ceph: use a shared zero page rather than one per messenger

Each messenger allocates a page to be used when writing zeroes
out in the event of error or other abnormal condition.  Instead,
use the kernel ZERO_PAGE() for that purpose.

Signed-off-by: Alex Elder <elder@dreamhost.com>
Signed-off-by: Sage Weil <sage@newdream.net>

diff --git a/include/linux/ceph/messenger.h b/include/linux/ceph/messenger.h
index ffbeb2c..6b5af5f 100644 (file)
--- a/include/linux/ceph/messenger.h
+++ b/include/linux/ceph/messenger.h
@@ -54,7 +54,6 @@ struct ceph_connection_operations {
 struct ceph_messenger {
        struct ceph_entity_inst inst;    /* my name+address */
        struct ceph_entity_addr my_enc_addr;
-       struct page *zero_page;          /* used in certain error cases */
 
        bool nocrc;
 

diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index d11f91b..7383562 100644 (file)
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -52,6 +52,9 @@ static char addr_str[MAX_ADDR_STR][MAX_ADDR_STR_LEN];
 static DEFINE_SPINLOCK(addr_str_lock);
 static int last_addr_str;
 
+static struct page *zero_page;         /* used in certain error cases */
+static void *zero_page_address;                /* kernel virtual addr of zero_page */
+
 const char *ceph_pr_addr(const struct sockaddr_storage *ss)
 {
        int i;
@@ -99,18 +102,41 @@ struct workqueue_struct *ceph_msgr_wq;
 
 int ceph_msgr_init(void)
 {
+       BUG_ON(zero_page != NULL);
+       zero_page = ZERO_PAGE(0);
+       page_cache_get(zero_page);
+
+       BUG_ON(zero_page_address != NULL);
+       zero_page_address = kmap(zero_page);
+
        ceph_msgr_wq = alloc_workqueue("ceph-msgr", WQ_NON_REENTRANT, 0);
        if (!ceph_msgr_wq) {
                pr_err("msgr_init failed to create workqueue\n");
+
+               zero_page_address = NULL;
+               kunmap(zero_page);
+               page_cache_release(zero_page);
+               zero_page = NULL;
+
                return -ENOMEM;
        }
+
        return 0;
 }
 EXPORT_SYMBOL(ceph_msgr_init);
 
 void ceph_msgr_exit(void)
 {
+       BUG_ON(ceph_msgr_wq == NULL);
        destroy_workqueue(ceph_msgr_wq);
+
+       BUG_ON(zero_page_address == NULL);
+       zero_page_address = NULL;
+
+       BUG_ON(zero_page == NULL);
+       kunmap(zero_page);
+       page_cache_release(zero_page);
+       zero_page = NULL;
 }
 EXPORT_SYMBOL(ceph_msgr_exit);
 
@@ -841,9 +867,9 @@ static int write_partial_msg_pages(struct ceph_connection *con)
                        max_write = bv->bv_len;
 #endif
                } else {
-                       page = con->msgr->zero_page;
+                       page = zero_page;
                        if (crc)
-                               kaddr = page_address(con->msgr->zero_page);
+                               kaddr = zero_page_address;
                }
                len = min_t(int, max_write - con->out_msg_pos.page_pos,
                            total_max_write);
@@ -914,7 +940,7 @@ static int write_partial_skip(struct ceph_connection *con)
 
        while (con->out_skip > 0) {
                struct kvec iov = {
-                       .iov_base = page_address(con->msgr->zero_page),
+                       .iov_base = zero_page_address,
                        .iov_len = min(con->out_skip, (int)PAGE_CACHE_SIZE)
                };
 
@@ -2222,15 +2248,6 @@ struct ceph_messenger *ceph_messenger_create(struct ceph_entity_addr *myaddr,
 
        spin_lock_init(&msgr->global_seq_lock);
 
-       /* the zero page is needed if a request is "canceled" while the message
-        * is being written over the socket */
-       msgr->zero_page = __page_cache_alloc(GFP_KERNEL | __GFP_ZERO);
-       if (!msgr->zero_page) {
-               kfree(msgr);
-               return ERR_PTR(-ENOMEM);
-       }
-       kmap(msgr->zero_page);
-
        if (myaddr)
                msgr->inst.addr = *myaddr;
 
@@ -2247,8 +2264,6 @@ EXPORT_SYMBOL(ceph_messenger_create);
 void ceph_messenger_destroy(struct ceph_messenger *msgr)
 {
        dout("destroy %p\n", msgr);
-       kunmap(msgr->zero_page);
-       __free_page(msgr->zero_page);
        kfree(msgr);
        dout("destroyed messenger %p\n", msgr);
 }