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-rw-r--r--nbd/client.c125
-rw-r--r--nbd/common.c23
-rw-r--r--nbd/nbd-internal.h40
-rw-r--r--nbd/server.c100
4 files changed, 144 insertions, 144 deletions
diff --git a/nbd/client.c b/nbd/client.c
index a58fb02cb4..595d99ed30 100644
--- a/nbd/client.c
+++ b/nbd/client.c
@@ -86,9 +86,9 @@ static QTAILQ_HEAD(, NBDExport) exports = QTAILQ_HEAD_INITIALIZER(exports);
 
 */
 
-/* Discard length bytes from channel.  Return -errno on failure, or
- * the amount of bytes consumed. */
-static ssize_t drop_sync(QIOChannel *ioc, size_t size)
+/* Discard length bytes from channel.  Return -errno on failure and 0 on
+ * success*/
+static int drop_sync(QIOChannel *ioc, size_t size, Error **errp)
 {
     ssize_t ret = 0;
     char small[1024];
@@ -96,14 +96,13 @@ static ssize_t drop_sync(QIOChannel *ioc, size_t size)
 
     buffer = sizeof(small) >= size ? small : g_malloc(MIN(65536, size));
     while (size > 0) {
-        ssize_t count = read_sync(ioc, buffer, MIN(65536, size));
+        ssize_t count = MIN(65536, size);
+        ret = read_sync(ioc, buffer, MIN(65536, size), errp);
 
-        if (count <= 0) {
+        if (ret < 0) {
             goto cleanup;
         }
-        assert(count <= size);
         size -= count;
-        ret += count;
     }
 
  cleanup:
@@ -136,13 +135,13 @@ static int nbd_send_option_request(QIOChannel *ioc, uint32_t opt,
     stl_be_p(&req.option, opt);
     stl_be_p(&req.length, len);
 
-    if (write_sync(ioc, &req, sizeof(req)) != sizeof(req)) {
-        error_setg(errp, "Failed to send option request header");
+    if (write_sync(ioc, &req, sizeof(req), errp) < 0) {
+        error_prepend(errp, "Failed to send option request header");
         return -1;
     }
 
-    if (len && write_sync(ioc, (char *) data, len) != len) {
-        error_setg(errp, "Failed to send option request data");
+    if (len && write_sync(ioc, (char *) data, len, errp) < 0) {
+        error_prepend(errp, "Failed to send option request data");
         return -1;
     }
 
@@ -170,8 +169,8 @@ static int nbd_receive_option_reply(QIOChannel *ioc, uint32_t opt,
                                     nbd_opt_reply *reply, Error **errp)
 {
     QEMU_BUILD_BUG_ON(sizeof(*reply) != 20);
-    if (read_sync(ioc, reply, sizeof(*reply)) != sizeof(*reply)) {
-        error_setg(errp, "failed to read option reply");
+    if (read_sync(ioc, reply, sizeof(*reply), errp) < 0) {
+        error_prepend(errp, "failed to read option reply");
         nbd_send_opt_abort(ioc);
         return -1;
     }
@@ -219,8 +218,8 @@ static int nbd_handle_reply_err(QIOChannel *ioc, nbd_opt_reply *reply,
             goto cleanup;
         }
         msg = g_malloc(reply->length + 1);
-        if (read_sync(ioc, msg, reply->length) != reply->length) {
-            error_setg(errp, "failed to read option error message");
+        if (read_sync(ioc, msg, reply->length, errp) < 0) {
+            error_prepend(errp, "failed to read option error message");
             goto cleanup;
         }
         msg[reply->length] = '\0';
@@ -321,8 +320,8 @@ static int nbd_receive_list(QIOChannel *ioc, const char *want, bool *match,
         nbd_send_opt_abort(ioc);
         return -1;
     }
-    if (read_sync(ioc, &namelen, sizeof(namelen)) != sizeof(namelen)) {
-        error_setg(errp, "failed to read option name length");
+    if (read_sync(ioc, &namelen, sizeof(namelen), errp) < 0) {
+        error_prepend(errp, "failed to read option name length");
         nbd_send_opt_abort(ioc);
         return -1;
     }
@@ -334,8 +333,8 @@ static int nbd_receive_list(QIOChannel *ioc, const char *want, bool *match,
         return -1;
     }
     if (namelen != strlen(want)) {
-        if (drop_sync(ioc, len) != len) {
-            error_setg(errp, "failed to skip export name with wrong length");
+        if (drop_sync(ioc, len, errp) < 0) {
+            error_prepend(errp, "failed to skip export name with wrong length");
             nbd_send_opt_abort(ioc);
             return -1;
         }
@@ -343,15 +342,15 @@ static int nbd_receive_list(QIOChannel *ioc, const char *want, bool *match,
     }
 
