diff --git a/block/nbd.c b/block/nbd.c
index 9972cdb655..25e52689d1 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -197,7 +197,7 @@ static int nbd_co_send_request(BDRVNBDState *s, struct nbd_request *request,
     qemu_aio_set_fd_handler(s->sock, nbd_reply_ready, nbd_restart_write,
                             nbd_have_request, NULL, s);
     rc = nbd_send_request(s->sock, request);
-    if (rc != -1 && iov) {
+    if (rc >= 0 && iov) {
         ret = qemu_co_sendv(s->sock, iov, request->len, offset);
         if (ret != request->len) {
             errno = -EIO;
@@ -260,7 +260,7 @@ static int nbd_establish_connection(BlockDriverState *bs)
     }
 
     /* Failed to establish connection */
-    if (sock == -1) {
+    if (sock < 0) {
         logout("Failed to establish connection to NBD server\n");
         return -errno;
     }
@@ -268,7 +268,7 @@ static int nbd_establish_connection(BlockDriverState *bs)
     /* NBD handshake */
     ret = nbd_receive_negotiate(sock, s->export_name, &s->nbdflags, &size,
                                 &blocksize);
-    if (ret == -1) {
+    if (ret < 0) {
         logout("Failed to negotiate with the NBD server\n");
         closesocket(sock);
         return -errno;
@@ -331,13 +331,15 @@ static int nbd_co_readv_1(BlockDriverState *bs, int64_t sector_num,
     BDRVNBDState *s = bs->opaque;
     struct nbd_request request;
     struct nbd_reply reply;
+    ssize_t ret;
 
     request.type = NBD_CMD_READ;
     request.from = sector_num * 512;
     request.len = nb_sectors * 512;
 
     nbd_coroutine_start(s, &request);
-    if (nbd_co_send_request(s, &request, NULL, 0) == -1) {
+    ret = nbd_co_send_request(s, &request, NULL, 0);
+    if (ret < 0) {
         reply.error = errno;
     } else {
         nbd_co_receive_reply(s, &request, &reply, qiov->iov, offset);
@@ -354,6 +356,7 @@ static int nbd_co_writev_1(BlockDriverState *bs, int64_t sector_num,
     BDRVNBDState *s = bs->opaque;
     struct nbd_request request;
     struct nbd_reply reply;
+    ssize_t ret;
 
     request.type = NBD_CMD_WRITE;
     if (!bdrv_enable_write_cache(bs) && (s->nbdflags & NBD_FLAG_SEND_FUA)) {
@@ -364,7 +367,8 @@ static int nbd_co_writev_1(BlockDriverState *bs, int64_t sector_num,
     request.len = nb_sectors * 512;
 
     nbd_coroutine_start(s, &request);
-    if (nbd_co_send_request(s, &request, qiov->iov, offset) == -1) {
+    ret = nbd_co_send_request(s, &request, qiov->iov, offset);
+    if (ret < 0) {
         reply.error = errno;
     } else {
         nbd_co_receive_reply(s, &request, &reply, NULL, 0);
@@ -416,6 +420,7 @@ static int nbd_co_flush(BlockDriverState *bs)
     BDRVNBDState *s = bs->opaque;
     struct nbd_request request;
     struct nbd_reply reply;
+    ssize_t ret;
 
     if (!(s->nbdflags & NBD_FLAG_SEND_FLUSH)) {
         return 0;
@@ -430,7 +435,8 @@ static int nbd_co_flush(BlockDriverState *bs)
     request.len = 0;
 
     nbd_coroutine_start(s, &request);
-    if (nbd_co_send_request(s, &request, NULL, 0) == -1) {
+    ret = nbd_co_send_request(s, &request, NULL, 0);
+    if (ret < 0) {
         reply.error = errno;
     } else {
         nbd_co_receive_reply(s, &request, &reply, NULL, 0);
@@ -445,6 +451,7 @@ static int nbd_co_discard(BlockDriverState *bs, int64_t sector_num,
     BDRVNBDState *s = bs->opaque;
     struct nbd_request request;
     struct nbd_reply reply;
+    ssize_t ret;
 
     if (!(s->nbdflags & NBD_FLAG_SEND_TRIM)) {
         return 0;
@@ -454,7 +461,8 @@ static int nbd_co_discard(BlockDriverState *bs, int64_t sector_num,
     request.len = nb_sectors * 512;
 
     nbd_coroutine_start(s, &request);
-    if (nbd_co_send_request(s, &request, NULL, 0) == -1) {
+    ret = nbd_co_send_request(s, &request, NULL, 0);
+    if (ret < 0) {
         reply.error = errno;
     } else {
         nbd_co_receive_reply(s, &request, &reply, NULL, 0);
diff --git a/nbd.c b/nbd.c
index 4a5849c91f..9832aa02c5 100644
--- a/nbd.c
+++ b/nbd.c
@@ -102,12 +102,16 @@ size_t nbd_wr_sync(int fd, void *buffer, size_t size, bool do_read)
             len = send(fd, buffer + offset, size - offset, 0);
         }
 
