before=1968 sectors, after=-2047 sectors DEVICE TOO SMALL
>           State : clean TRUNCATED DEVICE
>    Unused Space : before=1968 sectors, after=-2047 sectors DEVICE TOO SMALL
>           State : clean TRUNCATED DEVICE
> 
> Signed-off-by: NeilBrown <neilb@suse.de>
> ---
>  super1.c | 34 +++++++++++++++++++++++++++-------
>  1 file changed, 27 insertions(+), 7 deletions(-)
> 
> diff --git a/super1.c b/super1.c
> index 71af860c0e3e..4d8dba8a5a44 100644
> --- a/super1.c
> +++ b/super1.c
> @@ -406,12 +406,18 @@ static void examine_super1(struct supertype *st, char
> *homehost) 
>  	st->ss->getinfo_super(st, &info, NULL);
>  	if (info.space_after != 1 &&
> -	    !(__le32_to_cpu(sb->feature_map) & MD_FEATURE_NEW_OFFSET))
> -		printf("   Unused Space : before=%llu sectors, after=%llu
> sectors\n",
> -		       info.space_before, info.space_after);
> -
> -	printf("          State : %s\n",
> -	       (__le64_to_cpu(sb->resync_offset)+1)? "active":"clean");
> +	    !(__le32_to_cpu(sb->feature_map) & MD_FEATURE_NEW_OFFSET)) {
> +		printf("   Unused Space : before=%llu sectors, ",
> +		       info.space_before);
> +		if (info.space_after < INT64_MAX)
> +			printf("after=%llu sectors\n", info.space_after);
> +		else
> +			printf("after=-%llu sectors DEVICE TOO SMALL\n",
> +			       UINT64_MAX - info.space_after);
As above, for me this else here is not necessary.

> +	}
> +	printf("          State : %s%s\n",
> +	       (__le64_to_cpu(sb->resync_offset)+1)? "active":"clean",
> +	       info.space_after > INT64_MAX ? " TRUNCATED DEVICE" : "");

Could you use standard if instruction to make the code more readable? We are
avoiding ternary operators if possible now.

>  	printf("    Device UUID : ");
>  	for (i=0; i<16; i++) {
>  		if ((i&3)==0 && i != 0)
> @@ -2206,6 +2212,7 @@ static int load_super1(struct supertype *st, int fd,
> char *devname) tst.ss = &super1;
>  		for (tst.minor_version = 0; tst.minor_version <= 2;
>  		     tst.minor_version++) {
> +			tst.ignore_hw_compat = st->ignore_hw_compat;
>  			switch(load_super1(&tst, fd, devname)) {
>  			case 0: super = tst.sb;
>  				if (bestvers == -1 ||
> @@ -2312,7 +2319,6 @@ static int load_super1(struct supertype *st, int fd,
> char *devname) free(super);
>  		return 2;
>  	}
> -	st->sb = super;
>  
>  	bsb = (struct bitmap_super_s *)(((char*)super)+MAX_SB_SIZE);
>  
> @@ -2322,6 +2328,20 @@ static int load_super1(struct supertype *st, int fd,
> char *devname) if (st->data_offset == INVALID_SECTORS)
>  		st->data_offset = __le64_to_cpu(super->data_offset);
>  
> +	if (st->minor_version >= 1 &&
> +	    st->ignore_hw_compat == 0 &&
> +	    (__le64_to_cpu(super->data_offset) +
> +	     __le64_to_cpu(super->size) > dsize ||
> +	     __le64_to_cpu(super->data_offset) +
> +	     __le64_to_cpu(super->data_size) > dsize)) {
> +		if (devname)
> +			pr_err("Device %s is not large enough for data
> described in superblock\n",
> +			       devname);

why not just:
if (__le64_to_cpu(super->data_offset) + __le64_to_cpu(super->data_size) > dsize)
from my understanding, only this check matters.

Thanks,
Mariusz