     assert(namelen < sizeof(name));
-    if (read_sync(ioc, name, namelen) != namelen) {
-        error_setg(errp, "failed to read export name");
+    if (read_sync(ioc, name, namelen, errp) < 0) {
+        error_prepend(errp, "failed to read export name");
         nbd_send_opt_abort(ioc);
         return -1;
     }
     name[namelen] = '\0';
     len -= namelen;
-    if (drop_sync(ioc, len) != len) {
-        error_setg(errp, "failed to read export description");
+    if (drop_sync(ioc, len, errp) < 0) {
+        error_prepend(errp, "failed to read export description");
         nbd_send_opt_abort(ioc);
         return -1;
     }
@@ -477,8 +476,8 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char *name, uint16_t *flags,
         goto fail;
     }
 
-    if (read_sync(ioc, buf, 8) != 8) {
-        error_setg(errp, "Failed to read data");
+    if (read_sync(ioc, buf, 8, errp) < 0) {
+        error_prepend(errp, "Failed to read data");
         goto fail;
     }
 
@@ -503,8 +502,8 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char *name, uint16_t *flags,
         goto fail;
     }
 
-    if (read_sync(ioc, &magic, sizeof(magic)) != sizeof(magic)) {
-        error_setg(errp, "Failed to read magic");
+    if (read_sync(ioc, &magic, sizeof(magic), errp) < 0) {
+        error_prepend(errp, "Failed to read magic");
         goto fail;
     }
     magic = be64_to_cpu(magic);
@@ -515,9 +514,8 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char *name, uint16_t *flags,
         uint16_t globalflags;
         bool fixedNewStyle = false;
 
-        if (read_sync(ioc, &globalflags, sizeof(globalflags)) !=
-            sizeof(globalflags)) {
-            error_setg(errp, "Failed to read server flags");
+        if (read_sync(ioc, &globalflags, sizeof(globalflags), errp) < 0) {
+            error_prepend(errp, "Failed to read server flags");
             goto fail;
         }
         globalflags = be16_to_cpu(globalflags);
@@ -534,9 +532,8 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char *name, uint16_t *flags,
         }
         /* client requested flags */
         clientflags = cpu_to_be32(clientflags);
-        if (write_sync(ioc, &clientflags, sizeof(clientflags)) !=
-            sizeof(clientflags)) {
-            error_setg(errp, "Failed to send clientflags field");
+        if (write_sync(ioc, &clientflags, sizeof(clientflags), errp) < 0) {
+            error_prepend(errp, "Failed to send clientflags field");
             goto fail;
         }
         if (tlscreds) {
@@ -573,14 +570,14 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char *name, uint16_t *flags,
         }
 
         /* Read the response */
-        if (read_sync(ioc, &s, sizeof(s)) != sizeof(s)) {
-            error_setg(errp, "Failed to read export length");
+        if (read_sync(ioc, &s, sizeof(s), errp) < 0) {
+            error_prepend(errp, "Failed to read export length");
             goto fail;
         }
         *size = be64_to_cpu(s);
 
-        if (read_sync(ioc, flags, sizeof(*flags)) != sizeof(*flags)) {
-            error_setg(errp, "Failed to read export flags");
+        if (read_sync(ioc, flags, sizeof(*flags), errp) < 0) {
+            error_prepend(errp, "Failed to read export flags");
             goto fail;
         }
         be16_to_cpus(flags);
@@ -596,15 +593,15 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char *name, uint16_t *flags,
             goto fail;
         }
 
-        if (read_sync(ioc, &s, sizeof(s)) != sizeof(s)) {
-            error_setg(errp, "Failed to read export length");
+        if (read_sync(ioc, &s, sizeof(s), errp) < 0) {
+            error_prepend(errp, "Failed to read export length");
             goto fail;
         }
         *size = be64_to_cpu(s);
         TRACE("Size is %" PRIu64, *size);
 
-        if (read_sync(ioc, &oldflags, sizeof(oldflags)) != sizeof(oldflags)) {
-            error_setg(errp, "Failed to read export flags");
+        if (read_sync(ioc, &oldflags, sizeof(oldflags), errp) < 0) {
+            error_prepend(errp, "Failed to read export flags");
             goto fail;
         }
         be32_to_cpus(&oldflags);
@@ -619,8 +616,8 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char *name, uint16_t *flags,
     }
 
     TRACE("Size is %" PRIu64 ", export flags %" PRIx16, *size, *flags);
-    if (zeroes && drop_sync(ioc, 124) != 124) {
-        error_setg(errp, "Failed to read reserved block");
+    if (zeroes && drop_sync(ioc, 124, errp) < 0) {
+        error_prepend(errp, "Failed to read reserved block");
         goto fail;
     }
     rc = 0;
@@ -630,11 +627,13 @@ fail:
 }
 
 #ifdef __linux__
-int nbd_init(int fd, QIOChannelSocket *sioc, uint16_t flags, off_t size)
+int nbd_init(int fd, QIOChannelSocket *sioc, uint16_t flags, off_t size,
+             Error **errp)
 {
     unsigned long sectors = size / BDRV_SECTOR_SIZE;
     if (size / BDRV_SECTOR_SIZE != sectors) {
-        LOG("Export size %lld too large for 32-bit kernel", (long long) size);
+        error_setg(errp, "Export size %lld too large for 32-bit kernel",
+                   (long long) size);
         return -E2BIG;
     }
 
@@ -642,7 +641,7 @@ int nbd_init(int fd, QIOChannelSocket *sioc, uint16_t flags, off_t size)
 
     if (ioctl(fd, NBD_SET_SOCK, (unsigned long) sioc->fd) < 0) {
         int serrno = errno;
-        LOG("Failed to set NBD socket");
+        error_setg(errp, "Failed to set NBD socket");
         return -serrno;
     }
 
@@ -650,7 +649,7 @@ int nbd_init(int fd, QIOChannelSocket *sioc, uint16_t flags, off_t size)
 
     if (ioctl(fd, NBD_SET_BLKSIZE, (unsigned long)BDRV_SECTOR_SIZE) < 0) {
         int serrno = errno;
-        LOG("Failed setting NBD block size");
+        error_setg(errp, "Failed setting NBD block size");
         return -serrno;
     }
 
@@ -662,7 +661,7 @@ int nbd_init(int fd, QIOChannelSocket *sioc, uint16_t flags, off_t size)
 
     if (ioctl(fd, NBD_SET_SIZE_BLOCKS, sectors) < 0) {
         int serrno = errno;
-        LOG("Failed setting size (in blocks)");
+        error_setg(errp, "Failed setting size (in blocks)");
         return -serrno;
     }
 
@@ -673,12 +672,12 @@ int nbd_init(int fd, QIOChannelSocket *sioc, uint16_t flags, off_t size)
 
             if (ioctl(fd, BLKROSET, (unsigned long) &read_only) < 0) {
                 int serrno = errno;
-                LOG("Failed setting read-only attribute");
+                error_setg(errp, "Failed setting read-only attribute");
                 return -serrno;
             }
         } else {
             int serrno = errno;
-            LOG("Failed setting flags");
+            error_setg(errp, "Failed setting flags");
             return -serrno;
         }
     }
@@ -726,8 +725,10 @@ int nbd_disconnect(int fd)
 }
 
 #else
-int nbd_init(int fd, QIOChannelSocket *ioc, uint16_t flags, off_t size)
+int nbd_init(int fd, QIOChannelSocket *ioc, uint16_t flags, off_t size,
+	     Error **errp)
 {
+    error_setg(errp, "nbd_init is only supported on Linux");
     return -ENOTSUP;
 }
 
@@ -744,7 +745,6 @@ int nbd_disconnect(int fd)
 ssize_t nbd_send_request(QIOChannel *ioc, NBDRequest *request)
 {
     uint8_t buf[NBD_REQUEST_SIZE];
-    ssize_t ret;
 
