linux-kernel - Re: [PATCH v5 09/10] xfs: Allow block allocator to take an alignment hint

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Message-ID: <Z9E679YhzP6grfDV@infradead.org>
Date: Wed, 12 Mar 2025 00:42:39 -0700
From: Christoph Hellwig <hch@...radead.org>
To: John Garry <john.g.garry@...cle.com>
Cc: brauner@...nel.org, djwong@...nel.org, cem@...nel.org,
	linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, ojaswin@...ux.ibm.com,
	ritesh.list@...il.com, martin.petersen@...cle.com
Subject: Re: [PATCH v5 09/10] xfs: Allow block allocator to take an alignment
 hint

>  	else if (ap->datatype & XFS_ALLOC_USERDATA)
>  		align = xfs_get_extsz_hint(ap->ip);
> +
> +	if (align > 1 && (ap->flags & XFS_BMAPI_EXTSZALIGN))
> +		args->alignment = align;
> +

Add a comment please.

> +/* Try to align allocations to the extent size hint */
> +#define XFS_BMAPI_EXTSZALIGN	(1u << 11)

Shouldn't we be doing this by default for any extent size hint
based allocations?

>  	bool			found;
>  	bool			atomic_sw = flags & XFS_REFLINK_ATOMIC_SW;
> +	uint32_t		bmapi_flags = XFS_BMAPI_COWFORK |
> +					      XFS_BMAPI_PREALLOC;
> +
> +	if (atomic_sw)
> +		bmapi_flags |= XFS_BMAPI_EXTSZALIGN;

Please add a comment why you are doing this.