[PATCH] net/9p/client.c: fix misuse of spin_lock_irqsave for p9_client lock

[PATCH] net/9p/client.c: fix misuse of spin_lock_irqsave for p9_client lock

[piaojun]

In p9_read_work(), we use spin_lock for client->lock, but misuse
spin_lock_irqsave for it in p9_fid_create(). As p9_client lock won't be
locked in irq context, so spin_lock is enough. And that will improve the
performance.

Signed-off-by: Jun Piao <piaojun@huawei.com>
---
 net/9p/client.c   | 17 +++++++----------
 net/9p/trans_fd.c |  7 +++----
 2 files changed, 10 insertions(+), 14 deletions(-)

diff --git a/net/9p/client.c b/net/9p/client.c
index 8bc8b3e..b05cbfc 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -260,7 +260,6 @@ static struct p9_fcall *p9_fcall_alloc(int alloc_msize)
 static struct p9_req_t *
 p9_tag_alloc(struct p9_client *c, u16 tag, unsigned int max_size)
 {
-	unsigned long flags;
 	int row, col;
 	struct p9_req_t *req;
 	int alloc_msize = min(c->msize, max_size);
@@ -270,7 +269,7 @@ static struct p9_fcall *p9_fcall_alloc(int alloc_msize)
 	tag++;

 	if (tag >= c->max_tag) {
-		spin_lock_irqsave(&c->lock, flags);
+		spin_lock(&c->lock);
 		/* check again since original check was outside of lock */
 		while (tag >= c->max_tag) {
 			row = (tag / P9_ROW_MAXTAG);
@@ -279,7 +278,7 @@ static struct p9_fcall *p9_fcall_alloc(int alloc_msize)

 			if (!c->reqs[row]) {
 				pr_err("Couldn't grow tag array\n");
-				spin_unlock_irqrestore(&c->lock, flags);
+				spin_unlock(&c->lock);
 				return ERR_PTR(-ENOMEM);
 			}
 			for (col = 0; col < P9_ROW_MAXTAG; col++) {
@@ -288,7 +287,7 @@ static struct p9_fcall *p9_fcall_alloc(int alloc_msize)
 			}
 			c->max_tag += P9_ROW_MAXTAG;
 		}
-		spin_unlock_irqrestore(&c->lock, flags);
+		spin_unlock(&c->lock);
 	}
 	row = tag / P9_ROW_MAXTAG;
 	col = tag % P9_ROW_MAXTAG;
@@ -909,7 +908,6 @@ static struct p9_fid *p9_fid_create(struct p9_client *clnt)
 {
 	int ret;
 	struct p9_fid *fid;
-	unsigned long flags;

 	p9_debug(P9_DEBUG_FID, "clnt %p\n", clnt);
 	fid = kmalloc(sizeof(struct p9_fid), GFP_KERNEL);
@@ -928,9 +926,9 @@ static struct p9_fid *p9_fid_create(struct p9_client *clnt)
 	fid->uid = current_fsuid();
 	fid->clnt = clnt;
 	fid->rdir = NULL;
-	spin_lock_irqsave(&clnt->lock, flags);
+	spin_lock(&clnt->lock);
 	list_add(&fid->flist, &clnt->fidlist);
-	spin_unlock_irqrestore(&clnt->lock, flags);
+	spin_unlock(&clnt->lock);

 	return fid;

@@ -942,14 +940,13 @@ static struct p9_fid *p9_fid_create(struct p9_client *clnt)
 static void p9_fid_destroy(struct p9_fid *fid)
 {
 	struct p9_client *clnt;
-	unsigned long flags;

 	p9_debug(P9_DEBUG_FID, "fid %d\n", fid->fid);
 	clnt = fid->clnt;
 	p9_idpool_put(fid->fid, clnt->fidpool);
-	spin_lock_irqsave(&clnt->lock, flags);
+	spin_lock(&clnt->lock);
 	list_del(&fid->flist);
-	spin_unlock_irqrestore(&clnt->lock, flags);
+	spin_unlock(&clnt->lock);
 	kfree(fid->rdir);
 	kfree(fid);
 }
diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c
index 588bf88..96e1e68 100644
--- a/net/9p/trans_fd.c
+++ b/net/9p/trans_fd.c
@@ -197,15 +197,14 @@ static void p9_mux_poll_stop(struct p9_conn *m)
 static void p9_conn_cancel(struct p9_conn *m, int err)
 {
 	struct p9_req_t *req, *rtmp;
-	unsigned long flags;
 	LIST_HEAD(cancel_list);

 	p9_debug(P9_DEBUG_ERROR, "mux %p err %d\n", m, err);

-	spin_lock_irqsave(&m->client->lock, flags);
+	spin_lock(&m->client->lock);

 	if (m->err) {
-		spin_unlock_irqrestore(&m->client->lock, flags);
+		spin_unlock(&m->client->lock);
 		return;
 	}