     TRACE("Sending request to server: "
           "{ .from = %" PRIu64", .len = %" PRIu32 ", .handle = %" PRIu64
@@ -759,31 +759,22 @@ ssize_t nbd_send_request(QIOChannel *ioc, NBDRequest *request)
     stq_be_p(buf + 16, request->from);
     stl_be_p(buf + 24, request->len);
 
-    ret = write_sync(ioc, buf, sizeof(buf));
-    if (ret < 0) {
-        return ret;
-    }
-
-    if (ret != sizeof(buf)) {
-        LOG("writing to socket failed");
-        return -EINVAL;
-    }
-    return 0;
+    return write_sync(ioc, buf, sizeof(buf), NULL);
 }
 
-ssize_t nbd_receive_reply(QIOChannel *ioc, NBDReply *reply)
+ssize_t nbd_receive_reply(QIOChannel *ioc, NBDReply *reply, Error **errp)
 {
     uint8_t buf[NBD_REPLY_SIZE];
     uint32_t magic;
     ssize_t ret;
 
-    ret = read_sync(ioc, buf, sizeof(buf));
+    ret = read_sync_eof(ioc, buf, sizeof(buf), errp);
     if (ret <= 0) {
         return ret;
     }
 
     if (ret != sizeof(buf)) {
-        LOG("read failed");
+        error_setg(errp, "read failed");
         return -EINVAL;
     }
 
@@ -801,7 +792,7 @@ ssize_t nbd_receive_reply(QIOChannel *ioc, NBDReply *reply)
 
     if (reply->error == ESHUTDOWN) {
         /* This works even on mingw which lacks a native ESHUTDOWN */
-        LOG("server shutting down");
+        error_setg(errp, "server shutting down");
         return -EINVAL;
     }
     TRACE("Got reply: { magic = 0x%" PRIx32 ", .error = % " PRId32
@@ -809,7 +800,7 @@ ssize_t nbd_receive_reply(QIOChannel *ioc, NBDReply *reply)
           magic, reply->error, reply->handle);
 
     if (magic != NBD_REPLY_MAGIC) {
-        LOG("invalid magic (got 0x%" PRIx32 ")", magic);
+        error_setg(errp, "invalid magic (got 0x%" PRIx32 ")", magic);
         return -EINVAL;
     }
     return sizeof(buf);
diff --git a/nbd/common.c b/nbd/common.c
index dccbb8e9de..bd81637ab9 100644
--- a/nbd/common.c
+++ b/nbd/common.c
@@ -20,14 +20,18 @@
 #include "qapi/error.h"
 #include "nbd-internal.h"
 
+/* nbd_wr_syncv
+ * The function may be called from coroutine or from non-coroutine context.
+ * When called from non-coroutine context @ioc must be in blocking mode.
+ */
 ssize_t nbd_wr_syncv(QIOChannel *ioc,
                      struct iovec *iov,
                      size_t niov,
                      size_t length,
-                     bool do_read)
+                     bool do_read,
+                     Error **errp)
 {
     ssize_t done = 0;
-    Error *local_err = NULL;
     struct iovec *local_iov = g_new(struct iovec, niov);
     struct iovec *local_iov_head = local_iov;
     unsigned int nlocal_iov = niov;
@@ -37,22 +41,17 @@ ssize_t nbd_wr_syncv(QIOChannel *ioc,
     while (nlocal_iov > 0) {
         ssize_t len;
         if (do_read) {
-            len = qio_channel_readv(ioc, local_iov, nlocal_iov, &local_err);
+            len = qio_channel_readv(ioc, local_iov, nlocal_iov, errp);
         } else {
-            len = qio_channel_writev(ioc, local_iov, nlocal_iov, &local_err);
+            len = qio_channel_writev(ioc, local_iov, nlocal_iov, errp);
         }
         if (len == QIO_CHANNEL_ERR_BLOCK) {
-            if (qemu_in_coroutine()) {
-                qio_channel_yield(ioc, do_read ? G_IO_IN : G_IO_OUT);
-            } else {
-                return -EAGAIN;
-            }
+            /* errp should not be set */
+            assert(qemu_in_coroutine());
+            qio_channel_yield(ioc, do_read ? G_IO_IN : G_IO_OUT);
             continue;
         }
         if (len < 0) {
-            TRACE("I/O error: %s", error_get_pretty(local_err));
-            error_free(local_err);
-            /* XXX handle Error objects */
             done = -EIO;
             goto cleanup;
         }
diff --git a/nbd/nbd-internal.h b/nbd/nbd-internal.h
index f43d990a05..d6071640a0 100644
--- a/nbd/nbd-internal.h
+++ b/nbd/nbd-internal.h
@@ -94,7 +94,14 @@
 #define NBD_ENOSPC     28
 #define NBD_ESHUTDOWN  108
 
