linux-ext4 - Re: [PATCH v2 03/12] fs: only specify I_DIRTY_TIME when needed in generic_update

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Date:   Mon, 11 Jan 2021 15:50:29 +0100
From:   Jan Kara <jack@...e.cz>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     linux-fsdevel@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net,
        Theodore Ts'o <tytso@....edu>, Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v2 03/12] fs: only specify I_DIRTY_TIME when needed in
 generic_update_time()

On Fri 08-01-21 23:58:54, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@...gle.com>
> 
> generic_update_time() always passes I_DIRTY_TIME to
> __mark_inode_dirty(), which doesn't really make sense because (a)
> generic_update_time() might be asked to do only an i_version update, not
> also a timestamps update; and (b) I_DIRTY_TIME is only supposed to be
> set in i_state if the filesystem has lazytime enabled, so using it
> unconditionally in generic_update_time() is inconsistent.
> 
> As a result there is a weird edge case where if only an i_version update
> was requested (not also a timestamps update) but it is no longer needed
> (i.e. inode_maybe_inc_iversion() returns false), then I_DIRTY_TIME will
> be set in i_state even if the filesystem isn't mounted with lazytime.
> 
> Fix this by only passing I_DIRTY_TIME to __mark_inode_dirty() if the
> timestamps were updated and the filesystem has lazytime enabled.
> 
> Reviewed-by: Christoph Hellwig <hch@....de>
> Signed-off-by: Eric Biggers <ebiggers@...gle.com>

Looks good to me. You can add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza


> ---
>  fs/inode.c | 38 ++++++++++++++++++++------------------
>  1 file changed, 20 insertions(+), 18 deletions(-)
> 
> diff --git a/fs/inode.c b/fs/inode.c
> index 6442d97d9a4ab..d0fa43d8e9d5c 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -1743,24 +1743,26 @@ static int relatime_need_update(struct vfsmount *mnt, struct inode *inode,
>  
>  int generic_update_time(struct inode *inode, struct timespec64 *time, int flags)
>  {
> -	int iflags = I_DIRTY_TIME;
> -	bool dirty = false;
> -
> -	if (flags & S_ATIME)
> -		inode->i_atime = *time;
> -	if (flags & S_VERSION)
> -		dirty = inode_maybe_inc_iversion(inode, false);
> -	if (flags & S_CTIME)
> -		inode->i_ctime = *time;
> -	if (flags & S_MTIME)
> -		inode->i_mtime = *time;
> -	if ((flags & (S_ATIME | S_CTIME | S_MTIME)) &&
> -	    !(inode->i_sb->s_flags & SB_LAZYTIME))
> -		dirty = true;
> -
> -	if (dirty)
> -		iflags |= I_DIRTY_SYNC;
> -	__mark_inode_dirty(inode, iflags);
> +	int dirty_flags = 0;
> +
> +	if (flags & (S_ATIME | S_CTIME | S_MTIME)) {
> +		if (flags & S_ATIME)
> +			inode->i_atime = *time;
> +		if (flags & S_CTIME)
> +			inode->i_ctime = *time;
> +		if (flags & S_MTIME)
> +			inode->i_mtime = *time;
> +
> +		if (inode->i_sb->s_flags & SB_LAZYTIME)
> +			dirty_flags |= I_DIRTY_TIME;
> +		else
> +			dirty_flags |= I_DIRTY_SYNC;
> +	}
> +
> +	if ((flags & S_VERSION) && inode_maybe_inc_iversion(inode, false))
> +		dirty_flags |= I_DIRTY_SYNC;
> +
> +	__mark_inode_dirty(inode, dirty_flags);
>  	return 0;
>  }
>  EXPORT_SYMBOL(generic_update_time);
> -- 
> 2.30.0
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR