Re: [PATCH v9 24/43] xfsprogs: Split apart xfs_attr_leaf_addname

[Allison Collins <allison.henderson@oracle.com>]

On 5/4/20 10:32 AM, Darrick J. Wong wrote:
> On Thu, Apr 30, 2020 at 03:46:41PM -0700, Allison Collins wrote:
>> Split out new helper function xfs_attr_leaf_try_add from
>> xfs_attr_leaf_addname. Because new delayed attribute routines cannot
>> roll transactions, we split off the parts of xfs_attr_leaf_addname that
>> we can use, and move the commit into the calling function.
>>
>> Signed-off-by: Allison Collins <allison.henderson@oracle.com>
>> Reviewed-by: Brian Foster <bfoster@redhat.com>
>> Reviewed-by: Chandan Rajendra <chandanrlinux@gmail.com>
>> ---
>>   libxfs/xfs_attr.c | 94 +++++++++++++++++++++++++++++++++++--------------------
>>   1 file changed, 60 insertions(+), 34 deletions(-)
>>
>> diff --git a/libxfs/xfs_attr.c b/libxfs/xfs_attr.c
>> index 1cdebec..5f622c8 100644
>> --- a/libxfs/xfs_attr.c
>> +++ b/libxfs/xfs_attr.c
>> @@ -257,10 +257,30 @@ xfs_attr_set_args(
>>   		}
>>   	}
>>   
>> -	if (xfs_bmap_one_block(dp, XFS_ATTR_FORK))
>> +	if (xfs_bmap_one_block(dp, XFS_ATTR_FORK)) {
>>   		error = xfs_attr_leaf_addname(args);
>> -	else
>> -		error = xfs_attr_node_addname(args);
>> +		if (error != -ENOSPC)
>> +			return error;
>> +
>> +		/*
>> +		 * Commit that transaction so that the node_addname()
>> +		 * call can manage its own transactions.
>> +		 */
>> +		error = xfs_defer_finish(&args->trans);
>> +		if (error)
>> +			return error;
>> +
>> +		/*
>> +		 * Commit the current trans (including the inode) and
>> +		 * start a new one.
>> +		 */
>> +		error = xfs_trans_roll_inode(&args->trans, dp);
>> +		if (error)
>> +			return error;
> 
> I was just about to debate myself (again) on why it's still necessary to
> call _defer_finish and then _trans_roll_inode, but then I remembered the
> actual reason I unearthed for that, like 5 revisions ago.
> 
> xfs_defer_trans_roll looks for all buffer and inode items attached to a
> transaction.  If it finds bhold'ed buffers or inodes that were ijoined
> with lock_flags==0, it will log and rejoin those items to the new
> transaction after rolling.  Therefore, the xfs_trans_roll_inode here
> makes sure that any buffers that might have been bhold'ed have been
> released.  The goal here is to start each step of an xattr operation
> with the transaction in the same state (clean transaction, inode locked
> and joined) no matter how we got to that step.  That's what "manage its
> own transactions" means, though that's apparently too vague for me to
> pick up on.
> 
> With that in mind, could you change the comments for both to state why
> we're doing this more explicitly? e.g.
> 
> 	/*
> 	 * Finish any deferred work items and roll the transaction once
> 	 * more.  The goal here is to call node_addname with the inode
> 	 * and transaction in the same state (inode locked and joined,
> 	 * transaction clean) no matter how we got to this step.
> 	 */
> 	error = xfs_defer_finish(&args->trans);
> 	if (error)
> 		return error;
> 	error = xfs_trans_roll_inode(&args->trans, dp);
> 	if (error)
> 		return error;
> 
>> +
> 
> Unnecessary blank line here.
> 
Sure, will fix these.  Thanks for the reviews!

Allison

> --D
> 
>> +	}
>> +
>> +	error = xfs_attr_node_addname(args);
>>   	return error;
>>   }
>>   
>> @@ -508,20 +528,21 @@ xfs_attr_shortform_addname(xfs_da_args_t *args)
>>    *========================================================================*/
>>   
>>   /*
>> - * Add a name to the leaf attribute list structure
>> + * Tries to add an attribute to an inode in leaf form
>>    *
>> - * 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).
>> + * This function is meant to execute as part of a delayed operation and leaves
>> + * the transaction handling to the caller.  On success the attribute is added
>> + * and the inode and transaction are left dirty.  If there is not enough space,
>> + * the attr data is converted to node format and -ENOSPC is returned. Caller is
>> + * responsible for handling the dirty inode and transaction or adding the attr
>> + * in node format.
>>    */
>>   STATIC int
>> -xfs_attr_leaf_addname(
>> -	struct xfs_da_args	*args)
>> +xfs_attr_leaf_try_add(
>> +	struct xfs_da_args	*args,
>> +	struct xfs_buf		*bp)
>>   {
>> -	struct xfs_buf		*bp;
>> -	int			retval, error, forkoff;
>> -	struct xfs_inode	*dp = args->dp;
>> -
>> -	trace_xfs_attr_leaf_addname(args);
>> +	int			retval, error;
>>   
>>   	/*
>>   	 * Look up the given attribute in the leaf block.  Figure out if
>> @@ -563,31 +584,39 @@ xfs_attr_leaf_addname(
>>   	retval = xfs_attr3_leaf_add(bp, args);
>>   	if (retval == -ENOSPC) {
>>   		/*
>> -		 * Promote the attribute list to the Btree format, then
>> -		 * Commit that transaction so that the node_addname() call
>> -		 * can manage its own transactions.
>> +		 * Promote the attribute list to the Btree format. Unless an
>> +		 * error occurs, retain the -ENOSPC retval
>>   		 */
>>   		error = xfs_attr3_leaf_to_node(args);
>>   		if (error)
>>   			return error;
>> -		error = xfs_defer_finish(&args->trans);
>> -		if (error)
>> -			return error;
>> +	}
>> +	return retval;
>> +out_brelse:
>> +	xfs_trans_brelse(args->trans, bp);
>> +	return retval;
>> +}
>>   
>> -		/*
>> -		 * Commit the current trans (including the inode) and start
>> -		 * a new one.
>> -		 */
>> -		error = xfs_trans_roll_inode(&args->trans, dp);
>> -		if (error)
>> -			return error;
>>   
>> -		/*
>> -		 * Fob the whole rest of the problem off on the Btree code.
>> -		 */
>> -		error = xfs_attr_node_addname(args);
>> +/*
>> + * 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
>> @@ -682,9 +711,6 @@ xfs_attr_leaf_addname(
>>   		error = xfs_attr3_leaf_clearflag(args);
>>   	}
>>   	return error;
>> -out_brelse:
>> -	xfs_trans_brelse(args->trans, bp);
>> -	return retval;
>>   }
>>   
>>   /*
>> -- 
>> 2.7.4
>>