[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Qemu-block] [PATCH v3 34/44] nbd: Less allocation during NBD_OPT_LIST
From: |
Eric Blake |
Subject: |
[Qemu-block] [PATCH v3 34/44] nbd: Less allocation during NBD_OPT_LIST |
Date: |
Fri, 22 Apr 2016 17:40:42 -0600 |
Since we know that the maximum name we are willing to accept
is small enough to stack-allocate, rework the iteration over
NBD_OPT_LIST responses to reuse a stack buffer rather than
allocating every time. Furthermore, we don't even have to
allocate if we know the server's length doesn't match what
we are searching for.
Signed-off-by: Eric Blake <address@hidden>
Reviewed-by: Alex Bligh <address@hidden>
---
v3: tweak commit message
---
nbd/client.c | 130 +++++++++++++++++++++++++++++------------------------------
1 file changed, 65 insertions(+), 65 deletions(-)
diff --git a/nbd/client.c b/nbd/client.c
index d346c86..4debb5d 100644
--- a/nbd/client.c
+++ b/nbd/client.c
@@ -230,14 +230,17 @@ static int nbd_handle_reply_err(QIOChannel *ioc,
nbd_opt_reply *reply,
return result;
}
-static int nbd_receive_list(QIOChannel *ioc, char **name, Error **errp)
+/* Return -1 if unrecoverable error occurs, 0 if NBD_OPT_LIST is
+ * unsupported, 1 if iteration is done, 2 to keep looking, and 3 if
+ * this entry matches want. */
+static int nbd_receive_list(QIOChannel *ioc, const char *want, Error **errp)
{
nbd_opt_reply reply;
uint32_t len;
uint32_t namelen;
+ char name[NBD_MAX_NAME_SIZE + 1];
int error;
- *name = NULL;
if (nbd_receive_option_reply(ioc, NBD_OPT_LIST, &reply, errp) < 0) {
return -1;
}
@@ -252,97 +255,94 @@ static int nbd_receive_list(QIOChannel *ioc, char **name,
Error **errp)
error_setg(errp, "length too long for option end");
return -1;
}
- } else if (reply.type == NBD_REP_SERVER) {
- if (len < sizeof(namelen) || len > NBD_MAX_BUFFER_SIZE) {
- error_setg(errp, "incorrect option length %"PRIu32, len);
- return -1;
- }
- if (read_sync(ioc, &namelen, sizeof(namelen)) != sizeof(namelen)) {
- error_setg(errp, "failed to read option name length");
- return -1;
- }
- namelen = be32_to_cpu(namelen);
- len -= sizeof(namelen);
- if (len < namelen) {
- error_setg(errp, "incorrect option name length");
- return -1;
- }
- if (namelen > NBD_MAX_NAME_SIZE) {
- error_setg(errp, "export name length too long %" PRIu32, namelen);
- return -1;
- }
-
- *name = g_new0(char, namelen + 1);
- if (read_sync(ioc, *name, namelen) != namelen) {
- error_setg(errp, "failed to read export name");
- g_free(*name);
- *name = NULL;
- return -1;
- }
- (*name)[namelen] = '\0';
- len -= namelen;
- if (drop_sync(ioc, len) != len) {
- error_setg(errp, "failed to read export description");
- g_free(*name);
- *name = NULL;
- return -1;
- }
- } else {
+ return 1;
+ } else if (reply.type != NBD_REP_SERVER) {
error_setg(errp, "Unexpected reply type %" PRIx32 " expected %x",
reply.type, NBD_REP_SERVER);
return -1;
}
- return 1;
+
+ if (len < sizeof(namelen) || len > NBD_MAX_BUFFER_SIZE) {
+ error_setg(errp, "incorrect option length %"PRIu32, len);
+ return -1;
+ }
+ if (read_sync(ioc, &namelen, sizeof(namelen)) != sizeof(namelen)) {
+ error_setg(errp, "failed to read option name length");
+ return -1;
+ }
+ namelen = be32_to_cpu(namelen);