-        if (len == -1)
+        if (len < 0) {
             errno = socket_error();
 
-        /* recoverable error */
-        if (len == -1 && (errno == EAGAIN || errno == EINTR)) {
-            continue;
+            /* recoverable error */
+            if (errno == EINTR || errno == EAGAIN) {
+                continue;
+            }
+
+            /* unrecoverable error */
+            return 0;
         }
 
         /* eof */
@@ -115,11 +119,6 @@ size_t nbd_wr_sync(int fd, void *buffer, size_t size, bool do_read)
             break;
         }
 
-        /* unrecoverable error */
-        if (len == -1) {
-            return 0;
-        }
-
         offset += len;
     }
 
@@ -364,7 +363,7 @@ int nbd_init(int fd, int csock, uint32_t flags, off_t size, size_t blocksize)
 {
     TRACE("Setting NBD socket");
 
-    if (ioctl(fd, NBD_SET_SOCK, csock) == -1) {
+    if (ioctl(fd, NBD_SET_SOCK, csock) < 0) {
         int serrno = errno;
         LOG("Failed to set NBD socket");
         errno = serrno;
@@ -373,7 +372,7 @@ int nbd_init(int fd, int csock, uint32_t flags, off_t size, size_t blocksize)
 
     TRACE("Setting block size to %lu", (unsigned long)blocksize);
 
-    if (ioctl(fd, NBD_SET_BLKSIZE, blocksize) == -1) {
+    if (ioctl(fd, NBD_SET_BLKSIZE, blocksize) < 0) {
         int serrno = errno;
         LOG("Failed setting NBD block size");
         errno = serrno;
@@ -382,7 +381,7 @@ int nbd_init(int fd, int csock, uint32_t flags, off_t size, size_t blocksize)
 
         TRACE("Setting size to %zd block(s)", (size_t)(size / blocksize));
 
-    if (ioctl(fd, NBD_SET_SIZE_BLOCKS, size / blocksize) == -1) {
+    if (ioctl(fd, NBD_SET_SIZE_BLOCKS, size / blocksize) < 0) {
         int serrno = errno;
         LOG("Failed setting size (in blocks)");
         errno = serrno;
@@ -430,7 +429,7 @@ int nbd_client(int fd)
     TRACE("Doing NBD loop");
 
     ret = ioctl(fd, NBD_DO_IT);
-    if (ret == -1 && errno == EPIPE) {
+    if (ret < 0 && errno == EPIPE) {
         /* NBD_DO_IT normally returns EPIPE when someone has disconnected
          * the socket via NBD_DISCONNECT.  We do not want to return 1 in
          * that case.
@@ -714,20 +713,20 @@ static ssize_t nbd_co_send_reply(NBDRequest *req, struct nbd_reply *reply,
 
     if (!len) {
         rc = nbd_send_reply(csock, reply);
-        if (rc == -1) {
+        if (rc < 0) {
             rc = -errno;
         }
     } else {
         socket_set_cork(csock, 1);
         rc = nbd_send_reply(csock, reply);
-        if (rc != -1) {
+        if (rc >= 0) {
             ret = qemu_co_send(csock, req->data, len);
             if (ret != len) {
                 errno = EIO;
                 rc = -1;
             }
         }
-        if (rc == -1) {
+        if (rc < 0) {
             rc = -errno;
         }
         socket_set_cork(csock, 0);
@@ -746,7 +745,7 @@ static ssize_t nbd_co_receive_request(NBDRequest *req, struct nbd_request *reque
     ssize_t rc;
 
     client->recv_coroutine = qemu_coroutine_self();
-    if (nbd_receive_request(csock, request) == -1) {
+    if (nbd_receive_request(csock, request) < 0) {
         rc = -EIO;
         goto out;
     }
@@ -860,8 +859,9 @@ static void nbd_trip(void *opaque)
             }
         }
 
