[Devel] [PATCH RH8] config: enable BCACHE as a module

[Konstantin Khorenko]

i'm not going to apply this patch (i.e. enable BCACHE by default in vz8 kernel),
reasons:

* in vz7 (RHEL 7) kernel bcache does not work very good (read - does not work in "writeback" mode at all, the fs corrupts quite soon)

* in RHEL8 bcache is still disabled in kernel which means RedHat does not test it and as we also do not test it
   => it's a bad idea to give an untested gun, we can easily get many legs hurt.

* RedHat recommends "lvmcache" as a similar technology and supports it
   https://access.redhat.com/solutions/72133

--
Best regards,

Konstantin Khorenko,
Virtuozzo Linux Kernel Team

On 04/15/2021 10:58 AM, Andrey Zhadchenko wrote:
> From: Konstantin Khorenko <khorenko at virtuozzo.com>
>
> There are requests for bcache driver inclusion,
> local tests show that fsstress does not hurt the node
> with bcache configured => let's try once more to enable it
> and proceed with serious QA.
>
> https://jira.sw.ru/browse/PSBM-55594
> https://jira.sw.ru/browse/PSBM-79461
>
> Signed-off-by: Konstantin Khorenko <khorenko at virtuozzo.com>
>
> (cherry picked from 6259f9ebd0f2b89afd77203b6c904d730c9875cb)
> Signed-off-by: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>
> ---
>  configs/kernel-4.18.0-x86_64-debug.config | 5 +++++
>  configs/kernel-4.18.0-x86_64.config       | 5 +++++
>  2 files changed, 10 insertions(+)
>
> diff --git a/configs/kernel-4.18.0-x86_64-debug.config b/configs/kernel-4.18.0-x86_64-debug.config
> index 9f326c7..e4810cb 100644
> --- a/configs/kernel-4.18.0-x86_64-debug.config
> +++ b/configs/kernel-4.18.0-x86_64-debug.config
> @@ -7811,6 +7811,11 @@ CONFIG_OVERLAY_FS_NFS_EXPORT=y
>  CONFIG_PANIC_ON_OOPS=y
>  CONFIG_PANIC_ON_OOPS_VALUE=1
>
> +CONFIG_BCACHE=m
> +# CONFIG_BCACHE_DEBUG is not set
> +# CONFIG_BCACHE_EDEBUG is not set
> +# CONFIG_BCACHE_CLOSURES_DEBUG is not set
> +
>  #
>  # OpenVZ
>  #
> diff --git a/configs/kernel-4.18.0-x86_64.config b/configs/kernel-4.18.0-x86_64.config
> index 0b16635..d1c9a3a 100644
> --- a/configs/kernel-4.18.0-x86_64.config
> +++ b/configs/kernel-4.18.0-x86_64.config
> @@ -7763,6 +7763,11 @@ CONFIG_DEFAULT_MMAP_MIN_ADDR=69632
>  CONFIG_OVERLAY_FS_INDEX=y
>  CONFIG_OVERLAY_FS_NFS_EXPORT=y
>
> +CONFIG_BCACHE=m
> +# CONFIG_BCACHE_DEBUG is not set
> +# CONFIG_BCACHE_EDEBUG is not set
> +# CONFIG_BCACHE_CLOSURES_DEBUG is not set
> +
>  #
>  # OpenVZ
>  #
>