+ len -= sizeof(namelen);
+ if (len < namelen) {
+ error_setg(errp, "incorrect option name length");
+ return -1;
+ }
+ if (namelen != strlen(want)) {
+ if (drop_sync(ioc, len) != len) {
+ error_setg(errp, "failed to skip export name with wrong length");
+ return -1;
+ }
+ return 2;
+ }
+
+ assert(namelen < sizeof(name));
+ if (read_sync(ioc, name, namelen) != namelen) {
+ error_setg(errp, "failed to read export name");
+ return -1;
+ }
+ name[namelen] = '\0';
+ len -= namelen;
+ if (drop_sync(ioc, len) != len) {
+ error_setg(errp, "failed to read export description");
+ return -1;
+ }
+ return strcmp(name, want) == 0 ? 3 : 2;
}
+/* Return -1 on failure, 0 if wantname is an available export. */
static int nbd_receive_query_exports(QIOChannel *ioc,
const char *wantname,
Error **errp)
{
bool foundExport = false;
- TRACE("Querying export list");
+ TRACE("Querying export list for '%s'", wantname);
if (nbd_send_option_request(ioc, NBD_OPT_LIST, 0, NULL, errp) < 0) {
return -1;
}
TRACE("Reading available export names");
while (1) {
- char *name = NULL;
- int ret = nbd_receive_list(ioc, &name, errp);
+ int ret = nbd_receive_list(ioc, wantname, errp);
- if (ret < 0) {
- g_free(name);
- name = NULL;
+ switch (ret) {
+ default:
+ /* Server gave unexpected reply */
+ assert(ret < 0);
return -1;
- }
- if (ret == 0) {
+ case 0:
/* Server doesn't support export listing, so
* we will just assume an export with our
* wanted name exists */
- foundExport = true;
- break;
- }
- if (name == NULL) {
- TRACE("End of export name list");
+ return 0;
+ case 1:
+ /* Done iterating. */
+ if (!foundExport) {
+ error_setg(errp, "No export with name '%s' available",
+ wantname);
+ return -1;
+ }
+ return 0;
+ case 2:
+ /* Wasn't this one, keep going. */
break;
- }
- if (g_str_equal(name, wantname)) {
+ case 3:
+ /* Found a match, but must finish parsing reply. */
+ TRACE("Found desired export name '%s'", wantname);
foundExport = true;
- TRACE("Found desired export name '%s'", name);
- } else {
- TRACE("Ignored export name '%s'", name);
+ break;
}
- g_free(name);
- }
-
- if (!foundExport) {
- error_setg(errp, "No export with name '%s' available", wantname);
- return -1;
}
-
- return 0;
}
static QIOChannel *nbd_receive_starttls(QIOChannel *ioc,
--
2.5.5
- Re: [Qemu-block] [Qemu-devel] [PATCH v3 29/44] nbd: Avoid magic number for NBD max name size, (continued)
- [Qemu-block] [PATCH v3 38/44] block: Add blk_get_opt_transfer_length(), Eric Blake, 2016/04/22
- [Qemu-block] [PATCH v3 41/44] nbd: Implement NBD_CMD_WRITE_ZEROES on server, Eric Blake, 2016/04/22
- [Qemu-block] [PATCH v3 43/44] nbd: Implement NBD_OPT_BLOCK_SIZE on server, Eric Blake, 2016/04/22
- [Qemu-block] [PATCH v3 44/44] nbd: Implement NBD_OPT_BLOCK_SIZE on client, Eric Blake, 2016/04/22
- [Qemu-block] [PATCH v3 34/44] nbd: Less allocation during NBD_OPT_LIST,
Eric Blake <=
- [Qemu-block] [PATCH v3 32/44] nbd: Share common option-sending code in client, Eric Blake, 2016/04/22
- [Qemu-block] [PATCH v3 36/44] nbd: Improve handling of shutdown requests, Eric Blake, 2016/04/22
[Qemu-block] [PATCH v3 39/44] nbd: Implement NBD_OPT_GO on server, Eric Blake, 2016/04/22
[Qemu-block] [PATCH v3 40/44] nbd: Implement NBD_OPT_GO on client, Eric Blake, 2016/04/22