nbd: Don't inf-loop on early EOF
Commit 7d3123e converted a single read_sync() into a while loop
that assumed that read_sync() would either make progress or give
an error. But when the server hangs up early, the client sees
EOF (a read_sync() of 0) and never makes progress, which in turn
caused qemu-iotest './check -nbd 83' to go into an infinite loop.
Rework the loop to accomodate reads cut short by EOF.
Reported-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1478551093-32757-1-git-send-email-eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/nbd/client.c b/nbd/client.c
index 7db4301..ffb0743 100644
--- a/nbd/client.c
+++ b/nbd/client.c
@@ -90,20 +90,21 @@
* the amount of bytes consumed. */
static ssize_t drop_sync(QIOChannel *ioc, size_t size)
{
- ssize_t ret, dropped = size;
+ ssize_t ret = 0;
char small[1024];
char *buffer;
buffer = sizeof(small) < size ? small : g_malloc(MIN(65536, size));
while (size > 0) {
- ret = read_sync(ioc, buffer, MIN(65536, size));
- if (ret < 0) {
+ ssize_t count = read_sync(ioc, buffer, MIN(65536, size));
+
+ if (count <= 0) {
goto cleanup;
}
- assert(ret <= size);
- size -= ret;
+ assert(count <= size);
+ size -= count;
+ ret += count;
}
- ret = dropped;
cleanup:
if (buffer != small) {