Re: [PATCH v15 09/22] xfs: Hoist xfs_attr_leaf_addname

[Brian Foster <bfoster@redhat.com>]

On Wed, Feb 24, 2021 at 11:19:41PM -0700, Allison Henderson wrote:
> 
> 
> On 2/24/21 11:42 AM, Brian Foster wrote:
> > On Thu, Feb 18, 2021 at 09:53:35AM -0700, Allison Henderson wrote:
> > > This patch hoists xfs_attr_leaf_addname into the calling function.  The
> > > goal being to get all the code that will require state management into
> > > the same scope. This isn't particuarly asetheic right away, but it is a
> > > preliminary step to to manageing the state machine code.
> > > 
> > > Signed-off-by: Allison Henderson <allison.henderson@oracle.com>
> > > ---
> > >   fs/xfs/libxfs/xfs_attr.c | 209 ++++++++++++++++++++++-------------------------
> > >   1 file changed, 96 insertions(+), 113 deletions(-)
> > > 
> > > diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
> > > index 19a532a..bfd4466 100644
> > > --- a/fs/xfs/libxfs/xfs_attr.c
> > > +++ b/fs/xfs/libxfs/xfs_attr.c
> > ...
> > > @@ -286,10 +287,101 @@ xfs_attr_set_args(
> > ...
> > >   			return error;
> > > +		xfs_attr3_leaf_remove(bp, args);
> > > +
> > > +		/*
> > > +		 * If the result is small enough, shrink it all into the inode.
> > > +		 */
> > > +		forkoff = xfs_attr_shortform_allfit(bp, dp);
> > > +		if (forkoff)
> > > +			error = xfs_attr3_leaf_to_shortform(bp, args, forkoff);
> > > +			/* bp is gone due to xfs_da_shrink_inode */
> > > +
> > > +		return error;
> > > +node:
> > 
> > Hmm, I'm not a fan of this unconditional return followed by a jump label
> > in the middle of the function. It's a pretty clear indication that this
> > is just two functions smashed together, so I'm not sure what the
> > advantage of this is. I'll continue on to see what falls out of the next
> > patches..
> > 
> > Brian
> 
> Yes, it does kinda look a little displaced, but the point of it is to bring
> code that will require state management into the same scope so that the
> state switch can span all the operations it affects.  Which seemed to be
> what the RFC was striving for?  Looking ahead at the other reviews, I think
> it came together for you?
> 

Yes, I think so. If the subsequent patches line everything up nicely in
that single switch statement in one place (which it looks like we're
pretty close to), then I can probably live with this transient quirk.
That said, I might wait until at least the attr set path looks pretty
much finalized and come back and take a last look at this one, if
nothing else just to think about if there's any simple/unintrusive way
to avoid it..

Brian

> Allison
> 
> > 
> > >   		/*
> > >   		 * Promote the attribute list to the Btree format.
> > >   		 */
> > > @@ -731,115 +823,6 @@ xfs_attr_leaf_try_add(
> > >   	return retval;
> > >   }
> > > -
> > > -/*
> > > - * Add a name to the leaf attribute list structure
> > > - *
> > > - * This leaf block cannot have a "remote" value, we only call this routine
> > > - * if bmap_one_block() says there is only one block (ie: no remote blks).
> > > - */
> > > -STATIC int
> > > -xfs_attr_leaf_addname(
> > > -	struct xfs_da_args	*args)
> > > -{
> > > -	int			error, forkoff;
> > > -	struct xfs_buf		*bp = NULL;
> > > -	struct xfs_inode	*dp = args->dp;
> > > -
> > > -	trace_xfs_attr_leaf_addname(args);
> > > -
> > > -	error = xfs_attr_leaf_try_add(args, bp);
> > > -	if (error)
> > > -		return error;
> > > -
> > > -	/*
> > > -	 * Commit the transaction that added the attr name so that
> > > -	 * later routines can manage their own transactions.
> > > -	 */
> > > -	error = xfs_trans_roll_inode(&args->trans, dp);
> > > -	if (error)
> > > -		return error;
> > > -
> > > -	/*
> > > -	 * If there was an out-of-line value, allocate the blocks we
> > > -	 * identified for its storage and copy the value.  This is done
> > > -	 * after we create the attribute so that we don't overflow the
> > > -	 * maximum size of a transaction and/or hit a deadlock.
> > > -	 */
> > > -	if (args->rmtblkno > 0) {
> > > -		error = xfs_attr_rmtval_set(args);
> > > -		if (error)
> > > -			return error;
> > > -	}
> > > -
> > > -	if (!(args->op_flags & XFS_DA_OP_RENAME)) {
> > > -		/*
> > > -		 * Added a "remote" value, just clear the incomplete flag.
> > > -		 */
> > > -		if (args->rmtblkno > 0)
> > > -			error = xfs_attr3_leaf_clearflag(args);
> > > -
> > > -		return error;
> > > -	}
> > > -
> > > -	/*
> > > -	 * If this is an atomic rename operation, we must "flip" the incomplete
> > > -	 * flags on the "new" and "old" attribute/value pairs so that one
> > > -	 * disappears and one appears atomically.  Then we must remove the "old"
> > > -	 * attribute/value pair.
> > > -	 *
> > > -	 * In a separate transaction, set the incomplete flag on the "old" attr
> > > -	 * and clear the incomplete flag on the "new" attr.
> > > -	 */
> > > -
> > > -	error = xfs_attr3_leaf_flipflags(args);
> > > -	if (error)
> > > -		return error;
> > > -	/*
> > > -	 * Commit the flag value change and start the next trans in series.
> > > -	 */
> > > -	error = xfs_trans_roll_inode(&args->trans, args->dp);
> > > -	if (error)
> > > -		return error;
> > > -
> > > -	/*
> > > -	 * Dismantle the "old" attribute/value pair by removing a "remote" value
> > > -	 * (if it exists).
> > > -	 */
> > > -	xfs_attr_restore_rmt_blk(args);
> > > -
> > > -	if (args->rmtblkno) {
> > > -		error = xfs_attr_rmtval_invalidate(args);
> > > -		if (error)
> > > -			return error;
> > > -
> > > -		error = xfs_attr_rmtval_remove(args);
> > > -		if (error)
> > > -			return error;
> > > -	}
> > > -
> > > -	/*
> > > -	 * Read in the block containing the "old" attr, then remove the "old"
> > > -	 * attr from that block (neat, huh!)
> > > -	 */
> > > -	error = xfs_attr3_leaf_read(args->trans, args->dp, args->blkno,
> > > -				   &bp);
> > > -	if (error)
> > > -		return error;
> > > -
> > > -	xfs_attr3_leaf_remove(bp, args);
> > > -
> > > -	/*
> > > -	 * If the result is small enough, shrink it all into the inode.
> > > -	 */
> > > -	forkoff = xfs_attr_shortform_allfit(bp, dp);
> > > -	if (forkoff)
> > > -		error = xfs_attr3_leaf_to_shortform(bp, args, forkoff);
> > > -		/* bp is gone due to xfs_da_shrink_inode */
> > > -
> > > -	return error;
> > > -}
> > > -
> > >   /*
> > >    * Return EEXIST if attr is found, or ENOATTR if not
> > >    */
> > > -- 
> > > 2.7.4
> > > 
> > 
>