Re: [PATCH 2/3] xfs: drop IDONTCACHE on inodes when we mark them sick

[Carlos Maiolino <cmaiolino@redhat.com>]

Hi,

On Sun, Jun 06, 2021 at 10:54:17AM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@kernel.org>
> 
> When we decide to mark an inode sick, clear the DONTCACHE flag so that
> the incore inode will be kept around until memory pressure forces it out
> of memory.  This increases the chances that the sick status will be
> caught by someone compiling a health report later on.
> 
> Signed-off-by: Darrick J. Wong <djwong@kernel.org>

The patch looks ok, so you can add:

Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>


Now, I have a probably dumb question about this.

by removing the I_DONTCACHE flag, as you said, we are increasing the chances
that the sick status will be caught, so, in either case, it seems not reliable.
So, my dumb question is, is there reason having these inodes around will benefit
us somehow? I haven't read the whole code, but I assume, it can be used as a
fast path while scrubbing the FS?

Cheers.

> ---
>  fs/xfs/xfs_health.c |    9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> 
> diff --git a/fs/xfs/xfs_health.c b/fs/xfs/xfs_health.c
> index 8e0cb05a7142..806be8a93ea3 100644
> --- a/fs/xfs/xfs_health.c
> +++ b/fs/xfs/xfs_health.c
> @@ -231,6 +231,15 @@ xfs_inode_mark_sick(
>  	ip->i_sick |= mask;
>  	ip->i_checked |= mask;
>  	spin_unlock(&ip->i_flags_lock);
> +
> +	/*
> +	 * Keep this inode around so we don't lose the sickness report.  Scrub
> +	 * grabs inodes with DONTCACHE assuming that most inode are ok, which
> +	 * is not the case here.
> +	 */
> +	spin_lock(&VFS_I(ip)->i_lock);
> +	VFS_I(ip)->i_state &= ~I_DONTCACHE;
> +	spin_unlock(&VFS_I(ip)->i_lock);
>  }
>  
>  /* Mark parts of an inode healed. */
> 

-- 
Carlos