-static inline ssize_t read_sync(QIOChannel *ioc, void *buffer, size_t size)
+/* read_sync_eof
+ * Tries to read @size bytes from @ioc. Returns number of bytes actually read.
+ * May return a value >= 0 and < size only on EOF, i.e. when iteratively called
+ * qio_channel_readv() returns 0. So, there are no needs to call read_sync_eof
+ * iteratively.
+ */
+static inline ssize_t read_sync_eof(QIOChannel *ioc, void *buffer, size_t size,
+                                    Error **errp)
 {
     struct iovec iov = { .iov_base = buffer, .iov_len = size };
     /* Sockets are kept in blocking mode in the negotiation phase.  After
@@ -102,15 +109,38 @@ static inline ssize_t read_sync(QIOChannel *ioc, void *buffer, size_t size)
      * our request/reply.  Synchronization is done with recv_coroutine, so
      * that this is coroutine-safe.
      */
-    return nbd_wr_syncv(ioc, &iov, 1, size, true);
+    return nbd_wr_syncv(ioc, &iov, 1, size, true, errp);
+}
+
+/* read_sync
+ * Reads @size bytes from @ioc. Returns 0 on success.
+ */
+static inline int read_sync(QIOChannel *ioc, void *buffer, size_t size,
+                            Error **errp)
+{
+    ssize_t ret = read_sync_eof(ioc, buffer, size, errp);
+
+    if (ret >= 0 && ret != size) {
+        ret = -EINVAL;
+        error_setg(errp, "End of file");
+    }
+
+    return ret < 0 ? ret : 0;
 }
 
-static inline ssize_t write_sync(QIOChannel *ioc, const void *buffer,
-                                 size_t size)
+/* write_sync
+ * Writes @size bytes to @ioc. Returns 0 on success.
+ */
+static inline int write_sync(QIOChannel *ioc, const void *buffer, size_t size,
+                             Error **errp)
 {
     struct iovec iov = { .iov_base = (void *) buffer, .iov_len = size };
 
-    return nbd_wr_syncv(ioc, &iov, 1, size, false);
+    ssize_t ret = nbd_wr_syncv(ioc, &iov, 1, size, false, errp);
+
+    assert(ret < 0 || ret == size);
+
+    return ret < 0 ? ret : 0;
 }
 
 struct NBDTLSHandshakeData {
diff --git a/nbd/server.c b/nbd/server.c
index 924a1fe2db..49b55f6ede 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -112,7 +112,7 @@ static gboolean nbd_negotiate_continue(QIOChannel *ioc,
     return TRUE;
 }
 
-static ssize_t nbd_negotiate_read(QIOChannel *ioc, void *buffer, size_t size)
+static int nbd_negotiate_read(QIOChannel *ioc, void *buffer, size_t size)
 {
     ssize_t ret;
     guint watch;
@@ -124,14 +124,13 @@ static ssize_t nbd_negotiate_read(QIOChannel *ioc, void *buffer, size_t size)
                                   nbd_negotiate_continue,
                                   qemu_coroutine_self(),
                                   NULL);
-    ret = read_sync(ioc, buffer, size);
+    ret = read_sync(ioc, buffer, size, NULL);
     g_source_remove(watch);
     return ret;
 