-        if (nbd_co_send_reply(req, &reply, 0) < 0)
+        if (nbd_co_send_reply(req, &reply, 0) < 0) {
             goto out;
+        }
         break;
     case NBD_CMD_DISC:
         TRACE("Request type is DISCONNECT");
@@ -875,9 +875,9 @@ static void nbd_trip(void *opaque)
             LOG("flush failed");
             reply.error = -ret;
         }
-
-        if (nbd_co_send_reply(req, &reply, 0) < 0)
+        if (nbd_co_send_reply(req, &reply, 0) < 0) {
             goto out;
+        }
         break;
     case NBD_CMD_TRIM:
         TRACE("Request type is TRIM");
@@ -887,16 +887,18 @@ static void nbd_trip(void *opaque)
             LOG("discard failed");
             reply.error = -ret;
         }
-        if (nbd_co_send_reply(req, &reply, 0) < 0)
+        if (nbd_co_send_reply(req, &reply, 0) < 0) {
             goto out;
+        }
         break;
     default:
         LOG("invalid request type (%u) received", request.type);
     invalid_request:
         reply.error = -EINVAL;
     error_reply:
-        if (nbd_co_send_reply(req, &reply, 0) == -1)
+        if (nbd_co_send_reply(req, &reply, 0) < 0) {
             goto out;
+        }
         break;
     }
 
@@ -939,7 +941,7 @@ NBDClient *nbd_client_new(NBDExport *exp, int csock,
                           void (*close)(NBDClient *))
 {
     NBDClient *client;
-    if (nbd_send_negotiate(csock, exp->size, exp->nbdflags) == -1) {
+    if (nbd_send_negotiate(csock, exp->size, exp->nbdflags) < 0) {
         return NULL;
     }
     client = g_malloc0(sizeof(NBDClient));
diff --git a/qemu-nbd.c b/qemu-nbd.c
index d4e70410fc..19cfb04d96 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -186,7 +186,7 @@ static void *show_parts(void *arg)
      *     modprobe nbd max_part=63
      */
     nbd = open(device, O_RDWR);
-    if (nbd != -1) {
+    if (nbd >= 0) {
         close(nbd);
     }
     return NULL;
@@ -203,25 +203,25 @@ static void *nbd_client_thread(void *arg)
     pthread_t show_parts_thread;
 
     sock = unix_socket_outgoing(sockpath);
-    if (sock == -1) {
+    if (sock < 0) {
         goto out;
     }
 
     ret = nbd_receive_negotiate(sock, NULL, &nbdflags,
                                 &size, &blocksize);
-    if (ret == -1) {
+    if (ret < 0) {
         goto out;
     }
 
     fd = open(device, O_RDWR);
-    if (fd == -1) {
+    if (fd < 0) {
         /* Linux-only, we can use %m in printf.  */
         fprintf(stderr, "Failed to open %s: %m", device);
         goto out;
     }
 
     ret = nbd_init(fd, sock, nbdflags, size, blocksize);
-    if (ret == -1) {
+    if (ret < 0) {
         goto out;
     }
 
@@ -268,7 +268,7 @@ static void nbd_accept(void *opaque)
 
     int fd = accept(server_fd, (struct sockaddr *)&addr, &addr_len);
     nbd_started = true;
-    if (fd != -1 && nbd_client_new(exp, fd, nbd_client_closed)) {
+    if (fd >= 0 && nbd_client_new(exp, fd, nbd_client_closed)) {
         nb_fds++;
     }
 }
@@ -410,9 +410,9 @@ int main(int argc, char **argv)
 
     if (disconnect) {
         fd = open(argv[optind], O_RDWR);
-        if (fd == -1)
+        if (fd < 0) {
             err(EXIT_FAILURE, "Cannot open %s", argv[optind]);
-
+        }
         nbd_disconnect(fd);
 
         close(fd);
@@ -427,7 +427,7 @@ int main(int argc, char **argv)
         pid_t pid;
         int ret;
 
-        if (qemu_pipe(stderr_fd) == -1) {
+        if (qemu_pipe(stderr_fd) < 0) {
             err(EXIT_FAILURE, "Error setting up communication pipe");
         }
 
@@ -441,7 +441,7 @@ int main(int argc, char **argv)
 
             /* Temporarily redirect stderr to the parent's pipe...  */
             dup2(stderr_fd[1], STDERR_FILENO);
-            if (ret == -1) {
+            if (ret < 0) {
                 err(EXIT_FAILURE, "Failed to daemonize");
             }
 
@@ -459,11 +459,11 @@ int main(int argc, char **argv)
             while ((ret = read(stderr_fd[0], buf, 1024)) > 0) {
                 errors = true;
                 ret = qemu_write_full(STDERR_FILENO, buf, ret);
-                if (ret == -1) {
+                if (ret < 0) {
                     exit(EXIT_FAILURE);
                 }
             }
-            if (ret == -1) {
+            if (ret < 0) {
                 err(EXIT_FAILURE, "Cannot read from daemon");
             }
 
@@ -504,7 +504,7 @@ int main(int argc, char **argv)
         fd = tcp_socket_incoming(bindto, port);
     }
 
-    if (fd == -1) {
+    if (fd < 0) {
         return 1;
     }