linux-kernel - Re: [PATCH 1/2] swiotlb: Split up single swiotlb lock

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Date:   Wed, 29 Jun 2022 07:09:12 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Tianyu Lan <ltykernel@...il.com>
Cc:     corbet@....net, rafael@...nel.org, len.brown@...el.com,
        pavel@....cz, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
        hch@...radead.org, m.szyprowski@...sung.com, robin.murphy@....com,
        paulmck@...nel.org, akpm@...ux-foundation.org,
        keescook@...omium.org, songmuchun@...edance.com,
        rdunlap@...radead.org, damien.lemoal@...nsource.wdc.com,
        michael.h.kelley@...rosoft.com, kys@...rosoft.com,
        Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        iommu@...ts.linux-foundation.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        vkuznets@...hat.com, wei.liu@...nel.org, parri.andrea@...il.com,
        thomas.lendacky@....com, linux-hyperv@...r.kernel.org,
        kirill.shutemov@...el.com, andi.kleen@...el.com,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 1/2] swiotlb: Split up single swiotlb lock

On Mon, Jun 27, 2022 at 11:31:49AM -0400, Tianyu Lan wrote:
> +/**
> + * struct io_tlb_area - IO TLB memory area descriptor
> + *
> + * This is a single area with a single lock.
> + *
> + * @used:	The number of used IO TLB block.
> + * @index:	The slot index to start searching in this area for next round.
> + * @lock:	The lock to protect the above data structures in the map and
> + *		unmap calls.
> + */
> +struct io_tlb_area {
> +	unsigned long used;
> +	unsigned int index;
> +	spinlock_t lock;
> +};

As already mentioned last time, please move this into swiotlb.c,
swiotlb.h only uses a pointer to this structure.

>  static void swiotlb_init_io_tlb_mem(struct io_tlb_mem *mem, phys_addr_t start,
> -		unsigned long nslabs, unsigned int flags, bool late_alloc)
> +				    unsigned long nslabs, unsigned int flags,
> +				    bool late_alloc, unsigned int nareas)

Nit: the two tab indentation for prototype continuations is a lot easier
to maintain, so don't graciously switch away from it.

> +			alloc_size - (offset + ((i - slot_index) << IO_TLB_SHIFT));

Overly long line here.