smb: client: set replay flag on the read send-error retry path

smb2_async_readv() and smb2_async_writev() end with the same
send-error block: if the error is replayable and smb2_should_replay()
agrees, tell netfs to retry the subrequest. The write path also sets
wdata->replay. The read path does not set rdata->replay.

smb2_should_replay() is not a pure predicate. It consumes the retry
budget and computes the exponential back-off, doubling cur_sleep up to
CIFS_MAX_SLEEP. That back-off is only applied where the replay flag is
tested at the top of the reissued request:

	if (rdata->replay) {
		/* Back-off before retry */
		if (rdata->cur_sleep)
			msleep(rdata->cur_sleep);
		smb2_set_replay(server, &rqst);
	}

So on the read path the back-off is recomputed on every send-error
retry and then discarded, and SMB2_FLAGS_REPLAY_OPERATION is not set
on the reissued request.

netfs does not pace the retry either. netfs_reissue_read() calls
->issue_read() directly, and fs/netfs/read_retry.c contains no delay
of its own, so read send-error retries reissue immediately while the
equivalent write retries back off.

The read response callback already sets rdata->replay under the same
conditions, so the read path does use the replay mechanism. Only this
send-error path omits it.

Where the back-off belongs was settled while the commit below was
under review. David Howells asked whether netfslib should be doing the
back-off [1], and objected to sleeping inside the response callback
because that runs in the cifsd thread and would stall the socket [2].
The sleep was therefore taken out of smb2_should_replay() and moved to
just before the replay in smb2_async_readv() and smb2_async_writev()
[3]. Setting the flag here preserves that arrangement: the sleep still
happens at the top of the reissued request, not in a callback.

Set rdata->replay here, matching smb2_async_writev().

Fixes: 2c1238a747 ("cifs: make retry logic in read/write path consistent with other paths")
Link: https://lore.kernel.org/all/1652858.1769038134@warthog.procyon.org.uk/ [1]
Link: https://lore.kernel.org/all/1653031.1769038583@warthog.procyon.org.uk/ [2]
Link: https://lore.kernel.org/all/CANT5p=pXP3+CywpmK-on2uTvxO3S=31_B85_UDR7RoK1dQVtMA@mail.gmail.com/ [3]
Assisted-by: Codex:gpt-5.5
Assisted-by: Claude:claude-opus-5
Signed-off-by: Christopher Lusk <clusk@northecho.dev>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>

fs/smb/client/smb2pdu.c

@@ -4893,6 +4893,7 @@ smb2_async_readv(struct cifs_io_subrequest *rdata)
 	    smb2_should_replay(tcon,
 			       &rdata->retries,
 			       &rdata->cur_sleep)) {
+		rdata->replay = true;
 		trace_netfs_sreq(&rdata->subreq, netfs_sreq_trace_io_retry_needed);
 		__set_bit(NETFS_SREQ_NEED_RETRY, &rdata->subreq.flags);
 	}