linux-lvm.redhat.com archive mirror
 help / color / mirror / Atom feed
From: "heming.zhao@suse.com" <heming.zhao@suse.com>
To: LVM general discussion and development <linux-lvm@redhat.com>,
	Zhong Lidong <lidong.zhong@suse.com>
Cc: David Teigland <teigland@redhat.com>,
	agk@redhat.com, Zdenek Kabelac <zkabelac@redhat.com>
Subject: Re: [linux-lvm] [RFC PATCH] lvconvert: fix the size of log device when converting, from linear to mirror
Date: Thu, 15 Jul 2021 03:42:14 +0800	[thread overview]
Message-ID: <55eeddda-7190-5279-bd78-993c10dffd35@suse.com> (raw)
In-Reply-To: <177d20e6-71d1-37ff-f2af-59673e9cba09@suse.com>

Hello,

This patch looks good to me.

I give a little more explain.

Scenario:
there is a "--type mirror" LV with two legs: one leg is linear dev, another leg is striped devs.

the disks (LV) layout:
```
# lsblk
NAME               MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda                  8:0    0  200M  0 disk
└─vg1-lv1_mimage_0 254:4    0   96M  0 lvm
   └─vg1-lv1        254:2    0   96M  0 lvm
sdb                  8:16   0  200M  0 disk
└─vg1-lv1_mimage_1 254:5    0   96M  0 lvm
   └─vg1-lv1        254:2    0   96M  0 lvm
sdc                  8:32   0  200M  0 disk
└─vg1-lv1_mimage_1 254:5    0   96M  0 lvm
   └─vg1-lv1        254:2    0   96M  0 lvm
sdd                  8:48   0  200M  0 disk
├─vg1-lv1_mlog     254:3    0    4M  0 lvm
│ └─vg1-lv1        254:2    0   96M  0 lvm
└─vg1-lv1_mimage_1 254:5    0   96M  0 lvm
   └─vg1-lv1        254:2    0   96M  0 lvm

# dmsetup table
vg1-lv1: 0 196608 mirror disk 2 254:3 2048 2 254:4 0 254:5 0 1 handle_errors
vg1-lv1_mlog: 0 8192 linear 8:48 73728
vg1-lv1_mimage_1: 0 196608 striped 3 512 8:16 8192 8:32 8192 8:48 8192
vg1-lv1_mimage_0: 0 196608 linear 8:0 8192
```

Present lvm algorithm: "whole one leg size" / "striped devices number". (96MB / 3)
But kernel side dm-log module doesn't div "striped devices number". (96MB)
The kernel side algorithm is correct.
Let's image, in top layer, mirrored LV only know it has two same legs, disk log only related top
layer write IO.


It looks lvm2 algoritm is wrong from the first commit:
```
commit 16d9293bd7205c6ad2e932225aafca7513e540d9
Author: Alasdair Kergon <agk@redhat.com>
Date:   Mon Mar 1 20:00:20 2010 +0000

     Extend core allocation code in preparation for mirrored log areas.
```


The "--type mirror" is marked as deprecated many years ago. Does it block this patch to be accepted?

Maybe I miss somethings for the related code in lvm2 function _alloc_init()?

```_alloc_init@lib/metadata/lv_manip.c

     } else { //the "else" branch suites for other LV types except for "mirror"?
         ah->log_area_count = metadata_area_count;
         ah->log_len = !metadata_area_count ? 0 :
             _mirror_log_extents(ah->region_size, extent_size,
                         (existing_extents + new_extents) / ah->area_multiple);
     }

```

Thanks
Heming

On 7/6/21 10:57 AM, Zhong Lidong wrote:
> When converting a large linear device to mirror with --stripes parameter
> in lvconvert command, it will report the following error:
> 
> ioctl/libdm-iface.c:1895    device-mapper: reload ioctl on  (254:0)
> failed: Invalid argument
> 
> and the related kernel messages:
> 
> kernel: [ 2290.698171] device-mapper: dirty region log: log device 254:1
> too small: need 7078912 bytes
> kernel: [ 2290.698248] device-mapper: table: 254:0: mirror: Error
> creating mirror dirty log
> kernel: [ 2290.698251] device-mapper: ioctl: error adding target to table
> 
> Steps to reproduce this problem
> ~$:pvs
>    PV         VG Fmt  Attr PSize  PFree
>    /dev/loop0 vg lvm2 a--  10.00t 10.00t
>    /dev/loop1 vg lvm2 a--  10.00t 10.00t
>    /dev/loop2 vg lvm2 a--  10.00t 10.00t
>    /dev/loop3    lvm2 ---  10.00t 10.00t
>    /dev/loop4    lvm2 ---  10.00t 10.00t
>    /dev/loop5    lvm2 ---  10.00t 10.00t
> 
> ~$:lvcreate -nlv  -L27T vg
>    Logical volume "lv" created.
> 
> ~$:vgextend vg /dev/loop[3-5]
>    Volume group "vg" successfully extended
> 
> ~$:lvconvert  --type mirror --mirrors 1 --stripes 3 -I256  /dev/vg/lv
> /dev/loop3 /dev/loop4 /dev/loop5
>    device-mapper: reload ioctl on  (254:0) failed: Invalid argument
>    Failed to lock logical volume vg/lv.
> ~$: lvs
>    WARNING: Reading VG vg from disk because lvmetad metadata is invalid.
>    LV      VG Attr       LSize  Pool Origin Data%  Meta%  Move Log
> Cpy%Sync Convert
>    lv      vg -wi-a----- 27.00t
>    lv_mlog vg -wi-a-----  4.00m
> ~$: pvs
>    PV         VG Fmt  Attr PSize  PFree
>    /dev/loop0 vg lvm2 a--  10.00t     0
>    /dev/loop1 vg lvm2 a--  10.00t     0
>    /dev/loop2 vg lvm2 a--  10.00t  3.00t
>    /dev/loop3 vg lvm2 a--  10.00t 10.00t
>    /dev/loop4 vg lvm2 a--  10.00t 10.00t
>    /dev/loop5 vg lvm2 a--  10.00t 10.00t
> 
> Analysis: In kernel space the required log size depends on the whole
> target device size.But in user space, the log size is calculated from
> the whole target devices size divided by allocation area number, which
> leads to the mismatch here.
> 
> Signed-off-by: Lidong Zhong <lidong.zhong@suse.com>
> ---
>   lib/metadata/lv_manip.c | 3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/lib/metadata/lv_manip.c b/lib/metadata/lv_manip.c
> index 7e66afd9c..e8d67c79b 100644
> --- a/lib/metadata/lv_manip.c
> +++ b/lib/metadata/lv_manip.c
> @@ -3730,8 +3730,7 @@ static struct alloc_handle *_alloc_init(struct
> cmd_context *cmd,
>   	} else {
>   		ah->log_area_count = metadata_area_count;
>   		ah->log_len = !metadata_area_count ? 0 :
> -			_mirror_log_extents(ah->region_size, extent_size,
> -					    (existing_extents + new_extents) / ah->area_multiple);
> +			_mirror_log_extents(ah->region_size, extent_size, existing_extents +
> new_extents);
>   	}
> 
>   	if (total_extents || existing_extents)
> 


_______________________________________________
linux-lvm mailing list
linux-lvm@redhat.com
https://listman.redhat.com/mailman/listinfo/linux-lvm
read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

  reply	other threads:[~2021-07-14 19:43 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-06  2:57 Zhong Lidong
2021-07-14 19:42 ` heming.zhao [this message]
2021-07-07  3:20 [linux-lvm] [RFC PATCH] lvconvert: fix the size of log device when converting " Zhong Lidong

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=55eeddda-7190-5279-bd78-993c10dffd35@suse.com \
    --to=heming.zhao@suse.com \
    --cc=agk@redhat.com \
    --cc=lidong.zhong@suse.com \
    --cc=linux-lvm@redhat.com \
    --cc=teigland@redhat.com \
    --cc=zkabelac@redhat.com \
    --subject='Re: [linux-lvm] [RFC PATCH] lvconvert: fix the size of log device when converting, from linear to mirror' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).