[linux-lvm] hard-lock seems to have caused serious LVM problems

[dmeyer at dmeyer.net]

Thanks to help from Jan Niehusmann, I have more information, now.
After applying this patch:

> The following patch from Jan (with a minor correction "against" segfaults :-)
> corrected the problem for me:
------------------------------------------------------------------------------
*** pv_read_all_pv_of_vg.c.orig	Mon Nov 20 03:47:20 2000
--- pv_read_all_pv_of_vg.c.patched	Sat Jan 13 18:31:00 2001
***************
*** 101,117 ****
        for ( p = 0; pv_tmp[p] != NULL; p++) {
           if ( strncmp ( pv_tmp[p]->vg_name, vg_name, NAME_LEN) == 0) {
              pv_this_sav = pv_this;
              if ( ( pv_this = realloc ( pv_this,
!                                        ( np + 2) * sizeof ( pv_t*))) == NULL) {
                 fprintf ( stderr, "realloc error in %s [line %d]\n",
                                   __FILE__, __LINE__);
                 ret = -LVM_EPV_READ_ALL_PV_OF_VG_MALLOC;
                 if ( pv_this_sav != NULL) free ( pv_this_sav);
                 goto pv_read_all_pv_of_vg_end;
              }
!             pv_this[np] = pv_tmp[p];
!             pv_this[np+1] = NULL;
!             np++;
           }
        }
  
--- 101,117 ----
        for ( p = 0; pv_tmp[p] != NULL; p++) {
           if ( strncmp ( pv_tmp[p]->vg_name, vg_name, NAME_LEN) == 0) {
              pv_this_sav = pv_this;
+ 	    if ( np < pv_tmp[p]->pv_number) np = pv_tmp[p]->pv_number;
              if ( ( pv_this = realloc ( pv_this,
!                                        ( np + 1) * sizeof ( pv_t*))) == NULL) {
                 fprintf ( stderr, "realloc error in %s [line %d]\n",
                                   __FILE__, __LINE__);
                 ret = -LVM_EPV_READ_ALL_PV_OF_VG_MALLOC;
                 if ( pv_this_sav != NULL) free ( pv_this_sav);
                 goto pv_read_all_pv_of_vg_end;
              }
! 	    pv_this[pv_tmp[p]->pv_number-1] = pv_tmp[p];
!             pv_this[np] = NULL;
           }
        }
  
vgscan stopped giving me an error.  Unfortunately, it stopped
mentioning my second VG (named misc_vg) at all :-(.

misc_vg has 5 PVs, /dev/{hdb1,hdb5,hdb6,sda1,sda2}.  It turns out,
vgscan was ignoring misc_vg because it didn't think all the PVs were
online.  It was reading the uuid list from /dev/sda1, and /dev/sda1
only had 4 PVs in it's uuid list.  Commenting out the block of code in
pv_read_all_pv_of_vg.c that starts with "if (uuids > 0) {" fixes the
problem, though I kind of doubt that it's the right fix.

Does the following seem right?
# pvdata -U /dev/hdb1 /dev/hdb5 /dev/hdb6 /dev/sda1 /dev/sda2
--- List of physical volume UUIDs ---

000: pXMXm8FIECSb7mGPEIX3qVgQFbt21sKd
001: --- EMPTY ---
002: --- EMPTY ---
003: --- EMPTY ---
004: --- EMPTY ---
--- List of physical volume UUIDs ---

000: pXMXm8FIECSb7mGPEIX3qVgQFbt21sKd
001: efjtqFYhTIqyLO2cBURu5zN7rLJsG4dF
002: --- EMPTY ---
003: --- EMPTY ---
004: --- EMPTY ---
--- List of physical volume UUIDs ---

000: pXMXm8FIECSb7mGPEIX3qVgQFbt21sKd
001: efjtqFYhTIqyLO2cBURu5zN7rLJsG4dF
002: 931SNJ6F66g3n3qA9Nts3r4jqe4TOHW8
003: --- EMPTY ---
004: --- EMPTY ---
--- List of physical volume UUIDs ---

000: pXMXm8FIECSb7mGPEIX3qVgQFbt21sKd
001: efjtqFYhTIqyLO2cBURu5zN7rLJsG4dF
002: 931SNJ6F66g3n3qA9Nts3r4jqe4TOHW8
003: m2wuLpJ9AQmzXnbk4sCuQu8hjAev7pax
004: --- EMPTY ---
--- List of physical volume UUIDs ---

000: pXMXm8FIECSb7mGPEIX3qVgQFbt21sKd
001: efjtqFYhTIqyLO2cBURu5zN7rLJsG4dF
002: 931SNJ6F66g3n3qA9Nts3r4jqe4TOHW8
003: m2wuLpJ9AQmzXnbk4sCuQu8hjAev7pax
004: fdNejQ2DAp9A8KN0UrePxscwoY8vqVSu

Each PV only has the uuids from the PVs before it.  Should each PV
have the complete list of uuids in its VG (in which case there's
something screwy with my PVs)?  Or did pv_read_all_pv_of_vg somehow
pick the wrong PV to read the uuid list from?  Or something else?

     Dave