[Libguestfs] [libnbd PATCH 1/2] states: Track cmd->error as errno, not wire value

We want to allow the block_status callback to be able to report a full range of errno values, rather than the limited set of NBD_E* defined in the protocol. To do so, we need to convert from wire error values back into local errno values at a sooner point in the state machine. This also changes a structured reply that includes more than one error designation (theoretically possible at least for structured reads that uses NBD_REPLY_TYPE_ERROR_OFFSET more than once to NBD_CMD_READ - even if no existing NBD server actually does that) to preserve the first error encountered, as that is often more interesting than any follow-on errors. --- generator/states-reply-simple.c | 2 +- generator/states-reply-structured.c | 4 +++- lib/aio.c | 1 - lib/internal.h | 2 +- 4 files changed, 5 insertions(+), 4 deletions(-) diff --git a/generator/states-reply-simple.c b/generator/states-reply-simple.c index e170482..7e5340c 100644 --- a/generator/states-reply-simple.c +++ b/generator/states-reply-simple.c @@ -45,7 +45,7 @@ return 0; } - cmd->error = error; + cmd->error = nbd_internal_errno_of_nbd_error (error); if (cmd->error == 0 && cmd->type == NBD_CMD_READ) { h->rbuf = cmd->data; h->rlen = cmd->count; diff --git a/generator/states-reply-structured.c b/generator/states-reply-structured.c index c835713..c7ba892 100644 --- a/generator/states-reply-structured.c +++ b/generator/states-reply-structured.c @@ -179,7 +179,9 @@ } assert (cmd); /* guaranteed by CHECK */ - cmd->error = error; + /* Preserve first error encountered */ + if (cmd->error == 0) + cmd->error = nbd_internal_errno_of_nbd_error (error); if (flags & NBD_REPLY_FLAG_DONE) SET_NEXT_STATE (%^FINISH_COMMAND); diff --git a/lib/aio.c b/lib/aio.c index a129af2..8361854 100644 --- a/lib/aio.c +++ b/lib/aio.c @@ -165,7 +165,6 @@ nbd_unlocked_aio_command_completed (struct nbd_handle *h, return 1; /* The command failed, set an error indication and return an error. */ - error = nbd_internal_errno_of_nbd_error (error); set_error (error, "%s: command failed: %s", nbd_internal_name_of_nbd_cmd (type), strerror (error)); return -1; diff --git a/lib/internal.h b/lib/internal.h index c1a57ac..45fc6df 100644 --- a/lib/internal.h +++ b/lib/internal.h @@ -223,7 +223,7 @@ struct command_in_flight { uint32_t count; void *data; /* Buffer for read/write, opaque for block status */ extent_fn extent_fn; - uint32_t error; + uint32_t error; /* Local errno value */ }; /* crypto.c */ -- 2.20.1