linux-kernel - Re: [PATCH] Do not silently discard WRITE

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Date:	Mon, 20 Oct 2014 10:10:14 -0500
From:	Chris J Arges <chris.j.arges@...onical.com>
To:	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Petr Vandrovec <petr@...are.com>
CC:	Jens Axboe <axboe@...nel.dk>,
	Arvind Kumar <arvindkumar@...are.com>,
	Christoph Hellwig <hch@....de>, stable@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Do not silently discard WRITE_SAME requests

On 10/17/2014 06:46 PM, Martin K. Petersen wrote:
>>>>>> "Petr" == Petr Vandrovec <petr@...are.com> writes:
> 
> Petr> is there any reason to do blacklisting?  Why not let first request
> Petr> fail, and switch to non-write-same code path once that happens?
> 
> Well, we do. But we try to avoid confusing users with error messages if
> we can avoid it. And if we know it's not going to work we might as avoid
> trying.
> 

In addition it seems that after blkdev_issue_write_same fails and we try
to zero with __blkdev_issue_zeroout, we have issues where data is not
being zeroed properly as seem by the test case.

> 
> SCSI: Only blacklist WRITE SAME for VMware virtual disks
> 
> Commit 4089b71cc820 blacklisted WRITE SAME for all VMware disks.
> However, the WRITE SAME commands are supported for passthrough
> disks. Change the heuristic so we only blacklist virtual disks.
> 
> Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>
> Reported-by: Petr Vandrovec <petr@...are.com>
> 

I've tested with this patch applied and the original test case for the
bug does not fail. I only verified this with VMWare workstation. Feel
free to add:

Tested-by: Chris J Arges <chris.j.arges@...onical.com>

Thanks,
--chris j arges

> 
> diff --git a/drivers/message/fusion/mptspi.c b/drivers/message/fusion/mptspi.c
> index 613231c16194..787933d43d32 100644
> --- a/drivers/message/fusion/mptspi.c
> +++ b/drivers/message/fusion/mptspi.c
> @@ -1419,11 +1419,6 @@ mptspi_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>  		goto out_mptspi_probe;
>          }
>  
> -	/* VMWare emulation doesn't properly implement WRITE_SAME
> -	 */
> -	if (pdev->subsystem_vendor == 0x15AD)
> -		sh->no_write_same = 1;
> -
>  	spin_lock_irqsave(&ioc->FreeQlock, flags);
>  
>  	/* Attach the SCSI Host to the IOC structure
> diff --git a/drivers/scsi/scsi_devinfo.c b/drivers/scsi/scsi_devinfo.c
> index 49014a143c6a..8c228e049bb6 100644
> --- a/drivers/scsi/scsi_devinfo.c
> +++ b/drivers/scsi/scsi_devinfo.c
> @@ -249,6 +249,8 @@ static struct {
>  	{"TOSHIBA", "CD-ROM", NULL, BLIST_ISROM},
>  	{"Traxdata", "CDR4120", NULL, BLIST_NOLUN},	/* locks up */
>  	{"USB2.0", "SMARTMEDIA/XD", NULL, BLIST_FORCELUN | BLIST_INQUIRY_36},
> +	{"VMware", "Virtual disk", "1.0", BLIST_NO_WRITE_SAME }, /* ESX */
> +	{"VMware,", "VMware Virtual S", "1.0", BLIST_NO_WRITE_SAME }, /* WS,Fusion */
>  	{"WangDAT", "Model 2600", "01.7", BLIST_SELECT_NO_ATN},
>  	{"WangDAT", "Model 3200", "02.2", BLIST_SELECT_NO_ATN},
>  	{"WangDAT", "Model 1300", "02.4", BLIST_SELECT_NO_ATN},
> diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
> index ba3f1e8d0d57..c57daffe57af 100644
> --- a/drivers/scsi/scsi_scan.c
> +++ b/drivers/scsi/scsi_scan.c
> @@ -955,6 +955,9 @@ static int scsi_add_lun(struct scsi_device *sdev, unsigned char *inq_result,
>  	if (*bflags & BLIST_NO_DIF)
>  		sdev->no_dif = 1;
>  
> +	if (*bflags & BLIST_NO_WRITE_SAME)
> +		sdev->no_write_same = 1;
> +
>  	sdev->eh_timeout = SCSI_DEFAULT_EH_TIMEOUT;
>  
>  	if (*bflags & BLIST_TRY_VPD_PAGES)
> diff --git a/include/scsi/scsi_devinfo.h b/include/scsi/scsi_devinfo.h
> index 183eaab7c380..1a24efb4b1d6 100644
> --- a/include/scsi/scsi_devinfo.h
> +++ b/include/scsi/scsi_devinfo.h
> @@ -36,5 +36,6 @@
>  					     for sequential scan */
>  #define BLIST_TRY_VPD_PAGES	0x10000000 /* Attempt to read VPD pages */
>  #define BLIST_NO_RSOC		0x20000000 /* don't try to issue RSOC */
> +#define BLIST_NO_WRITE_SAME	0x40000000 /* don't try to issue WRITE SAME */
>  
>  #endif
> 
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