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From: "Theodore Ts'o" <tytso@mit.edu>
To: Christoph Hellwig <hch@lst.de>
Cc: Eric Biggers <ebiggers@kernel.org>,
	linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org,
	linux-ext4@vger.kernel.org,
	linux-f2fs-devel@lists.sourceforge.net
Subject: Re: [PATCH v2 11/12] ext4: simplify i_state checks in __ext4_update_other_inode_time()
Date: Wed, 3 Feb 2021 00:16:57 -0500	[thread overview]
Message-ID: <YBoxyQIdqRQT3jX5@mit.edu> (raw)
In-Reply-To: <20210112132521.GB13780@lst.de>

On Tue, Jan 12, 2021 at 02:25:21PM +0100, Christoph Hellwig wrote:
> > 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?
> 
> For my taste these checks for flags is way too much black magic and will
> trivially break when people add new flags.  So having a helper next to
> the definition of the I_* flags that is well documented would be very,
> very helpful.  My preferred naming would be something along the lines
> of 'inode_is_dirty_lazytime_only()'.

The name makes sense to me.  I'm not sure it's likely that there will
be new types of dirtiness --- as near I can tell the I_DIRTY_TIME was
the first time there has been any changes in a _really_ long time, but
I agree that how the flags interact (even before we added
I_DIRTY_TIME) involved no small amount of black magic, and it's the
kind of thing that requires deep meditation before trying to make any
changes, and then immediately slips out of one's L1 cache very shortly
afterwards.  :-)

					- Ted

WARNING: multiple messages have this Message-ID
From: "Theodore Ts'o" <tytso@mit.edu>
To: Christoph Hellwig <hch@lst.de>
Cc: Eric Biggers <ebiggers@kernel.org>,
	linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
	linux-xfs@vger.kernel.org,
	linux-f2fs-devel@lists.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH v2 11/12] ext4: simplify i_state checks in __ext4_update_other_inode_time()
Date: Wed, 3 Feb 2021 00:16:57 -0500	[thread overview]
Message-ID: <YBoxyQIdqRQT3jX5@mit.edu> (raw)
In-Reply-To: <20210112132521.GB13780@lst.de>

On Tue, Jan 12, 2021 at 02:25:21PM +0100, Christoph Hellwig wrote:
> > 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?
> 
> For my taste these checks for flags is way too much black magic and will
> trivially break when people add new flags.  So having a helper next to
> the definition of the I_* flags that is well documented would be very,
> very helpful.  My preferred naming would be something along the lines
> of 'inode_is_dirty_lazytime_only()'.

The name makes sense to me.  I'm not sure it's likely that there will
be new types of dirtiness --- as near I can tell the I_DIRTY_TIME was
the first time there has been any changes in a _really_ long time, but
I agree that how the flags interact (even before we added
I_DIRTY_TIME) involved no small amount of black magic, and it's the
kind of thing that requires deep meditation before trying to make any
changes, and then immediately slips out of one's L1 cache very shortly
afterwards.  :-)

					- Ted


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  reply	other threads:[~2021-02-03  5:18 UTC|newest]

