Re: [PATCH v15 17/22] xfs: Skip flip flags for delayed attrs

From: Allison Henderson <allison.henderson@oracle.com>
To: "Darrick J. Wong" <djwong@kernel.org>
Cc: linux-xfs@vger.kernel.org
Subject: Re: [PATCH v15 17/22] xfs: Skip flip flags for delayed attrs
Date: Fri, 26 Feb 2021 17:56:52 -0700	[thread overview]
Message-ID: <1a02f8a4-f6fd-de0e-c044-367f819abcce@oracle.com> (raw)
In-Reply-To: <20210226050241.GZ7272@magnolia>

On 2/25/21 10:02 PM, Darrick J. Wong wrote:
> On Thu, Feb 18, 2021 at 09:53:43AM -0700, Allison Henderson wrote:
>> This is a clean up patch that skips the flip flag logic for delayed attr
>> renames.  Since the log replay keeps the inode locked, we do not need to
>> worry about race windows with attr lookups.  So we can skip over
>> flipping the flag and the extra transaction roll for it
>>
>> Signed-off-by: Allison Henderson <allison.henderson@oracle.com>
> 
> I wonder, have you done much performance analysis of the old vs. new
> xattr code paths?  Does skipping the extra step + roll make attr
> operations faster?
I dont have any analysis right now, but maybe I could put some together. 
  I'm sure there's some impact, but not sure how much.  If it does, I 
suspect it will become of more interest when we bring in pptrs since the 
code path with be in heavier use then.

> 
> This looks pretty straightforward though:
> Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Thank you!

Allison

> 
> --D
> 
>> ---
>>   fs/xfs/libxfs/xfs_attr.c      | 51 +++++++++++++++++++++++++------------------
>>   fs/xfs/libxfs/xfs_attr_leaf.c |  3 ++-
>>   2 files changed, 32 insertions(+), 22 deletions(-)
>>
>> diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
>> index e4c1b4b..666cc69 100644
>> --- a/fs/xfs/libxfs/xfs_attr.c
>> +++ b/fs/xfs/libxfs/xfs_attr.c
>> @@ -337,6 +337,7 @@ xfs_attr_set_iter(
>>   	struct xfs_da_state		*state = NULL;
>>   	int				forkoff, error = 0;
>>   	int				retval = 0;
>> +	struct xfs_mount		*mp = args->dp->i_mount;
>>   
>>   	/* State machine switch */
>>   	switch (dac->dela_state) {
>> @@ -470,16 +471,21 @@ xfs_attr_set_iter(
>>   		 * "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.
>> -		 */
>> -		dac->dela_state = XFS_DAS_FLIP_LFLAG;
>> -		trace_xfs_attr_set_iter_return(dac->dela_state, args->dp);
>> -		return -EAGAIN;
>> +		if (!xfs_hasdelattr(mp)) {
>> +			error = xfs_attr3_leaf_flipflags(args);
>> +			if (error)
>> +				return error;
>> +			/*
>> +			 * Commit the flag value change and start the next trans
>> +			 * in series.
>> +			 */
>> +			dac->dela_state = XFS_DAS_FLIP_LFLAG;
>> +			trace_xfs_attr_set_iter_return(dac->dela_state,
>> +						       args->dp);
>> +			return -EAGAIN;
>> +		}
>> +
>> +		/* fallthrough */
>>   	case XFS_DAS_FLIP_LFLAG:
>>   		/*
>>   		 * Dismantle the "old" attribute/value pair by removing a
>> @@ -588,17 +594,21 @@ xfs_attr_set_iter(
>>   		 * 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)
>> -			goto out;
>> -		/*
>> -		 * Commit the flag value change and start the next trans in
>> -		 * series
>> -		 */
>> -		dac->dela_state = XFS_DAS_FLIP_NFLAG;
>> -		trace_xfs_attr_set_iter_return(dac->dela_state, args->dp);
>> -		return -EAGAIN;
>> +		if (!xfs_hasdelattr(mp)) {
>> +			error = xfs_attr3_leaf_flipflags(args);
>> +			if (error)
>> +				goto out;
>> +			/*
>> +			 * Commit the flag value change and start the next trans
>> +			 * in series
>> +			 */
>> +			dac->dela_state = XFS_DAS_FLIP_NFLAG;
>> +			trace_xfs_attr_set_iter_return(dac->dela_state,
>> +						       args->dp);
>> +			return -EAGAIN;
>> +		}
>>   
>> +		/* fallthrough */
>>   	case XFS_DAS_FLIP_NFLAG:
>>   		/*
>>   		 * Dismantle the "old" attribute/value pair by removing a
>> @@ -1277,7 +1287,6 @@ int xfs_attr_node_addname_work(
>>   	 * Re-find the "old" attribute entry after any split ops. The INCOMPLETE
>>   	 * flag means that we will find the "old" attr, not the "new" one.
>>   	 */
>> -	args->attr_filter |= XFS_ATTR_INCOMPLETE;
>>   	state = xfs_da_state_alloc(args);
>>   	state->inleaf = 0;
>>   	error = xfs_da3_node_lookup_int(state, &retval);
>> diff --git a/fs/xfs/libxfs/xfs_attr_leaf.c b/fs/xfs/libxfs/xfs_attr_leaf.c
>> index 3780141..ec707bd 100644
>> --- a/fs/xfs/libxfs/xfs_attr_leaf.c
>> +++ b/fs/xfs/libxfs/xfs_attr_leaf.c
>> @@ -1486,7 +1486,8 @@ xfs_attr3_leaf_add_work(
>>   	if (tmp)
>>   		entry->flags |= XFS_ATTR_LOCAL;
>>   	if (args->op_flags & XFS_DA_OP_RENAME) {
>> -		entry->flags |= XFS_ATTR_INCOMPLETE;
>> +		if (!xfs_hasdelattr(mp))
>> +			entry->flags |= XFS_ATTR_INCOMPLETE;
>>   		if ((args->blkno2 == args->blkno) &&
>>   		    (args->index2 <= args->index)) {
>>   			args->index2++;
>> -- 
>> 2.7.4
>>