linux-kernel - Re: [PATCH] ext4: deaccount delayed allocations at freeing inode in ext4_evict

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Message-Id: <20191108020827.15D1EAE056@d06av26.portsmouth.uk.ibm.com>
Date:   Fri, 8 Nov 2019 07:38:26 +0530
From:   Ritesh Harjani <riteshh@...ux.ibm.com>
To:     Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        linux-ext4@...r.kernel.org, "Theodore Ts'o" <tytso@....edu>,
        linux-kernel@...r.kernel.org
Cc:     Dmitry Monakhov <dmtrmonakhov@...dex-team.ru>,
        Eric Whitney <enwlinux@...il.com>
Subject: Re: [PATCH] ext4: deaccount delayed allocations at freeing inode in
 ext4_evict_inode()



On 10/29/19 12:47 PM, Konstantin Khlebnikov wrote:
> If inode->i_blocks is zero then ext4_evict_inode() skips ext4_truncate().
> Delayed allocation extents are freed later in ext4_clear_inode() but this
> happens when quota reference is already dropped. This leads to leak of
> reserved space in quota block, which disappears after umount-mount.
> 
> This seems broken for a long time but worked somehow until recent changes
> in delayed allocation.

Sorry, I may have missed it, but could you please help understand
what recent changes in delayed allocation make this break or worse?


A silly query, since I couldn't figure it out. Maybe the code has been
there ever since like this:-
So why can't we just move drop_dquot later after the 
ext4_es_remove_extent() (in function ext4_clear_inode)? Any known
problems around that?

-ritesh


> 
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
> ---
>   fs/ext4/inode.c |    9 +++++++++
>   1 file changed, 9 insertions(+)
> 
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 516faa280ced..580898145e8f 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -293,6 +293,15 @@ void ext4_evict_inode(struct inode *inode)
>   				   inode->i_ino, err);
>   			goto stop_handle;
>   		}
> +	} else if (EXT4_I(inode)->i_reserved_data_blocks) {
> +		/* Deaccount reserve if inode has only delayed allocations. */
> +		err = ext4_es_remove_extent(inode, 0, EXT_MAX_BLOCKS);
> +		if (err) {
> +			ext4_warning(inode->i_sb,
> +				     "couldn't remove extents %lu (err %d)",
> +				     inode->i_ino, err);
> +			goto stop_handle;
> +		}
>   	}
> 
>   	/* Remove xattr references. */
>