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

PATCH In review piaojun 2 participants 3 messages Jul 17, 2018 – Jul 18, 2018 9P file system

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piaojun

author

2018-07-17 06:26 UTC #0 lore raw

PATCH v2 1/1 net/9p/client.c: fix misuse of spin_lock_irqsave for p9_client lock

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.

Rebased on 9p-next.

Signed-off-by Jun Piao <[email protected]>

---
 net/9p/client.c   | 18 ++++++++----------
 net/9p/trans_fd.c |  7 +++----
 2 files changed, 11 insertions(+), 14 deletions(-)

net/9p/client.c +8 ~~-10~~

index 30f9aee..f6897ee 100644
@@ -275,14 +275,14 @@ static struct p9_fcall *p9_fcall_alloc(int alloc_msize)
 	INIT_LIST_HEAD(&req->req_list);
 
 	idr_preload(GFP_NOFS);
-	spin_lock_irq(&c->lock);
+	spin_lock(&c->lock);
 	if (type == P9_TVERSION)
 		tag = idr_alloc(&c->reqs, req, P9_NOTAG, P9_NOTAG + 1,
 				GFP_NOWAIT);
 	else
 		tag = idr_alloc(&c->reqs, req, 0, P9_NOTAG, GFP_NOWAIT);
 	req->tc->tag = tag;
-	spin_unlock_irq(&c->lock);
+	spin_unlock(&c->lock);
 	idr_preload_end();
 	if (tag < 0)
 		goto free;

@@ -328,13 +328,12 @@ struct p9_req_t *p9_tag_lookup(struct p9_client *c, u16 tag)
  */
 static void p9_free_req(struct p9_client *c, struct p9_req_t *r)
 {
-	unsigned long flags;
 	u16 tag = r->tc->tag;
 
 	p9_debug(P9_DEBUG_MUX, "clnt %p req %p tag: %d\n", c, r, tag);
-	spin_lock_irqsave(&c->lock, flags);
+	spin_lock(&c->lock);
 	idr_remove(&c->reqs, tag);
-	spin_unlock_irqrestore(&c->lock, flags);
+	spin_unlock(&c->lock);
 	kfree(r->tc);
 	kfree(r->rc);
 	kmem_cache_free(p9_req_cache, r);

@@ -846,10 +845,10 @@ static struct p9_fid *p9_fid_create(struct p9_client *clnt)
 	fid->fid = 0;
 
 	idr_preload(GFP_KERNEL);
-	spin_lock_irq(&clnt->lock);
+	spin_lock(&clnt->lock);
 	ret = idr_alloc_u32(&clnt->fids, fid, &fid->fid, P9_NOFID - 1,
 			    GFP_NOWAIT);
-	spin_unlock_irq(&clnt->lock);
+	spin_unlock(&clnt->lock);
 	idr_preload_end();
 
 	if (!ret)

@@ -862,13 +861,12 @@ 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;
-	spin_lock_irqsave(&clnt->lock, flags);
+	spin_lock(&clnt->lock);
 	idr_remove(&clnt->fids, fid->fid);
-	spin_unlock_irqrestore(&clnt->lock, flags);
+	spin_unlock(&clnt->lock);
 	kfree(fid->rdir);
 	kfree(fid);
 }

net/9p/trans_fd.c +3 -4

index bf459ee..94ef685 100644
@@ -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);

Dominique Martinet

maintainer

2018-07-17 11:57 UTC #1 lore raw

piaojun wrote on Tue, Jul 17, 2018:

Quoted 4 lines

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.

(I didn't say in v1, but the commit message sounds a bit odd to me, if there is any other change to the patch could you please rephrase it a bit?)

Quoted 1 line

Rebased on 9p-next.

(Likewise, this should probably go below the '---' mark to not be in the final commit message, 9p-next does not make sense to linux as a whole)

Quoted 2 lines

Signed-off-by Jun Piao <[email protected]>

Nitpicks aside this still looks good to me, I'm not expert in locking but I believe the conn_cancel stuff in trans_fd is called either from user context or workqueue which also is process context, while the rest comes from user context only.

There *are* common functions called from interrupt context (I see:
p9_tag_lookup, p9_client_cb, p9_parse_header) but luckily enough none of these take the lock.

I'll give this one a little bit of time for others to review before picking it up, just in case, but will do if no-one complains.

Quoted 103 lines

---
 net/9p/client.c   | 18 ++++++++----------
 net/9p/trans_fd.c |  7 +++----
 2 files changed, 11 insertions(+), 14 deletions(-)

net/9p/client.c +8 ~~-10~~

index 30f9aee..f6897ee 100644
@@ -275,14 +275,14 @@ static struct p9_fcall *p9_fcall_alloc(int alloc_msize)
 	INIT_LIST_HEAD(&req->req_list);
 
 	idr_preload(GFP_NOFS);
-	spin_lock_irq(&c->lock);
+	spin_lock(&c->lock);
 	if (type == P9_TVERSION)
 		tag = idr_alloc(&c->reqs, req, P9_NOTAG, P9_NOTAG + 1,
 				GFP_NOWAIT);
 	else
 		tag = idr_alloc(&c->reqs, req, 0, P9_NOTAG, GFP_NOWAIT);
 	req->tc->tag = tag;
-	spin_unlock_irq(&c->lock);
+	spin_unlock(&c->lock);
 	idr_preload_end();
 	if (tag < 0)
 		goto free;

