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author | Venkateswararao Jujjuri (JV) <jvrao@linux.vnet.ibm.com> | 2011-01-28 14:11:13 -0800 |
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committer | Eric Van Hensbergen <ericvh@gmail.com> | 2011-03-15 09:57:34 -0500 |
commit | 022cae36551ba805bf82084047945b2901d75f36 (patch) | |
tree | 5d8a8ff0eb2102d0449f58ddfcb8907bd3625682 /net/9p/trans_common.c | |
parent | 6752a1ebd13f69b9d5ff08914fe29ee2813cbeea (diff) | |
download | lwn-022cae36551ba805bf82084047945b2901d75f36.tar.gz lwn-022cae36551ba805bf82084047945b2901d75f36.zip |
[net/9p] Preparation and helper functions for zero copy
This patch prepares p9_fcall structure for zero copy. Added
fields send the payload buffer information to the transport layer.
In addition it adds a 'private' field for the transport layer to
store mapped/pinned page information so that it can be freed/unpinned
during req_done.
This patch also creates trans_common.[ch] to house helper functions.
It adds the following helper functions.
p9_release_req_pages - Release pages after the transaction.
p9_nr_pages - Return number of pages needed to accomodate the payload.
payload_gup - Translates user buffer into kernel pages.
Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
Diffstat (limited to 'net/9p/trans_common.c')
-rw-r--r-- | net/9p/trans_common.c | 97 |
1 files changed, 97 insertions, 0 deletions
diff --git a/net/9p/trans_common.c b/net/9p/trans_common.c new file mode 100644 index 000000000000..d62b9aa58df8 --- /dev/null +++ b/net/9p/trans_common.c @@ -0,0 +1,97 @@ +/* + * Copyright IBM Corporation, 2010 + * Author Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com> + * + * This program is free software; you can redistribute it and/or modify it + * under the terms of version 2.1 of the GNU Lesser General Public License + * as published by the Free Software Foundation. + * + * This program is distributed in the hope that it would be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. + * + */ + +#include <linux/slab.h> +#include <linux/module.h> +#include <net/9p/9p.h> +#include <net/9p/client.h> +#include <linux/scatterlist.h> +#include "trans_common.h" + +/** + * p9_release_req_pages - Release pages after the transaction. + * @*private: PDU's private page of struct trans_rpage_info + */ +void +p9_release_req_pages(struct trans_rpage_info *rpinfo) +{ + int i = 0; + + while (rpinfo->rp_data[i] && rpinfo->rp_nr_pages--) { + put_page(rpinfo->rp_data[i]); + i++; + } +} +EXPORT_SYMBOL(p9_release_req_pages); + +/** + * p9_nr_pages - Return number of pages needed to accomodate the payload. + */ +int +p9_nr_pages(struct p9_req_t *req) +{ + int start_page, end_page; + start_page = (unsigned long long)req->tc->pubuf >> PAGE_SHIFT; + end_page = ((unsigned long long)req->tc->pubuf + req->tc->pbuf_size + + PAGE_SIZE - 1) >> PAGE_SHIFT; + return end_page - start_page; +} +EXPORT_SYMBOL(p9_nr_pages); + +/** + * payload_gup - Translates user buffer into kernel pages and + * pins them either for read/write through get_user_pages_fast(). + * @req: Request to be sent to server. + * @pdata_off: data offset into the first page after translation (gup). + * @pdata_len: Total length of the IO. gup may not return requested # of pages. + * @nr_pages: number of pages to accomodate the payload + * @rw: Indicates if the pages are for read or write. + */ +int +p9_payload_gup(struct p9_req_t *req, size_t *pdata_off, int *pdata_len, + int nr_pages, u8 rw) +{ + uint32_t first_page_bytes = 0; + uint32_t pdata_mapped_pages; + struct trans_rpage_info *rpinfo; + + *pdata_off = (size_t)req->tc->pubuf & (PAGE_SIZE-1); + + if (*pdata_off) + first_page_bytes = min((PAGE_SIZE - *pdata_off), + req->tc->pbuf_size); + + rpinfo = req->tc->private; + pdata_mapped_pages = get_user_pages_fast((unsigned long)req->tc->pubuf, + nr_pages, rw, &rpinfo->rp_data[0]); + + if (pdata_mapped_pages < 0) { + printk(KERN_ERR "get_user_pages_fast failed:%d udata:%p" + "nr_pages:%d\n", pdata_mapped_pages, + req->tc->pubuf, nr_pages); + pdata_mapped_pages = 0; + return -EIO; + } + rpinfo->rp_nr_pages = pdata_mapped_pages; + if (*pdata_off) { + *pdata_len = first_page_bytes; + *pdata_len += min((req->tc->pbuf_size - *pdata_len), + ((size_t)pdata_mapped_pages - 1) << PAGE_SHIFT); + } else { + *pdata_len = min(req->tc->pbuf_size, + (size_t)pdata_mapped_pages << PAGE_SHIFT); + } + return 0; +} +EXPORT_SYMBOL(p9_payload_gup); |