Latchesar Ionkov wrote:
> pdu_fill_pages doesn't calculate correctly pdata_len. first_page_bytes
> should be min(PAGE_SIZE-pdu->pdata_off, size)
Good Catch. Thanks for finding it out. Will correct it in my next version.
Thanks,
JV
>
> Thanks,
> Lucho
>
> On Tue, Aug 17, 2010 at 11:27 AM, Venkateswararao Jujjuri (JV)
> <jvrao@xxxxxxxxxxxxxxxxxx> wrote:
>> This patch avoids copy_from_user by employing get_user_pages_fast() on the
>> udata buffer. This will eliminate an additonal copy of user buffer into
>> kernel buffer befre placing on the virtio ring.
>>
>> Signed-off-by: Venkateswararao Jujjuri <jvrao@xxxxxxxxxxxxxxxxxx>
>> Signed-off-by: Badari Pulavarty <pbadari@xxxxxxxxxx>
>> ---
>> net/9p/client.c | 32 ++++++++++++++++++++-
>> net/9p/protocol.c | 83 +++++++++++++++++++++++++++++++++++++++++++++++------
>> 2 files changed, 105 insertions(+), 10 deletions(-)
>>
>> diff --git a/net/9p/client.c b/net/9p/client.c
>> index 5487896..7ce58fb 100644
>> --- a/net/9p/client.c
>> +++ b/net/9p/client.c
>> @@ -36,6 +36,7 @@
>> #include <linux/parser.h>
>> #include <net/9p/client.h>
>> #include <net/9p/transport.h>
>> +#include <linux/mm.h>
>> #include "protocol.h"
>>
>> /*
>> @@ -521,6 +522,25 @@ static int p9_client_flush(struct p9_client *c, struct p9_req_t *oldreq)
>> }
>>
>> /**
>> + * p9_release_req_pages - Release pages after the transaction.
>> + * @req - Request buffer.
>> + *
>> + */
>> +static void
>> +p9_release_req_pages(struct p9_req_t *req)
>> +{
>> + int i = 0;
>> + while (req->tc->pdata[i] && req->tc->pdata_mapped_pages--) {
>> + put_page(req->tc->pdata[i]);
>> + req->tc->pdata[i] = NULL;
>> + i++;
>> + }
>> + req->tc->pdata_write_len = 0;
>> + req->tc->pdata_read_len = 0;
>> +}
>> +
>> +
>> +/**
>> * p9_client_rpc - issue a request and wait for a response
>> * @c: client session
>> * @type: type of request
>> @@ -575,6 +595,8 @@ p9_client_rpc(struct p9_client *c, int8_t type, const char *fmt, ...)
>> err = c->trans_mod->request(c, req);
>> if (err < 0) {
>> c->status = Disconnected;
>> + if (req->tc->pdata_write_len || req->tc->pdata_read_len)
>> + p9_release_req_pages(req);
>> goto reterr;
>> }
>>
>> @@ -583,6 +605,8 @@ p9_client_rpc(struct p9_client *c, int8_t type, const char *fmt, ...)
>> req->status >= REQ_STATUS_RCVD);
>> P9_DPRINTK(P9_DEBUG_MUX, "wait %p tag: %d returned %d\n",
>> req->wq, tag, err);
>> + if (req->tc->pdata_write_len || req->tc->pdata_read_len)
>> + p9_release_req_pages(req);
>>
>> if (req->status == REQ_STATUS_ERROR) {
>> P9_DPRINTK(P9_DEBUG_ERROR, "req_status error %d\n", req->t_err);
>> @@ -1331,9 +1355,15 @@ p9_client_write(struct p9_fid *fid, char *data, const char __user *udata,
>> if (data)
>> req = p9_client_rpc(clnt, P9_TWRITE, "dqD", fid->fid, offset,
>> rsize, data);
>> - else
>> + else {
>> + if (clnt->trans_mod->capability &&
>> + clnt->trans_mod->capability(P9_CAP_GET_MAX_SG_PAGES)) {
>> +
>> + rsize = count;
>> + }
>> req = p9_client_rpc(clnt, P9_TWRITE, "dqU", fid->fid, offset,
>> rsize, udata);
>> + }
>> if (IS_ERR(req)) {
>> err = PTR_ERR(req);
>> goto error;
>> diff --git a/net/9p/protocol.c b/net/9p/protocol.c
>> index ca63aff..97f313d 100644
>> --- a/net/9p/protocol.c
>> +++ b/net/9p/protocol.c
>> @@ -31,9 +31,12 @@
>> #include <linux/slab.h>
>> #include <linux/sched.h>
>> #include <linux/types.h>
>> +#include <linux/parser.h>
>> #include <net/9p/9p.h>
>> #include <net/9p/client.h>
>> #include "protocol.h"