@@ -217,7 +216,7 @@ static void p9_conn_cancel(struct p9_conn *m, int err)
 	list_for_each_entry_safe(req, rtmp, &m->unsent_req_list, req_list) {
 		list_move(&req->req_list, &cancel_list);
 	}
-	spin_unlock_irqrestore(&m->client->lock, flags);
+	spin_unlock(&m->client->lock);

 	list_for_each_entry_safe(req, rtmp, &cancel_list, req_list) {
 		p9_debug(P9_DEBUG_ERROR, "call back req %p\n", req);
-- 

Re: [V9fs-developer] [PATCH] net/9p/client.c: fix misuse of spin_lock_irqsave for p9_client lock

[Dominique Martinet]

piaojun wrote on Thu, Jul 12, 2018:
> In p9_read_work(), we use spin_lock for client->lock, but misuse
> spin_lock_irqsave for it in p9_fid_create(). As p9_client lock won't be
> locked in irq context, so spin_lock is enough. And that will improve the
> performance.

Agreed on principle, see remark below

> Signed-off-by: Jun Piao <piaojun@huawei.com>
> ---
>  net/9p/client.c   | 17 +++++++----------
>  net/9p/trans_fd.c |  7 +++----
>  2 files changed, 10 insertions(+), 14 deletions(-)
> 
> diff --git a/net/9p/client.c b/net/9p/client.c
> index 8bc8b3e..b05cbfc 100644
> --- a/net/9p/client.c
> +++ b/net/9p/client.c
> @@ -260,7 +260,6 @@ static struct p9_fcall *p9_fcall_alloc(int alloc_msize)
>  static struct p9_req_t *
>  p9_tag_alloc(struct p9_client *c, u16 tag, unsigned int max_size)
>  {
> -	unsigned long flags;
>  	int row, col;
>  	struct p9_req_t *req;
>  	int alloc_msize = min(c->msize, max_size);
> @@ -270,7 +269,7 @@ static struct p9_fcall *p9_fcall_alloc(int alloc_msize)
>  	tag++;
> 
>  	if (tag >= c->max_tag) {
> -		spin_lock_irqsave(&c->lock, flags);
> +		spin_lock(&c->lock);

This code doesn't exist anymore with Matthew's idr rework, could you
submit that patch based on top of my 9p-next branch?
(unless you really want Andrew to take this for the next 4.18-rc, but
I'm not convinced this qualifies)

Please see my "Current 9P patches - test branch" for details:
https://sourceforge.net/p/v9fs/mailman/message/36365359/

-- 
Dominique Martinet

Re: [V9fs-developer] [PATCH] net/9p/client.c: fix misuse of spin_lock_irqsave for p9_client lock

[piaojun]

Hi Dominique,

On 2018/7/12 15:01, Dominique Martinet wrote:
> piaojun wrote on Thu, Jul 12, 2018:
>> In p9_read_work(), we use spin_lock for client->lock, but misuse
>> spin_lock_irqsave for it in p9_fid_create(). As p9_client lock won't be
>> locked in irq context, so spin_lock is enough. And that will improve the
>> performance.
> 
> Agreed on principle, see remark below
> 
>> Signed-off-by: Jun Piao <piaojun@huawei.com>
>> ---
>>  net/9p/client.c   | 17 +++++++----------
>>  net/9p/trans_fd.c |  7 +++----
>>  2 files changed, 10 insertions(+), 14 deletions(-)
>>
>> diff --git a/net/9p/client.c b/net/9p/client.c
>> index 8bc8b3e..b05cbfc 100644
>> --- a/net/9p/client.c
>> +++ b/net/9p/client.c
>> @@ -260,7 +260,6 @@ static struct p9_fcall *p9_fcall_alloc(int alloc_msize)
>>  static struct p9_req_t *
>>  p9_tag_alloc(struct p9_client *c, u16 tag, unsigned int max_size)
>>  {
>> -	unsigned long flags;
>>  	int row, col;
>>  	struct p9_req_t *req;
>>  	int alloc_msize = min(c->msize, max_size);
>> @@ -270,7 +269,7 @@ static struct p9_fcall *p9_fcall_alloc(int alloc_msize)
>>  	tag++;
>>
>>  	if (tag >= c->max_tag) {
>> -		spin_lock_irqsave(&c->lock, flags);
>> +		spin_lock(&c->lock);
> 
> This code doesn't exist anymore with Matthew's idr rework, could you
> submit that patch based on top of my 9p-next branch?
> (unless you really want Andrew to take this for the next 4.18-rc, but
> I'm not convinced this qualifies)

OK, I will rebase my patch and resend later.

Thanks,
Jun

> 
> Please see my "Current 9P patches - test branch" for details:
> https://sourceforge.net/p/v9fs/mailman/message/36365359/
>