RE: [PATCH 6/7] scsi: storvsc: Don't assume that the scatterlist is not chained

[Long Li <longli@microsoft.com>]

> -----Original Message-----
> From: devel [mailto:driverdev-devel-bounces@linuxdriverproject.org] On
> Behalf Of K. Y. Srinivasan
> Sent: Monday, March 23, 2015 2:07 PM
> To: gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org;
> devel@linuxdriverproject.org; ohering@suse.com; jbottomley@parallels.com;
> hch@infradead.org; linux-scsi@vger.kernel.org; apw@canonical.com;
> vkuznets@redhat.com; jasowang@redhat.com
> Subject: [PATCH 6/7] scsi: storvsc: Don't assume that the scatterlist is not
> chained
> 
> The current code assumes that the scatterlists presented are not chained.
> Fix the code to not make this assumption.
> 
> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: Long Li <longli@microsoft.com>

> ---
>  drivers/scsi/storvsc_drv.c |   98 +++++++++++++++++++++++++------------------
>  1 files changed, 57 insertions(+), 41 deletions(-)
> 
> diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c index
> 88f5d79..a599677 100644
> --- a/drivers/scsi/storvsc_drv.c
> +++ b/drivers/scsi/storvsc_drv.c
> @@ -626,19 +626,6 @@ cleanup:
>  	return NULL;
>  }
> 
> -/* Disgusting wrapper functions */
> -static inline unsigned long sg_kmap_atomic(struct scatterlist *sgl, int idx) -{
> -	void *addr = kmap_atomic(sg_page(sgl + idx));
> -	return (unsigned long)addr;
> -}
> -
> -static inline void sg_kunmap_atomic(unsigned long addr) -{
> -	kunmap_atomic((void *)addr);
> -}
> -
> -
>  /* Assume the original sgl has enough room */  static unsigned int
> copy_from_bounce_buffer(struct scatterlist *orig_sgl,
>  					    struct scatterlist *bounce_sgl, @@ -
> 653,32 +640,39 @@ static unsigned int copy_from_bounce_buffer(struct
> scatterlist *orig_sgl,
>  	unsigned long bounce_addr = 0;
>  	unsigned long dest_addr = 0;
>  	unsigned long flags;
> +	struct scatterlist *cur_dest_sgl;
> +	struct scatterlist *cur_src_sgl;
> 
>  	local_irq_save(flags);
> -
> +	cur_dest_sgl = orig_sgl;
> +	cur_src_sgl = bounce_sgl;
>  	for (i = 0; i < orig_sgl_count; i++) {
> -		dest_addr = sg_kmap_atomic(orig_sgl,i) + orig_sgl[i].offset;
> +		dest_addr = (unsigned long)
> +				kmap_atomic(sg_page(cur_dest_sgl)) +
> +				cur_dest_sgl->offset;
>  		dest = dest_addr;
>  		destlen = orig_sgl[i].length;
> +		destlen = cur_dest_sgl->length;
> 
>  		if (bounce_addr == 0)
> -			bounce_addr = sg_kmap_atomic(bounce_sgl,j);
> +			bounce_addr = (unsigned long)kmap_atomic(
> +							sg_page(cur_src_sgl));
> 
>  		while (destlen) {
> -			src = bounce_addr + bounce_sgl[j].offset;
> -			srclen = bounce_sgl[j].length - bounce_sgl[j].offset;
> +			src = bounce_addr + cur_src_sgl->offset;
> +			srclen = cur_src_sgl->length - cur_src_sgl->offset;
> 
>  			copylen = min(srclen, destlen);
>  			memcpy((void *)dest, (void *)src, copylen);
> 
>  			total_copied += copylen;
> -			bounce_sgl[j].offset += copylen;
> +			cur_src_sgl->offset += copylen;
>  			destlen -= copylen;
>  			dest += copylen;
> 
> -			if (bounce_sgl[j].offset == bounce_sgl[j].length) {
> +			if (cur_src_sgl->offset == cur_src_sgl->length) {
>  				/* full */
> -				sg_kunmap_atomic(bounce_addr);
> +				kunmap_atomic((void *)bounce_addr);
>  				j++;
> 
>  				/*
> @@ -692,21 +686,27 @@ static unsigned int copy_from_bounce_buffer(struct
> scatterlist *orig_sgl,
>  					/*
>  					 * We are done; cleanup and return.
>  					 */
> -					sg_kunmap_atomic(dest_addr -
> orig_sgl[i].offset);
> +					kunmap_atomic((void *)(dest_addr -
> +						cur_dest_sgl->offset));
>  					local_irq_restore(flags);
>  					return total_copied;
>  				}
> 
>  				/* if we need to use another bounce buffer */
> -				if (destlen || i != orig_sgl_count - 1)
> -					bounce_addr =
