Re: [PATCH] cifs: Fix kmap_local_page() unmapping

["Fabio M. De Francesco" <fmdefrancesco@gmail.com>]

On giovedì 29 dicembre 2022 23:04:46 CET Ira Weiny wrote:
> kmap_local_page() requires kunmap_local() to unmap the mapping.  In
> addition memcpy_page() is provided to perform this common memcpy
> pattern.
> 
> Replace the kmap_local_page() and broken kunmap() with memcpy_page()
> 
> Fixes: d406d26745ab ("cifs: skip alloc when request has no pages")
> Cc: Paulo Alcantara <pc@cjr.nz>
> Cc: Steve French <sfrench@samba.org>
> Cc: "Fabio M. De Francesco" <fmdefrancesco@gmail.com>
> Cc: linux-cifs@vger.kernel.org
> Cc: samba-technical@lists.samba.org
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>
> ---
>  fs/cifs/smb2ops.c | 9 ++-------
>  1 file changed, 2 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
> index dc160de7a6de..0d7e9bcd9f34 100644
> --- a/fs/cifs/smb2ops.c
> +++ b/fs/cifs/smb2ops.c
> @@ -4488,17 +4488,12 @@ smb3_init_transform_rq(struct TCP_Server_Info 
*server,
> int num_rqst,
> 
>  		/* copy pages form the old */
>  		for (j = 0; j < npages; j++) {
> -			char *dst, *src;
>  			unsigned int offset, len;
> 
>  			rqst_page_get_length(new, j, &len, &offset);
> 
> -			dst = kmap_local_page(new->rq_pages[j]) + 
offset;
> -			src = kmap_local_page(old->rq_pages[j]) + 
offset;
> -
> -			memcpy(dst, src, len);
> -			kunmap(new->rq_pages[j]);
> -			kunmap(old->rq_pages[j]);
> +			memcpy_page(new->rq_pages[j], offset,
> +				    old->rq_pages[j], offset, len);
>
FWIW, it looks good to me...

Reviewed-by: Fabio M. De Francesco

Thanks,

Fabio
>  		}
>  	}
> 
> 
> ---
> base-commit: 1b929c02afd37871d5afb9d498426f83432e71c2
> change-id: 20221229-cifs-kmap-6700dabafcdf
> 
> Best regards,
> --
> Ira Weiny <ira.weiny@intel.com>