 }
 
-static ssize_t nbd_negotiate_write(QIOChannel *ioc, const void *buffer,
-                                   size_t size)
+static int nbd_negotiate_write(QIOChannel *ioc, const void *buffer, size_t size)
 {
     ssize_t ret;
     guint watch;
@@ -143,29 +142,29 @@ static ssize_t nbd_negotiate_write(QIOChannel *ioc, const void *buffer,
                                   nbd_negotiate_continue,
                                   qemu_coroutine_self(),
                                   NULL);
-    ret = write_sync(ioc, buffer, size);
+    ret = write_sync(ioc, buffer, size, NULL);
     g_source_remove(watch);
     return ret;
 }
 
-static ssize_t nbd_negotiate_drop_sync(QIOChannel *ioc, size_t size)
+static int nbd_negotiate_drop_sync(QIOChannel *ioc, size_t size)
 {
-    ssize_t ret, dropped = size;
+    ssize_t ret;
     uint8_t *buffer = g_malloc(MIN(65536, size));
 
     while (size > 0) {
-        ret = nbd_negotiate_read(ioc, buffer, MIN(65536, size));
+        size_t count = MIN(65536, size);
+        ret = nbd_negotiate_read(ioc, buffer, count);
         if (ret < 0) {
             g_free(buffer);
             return ret;
         }
 
-        assert(ret <= size);
-        size -= ret;
+        size -= count;
     }
 
     g_free(buffer);
-    return dropped;
+    return 0;
 }
 
 /* Basic flow for negotiation
@@ -206,22 +205,22 @@ static int nbd_negotiate_send_rep_len(QIOChannel *ioc, uint32_t type,
           type, opt, len);
 
     magic = cpu_to_be64(NBD_REP_MAGIC);
-    if (nbd_negotiate_write(ioc, &magic, sizeof(magic)) != sizeof(magic)) {
+    if (nbd_negotiate_write(ioc, &magic, sizeof(magic)) < 0) {
         LOG("write failed (rep magic)");
         return -EINVAL;
     }
     opt = cpu_to_be32(opt);
-    if (nbd_negotiate_write(ioc, &opt, sizeof(opt)) != sizeof(opt)) {
+    if (nbd_negotiate_write(ioc, &opt, sizeof(opt)) < 0) {
         LOG("write failed (rep opt)");
         return -EINVAL;
     }
     type = cpu_to_be32(type);
-    if (nbd_negotiate_write(ioc, &type, sizeof(type)) != sizeof(type)) {
+    if (nbd_negotiate_write(ioc, &type, sizeof(type)) < 0) {
         LOG("write failed (rep type)");
         return -EINVAL;
     }
     len = cpu_to_be32(len);
-    if (nbd_negotiate_write(ioc, &len, sizeof(len)) != sizeof(len)) {
+    if (nbd_negotiate_write(ioc, &len, sizeof(len)) < 0) {
         LOG("write failed (rep data length)");
         return -EINVAL;
     }
@@ -256,7 +255,7 @@ nbd_negotiate_send_rep_err(QIOChannel *ioc, uint32_t type,
     if (ret < 0) {
         goto out;
     }
-    if (nbd_negotiate_write(ioc, msg, len) != len) {
+    if (nbd_negotiate_write(ioc, msg, len) < 0) {
         LOG("write failed (error message)");
         ret = -EIO;
     } else {
@@ -287,15 +286,15 @@ static int nbd_negotiate_send_rep_list(QIOChannel *ioc, NBDExport *exp)
     }
 
     len = cpu_to_be32(name_len);
-    if (nbd_negotiate_write(ioc, &len, sizeof(len)) != sizeof(len)) {
+    if (nbd_negotiate_write(ioc, &len, sizeof(len)) < 0) {
         LOG("write failed (name length)");
         return -EINVAL;
     }
-    if (nbd_negotiate_write(ioc, name, name_len) != name_len) {
+    if (nbd_negotiate_write(ioc, name, name_len) < 0) {
         LOG("write failed (name buffer)");
         return -EINVAL;
     }
-    if (nbd_negotiate_write(ioc, desc, desc_len) != desc_len) {
+    if (nbd_negotiate_write(ioc, desc, desc_len) < 0) {
         LOG("write failed (description buffer)");
         return -EINVAL;
     }
@@ -309,7 +308,7 @@ static int nbd_negotiate_handle_list(NBDClient *client, uint32_t length)
     NBDExport *exp;
 
     if (length) {
-        if (nbd_negotiate_drop_sync(client->ioc, length) != length) {
+        if (nbd_negotiate_drop_sync(client->ioc, length) < 0) {
             return -EIO;
         }
         return nbd_negotiate_send_rep_err(client->ioc,
@@ -340,7 +339,7 @@ static int nbd_negotiate_handle_export_name(NBDClient *client, uint32_t length)
         LOG("Bad length received");
         goto fail;
     }
-    if (nbd_negotiate_read(client->ioc, name, length) != length) {
+    if (nbd_negotiate_read(client->ioc, name, length) < 0) {
         LOG("read failed");
         goto fail;
     }
@@ -373,7 +372,7 @@ static QIOChannel *nbd_negotiate_handle_starttls(NBDClient *client,
     TRACE("Setting up TLS");
     ioc = client->ioc;
     if (length) {
-        if (nbd_negotiate_drop_sync(ioc, length) != length) {
+        if (nbd_negotiate_drop_sync(ioc, length) < 0) {
             return NULL;
         }
         nbd_negotiate_send_rep_err(ioc, NBD_REP_ERR_INVALID, NBD_OPT_STARTTLS,
@@ -437,8 +436,7 @@ static int nbd_negotiate_options(NBDClient *client)
         ...           Rest of request
     */
 
-    if (nbd_negotiate_read(client->ioc, &flags, sizeof(flags)) !=
-        sizeof(flags)) {
+    if (nbd_negotiate_read(client->ioc, &flags, sizeof(flags)) < 0) {
         LOG("read failed");
         return -EIO;
     }
@@ -464,8 +462,7 @@ static int nbd_negotiate_options(NBDClient *client)
         uint32_t clientflags, length;
         uint64_t magic;
 
-        if (nbd_negotiate_read(client->ioc, &magic, sizeof(magic)) !=
-            sizeof(magic)) {
+        if (nbd_negotiate_read(client->ioc, &magic, sizeof(magic)) < 0) {
             LOG("read failed");
             return -EINVAL;
         }
@@ -476,14 +473,14 @@ static int nbd_negotiate_options(NBDClient *client)
         }
 
         if (nbd_negotiate_read(client->ioc, &clientflags,
-                               sizeof(clientflags)) != sizeof(clientflags)) {
+                               sizeof(clientflags)) < 0)
+        {
             LOG("read failed");
             return -EINVAL;
         }
         clientflags = be32_to_cpu(clientflags);
 
-        if (nbd_negotiate_read(client->ioc, &length, sizeof(length)) !=
-            sizeof(length)) {
+        if (nbd_negotiate_read(client->ioc, &length, sizeof(length)) < 0) {
             LOG("read failed");
             return -EINVAL;
         }
@@ -513,7 +510,7 @@ static int nbd_negotiate_options(NBDClient *client)
                 return -EINVAL;
 
             default:
-                if (nbd_negotiate_drop_sync(client->ioc, length) != length) {
+                if (nbd_negotiate_drop_sync(client->ioc, length) < 0) {
                     return -EIO;
                 }
                 ret = nbd_negotiate_send_rep_err(client->ioc,
@@ -551,7 +548,7 @@ static int nbd_negotiate_options(NBDClient *client)
                 return nbd_negotiate_handle_export_name(client, length);
 