@@ -328,13 +328,12 @@ struct p9_req_t *p9_tag_lookup(struct p9_client *c, u16 tag)
  */
 static void p9_free_req(struct p9_client *c, struct p9_req_t *r)
 {
-	unsigned long flags;
 	u16 tag = r->tc->tag;
 
 	p9_debug(P9_DEBUG_MUX, "clnt %p req %p tag: %d\n", c, r, tag);
-	spin_lock_irqsave(&c->lock, flags);
+	spin_lock(&c->lock);
 	idr_remove(&c->reqs, tag);
-	spin_unlock_irqrestore(&c->lock, flags);
+	spin_unlock(&c->lock);
 	kfree(r->tc);
 	kfree(r->rc);
 	kmem_cache_free(p9_req_cache, r);

@@ -846,10 +845,10 @@ static struct p9_fid *p9_fid_create(struct p9_client *clnt)
 	fid->fid = 0;
 
 	idr_preload(GFP_KERNEL);
-	spin_lock_irq(&clnt->lock);
+	spin_lock(&clnt->lock);
 	ret = idr_alloc_u32(&clnt->fids, fid, &fid->fid, P9_NOFID - 1,
 			    GFP_NOWAIT);
-	spin_unlock_irq(&clnt->lock);
+	spin_unlock(&clnt->lock);
 	idr_preload_end();
 
 	if (!ret)

@@ -862,13 +861,12 @@ 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;
-	spin_lock_irqsave(&clnt->lock, flags);
+	spin_lock(&clnt->lock);
 	idr_remove(&clnt->fids, fid->fid);
-	spin_unlock_irqrestore(&clnt->lock, flags);
+	spin_unlock(&clnt->lock);
 	kfree(fid->rdir);
 	kfree(fid);
 }

net/9p/trans_fd.c +3 -4

index bf459ee..94ef685 100644
@@ -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);

Signature · 1 line

Dominique Martinet

piaojun

author

2018-07-18 02:19 UTC #2 lore raw

Hi Dominique,

Quoted 9 lines · Dominique Martinet

piaojun wrote on Tue, Jul 17, 2018:
Quoted 4 lines
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.
(I didn't say in v1, but the commit message sounds a bit odd to me, if there is any other change to the patch could you please rephrase it a bit?)

Yes, I will rephrase it if there is any change to the patch.

Quoted 6 lines

Quoted 2 lines
Rebased on 9p-next.
(Likewise, this should probably go below the '---' mark to not be in the final commit message, 9p-next does not make sense to linux as a whole)

Thanks for your suggestion.

Quoted 119 lines

Quoted 2 lines

Signed-off-by Jun Piao <[email protected]>

There *are* common functions called from interrupt context (I see:
p9_tag_lookup, p9_client_cb, p9_parse_header) but luckily enough none of these take the lock.

I'll give this one a little bit of time for others to review before picking it up, just in case, but will do if no-one complains.

Quoted 103 lines

---
 net/9p/client.c   | 18 ++++++++----------
 net/9p/trans_fd.c |  7 +++----
 2 files changed, 11 insertions(+), 14 deletions(-)

net/9p/client.c +8 ~~-10~~

index 30f9aee..f6897ee 100644
@@ -275,14 +275,14 @@ static struct p9_fcall *p9_fcall_alloc(int alloc_msize)
 	INIT_LIST_HEAD(&req->req_list);
 
 	idr_preload(GFP_NOFS);
-	spin_lock_irq(&c->lock);
+	spin_lock(&c->lock);
 	if (type == P9_TVERSION)
 		tag = idr_alloc(&c->reqs, req, P9_NOTAG, P9_NOTAG + 1,
 				GFP_NOWAIT);
 	else
 		tag = idr_alloc(&c->reqs, req, 0, P9_NOTAG, GFP_NOWAIT);
 	req->tc->tag = tag;
-	spin_unlock_irq(&c->lock);
+	spin_unlock(&c->lock);
 	idr_preload_end();
 	if (tag < 0)
 		goto free;

@@ -328,13 +328,12 @@ struct p9_req_t *p9_tag_lookup(struct p9_client *c, u16 tag)
  */
 static void p9_free_req(struct p9_client *c, struct p9_req_t *r)
 {
-	unsigned long flags;
 	u16 tag = r->tc->tag;
 
 	p9_debug(P9_DEBUG_MUX, "clnt %p req %p tag: %d\n", c, r, tag);
-	spin_lock_irqsave(&c->lock, flags);
+	spin_lock(&c->lock);
 	idr_remove(&c->reqs, tag);
-	spin_unlock_irqrestore(&c->lock, flags);
+	spin_unlock(&c->lock);
 	kfree(r->tc);
 	kfree(r->rc);
 	kmem_cache_free(p9_req_cache, r);

@@ -846,10 +845,10 @@ static struct p9_fid *p9_fid_create(struct p9_client *clnt)
 	fid->fid = 0;
 
 	idr_preload(GFP_KERNEL);
-	spin_lock_irq(&clnt->lock);
+	spin_lock(&clnt->lock);
 	ret = idr_alloc_u32(&clnt->fids, fid, &fid->fid, P9_NOFID - 1,
 			    GFP_NOWAIT);
-	spin_unlock_irq(&clnt->lock);
+	spin_unlock(&clnt->lock);
 	idr_preload_end();
 
 	if (!ret)

@@ -862,13 +861,12 @@ 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;
-	spin_lock_irqsave(&clnt->lock, flags);
+	spin_lock(&clnt->lock);
 	idr_remove(&clnt->fids, fid->fid);
-	spin_unlock_irqrestore(&clnt->lock, flags);
+	spin_unlock(&clnt->lock);
 	kfree(fid->rdir);
 	kfree(fid);
 }

net/9p/trans_fd.c +3 -4

index bf459ee..94ef685 100644
@@ -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);