9p: Add mempools for RPCs9p_mempool

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Cc: Eric Van Hensbergen <ericvh@gmail.com>
Cc: Latchesar Ionkov <lucho@ionkov.net>
Cc: Dominique Martinet <asmadeus@codewreck.org>

4 files changed, 54 insertions, 32 deletions

diff --git a/include/net/9p/9p.h b/include/net/9p/9p.h
index 24a509f559ee..0b20ee6854d6 100644
--- a/include/net/9p/9p.h
+++ b/include/net/9p/9p.h
@@ -539,12 +539,12 @@ struct p9_rstatfs {
 struct p9_fcall {
 	u32 size;
 	u8 id;
+	bool used_mempool;
 	u16 tag;
 
 	size_t offset;
 	size_t capacity;
 
-	struct kmem_cache *cache;
 	u8 *sdata;
 };
 
diff --git a/include/net/9p/client.h b/include/net/9p/client.h
index cb78e0e33332..832dcc866a20 100644
--- a/include/net/9p/client.h
+++ b/include/net/9p/client.h
@@ -9,6 +9,7 @@
 #ifndef NET_9P_CLIENT_H
 #define NET_9P_CLIENT_H
 
+#include <linux/mempool.h>
 #include <linux/utsname.h>
 #include <linux/idr.h>
 
@@ -107,6 +108,14 @@ struct p9_client {
 	void *trans;
 	struct kmem_cache *fcall_cache;
 
+	/*
+	 * We need two identical mempools because it's not safe to allocate
+	 * multiple elements from the same pool (without freeing the first);
+	 * that will deadlock if multiple threads need the last element at the
+	 * same time.
+	 */
+	mempool_t pools[2];
+
 	union {
 		struct {
 			int rfd;
@@ -222,7 +231,8 @@ int p9_client_mkdir_dotl(struct p9_fid *fid, const char *name, int mode,
 				kgid_t gid, struct p9_qid *qid);
 int p9_client_lock_dotl(struct p9_fid *fid, struct p9_flock *flock, u8 *status);
 int p9_client_getlock_dotl(struct p9_fid *fid, struct p9_getlock *fl);
-void p9_fcall_fini(struct p9_fcall *fc);
+void p9_fcall_fini(struct p9_client *c, struct p9_fcall *fc,
+		   int fc_idx);
 struct p9_req_t *p9_tag_lookup(struct p9_client *c, u16 tag);
 
 static inline void p9_req_get(struct p9_req_t *r)
diff --git a/net/9p/client.c b/net/9p/client.c
index a36a40137caa..e14074d031c6 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -218,23 +218,29 @@ free_and_return:
 	return ret;
 }
 
-static int p9_fcall_init(struct p9_client *c, struct p9_fcall *fc,
-			 int alloc_msize)
+static void p9_fcall_init(struct p9_client *c, struct p9_fcall *fc,
+			  int fc_idx, unsigned alloc_msize)
 {
-	if (likely(c->fcall_cache) && alloc_msize == c->msize) {
-		fc->sdata = kmem_cache_alloc(c->fcall_cache, GFP_NOFS);
-		fc->cache = c->fcall_cache;
-	} else {
-		fc->sdata = kmalloc(alloc_msize, GFP_NOFS);
-		fc->cache = NULL;
-	}
-	if (!fc->sdata)
-		return -ENOMEM;
+	gfp_t gfp = GFP_NOFS|__GFP_NOWARN;
+
+	BUG_ON(alloc_msize > c->msize);
+
+	fc->sdata = NULL;
+	fc->used_mempool = false;
 	fc->capacity = alloc_msize;
-	return 0;
+
+	if (alloc_msize < c->msize)
+		fc->sdata = kmalloc(alloc_msize, gfp);
+
+	if (!fc->sdata) {
+		fc->sdata = mempool_alloc(&c->pools[fc_idx], gfp);
+		fc->used_mempool = true;
+		fc->capacity = c->msize;
+	}
 }
 
-void p9_fcall_fini(struct p9_fcall *fc)
+void p9_fcall_fini(struct p9_client *c, struct p9_fcall *fc,
+		   int fc_idx)
 {
 	/* sdata can be NULL for interrupted requests in trans_rdma,
 	 * and kmem_cache_free does not do NULL-check for us
@@ -242,8 +248,8 @@ void p9_fcall_fini(struct p9_fcall *fc)
 	if (unlikely(!fc->sdata))
 		return;
 
