linux-kernel - Re: [RFC PATCH v1 34/57] sata_sil24: Remove PAGE

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Message-ID: <ZxY1KAvGpyIzARtX@ryzen.lan>
Date: Mon, 21 Oct 2024 13:04:08 +0200
From: Niklas Cassel <cassel@...nel.org>
To: Ryan Roberts <ryan.roberts@....com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Anshuman Khandual <anshuman.khandual@....com>,
	Ard Biesheuvel <ardb@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Damien Le Moal <dlemoal@...nel.org>,
	David Hildenbrand <david@...hat.com>,
	Greg Marsden <greg.marsden@...cle.com>,
	Ivan Ivanov <ivan.ivanov@...e.com>,
	Kalesh Singh <kaleshsingh@...gle.com>,
	Marc Zyngier <maz@...nel.org>, Mark Rutland <mark.rutland@....com>,
	Matthias Brugger <mbrugger@...e.com>,
	Miroslav Benes <mbenes@...e.cz>, Will Deacon <will@...nel.org>,
	linux-arm-kernel@...ts.infradead.org, linux-ide@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Kees Cook <kees@...nel.org>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>
Subject: Re: [RFC PATCH v1 34/57] sata_sil24: Remove PAGE_SIZE compile-time
 constant assumption

On Mon, Oct 21, 2024 at 10:24:37AM +0100, Ryan Roberts wrote:
> On 17/10/2024 13:51, Niklas Cassel wrote:
> > On Thu, Oct 17, 2024 at 01:42:22PM +0100, Ryan Roberts wrote:

(snip)

> That said, while investigating this, I've spotted a bug in my change. paddr calculation in sil24_qc_issue() is incorrect since sizeof(*pp->cmd_block) is no longer PAGE_SIZE. Based on feedback in another patch, I'm also converting the BUG_ONs to WARN_ON_ONCEs.

Side note: Please wrap you lines to 80 characters max.


> 
> Additional proposed change, which I'll plan to include in the next version:
> 
> ---8<---
> diff --git a/drivers/ata/sata_sil24.c b/drivers/ata/sata_sil24.c
> index 85c6382976626..c402bf998c4ee 100644
> --- a/drivers/ata/sata_sil24.c
> +++ b/drivers/ata/sata_sil24.c
> @@ -257,6 +257,10 @@ union sil24_cmd_block {
>         struct sil24_atapi_block atapi;
>  };
>  
> +#define SIL24_ATA_BLOCK_SIZE   struct_size_t(struct sil24_ata_block, sge, SIL24_MAX_SGE)
> +#define SIL24_ATAPI_BLOCK_SIZE struct_size_t(struct sil24_atapi_block, sge, SIL24_MAX_SGE)
> +#define SIL24_CMD_BLOCK_SIZE   max(SIL24_ATA_BLOCK_SIZE, SIL24_ATAPI_BLOCK_SIZE)
> +
>  static const struct sil24_cerr_info {
>         unsigned int err_mask, action;
>         const char *desc;
> @@ -886,7 +890,7 @@ static unsigned int sil24_qc_issue(struct ata_queued_cmd *qc)
>         dma_addr_t paddr;
>         void __iomem *activate;
>  
> -       paddr = pp->cmd_block_dma + tag * sizeof(*pp->cmd_block);
> +       paddr = pp->cmd_block_dma + tag * SIL24_CMD_BLOCK_SIZE;
>         activate = port + PORT_CMD_ACTIVATE + tag * 8;
>  
>         /*
> @@ -1192,7 +1196,7 @@ static int sil24_port_start(struct ata_port *ap)
>         struct device *dev = ap->host->dev;
>         struct sil24_port_priv *pp;
>         union sil24_cmd_block *cb;
> -       size_t cb_size = PAGE_SIZE * SIL24_MAX_CMDS;
> +       size_t cb_size = SIL24_CMD_BLOCK_SIZE * SIL24_MAX_CMDS;
>         dma_addr_t cb_dma;
>  
>         pp = devm_kzalloc(dev, sizeof(*pp), GFP_KERNEL);
> @@ -1265,8 +1269,8 @@ static int sil24_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
>         u32 tmp;
>  
>         /* union sil24_cmd_block must be PAGE_SIZE */

This comment should probably be rephrased to be more clear then, since like
you said sizeof(union sil24_cmd_block) will no longer be PAGE_SIZE.


> -       BUG_ON(struct_size_t(struct sil24_atapi_block, sge, SIL24_MAX_SGE) != PAGE_SIZE);
> -       BUG_ON(struct_size_t(struct sil24_ata_block, sge, SIL24_MAX_SGE) > PAGE_SIZE);
> +       WARN_ON_ONCE(SIL24_ATAPI_BLOCK_SIZE != PAGE_SIZE);
> +       WARN_ON_ONCE(SIL24_ATA_BLOCK_SIZE != PAGE_SIZE - 16);
>  
>         ata_print_version_once(&pdev->dev, DRV_VERSION);
> ---8<---