>> +#include <net/9p/transport.h>
>> +#include <linux/pagemap.h>
>>
>> #ifndef MIN
>> #define MIN(a, b) (((a) < (b)) ? (a) : (b))
>> @@ -110,6 +113,51 @@ static size_t pdu_read(struct p9_fcall *pdu, void *data, size_t size)
>> return size - len;
>> }
>>
>> +static int
>> +pdu_fill_pages(struct p9_fcall *pdu, const char __user *udata, size_t size,
>> + int rw, int max_sg_pages)
>> +{
>> + int nr_pages;
>> + uint32_t first_page_bytes = 0;
>> + int pdata_len;
>> +
>> + nr_pages = size >> PAGE_SHIFT;
>> + pdu->pdata_off = (size_t)udata & (PAGE_SIZE-1);
>> + if (pdu->pdata_off)
>> + first_page_bytes = PAGE_SIZE - pdu->pdata_off;
>> + if (size - (first_page_bytes + (nr_pages << PAGE_SHIFT))) {
>> + /* trailing partial page */
>> + nr_pages++;
>> + }
>> + if (first_page_bytes) {
>> + /* leading partial page */
>> + nr_pages++;
>> + }
>> + nr_pages = min(max_sg_pages, nr_pages);
>> + pdu->pdata = (struct page **)(pdu->sdata + pdu->size);
>> + pdu->pdata_write_len = 0;
>> + pdu->pdata_read_len = 0;
>> + pdu->pdata_mapped_pages = get_user_pages_fast((unsigned long)udata,
>> + nr_pages, rw, pdu->pdata);
>> + if (pdu->pdata_mapped_pages < 0) {
>> + printk(KERN_WARNING "get_user_pages_fast failed:%d udata:%p"
>> + "nr_pages:%d\n", pdu->pdata_mapped_pages,
>> + udata, nr_pages);
>> + pdu->pdata_mapped_pages = 0;
>> + return -1;
>> + }
>> + if (pdu->pdata_off) {
>> + pdata_len = first_page_bytes;
>> + pdata_len += min((size - pdata_len),
>> + ((size_t)pdu->pdata_mapped_pages - 1) <<
>> + PAGE_SHIFT);
>> + } else {
>> + pdata_len = min(size, (size_t)pdu->pdata_mapped_pages <<
>> + PAGE_SHIFT);
>> + }
>> + return pdata_len;
>> +}
>> +
>> static size_t pdu_write(struct p9_fcall *pdu, const void *data, size_t size)
>> {
>> size_t len = MIN(pdu->capacity - pdu->size, size);
>> @@ -119,15 +167,31 @@ static size_t pdu_write(struct p9_fcall *pdu, const void *data, size_t size)
>> }
>>
>> static size_t
>> -pdu_write_u(struct p9_fcall *pdu, const char __user *udata, size_t size)
>> +pdu_write_u(struct p9_fcall *pdu, struct p9_client *c, const char __user *udata,
>> + size_t size)
>> {
>> - size_t len = MIN(pdu->capacity - pdu->size, size);
>> - int err = copy_from_user(&pdu->sdata[pdu->size], udata, len);
>> - if (err)
>> - printk(KERN_WARNING "pdu_write_u returning: %d\n", err);
>> + size_t len;
>> + int err;
>> + int max_req_sg_pages = 0;
>>
>> - pdu->size += len;
>> - return size - len;
>> + if (c->trans_mod->capability &&
>> + (udata && !segment_eq(get_fs(), KERNEL_DS))) {
>> + max_req_sg_pages =
>> + c->trans_mod->capability(P9_CAP_GET_MAX_SG_PAGES);
>> + }
>> + if (max_req_sg_pages) {
>> + len = pdu_fill_pages(pdu, udata, size, 0, max_req_sg_pages);
>> + if (len < 0)
>> + return len;
>> + pdu->pdata_write_len = len;
>> + } else {
>> + len = MIN(pdu->capacity - pdu->size, size);
>> + err = copy_from_user(&pdu->sdata[pdu->size], udata, len);
>> + if (err)
>> + printk(KERN_WARNING "pdu_write_u returning: %d\n", err);
>> + pdu->size += len;
>> + }
>> + return len;
>> }
>>
>> /*
>> @@ -467,7 +531,8 @@ p9pdu_vwritef(struct p9_fcall *pdu, struct p9_client *c, const char *fmt,
>> const char __user *udata =
>> va_arg(ap, const void __user *);
>> errcode = p9pdu_writef(pdu, c, "d", count);
>> - if (!errcode && pdu_write_u(pdu, udata, count))
>> + if (!errcode &&
>> + pdu_write_u(pdu, c, udata, count) < 0)
>> errcode = -EFAULT;
>> }
>> break;
>> --
>> 1.6.5.2
>>
>>
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