FLUSH(5)FLUSH(5)NAMEflush - abort a message
size Tflush tag oldtag
size Rflush tag
When the response to a request is no longer needed, such as when a user
interrupts a process doing a read(2), a Tflush request is sent to the
server to purge the pending response. The message being flushed is
identified by oldtag. The semantics of flush depends on messages
arriving in order.
The server should answer the flush message immediately. If it recog‐
nizes oldtag as the tag of a pending transaction, it should abort any
pending response and discard that tag. In either case, it should
respond with an Rflush echoing the tag (not oldtag) of the Tflush mes‐
sage. A Tflush can never be responded to by an Rerror message.
The server may respond to the pending request before responding to the
Tflush. It is possible for a client to send multiple Tflush messages
for a particular pending request. Each subsequent Tflush must contain
as oldtag the tag of the pending request (not a previous Tflush).
Should multiple Tflushes be received for a pending request, they must
be answered in order. A Rflush for any of the multiple Tflushes
implies an answer for all previous ones. Therefore, should a server
receive a request and then multiple flushes for that request, it need
respond only to the last flush.
When the client sends a Tflush, it must wait to receive the correspond‐
ing Rflush before reusing oldtag for subsequent messages. If a
response to the flushed request is received before the Rflush, the
client must honor the response as if it had not been flushed, since the
completed request may signify a state change in the server. For
instance, Tcreate may have created a file and Twalk may have allocated
a fid. If no response is received before the Rflush, the flushed
transaction is considered to have been canceled, and should be treated
as though it had never been sent.
Several exceptional conditions are handled correctly by the above spec‐
ification: sending multiple flushes for a single tag, flushing after a
transaction is completed, flushing a Tflush, and flushing an invalid