cifs: Fix cifs readv callback merge resolution issue

cifs: Fix cifs readv callback merge resolution issue

Fix an upstream merge resolution issue[1].  Prior to the netfs read
healpers, the SMB1 asynchronous read callback, cifs_readv_worker()
performed the cleanup for the operation in the network message processing
loop, potentially slowing down the processing of incoming SMB messages.

With commit a68c74865f51 ("cifs: Fix SMB1 readv/writev callback in the same
way as SMB2/3"), this was moved to a worker thread (as is done in the
SMB2/3 transport variant).  However, the "was_async" argument to
netfs_subreq_terminated (which was originally incorrectly "false" got
flipped to "true" - which was then incorrect because, being in a kernel
thread, it's not in an async context).

This got corrected in the sample merge[2], but Linus, not unreasonably,
switched it back to its previous value.

Note that this value tells netfslib whether or not it can run sleepable
stuff or stuff that takes a long time, such as retries and cleanups, in the
calling thread, or whether it should offload to a worker thread.

Fix this so that it is "false".  The callback to netfslib in both SMB1 and
SMB2/3 now gets offloaded from the network message thread to a separate
worker thread and thus it's fine to do the slow work in this thread.

Fixes: 35219bc5c71f ("Merge tag 'vfs-6.12.netfs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs")
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Steve French <stfrench@microsoft.com>
cc: Paulo Alcantara <pc@manguebit.com>
cc: Christian Brauner <brauner@kernel.org>
cc: Jeff Layton <jlayton@kernel.org>
cc: linux-cifs@vger.kernel.org
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
Link: https://lore.kernel.org/r/CAHk-=wjr8fxk20-wx=63mZruW1LTvBvAKya1GQ1EhyzXb-okMA@mail.gmail.com/
Link: https://lore.kernel.org/linux-fsdevel/20240913-vfs-netfs-39ef6f974061@brauner/
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>