On 03/02/2012 11:21 AM, Sage Weil wrote:
On Wed, 29 Feb 2012, Alex Elder wrote: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@xxxxxxxxxxxxx> --- v2: Updated to use kernel ZERO_PAGE() include/linux/ceph/messenger.h | 1 net/ceph/messenger.c | 43 +++++++++++++++++++++++++++-------------- 2 files changed, 29 insertions(+), 15 deletions(-) Index: b/include/linux/ceph/messenger.h =================================================================== --- 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; Index: b/net/ceph/messenger.c =================================================================== --- a/net/ceph/messenger.c +++ b/net/ceph/messenger.c @@ -52,6 +52,9 @@ static char addr_str[MAX_ADDR_STR][MAX_A 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);I've always assumed that kmap() used up an expensive slot, and that pages should be kmapped only when needed. Myabe this should still be done inside write_partial_msg_pages()?
I think that's only for high memory pages, and especially for the kernel zero page I doubt that's where it sits. But you make a good point. I'll look into it a bit and if we're not guaranteed it's "free" to do this I'll re-post with the kmap done inside where it's needed. I'll follow up either way. -Alex
+ 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(struc 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 cep 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_cr 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); } -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html-- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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