linux-ext4 - Re: [PATCH v3 2/3] fs: record I_DIRTY_TIME even if inode already has I_DIRTY

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Date:   Fri, 12 Aug 2022 11:01:35 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     Lukas Czerner <lczerner@...hat.com>
Cc:     linux-ext4@...r.kernel.org, tytso@....edu, jlayton@...nel.org,
        jack@...e.cz, linux-fsdevel@...r.kernel.org, david@...morbit.com,
        Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH v3 2/3] fs: record I_DIRTY_TIME even if inode already has
 I_DIRTY_INODE

On Fri, Aug 12, 2022 at 02:37:26PM +0200, Lukas Czerner wrote:
> Fix it by allowing I_DIRTY_TIME to be set even if the inode already has
> I_DIRTY_INODE.

How can this be reconciled with the below code in __mark_inode_dirty(), which
this patch doesn't touch?

	/* I_DIRTY_INODE supersedes I_DIRTY_TIME. */
	flags &= ~I_DIRTY_TIME;

Also inode_is_dirtytime_only(), which I thought I mentioned before:

	/*
	 * Returns true if the given inode itself only has dirty timestamps (its pages
	 * may still be dirty) and isn't currently being allocated or freed.
	 * Filesystems should call this if when writing an inode when lazytime is
	 * enabled, they want to opportunistically write the timestamps of other inodes
	 * located very nearby on-disk, e.g. in the same inode block.  This returns true
	 * if the given inode is in need of such an opportunistic update.  Requires
	 * i_lock, or at least later re-checking under i_lock.
	 */
	static inline bool inode_is_dirtytime_only(struct inode *inode)
	{
		return (inode->i_state & (I_DIRTY_TIME | I_NEW |
					I_FREEING | I_WILL_FREE)) == I_DIRTY_TIME;
	}

- Eric