             case NBD_OPT_STARTTLS:
-                if (nbd_negotiate_drop_sync(client->ioc, length) != length) {
+                if (nbd_negotiate_drop_sync(client->ioc, length) < 0) {
                     return -EIO;
                 }
                 if (client->tlscreds) {
@@ -570,7 +567,7 @@ static int nbd_negotiate_options(NBDClient *client)
                 }
                 break;
             default:
-                if (nbd_negotiate_drop_sync(client->ioc, length) != length) {
+                if (nbd_negotiate_drop_sync(client->ioc, length) < 0) {
                     return -EIO;
                 }
                 ret = nbd_negotiate_send_rep_err(client->ioc,
@@ -659,12 +656,12 @@ static coroutine_fn int nbd_negotiate(NBDClientNewData *data)
             TRACE("TLS cannot be enabled with oldstyle protocol");
             goto fail;
         }
-        if (nbd_negotiate_write(client->ioc, buf, sizeof(buf)) != sizeof(buf)) {
+        if (nbd_negotiate_write(client->ioc, buf, sizeof(buf)) < 0) {
             LOG("write failed");
             goto fail;
         }
     } else {
-        if (nbd_negotiate_write(client->ioc, buf, 18) != 18) {
+        if (nbd_negotiate_write(client->ioc, buf, 18) < 0) {
             LOG("write failed");
             goto fail;
         }
@@ -679,7 +676,7 @@ static coroutine_fn int nbd_negotiate(NBDClientNewData *data)
         stq_be_p(buf + 18, client->exp->size);
         stw_be_p(buf + 26, client->exp->nbdflags | myflags);
         len = client->no_zeroes ? 10 : sizeof(buf) - 18;
-        if (nbd_negotiate_write(client->ioc, buf + 18, len) != len) {
+        if (nbd_negotiate_write(client->ioc, buf + 18, len) < 0) {
             LOG("write failed");
             goto fail;
         }
@@ -697,16 +694,11 @@ static ssize_t nbd_receive_request(QIOChannel *ioc, NBDRequest *request)
     uint32_t magic;
     ssize_t ret;
 
-    ret = read_sync(ioc, buf, sizeof(buf));
+    ret = read_sync(ioc, buf, sizeof(buf), NULL);
     if (ret < 0) {
         return ret;
     }
 
-    if (ret != sizeof(buf)) {
-        LOG("read failed");
-        return -EINVAL;
-    }
-
     /* Request
        [ 0 ..  3]   magic   (NBD_REQUEST_MAGIC)
        [ 4 ..  5]   flags   (NBD_CMD_FLAG_FUA, ...)
@@ -737,7 +729,6 @@ static ssize_t nbd_receive_request(QIOChannel *ioc, NBDRequest *request)
 static ssize_t nbd_send_reply(QIOChannel *ioc, NBDReply *reply)
 {
     uint8_t buf[NBD_REPLY_SIZE];
-    ssize_t ret;
 
     reply->error = system_errno_to_nbd_errno(reply->error);
 
@@ -754,16 +745,7 @@ static ssize_t nbd_send_reply(QIOChannel *ioc, NBDReply *reply)
     stl_be_p(buf + 4, reply->error);
     stq_be_p(buf + 8, reply->handle);
 
-    ret = write_sync(ioc, buf, sizeof(buf));
-    if (ret < 0) {
-        return ret;
-    }
-
-    if (ret != sizeof(buf)) {
-        LOG("writing to socket failed");
-        return -EINVAL;
-    }
-    return 0;
+    return write_sync(ioc, buf, sizeof(buf), NULL);
 }
 
 #define MAX_NBD_REQUESTS 16
@@ -1066,8 +1048,8 @@ static ssize_t nbd_co_send_reply(NBDRequestData *req, NBDReply *reply,
         qio_channel_set_cork(client->ioc, true);
         rc = nbd_send_reply(client->ioc, reply);
         if (rc >= 0) {
-            ret = write_sync(client->ioc, req->data, len);
-            if (ret != len) {
+            ret = write_sync(client->ioc, req->data, len, NULL);
+            if (ret < 0) {
                 rc = -EIO;
             }
         }
@@ -1141,7 +1123,7 @@ static ssize_t nbd_co_receive_request(NBDRequestData *req,
     if (request->type == NBD_CMD_WRITE) {
         TRACE("Reading %" PRIu32 " byte(s)", request->len);
 
-        if (read_sync(client->ioc, req->data, request->len) != request->len) {
+        if (read_sync(client->ioc, req->data, request->len, NULL) < 0) {
             LOG("reading from socket failed");
             rc = -EIO;
             goto out;
@@ -1376,16 +1358,14 @@ static coroutine_fn void nbd_co_client_start(void *opaque)
 
     if (exp) {
         nbd_export_get(exp);
+        QTAILQ_INSERT_TAIL(&exp->clients, client, next);
     }
+    qemu_co_mutex_init(&client->send_lock);
+
     if (nbd_negotiate(data)) {
         client_close(client);
         goto out;
     }
-    qemu_co_mutex_init(&client->send_lock);
-
-    if (exp) {
-        QTAILQ_INSERT_TAIL(&exp->clients, client, next);
-    }
 
     nbd_client_receive_next_request(client);