Re: [Libguestfs] [libnbd PATCH 4/8] states: Prepare for read callback

The next patch will add a new 'nbd_aio_pread_callback' function for allowing the user more immediate access as each chunk of a structured reply read is received. But before we do that, let's refactor the command code. This includes a revert of 12843a1a, since the read callback will need both a buffer and the user's opaque object at the same time.

generator/states-reply-structured.c | 8 ++++---- lib/internal.h | 17 +++++++++++++---- lib/rw.c | 9 ++++++--- 3 files changed, 23 insertions(+), 11 deletions(-) diff --git a/generator/states-reply-structured.c b/generator/states-reply-structured.c index 6740400..657106e 100644 --- a/generator/states-reply-structured.c +++ b/generator/states-reply-structured.c @@ -123,7 +123,7 @@ set_error (0, "invalid length in NBD_REPLY_TYPE_BLOCK_STATUS"); return -1; } - if (cmd->extent_fn == NULL) { + if (cmd->cb.fn.extent == NULL) { SET_NEXT_STATE (%.DEAD); set_error (0, "not expecting NBD_REPLY_TYPE_BLOCK_STATUS here"); return -1; @@ -375,7 +375,7 @@ length = be32toh (h->sbuf.sr.structured_reply.length); assert (cmd); /* guaranteed by CHECK */ - assert (cmd->extent_fn); + assert (cmd->cb.fn.extent); assert (h->bs_entries); assert (length >= 12); @@ -401,8 +401,8 @@ if (meta_context) { /* Call the caller's extent function. */ errno = 0; - if (cmd->extent_fn (cmd->data, meta_context->name, cmd->offset, - &h->bs_entries[1], (length-4) / 4) == -1) + if (cmd->cb.fn.extent (cmd->cb.opaque, meta_context->name, cmd->offset, + &h->bs_entries[1], (length-4) / 4) == -1) cmd->error = errno ? errno : EPROTO; } else diff --git a/lib/internal.h b/lib/internal.h index 1f8f789..cb0e170 100644 --- a/lib/internal.h +++ b/lib/internal.h @@ -231,7 +231,16 @@ struct socket { const struct socket_ops *ops; }; -typedef int (*extent_fn) (void *data, const char *metacontext, uint64_t offset, uint32_t *entries, size_t nr_entries); +typedef int (*extent_fn) (void *data, const char *metacontext, uint64_t offset, + uint32_t *entries, size_t nr_entries); + +struct command_cb { + void *opaque; + union { + extent_fn extent; + /* More to come */ + } fn; +}; struct command_in_flight { struct command_in_flight *next; @@ -240,8 +249,8 @@ struct command_in_flight { uint64_t handle; uint64_t offset; uint32_t count; - void *data; /* Buffer for read/write, opaque for block status */ - extent_fn extent_fn; + void *data; /* Buffer for read/write */ + struct command_cb cb; bool data_seen; /* For read, true if at least one data chunk seen */ uint32_t error; /* Local errno value */ }; @@ -300,7 +309,7 @@ extern const char *nbd_internal_name_of_nbd_cmd (uint16_t type); extern int64_t nbd_internal_command_common (struct nbd_handle *h, uint16_t flags, uint16_t type, uint64_t offset, uint64_t count, - void *data, extent_fn extent); + void *data, struct command_cb *cb); /* socket.c */ struct socket *nbd_internal_socket_create (int fd); diff --git a/lib/rw.c b/lib/rw.c index ad9c8a0..dc81c57 100644 --- a/lib/rw.c +++ b/lib/rw.c @@ -143,7 +143,7 @@ int64_t nbd_internal_command_common (struct nbd_handle *h, uint16_t flags, uint16_t type, uint64_t offset, uint64_t count, void *data, - extent_fn extent) + struct command_cb *cb) { struct command_in_flight *cmd, *prev_cmd; @@ -183,7 +183,8 @@ nbd_internal_command_common (struct nbd_handle *h, cmd->offset = offset; cmd->count = count; cmd->data = data; - cmd->extent_fn = extent; + if (cb) + cmd->cb = *cb; /* If structured replies were negotiated then we trust the server to * send back sufficient data to cover the whole buffer. It's tricky @@ -360,6 +361,8 @@ nbd_unlocked_aio_block_status (struct nbd_handle *h, void *data, extent_fn extent, uint32_t flags) { + struct command_cb cb = { .opaque = data, .fn.extent = extent, }; + if (!h->structured_replies) { set_error (ENOTSUP, "server does not support structured replies"); return -1; @@ -383,5 +386,5 @@ nbd_unlocked_aio_block_status (struct nbd_handle *h, } return nbd_internal_command_common (h, flags, NBD_CMD_BLOCK_STATUS, offset, - count, data, extent); + count, NULL, &cb); } -- 2.20.1 _______________________________________________ Libguestfs mailing list Libguestfs(a)redhat.com https://www.redhat.com/mailman/listinfo/libguestfs