linux-ext4 - Re: [PATCH v2 11/12] ext4: simplify i_state checks in __ext4_update_other_inode

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Date:   Mon, 11 Jan 2021 12:23:40 -0800
From:   Eric Biggers <ebiggers@...nel.org>
To:     Christoph Hellwig <hch@....de>
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>
Subject: Re: [PATCH v2 11/12] ext4: simplify i_state checks in
 __ext4_update_other_inode_time()

On Mon, Jan 11, 2021 at 11:53:42AM +0100, Christoph Hellwig wrote:
> On Fri, Jan 08, 2021 at 11:59:02PM -0800, Eric Biggers wrote:
> >  	if ((inode->i_state & (I_FREEING | I_WILL_FREE | I_NEW |
> > -			       I_DIRTY_INODE)) ||
> > -	    ((inode->i_state & I_DIRTY_TIME) == 0))
> > +			       I_DIRTY_TIME)) != I_DIRTY_TIME)
> >  		return;
> >  
> >  	spin_lock(&inode->i_lock);
> > -	if (((inode->i_state & (I_FREEING | I_WILL_FREE | I_NEW |
> > -				I_DIRTY_INODE)) == 0) &&
> > -	    (inode->i_state & I_DIRTY_TIME)) {
> > +	if ((inode->i_state & (I_FREEING | I_WILL_FREE | I_NEW |
> > +			       I_DIRTY_TIME)) == I_DIRTY_TIME) {
> 
> I think a descriptively named inline helper in fs.h would really improve
> this..

Do you want this even though it is specific to how ext4 opportunisticly updates
other inodes in the same inode block as the inode being updated?  That's the
only reason that I_FREEING|I_WILL_FREE|I_NEW need to be checked; everywhere else
justs want I_DIRTY_TIME.

We could add:

	static inline bool other_inode_has_dirtytime(struct inode *inode)
	{
		return (inode->state & (I_FREEING | I_WILL_FREE |
					I_NEW | I_DIRTY_TIME)) == I_DIRTY_TIME;
	}

But it seems a bit weird when it's specific to ext4 at the moment.

Are you thinking that other filesystems will implement the same sort of
opportunistic update, so we should add the helper now?

- Eric