linux-ext4 - Re: [PATCH 7/9] e2scrub_all: make sure there's enough free space for a snapshot

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Date:   Thu, 21 Mar 2019 12:18:56 +0100
From:   Lukas Czerner <lczerner@...hat.com>
To:     Theodore Ts'o <tytso@....edu>
Cc:     Ext4 Developers List <linux-ext4@...r.kernel.org>,
        darrick.wong@...cle.com
Subject: Re: [PATCH 7/9] e2scrub_all: make sure there's enough free space for
 a snapshot

On Wed, Mar 20, 2019 at 10:02:16PM -0400, Theodore Ts'o wrote:
> If there isn't, skip the volume so we don't spam the system
> administrator with error messages.  It's quite commkon that there is
> is zero free space in the volume group.
> 
> Addresses-Debian-Bug: #924301
> 
> Signed-off-by: Theodore Ts'o <tytso@....edu>
> ---
>  scrub/e2scrub_all.in | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/scrub/e2scrub_all.in b/scrub/e2scrub_all.in
> index 8bc868aa0..4cb90a0de 100644
> --- a/scrub/e2scrub_all.in
> +++ b/scrub/e2scrub_all.in
> @@ -21,6 +21,7 @@
>  PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
>  
>  scrub_all=0
> +snap_size_mb=256
>  conffile="@root_sysconfdir@...scrub.conf"
>  
>  test -f "${conffile}" && . "${conffile}"
> @@ -108,6 +109,9 @@ ls_scrub_targets() {
>  		eval "${lvm_vars}"
>  		echo "${LVM2_LV_ROLE}" | grep -q "snapshot" && continue
>  
> +		free_space="$(vgs -o vg_free --units m --noheadings --no-suffix "${LVM2_VG_NAME}" 2> /dev/null | sed -e 's/\..*//')"
> +		test "${snap_size_mb}" -gt "${free_space}" && continue

So you're going to be calling vgs for every lvs even though you can have
a whole bunch of them in the same vg. That's not very efficient.

You can just filter it out with the lvs at the start of the loop by
adding the proper select string.

-S vg_free\>${snap_size_mb}

-Lukas


> +
>  		if [ -n "${MOUNTPOINT}" ]; then
>  			echo "${MOUNTPOINT}"
>  		else
> -- 
> 2.19.1
>