-	if (fc->cache)
-		kmem_cache_free(fc->cache, fc->sdata);
+	if (fc->used_mempool)
+		mempool_free(fc->sdata, &c->pools[fc_idx]);
 	else
 		kfree(fc->sdata);
 }
@@ -270,10 +276,8 @@ p9_tag_alloc(struct p9_client *c, int8_t type, unsigned int max_size)
 	if (!req)
 		return ERR_PTR(-ENOMEM);
 
-	if (p9_fcall_init(c, &req->tc, alloc_msize))
-		goto free_req;
-	if (p9_fcall_init(c, &req->rc, alloc_msize))
-		goto free;
+	p9_fcall_init(c, &req->tc, 0, alloc_msize);
+	p9_fcall_init(c, &req->rc, 1, alloc_msize);
 
 	p9pdu_reset(&req->tc);
 	p9pdu_reset(&req->rc);
@@ -310,9 +314,8 @@ p9_tag_alloc(struct p9_client *c, int8_t type, unsigned int max_size)
 	return req;
 
 free:
-	p9_fcall_fini(&req->tc);
-	p9_fcall_fini(&req->rc);
-free_req:
+	p9_fcall_fini(c, &req->tc, 0);
+	p9_fcall_fini(c, &req->rc, 1);
 	kmem_cache_free(p9_req_cache, req);
 	return ERR_PTR(-ENOMEM);
 }
@@ -373,8 +376,8 @@ static int p9_tag_remove(struct p9_client *c, struct p9_req_t *r)
 int p9_req_put(struct p9_client *c, struct p9_req_t *r)
 {
 	if (refcount_dec_and_test(&r->refcount)) {
-		p9_fcall_fini(&r->tc);
-		p9_fcall_fini(&r->rc);
+		p9_fcall_fini(c, &r->tc, 0);
+		p9_fcall_fini(c, &r->rc, 1);
 		kmem_cache_free(p9_req_cache, r);
 		return 1;
 	}
@@ -999,7 +1002,7 @@ struct p9_client *p9_client_create(const char *dev_name, char *options)
 	char *client_id;
 
 	err = 0;
-	clnt = kmalloc(sizeof(*clnt), GFP_KERNEL);
+	clnt = kzalloc(sizeof(*clnt), GFP_KERNEL);
 	if (!clnt)
 		return ERR_PTR(-ENOMEM);
 
@@ -1050,10 +1053,6 @@ struct p9_client *p9_client_create(const char *dev_name, char *options)
 		goto close_trans;
 	}
 
-	err = p9_client_version(clnt);
-	if (err)
-		goto close_trans;
-
 	/* P9_HDRSZ + 4 is the smallest packet header we can have that is
 	 * followed by data accessed from userspace by read
 	 */
@@ -1063,6 +1062,15 @@ struct p9_client *p9_client_create(const char *dev_name, char *options)
 					   clnt->msize - (P9_HDRSZ + 4),
 					   NULL);
 
+	err =   mempool_init_slab_pool(&clnt->pools[0], 4, clnt->fcall_cache) ?:
+		mempool_init_slab_pool(&clnt->pools[1], 4, clnt->fcall_cache);
+	if (err)
+		goto close_trans;
+
+	err = p9_client_version(clnt);
+	if (err)
+		goto close_trans;
+
 	return clnt;
 
 close_trans:
@@ -1070,6 +1078,8 @@ close_trans:
 put_trans:
 	v9fs_put_trans(clnt->trans_mod);
 free_client:
+	mempool_exit(&clnt->pools[1]);
+	mempool_exit(&clnt->pools[0]);
 	kfree(clnt);
 	return ERR_PTR(err);
 }
@@ -1094,6 +1104,8 @@ void p9_client_destroy(struct p9_client *clnt)
 
 	p9_tag_cleanup(clnt);
 
+	mempool_exit(&clnt->pools[1]);
+	mempool_exit(&clnt->pools[0]);
 	kmem_cache_destroy(clnt->fcall_cache);
 	kfree(clnt);
 }
diff --git a/net/9p/trans_rdma.c b/net/9p/trans_rdma.c
index d817d3745238..99d878d70d56 100644
--- a/net/9p/trans_rdma.c
+++ b/net/9p/trans_rdma.c
@@ -431,7 +431,7 @@ static int rdma_request(struct p9_client *client, struct p9_req_t *req)
 	if (unlikely(atomic_read(&rdma->excess_rc) > 0)) {
 		if ((atomic_sub_return(1, &rdma->excess_rc) >= 0)) {
 			/* Got one! */
-			p9_fcall_fini(&req->rc);
+			p9_fcall_fini(client, &req->rc, 1);
 			req->rc.sdata = NULL;
 			goto dont_need_post_recv;
 		} else {