On 8/29/19 10:08 PM, Eric Blake wrote: > Similar to the previous patch in caching size, we want to avoid > calling into the plugin more than once per connection on any of the > flag determination callbacks. >
> +++ b/server/protocol-handshake.c
> @@ -51,87 +51,72 @@ protocol_compute_eflags (struct connection *conn,
> uint16_t *flags)
> {
> uint16_t eflags = NBD_FLAG_HAS_FLAGS;
> int fl;
> + bool can_write = true;
>
> fl = backend_can_write (backend, conn);
> if (fl == -1)
> return -1;
> if (readonly || !fl) {
> eflags |= NBD_FLAG_READ_ONLY;
> - conn->readonly = true;
> + can_write = false;
The old code set conn->readonly=false if either the command line -r was
present or if the backend failed .can_write...
> +++ b/server/protocol.c
> @@ -64,14 +64,19 @@ validate_request (struct connection *conn,
> uint16_t cmd, uint16_t flags, uint64_t offset, uint32_t
> count,
> uint32_t *error)
> {
> + int r;
> +
> /* Readonly connection? */
> - if (conn->readonly &&
> - (cmd == NBD_CMD_WRITE || cmd == NBD_CMD_TRIM ||
> - cmd == NBD_CMD_WRITE_ZEROES)) {
> - nbdkit_error ("invalid request: %s: write request on readonly
> connection",
> - name_of_nbd_cmd (cmd));
> - *error = EROFS;
> - return false;
> + if (cmd == NBD_CMD_WRITE || cmd == NBD_CMD_TRIM ||
> + cmd == NBD_CMD_WRITE_ZEROES) {
> + r = backend_can_write (backend, conn);
...but the new code is only checking if the backend supports .can_write
(if the backend says yes, then this permits a broken client to write in
spite of the -r command line flag). I'll fix that.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
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