[PATCH] net/9p: Handle get_user_pages_fast return properly

[PATCH] net/9p: Handle get_user_pages_fast return properly

[M. Mohan Kumar]

Use proper data type to handle get_user_pages_fast error condition. Also
do not treat EFAULT error as fatal.

Signed-off-by: M. Mohan Kumar <mohan@in.ibm.com>
---
 net/9p/client.c       |    2 +-
 net/9p/trans_common.c |   11 +++--------
 2 files changed, 4 insertions(+), 9 deletions(-)

diff --git a/net/9p/client.c b/net/9p/client.c
index 691a04a..1612142 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -614,7 +614,7 @@ p9_client_rpc(struct p9_client *c, int8_t type, const char *fmt, ...)
 
 	err = c->trans_mod->request(c, req);
 	if (err < 0) {
-		if (err != -ERESTARTSYS)
+		if (err != -ERESTARTSYS && err != -EFAULT)
 			c->status = Disconnected;
 		goto reterr;
 	}
diff --git a/net/9p/trans_common.c b/net/9p/trans_common.c
index 14265e8..f020da9 100644
--- a/net/9p/trans_common.c
+++ b/net/9p/trans_common.c
@@ -63,7 +63,7 @@ p9_payload_gup(struct p9_req_t *req, size_t *pdata_off, int *pdata_len,
 		int nr_pages, u8 rw)
 {
 	uint32_t first_page_bytes = 0;
-	uint32_t pdata_mapped_pages;
+	int32_t pdata_mapped_pages;
 	struct trans_rpage_info  *rpinfo;
 
 	*pdata_off = (__force size_t)req->tc->pubuf & (PAGE_SIZE-1);
@@ -75,14 +75,9 @@ p9_payload_gup(struct p9_req_t *req, size_t *pdata_off, int *pdata_len,
 	rpinfo = req->tc->private;
 	pdata_mapped_pages = get_user_pages_fast((unsigned long)req->tc->pubuf,
 			nr_pages, rw, &rpinfo->rp_data[0]);
+	if (pdata_mapped_pages <= 0)
+		return pdata_mapped_pages;
 
-	if (pdata_mapped_pages < 0) {
-		printk(KERN_ERR "get_user_pages_fast failed:%d udata:%p"
-				"nr_pages:%d\n", pdata_mapped_pages,
-				req->tc->pubuf, nr_pages);
-		pdata_mapped_pages = 0;
-		return -EIO;
-	}
 	rpinfo->rp_nr_pages = pdata_mapped_pages;
 	if (*pdata_off) {
 		*pdata_len = first_page_bytes;
-- 
1.7.4

Re: [V9fs-developer] [PATCH] net/9p: Handle get_user_pages_fast return properly

[Venkateswararao Jujjuri]

On 04/15/2011 01:29 AM, M. Mohan Kumar wrote:
> Use proper data type to handle get_user_pages_fast error condition. Also
> do not treat EFAULT error as fatal.
>
> Signed-off-by: M. Mohan Kumar<mohan@in.ibm.com>
> ---
>   net/9p/client.c       |    2 +-
>   net/9p/trans_common.c |   11 +++--------
>   2 files changed, 4 insertions(+), 9 deletions(-)
>
> diff --git a/net/9p/client.c b/net/9p/client.c
> index 691a04a..1612142 100644
> --- a/net/9p/client.c
> +++ b/net/9p/client.c
> @@ -614,7 +614,7 @@ p9_client_rpc(struct p9_client *c, int8_t type, const char *fmt, ...)
>
>   	err = c->trans_mod->request(c, req);
>   	if (err<  0) {
> -		if (err != -ERESTARTSYS)
> +		if (err != -ERESTARTSYS&&  err != -EFAULT)
Please analyze other errors that could be returned by 
c->trans_mod->request()
if they need any handling here.

>   			c->status = Disconnected;
>   		goto reterr;
>   	}
> diff --git a/net/9p/trans_common.c b/net/9p/trans_common.c
> index 14265e8..f020da9 100644
> --- a/net/9p/trans_common.c
> +++ b/net/9p/trans_common.c
> @@ -63,7 +63,7 @@ p9_payload_gup(struct p9_req_t *req, size_t *pdata_off, int *pdata_len,
>   		int nr_pages, u8 rw)
>   {
>   	uint32_t first_page_bytes = 0;
> -	uint32_t pdata_mapped_pages;
> +	int32_t pdata_mapped_pages;
>   	struct trans_rpage_info  *rpinfo;
>
>   	*pdata_off = (__force size_t)req->tc->pubuf&  (PAGE_SIZE-1);
> @@ -75,14 +75,9 @@ p9_payload_gup(struct p9_req_t *req, size_t *pdata_off, int *pdata_len,
>   	rpinfo = req->tc->private;
>   	pdata_mapped_pages = get_user_pages_fast((unsigned long)req->tc->pubuf,
>   			nr_pages, rw,&rpinfo->rp_data[0]);
> +	if (pdata_mapped_pages<= 0)
> +		return pdata_mapped_pages;
>
> -	if (pdata_mapped_pages<  0) {
> -		printk(KERN_ERR "get_user_pages_fast failed:%d udata:%p"
> -				"nr_pages:%d\n", pdata_mapped_pages,
> -				req->tc->pubuf, nr_pages);
> -		pdata_mapped_pages = 0;
> -		return -EIO;
> -	}
I would keep the printk and return  the pdata_mapped_pages inside the if 
condition.

Thanks,
JV

>   	rpinfo->rp_nr_pages = pdata_mapped_pages;
>   	if (*pdata_off) {
>   		*pdata_len = first_page_bytes;

Re: [V9fs-developer] [PATCH] net/9p: Handle get_user_pages_fast return properly

[M. Mohan Kumar]

On Friday 15 April 2011 8:23:16 pm Venkateswararao Jujjuri wrote:
> > 
> > -		if (err != -ERESTARTSYS)
> > +		if (err != -ERESTARTSYS&&  err != -EFAULT)
> 
> Please analyze other errors that could be returned by
> c->trans_mod->request()
> if they need any handling here.

Thanks JV, but we don't need to handle other errors as of now.

I will post a V2 patch with retaining printing error message.
----
M. Mohan Kumar

Re: [V9fs-developer] [PATCH] net/9p: Handle get_user_pages_fast return properly

[Venkateswararao Jujjuri]

On 04/19/2011 08:24 AM, M. Mohan Kumar wrote:
> On Friday 15 April 2011 8:23:16 pm Venkateswararao Jujjuri wrote:
>>> -		if (err != -ERESTARTSYS)
>>> +		if (err != -ERESTARTSYS&&   err != -EFAULT)
>> Please analyze other errors that could be returned by
>> c->trans_mod->request()
>> if they need any handling here.
> Thanks JV, but we don't need to handle other errors as of now.
*request could also return -EIO and -ENOMEM.
As you said, may be we should leave the default behavior on these 
errors(suspend the channel).

Thanks,
JV
> I will post a V2 patch with retaining printing error message.
> ----
> M. Mohan Kumar