linux-kernel - Re: [PATCH] btrfs: update target inode's ctime on unlink

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Message-ID: <cd06772c-b4be-4416-9f0f-6d849146ffe0@suse.com>
Date: Tue, 13 Aug 2024 08:57:04 +0930
From: Qu Wenruo <wqu@...e.com>
To: Jeff Layton <jlayton@...nel.org>, Chris Mason <clm@...com>,
 Josef Bacik <josef@...icpanda.com>, David Sterba <dsterba@...e.com>
Cc: linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org,
 bpf@...r.kernel.org
Subject: Re: [PATCH] btrfs: update target inode's ctime on unlink



在 2024/8/13 02:00, Jeff Layton 写道:
> Unlink changes the link count on the target inode. POSIX mandates that
> the ctime must also change when this occurs.
> 
> Signed-off-by: Jeff Layton <jlayton@...nel.org>

Reviewed-by: Qu Wenruo <wqu@...e.com>

And since we decreased the nlink of the target inode already, updating 
the timestamp will not cause extra COW overhead.

So this won't cause any extra performance penalty.

Thanks,
Qu

> ---
> Found using the nfstest_posix testsuite with knfsd exporting btrfs.
> ---
>   fs/btrfs/inode.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index 333b0e8587a2..b1b6564ab68f 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -4195,6 +4195,7 @@ static int __btrfs_unlink_inode(struct btrfs_trans_handle *trans,
>   
>   	btrfs_i_size_write(dir, dir->vfs_inode.i_size - name->len * 2);
>   	inode_inc_iversion(&inode->vfs_inode);
> +	inode_set_ctime_current(&inode->vfs_inode);
>   	inode_inc_iversion(&dir->vfs_inode);
>    	inode_set_mtime_to_ts(&dir->vfs_inode, inode_set_ctime_current(&dir->vfs_inode));
>   	ret = btrfs_update_inode(trans, dir);
> 
> ---
> base-commit: 7c626ce4bae1ac14f60076d00eafe71af30450ba
> change-id: 20240812-btrfs-unlink-77293421e416
> 
> Best regards,