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>

1 files changed, 29 insertions, 14 deletions

diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index d11f91b05452..738356255e0b 100644
--- 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);
 }