Bug#574863: [PATCH] Updated fix for Debian Bug#574863: boot failure with lvm2 and snapshot volumes

[sean finney]

and here is a slightly updated patch.  there is no functional change in the
code, i have only reformatted the whitespace etc so that the code matches
with the style of the surrounding code.

i have also tested this now on my primary testing system and haven't
noticed any problems.


	sean

On Thu, Jun 03, 2010 at 12:41:32AM +0200, sean finney wrote:
> okay, I think the attached patch should fix the problem.
> 
> I haven't tested it thoroughly, though my system does boot.  It seems
> there may be a seperate issue with os-prober that results in some junk
> entries being added to grub.conf if the snapshot volumes happen to be
> root filesystems, but that probably needs to be taken up seperately and
> the critical aspect of the bug is fixed anyway.
> 
> 
> 	sean

> Author: Sean Finney <seanius at debian.org>
> Description: Fix for lvm2 parsing failures with snapshot logical volumes
> 
> This patch prevents the lvm2 parsing code from prematurely aborting
> when encountering LV and segment metadata related to snapshot volumes.
> Instead, the parser will now skip over these as if it never saw them,
> which is probably the safest thing to do without a major injection of
> lvm2 support code.
> 
> Bug-Debian: #574863
> --- disk/lvm.c	2010-04-27 15:25:12 +0000
> +++ disk/lvm.c	2010-06-02 22:12:58 +0000
> @@ -420,9 +420,11 @@
>  	  /* And add all the lvs to the volume group. */
>  	  while (1)
>  	    {
> -	      int s;
> +	      int s, skip_lv = 0, status_visible = 0;
>  	      struct grub_lvm_lv *lv;
>  	      struct grub_lvm_segment *seg;
> +	      char *status = NULL, *status_end = NULL;
> +	      grub_size_t status_len = 0;
>  
>  	      while (grub_isspace (*p))
>  		p++;
> @@ -431,6 +433,8 @@
>  		break;
>  
>  	      lv = grub_malloc (sizeof (*lv));
> +		skip_lv = 0; /*Flag to skip snapshots */
> +		status_visible = 0; /*Flag to skip non-visible LV's */
>  
>  	      q = p;
>  	      while (*q != ' ')
> @@ -445,6 +449,25 @@
>  
>  	      lv->size = 0;
>  
> +		/* read LV status and ignore ones not listed as "VISIBLE" */
> +		p = grub_strstr (p, "status = ");
> +		if (p == NULL)
> +			goto lvs_fail;
> +		status_end = grub_strchr(p, ']');
> +		if (status_end == NULL)
> +			goto lvs_fail;
> +		status_len = (status_end - p) + 1;
> +		status = grub_malloc(status_len + 1);
> +		if (status == NULL)
> +			goto lvs_fail;
> +		grub_memcpy(status, p, status_len);
> +		status[status_len] = '\0';
> +		if (grub_strstr(status, "VISIBLE") != NULL)
> +			status_visible = 1;
> +		grub_free(status);
> +		if (!status_visible)
> +			goto lv_parsed;  /* don't bother parsing this one */
> +
>  	      lv->segment_count = grub_lvm_getvalue (&p, "segment_count = ");
>  	      if (p == NULL)
>  		goto lvs_fail;
> @@ -465,6 +488,18 @@
>  		  seg->extent_count = grub_lvm_getvalue (&p, "extent_count = ");
>  		  if (p == NULL)
>  		    goto lvs_segment_fail;
> +
> +			/* Skip LV's that have snapshot segments */
> +			p = grub_strstr (p, "type = ");
> +			if (p == NULL)
> +				goto lvs_segment_fail;
> +			p += sizeof("type = ") - 1;
> +			if (!grub_strncmp(p, "\"snapshot\"", 10)) {
> +				/* Found a snapshot, give up and move on */
> +				skip_lv=1;
> +				break;
> +			}
> +
>  		  seg->stripe_count = grub_lvm_getvalue (&p, "stripe_count = ");
>  		  if (p == NULL)
>  		    goto lvs_segment_fail;
> @@ -531,12 +566,19 @@
>  		  goto fail4;
>  		}
>  
> +	    lv_parsed: /* all done with parsing this LV, seek to the end */
>  	      if (p != NULL)
>  		p = grub_strchr (p, '}');
>  	      if (p == NULL)
>  		goto lvs_fail;
>  	      p += 3;
>  
> +		if (skip_lv || ! status_visible) {
> +			grub_free (lv->name);
> +			grub_free (lv);
> +			continue;
> +		}
> +
>  	      lv->number = lv_count++;
>  	      lv->vg = vg;
>  	      lv->next = vg->lvs;
> 




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