diff mbox series

[v2,11/12] ext4: simplify i_state checks in __ext4_update_other_inode_time()

Message ID 20210109075903.208222-12-ebiggers@kernel.org (mailing list archive)
State New, archived
Headers show
Series lazytime fix and cleanups | expand

Commit Message

Eric Biggers Jan. 9, 2021, 7:59 a.m. UTC 
From: Eric Biggers <ebiggers@google.com>

Since I_DIRTY_TIME and I_DIRTY_INODE are mutually exclusive in i_state,
there's no need to check for I_DIRTY_TIME && !I_DIRTY_INODE.  Just check
for I_DIRTY_TIME.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/ext4/inode.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

Comments

Christoph Hellwig Jan. 11, 2021, 10:53 a.m. UTC | #1 
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..
Jan Kara Jan. 11, 2021, 3:11 p.m. UTC | #2 
On Fri 08-01-21 23:59:02, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> Since I_DIRTY_TIME and I_DIRTY_INODE are mutually exclusive in i_state,
> there's no need to check for I_DIRTY_TIME && !I_DIRTY_INODE.  Just check
> for I_DIRTY_TIME.
> 
> Signed-off-by: Eric Biggers <ebiggers@google.com>

Looks good to me. Feel free to add:

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

								Honza

> ---
>  fs/ext4/inode.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 4cc6c7834312f..00bca5c18eb65 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4962,14 +4962,12 @@ static void __ext4_update_other_inode_time(struct super_block *sb,
>  		return;
>  
>  	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) {
>  		struct ext4_inode_info	*ei = EXT4_I(inode);
>  
>  		inode->i_state &= ~I_DIRTY_TIME;
> -- 
> 2.30.0
>
Eric Biggers Jan. 11, 2021, 8:23 p.m. UTC | #3 
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
Christoph Hellwig Jan. 12, 2021, 1:25 p.m. UTC | #4 
On Mon, Jan 11, 2021 at 12:23:40PM -0800, Eric Biggers wrote:
> > 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?

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()'.
Theodore Ts'o Feb. 3, 2021, 5:16 a.m. UTC | #5 
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
diff mbox series

Patch

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 4cc6c7834312f..00bca5c18eb65 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4962,14 +4962,12 @@  static void __ext4_update_other_inode_time(struct super_block *sb,
 		return;
 
 	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) {
 		struct ext4_inode_info	*ei = EXT4_I(inode);
 
 		inode->i_state &= ~I_DIRTY_TIME;