> sg_kmap_atomic(bounce_sgl,j);
> +				if (destlen || i != orig_sgl_count - 1) {
> +					cur_src_sgl = sg_next(cur_src_sgl);
> +					bounce_addr = (unsigned long)
> +							kmap_atomic(
> +							sg_page(cur_src_sgl));
> +				}
>  			} else if (destlen == 0 && i == orig_sgl_count - 1) {
>  				/* unmap the last bounce that is < PAGE_SIZE
> */
> -				sg_kunmap_atomic(bounce_addr);
> +				kunmap_atomic((void *)bounce_addr);
>  			}
>  		}
> 
> -		sg_kunmap_atomic(dest_addr - orig_sgl[i].offset);
> +		kunmap_atomic((void *)(dest_addr - cur_dest_sgl->offset));
> +		cur_dest_sgl = sg_next(cur_dest_sgl);
>  	}
> 
>  	local_irq_restore(flags);
> @@ -727,48 +727,61 @@ static unsigned int copy_to_bounce_buffer(struct
> scatterlist *orig_sgl,
>  	unsigned long bounce_addr = 0;
>  	unsigned long src_addr = 0;
>  	unsigned long flags;
> +	struct scatterlist *cur_src_sgl;
> +	struct scatterlist *cur_dest_sgl;
> 
>  	local_irq_save(flags);
> 
> +	cur_src_sgl = orig_sgl;
> +	cur_dest_sgl = bounce_sgl;
> +
>  	for (i = 0; i < orig_sgl_count; i++) {
> -		src_addr = sg_kmap_atomic(orig_sgl,i) + orig_sgl[i].offset;
> +		src_addr = (unsigned long)
> +				kmap_atomic(sg_page(cur_src_sgl)) +
> +				cur_src_sgl->offset;
>  		src = src_addr;
> -		srclen = orig_sgl[i].length;
> +		srclen = cur_src_sgl->length;
> 
>  		if (bounce_addr == 0)
> -			bounce_addr = sg_kmap_atomic(bounce_sgl,j);
> +			bounce_addr = (unsigned long)
> +					kmap_atomic(sg_page(cur_dest_sgl));
> 
>  		while (srclen) {
>  			/* assume bounce offset always == 0 */
> -			dest = bounce_addr + bounce_sgl[j].length;
> -			destlen = PAGE_SIZE - bounce_sgl[j].length;
> +			dest = bounce_addr + cur_dest_sgl->length;
> +			destlen = PAGE_SIZE - cur_dest_sgl->length;
> 
>  			copylen = min(srclen, destlen);
>  			memcpy((void *)dest, (void *)src, copylen);
> 
>  			total_copied += copylen;
> -			bounce_sgl[j].length += copylen;
> +			cur_dest_sgl->length += copylen;
>  			srclen -= copylen;
>  			src += copylen;
> 
> -			if (bounce_sgl[j].length == PAGE_SIZE) {
> +			if (cur_dest_sgl->length == PAGE_SIZE) {
>  				/* full..move to next entry */
> -				sg_kunmap_atomic(bounce_addr);
> +				kunmap_atomic((void *)bounce_addr);
>  				bounce_addr = 0;
>  				j++;
>  			}
> 
>  			/* if we need to use another bounce buffer */
> -			if (srclen && bounce_addr == 0)
> -				bounce_addr = sg_kmap_atomic(bounce_sgl,
> j);
> +			if (srclen && bounce_addr == 0) {
> +				cur_dest_sgl = sg_next(cur_dest_sgl);
> +				bounce_addr = (unsigned long)
> +						kmap_atomic(
> +						sg_page(cur_dest_sgl));
> +			}
> 
>  		}
> 
> -		sg_kunmap_atomic(src_addr - orig_sgl[i].offset);
> +		kunmap_atomic((void *)(src_addr - cur_src_sgl->offset));
> +		cur_src_sgl = sg_next(cur_src_sgl);
>  	}
> 
>  	if (bounce_addr)
> -		sg_kunmap_atomic(bounce_addr);
> +		kunmap_atomic((void *)bounce_addr);
> 
>  	local_irq_restore(flags);
> 
> @@ -1536,6 +1549,7 @@ static int storvsc_queuecommand(struct Scsi_Host
> *host, struct scsi_cmnd *scmnd)
>  	struct scatterlist *sgl;
>  	unsigned int sg_count = 0;
>  	struct vmscsi_request *vm_srb;
> +	struct scatterlist *cur_sgl;
> 
>  	if (vmstor_current_major <= VMSTOR_WIN8_MAJOR) {
>  		/*
> @@ -1617,10 +1631,12 @@ static int storvsc_queuecommand(struct
> Scsi_Host *host, struct scsi_cmnd *scmnd)
>  		}
> 
>  		cmd_request->data_buffer.offset = sgl[0].offset;
> -
> -		for (i = 0; i < sg_count; i++)
> +		cur_sgl = sgl;
> +		for (i = 0; i < sg_count; i++) {
>  			cmd_request->data_buffer.pfn_array[i] =
> -				page_to_pfn(sg_page((&sgl[i])));
> +				page_to_pfn(sg_page((cur_sgl)));
> +			cur_sgl = sg_next(cur_sgl);
> +		}
> 
>  	} else if (scsi_sglist(scmnd)) {
>  		cmd_request->data_buffer.offset =
> --
> 1.7.4.1
> 
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