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9pnet: allow making incomplete read requests

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A user doesn't necessarily want to wait for all the requested data to
be available, since the waiting time for each request is unbounded.

The new method permits sending one read request at a time and getting
the response ASAP, allowing to use 9pnet with synthetic file systems
representing arbitrary data streams.

Link: http://lkml.kernel.org/r/20200205204053.12751-1-l29ah@cock.li
Signed-off-by: Sergey Alirzaev <l29ah@cock.li>
Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>
This commit is contained in:
Sergey Alirzaev
2020-02-05 23:40:53 +03:00
committed by Dominique Martinet
parent 5195881739
commit 388f6966b0
2 changed files with 80 additions and 66 deletions
Download Patch File Download Diff File Expand all files Collapse all files

144
net/9p/client.c
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@@ -1549,83 +1549,95 @@ EXPORT_SYMBOL(p9_client_unlinkat);
int
p9_client_read(struct p9_fid *fid, u64 offset, struct iov_iter *to, int *err)
{
struct p9_client *clnt = fid->clnt;
struct p9_req_t *req;
int total = 0;
*err = 0;
p9_debug(P9_DEBUG_9P, ">>> TREAD fid %d offset %llu %d\n",
fid->fid, (unsigned long long) offset, (int)iov_iter_count(to));
while (iov_iter_count(to)) {
int count = iov_iter_count(to);
int rsize, non_zc = 0;
char *dataptr;
int count;
rsize = fid->iounit;
if (!rsize || rsize > clnt->msize-P9_IOHDRSZ)
rsize = clnt->msize - P9_IOHDRSZ;
if (count < rsize)
rsize = count;
/* Don't bother zerocopy for small IO (< 1024) */
if (clnt->trans_mod->zc_request && rsize > 1024) {
/*
* response header len is 11
* PDU Header(7) + IO Size (4)
*/
req = p9_client_zc_rpc(clnt, P9_TREAD, to, NULL, rsize,
0, 11, "dqd", fid->fid,
offset, rsize);
} else {
non_zc = 1;
req = p9_client_rpc(clnt, P9_TREAD, "dqd", fid->fid, offset,
rsize);
}
if (IS_ERR(req)) {
*err = PTR_ERR(req);
count = p9_client_read_once(fid, offset, to, err);
if (!count || *err)
break;
}
*err = p9pdu_readf(&req->rc, clnt->proto_version,
"D", &count, &dataptr);
if (*err) {
trace_9p_protocol_dump(clnt, &req->rc);
p9_tag_remove(clnt, req);
break;
}
if (rsize < count) {
pr_err("bogus RREAD count (%d > %d)\n", count, rsize);
count = rsize;
}
p9_debug(P9_DEBUG_9P, "<<< RREAD count %d\n", count);
if (!count) {
p9_tag_remove(clnt, req);
break;
}
if (non_zc) {
int n = copy_to_iter(dataptr, count, to);
total += n;
offset += n;
if (n != count) {
*err = -EFAULT;
p9_tag_remove(clnt, req);
break;
}
} else {
iov_iter_advance(to, count);
total += count;
offset += count;
}
p9_tag_remove(clnt, req);
offset += count;
total += count;
}
return total;
}
EXPORT_SYMBOL(p9_client_read);
int
p9_client_read_once(struct p9_fid *fid, u64 offset, struct iov_iter *to,
int *err)
{
struct p9_client *clnt = fid->clnt;
struct p9_req_t *req;
int count = iov_iter_count(to);
int rsize, non_zc = 0;
char *dataptr;
*err = 0;
p9_debug(P9_DEBUG_9P, ">>> TREAD fid %d offset %llu %d\n",
fid->fid, (unsigned long long) offset, (int)iov_iter_count(to));
rsize = fid->iounit;
if (!rsize || rsize > clnt->msize - P9_IOHDRSZ)
rsize = clnt->msize - P9_IOHDRSZ;
if (count < rsize)
rsize = count;
/* Don't bother zerocopy for small IO (< 1024) */
if (clnt->trans_mod->zc_request && rsize > 1024) {
/* response header len is 11
* PDU Header(7) + IO Size (4)
*/
req = p9_client_zc_rpc(clnt, P9_TREAD, to, NULL, rsize,
0, 11, "dqd", fid->fid,
offset, rsize);
} else {
non_zc = 1;
req = p9_client_rpc(clnt, P9_TREAD, "dqd", fid->fid, offset,
rsize);
}
if (IS_ERR(req)) {
*err = PTR_ERR(req);
return 0;
}
*err = p9pdu_readf(&req->rc, clnt->proto_version,
"D", &count, &dataptr);
if (*err) {
trace_9p_protocol_dump(clnt, &req->rc);
p9_tag_remove(clnt, req);
return 0;
}
if (rsize < count) {
pr_err("bogus RREAD count (%d > %d)\n", count, rsize);
count = rsize;
}
p9_debug(P9_DEBUG_9P, "<<< RREAD count %d\n", count);
if (!count) {
p9_tag_remove(clnt, req);
return 0;
}
if (non_zc) {
int n = copy_to_iter(dataptr, count, to);
if (n != count) {
*err = -EFAULT;
p9_tag_remove(clnt, req);
return n;
}
} else {
iov_iter_advance(to, count);
}
p9_tag_remove(clnt, req);
return count;
}
EXPORT_SYMBOL(p9_client_read_once);
int
p9_client_write(struct p9_fid *fid, u64 offset, struct iov_iter *from, int *err)
{