Thread overview: 82+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-09  7:58 [PATCH v2 00/12] lazytime fix and cleanups Eric Biggers
2021-01-09  7:58 ` [f2fs-dev] " Eric Biggers
2021-01-09  7:58 ` [PATCH v2 01/12] fs: fix lazytime expiration handling in __writeback_single_inode() Eric Biggers
2021-01-09  7:58   ` [f2fs-dev] " Eric Biggers
2021-01-11 10:48   ` Christoph Hellwig
2021-01-11 10:48     ` [f2fs-dev] " Christoph Hellwig
2021-01-11 14:46   ` Jan Kara
2021-01-11 14:46     ` [f2fs-dev] " Jan Kara
2021-01-09  7:58 ` [PATCH v2 02/12] fs: correctly document the inode dirty flags Eric Biggers
2021-01-09  7:58   ` [f2fs-dev] " Eric Biggers
2021-01-11 14:48   ` Jan Kara
2021-01-11 14:48     ` [f2fs-dev] " Jan Kara
2021-01-09  7:58 ` [PATCH v2 03/12] fs: only specify I_DIRTY_TIME when needed in generic_update_time() Eric Biggers
2021-01-09  7:58   ` [f2fs-dev] " Eric Biggers
2021-01-11 14:50   ` Jan Kara
2021-01-11 14:50     ` [f2fs-dev] " Jan Kara
2021-01-09  7:58 ` [PATCH v2 04/12] fat: only specify I_DIRTY_TIME when needed in fat_update_time() Eric Biggers
2021-01-09  7:58   ` [f2fs-dev] " Eric Biggers
2021-01-11 10:52   ` Christoph Hellwig
2021-01-11 10:52     ` [f2fs-dev] " Christoph Hellwig
2021-01-11 19:50     ` Eric Biggers
2021-01-11 19:50       ` [f2fs-dev] " Eric Biggers
2021-01-12  5:21       ` Dave Chinner
2021-01-12  5:21         ` [f2fs-dev] " Dave Chinner
2021-01-12 13:23       ` Christoph Hellwig
2021-01-12 13:23         ` [f2fs-dev] " Christoph Hellwig
2021-01-11 14:52   ` Jan Kara
2021-01-11 14:52     ` [f2fs-dev] " Jan Kara
2021-01-09  7:58 ` [PATCH v2 05/12] fs: don't call ->dirty_inode for lazytime timestamp updates Eric Biggers
2021-01-09  7:58   ` [f2fs-dev] " Eric Biggers
2021-01-11 14:54   ` Jan Kara
2021-01-11 14:54     ` [f2fs-dev] " Jan Kara
2021-01-09  7:58 ` [PATCH v2 06/12] fs: pass only I_DIRTY_INODE flags to ->dirty_inode Eric Biggers
2021-01-09  7:58   ` [f2fs-dev] " Eric Biggers
2021-01-11 14:56   ` Jan Kara
2021-01-11 14:56     ` [f2fs-dev] " Jan Kara
2021-01-09  7:58 ` [PATCH v2 07/12] fs: clean up __mark_inode_dirty() a bit Eric Biggers
2021-01-09  7:58   ` [f2fs-dev] " Eric Biggers
2021-01-11 14:59   ` Jan Kara
2021-01-11 14:59     ` [f2fs-dev] " Jan Kara
2021-01-09  7:58 ` [PATCH v2 08/12] fs: drop redundant check from __writeback_single_inode() Eric Biggers
2021-01-09  7:58   ` [f2fs-dev] " Eric Biggers
2021-01-11 10:52   ` Christoph Hellwig
2021-01-11 10:52     ` [f2fs-dev] " Christoph Hellwig
2021-01-11 15:00   ` Jan Kara
2021-01-11 15:00     ` [f2fs-dev] " Jan Kara
2021-01-09  7:59 ` [PATCH v2 09/12] fs: improve comments for writeback_single_inode() Eric Biggers
2021-01-09  7:59   ` [f2fs-dev] " Eric Biggers
2021-01-11 10:53   ` Christoph Hellwig
2021-01-11 10:53     ` [f2fs-dev] " Christoph Hellwig
2021-01-11 15:05   ` Jan Kara
2021-01-11 15:05     ` [f2fs-dev] " Jan Kara
2021-01-09  7:59 ` [PATCH v2 10/12] gfs2: don't worry about I_DIRTY_TIME in gfs2_fsync() Eric Biggers
2021-01-09  7:59   ` [f2fs-dev] " Eric Biggers
2021-01-11 15:06   ` Jan Kara
2021-01-11 15:06     ` [f2fs-dev] " Jan Kara
2021-01-09  7:59 ` [PATCH v2 11/12] ext4: simplify i_state checks in __ext4_update_other_inode_time() Eric Biggers
2021-01-09  7:59   ` [f2fs-dev] " Eric Biggers
2021-01-11 10:53   ` Christoph Hellwig
2021-01-11 10:53     ` [f2fs-dev] " Christoph Hellwig
2021-01-11 20:23     ` Eric Biggers
2021-01-11 20:23       ` [f2fs-dev] " Eric Biggers
2021-01-12 13:25       ` Christoph Hellwig
2021-01-12 13:25         ` [f2fs-dev] " Christoph Hellwig
2021-02-03  5:16         ` Theodore Ts'o [this message]
2021-02-03  5:16           ` Theodore Ts'o
2021-01-11 15:11   ` Jan Kara
2021-01-11 15:11     ` [f2fs-dev] " Jan Kara
2021-01-09  7:59 ` [PATCH v2 12/12] xfs: remove a stale comment from xfs_file_aio_write_checks() Eric Biggers
2021-01-09  7:59   ` [f2fs-dev] " Eric Biggers
2021-01-12 17:31   ` Darrick J. Wong
2021-01-12 17:31     ` [f2fs-dev] " Darrick J. Wong
2021-01-11 15:15 ` [PATCH v2 00/12] lazytime fix and cleanups Jan Kara
2021-01-11 15:15   ` [f2fs-dev] " Jan Kara
2021-01-11 20:44   ` Eric Biggers
2021-01-11 20:44     ` [f2fs-dev] " Eric Biggers
2021-02-03  5:11     ` Theodore Ts'o
2021-02-03  5:11       ` [f2fs-dev] " Theodore Ts'o
2021-02-03  5:22       ` Eric Biggers
2021-02-03  5:22         ` [f2fs-dev] " Eric Biggers
2021-02-03 15:49         ` Theodore Ts'o
2021-02-03 15:49           ` [f2fs-dev] " Theodore Ts'o

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