[Devel] [PATCH RHEL7 COMMIT] fuse: skip invalidate_inode_pages2 on truncate

[Konstantin Khorenko]

Please consider to prepare a ReaddyKernel patch for it.

https://readykernel.com/

--
Best regards,

Konstantin Khorenko,
Virtuozzo Linux Kernel Team

On 10/31/2017 01:23 PM, Konstantin Khorenko wrote:
> The commit is pushed to "branch-rh7-3.10.0-693.1.1.vz7.37.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
> after rh7-3.10.0-693.1.1.vz7.37.20
> ------>
> commit aa06cce9cfe8e16c2f4c6c8a5f9c383e7567150f
> Author: Maxim Patlasov <mpatlasov at virtuozzo.com>
> Date:   Tue Oct 31 13:23:23 2017 +0300
>
>     fuse: skip invalidate_inode_pages2 on truncate
>
>     Using writeback mode in kernel fuse is safe only if we are sure that a file
>     cannot be modified externally while we write to it. But then it's useless
>     to invalidate page-cache in course of truncate: truncate_pagecache() shrinks
>     everything beyond new EOF and all remaining pages are valid as they used to
>     be before truncate operation.
>
>     Thank you to Alexey Kuznetsov for pointing out.
>
>     https://jira.sw.ru/browse/PSBM-76437
>     Signed-off-by: Maxim Patlasov <mpatlasov at virtuozzo.com>
> ---
>  fs/fuse/dir.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
> index c5ff349..79c78291 100644
> --- a/fs/fuse/dir.c
> +++ b/fs/fuse/dir.c
> @@ -1841,7 +1841,8 @@ int fuse_do_setattr(struct inode *inode, struct iattr *attr,
>  	if ((is_truncate || !is_wb) &&
>  			S_ISREG(inode->i_mode) && oldsize != outarg.attr.size) {
>  		truncate_pagecache(inode, outarg.attr.size);
> -		invalidate_inode_pages2(inode->i_mapping);
> +		if (!is_wb)
> +			invalidate_inode_pages2(inode->i_mapping);
>  	}
>
>  	clear_bit(FUSE_I_SIZE_UNSTABLE, &fi->state);
> .
>