[v2,11/15] CIFS: Pass page offset for calculating signature

Message ID 20180530194807.31657-12-longli@linuxonhyperv.com
State New
Headers show
Series
  • CIFS: Add direct I/O support
Related show

Commit Message

Long Li May 30, 2018, 7:48 p.m.
From: Long Li <longli@microsoft.com>

When calculating signature for the packet, it needs to read into the
correct page offset for the data.

Signed-off-by: Long Li <longli@microsoft.com>
---
 fs/cifs/cifsencrypt.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

Comments

Tom Talpey June 24, 2018, 2:27 a.m. | #1
On 5/30/2018 3:48 PM, Long Li wrote:
> From: Long Li <longli@microsoft.com>
> 
> When calculating signature for the packet, it needs to read into the
> correct page offset for the data.
> 
> Signed-off-by: Long Li <longli@microsoft.com>
> ---
>   fs/cifs/cifsencrypt.c | 9 +++++----
>   1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/cifs/cifsencrypt.c b/fs/cifs/cifsencrypt.c
> index a6ef088..e88303c 100644
> --- a/fs/cifs/cifsencrypt.c
> +++ b/fs/cifs/cifsencrypt.c
> @@ -68,11 +68,12 @@ int __cifs_calc_signature(struct smb_rqst *rqst,
>   
>   	/* now hash over the rq_pages array */
>   	for (i = 0; i < rqst->rq_npages; i++) {
> -		void *kaddr = kmap(rqst->rq_pages[i]);
> -		size_t len = rqst->rq_pagesz;
> +		void *kaddr;
> +		unsigned int len, offset;
>   
> -		if (i == rqst->rq_npages - 1)
> -			len = rqst->rq_tailsz;
> +		rqst_page_get_length(rqst, i, &len, &offset);
> +
> +		kaddr = (char *) kmap(rqst->rq_pages[i]) + offset;

I suppose it's more robust to map a page at a time, but it's pretty
expensive. Is this the only way to iterate over a potentially very
large block of data? For example, a 1MB segment means 256 kmap/kunmaps.

Tom.

>   
>   		crypto_shash_update(shash, kaddr, len);
>   
> 
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Long Li June 26, 2018, 4:15 a.m. | #2
> Subject: Re: [Patch v2 11/15] CIFS: Pass page offset for calculating signature
> 
> On 5/30/2018 3:48 PM, Long Li wrote:
> > From: Long Li <longli@microsoft.com>
> >
> > When calculating signature for the packet, it needs to read into the
> > correct page offset for the data.
> >
> > Signed-off-by: Long Li <longli@microsoft.com>
> > ---
> >   fs/cifs/cifsencrypt.c | 9 +++++----
> >   1 file changed, 5 insertions(+), 4 deletions(-)
> >
> > diff --git a/fs/cifs/cifsencrypt.c b/fs/cifs/cifsencrypt.c index
> > a6ef088..e88303c 100644
> > --- a/fs/cifs/cifsencrypt.c
> > +++ b/fs/cifs/cifsencrypt.c
> > @@ -68,11 +68,12 @@ int __cifs_calc_signature(struct smb_rqst *rqst,
> >
> >   	/* now hash over the rq_pages array */
> >   	for (i = 0; i < rqst->rq_npages; i++) {
> > -		void *kaddr = kmap(rqst->rq_pages[i]);
> > -		size_t len = rqst->rq_pagesz;
> > +		void *kaddr;
> > +		unsigned int len, offset;
> >
> > -		if (i == rqst->rq_npages - 1)
> > -			len = rqst->rq_tailsz;
> > +		rqst_page_get_length(rqst, i, &len, &offset);
> > +
> > +		kaddr = (char *) kmap(rqst->rq_pages[i]) + offset;
> 
> I suppose it's more robust to map a page at a time, but it's pretty expensive.
> Is this the only way to iterate over a potentially very large block of data? For
> example, a 1MB segment means 256 kmap/kunmaps.

I will look into not mapping those pages while doing I/O.

This code path is for RDMA send/receive, and it's rarely used for transferring large amount of data.

> 
> Tom.
> 
> >
> >   		crypto_shash_update(shash, kaddr, len);
> >
> >

Patch

diff --git a/fs/cifs/cifsencrypt.c b/fs/cifs/cifsencrypt.c
index a6ef088..e88303c 100644
--- a/fs/cifs/cifsencrypt.c
+++ b/fs/cifs/cifsencrypt.c
@@ -68,11 +68,12 @@  int __cifs_calc_signature(struct smb_rqst *rqst,
 
 	/* now hash over the rq_pages array */
 	for (i = 0; i < rqst->rq_npages; i++) {
-		void *kaddr = kmap(rqst->rq_pages[i]);
-		size_t len = rqst->rq_pagesz;
+		void *kaddr;
+		unsigned int len, offset;
 
-		if (i == rqst->rq_npages - 1)
-			len = rqst->rq_tailsz;
+		rqst_page_get_length(rqst, i, &len, &offset);
+
+		kaddr = (char *) kmap(rqst->rq_pages[i]) + offset;
 
 		crypto_shash_update(shash, kaddr, len);