netfs: Fix rolling_buffer_load_from_ra() to not clear mark bits

rolling_buffer_load_from_ra() looms large in the perf report because it
loops around doing an atomic clear for each of the three mark bits per
folio.  However, this is both inefficient (it would be better to build a
mask and atomically AND them out) and unnecessary as they shouldn't be set.

Fix this by removing the loop.

Fixes: ee4cdf7b ("netfs: Speed up buffered reading")
Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/20250314164201.1993231-4-dhowells@redhat.com


Acked-by: "Paulo Alcantara (Red Hat)" <pc@manguebit.com>
cc: Jeff Layton <jlayton@kernel.org>
cc: Steve French <sfrench@samba.org>
cc: Paulo Alcantara <pc@manguebit.com>
cc: netfs@lists.linux.dev
cc: linux-cifs@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>