netfs: Make netfs_io_request::subreq_counter an atomic_t

Make the netfs_io_request::subreq_counter, used to generate values for
netfs_io_subrequest::debug_index, into an atomic_t so that it can be called
from the retry thread at the same time as the app thread issuing writes.
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org

fs/netfs/output.c

@@ -37,7 +37,7 @@ struct netfs_io_subrequest *netfs_create_write_request(struct netfs_io_request *
 		subreq->source	= dest;
 		subreq->start	= start;
 		subreq->len	= len;
-		subreq->debug_index = wreq->subreq_counter++;
+		subreq->debug_index = atomic_inc_return(&wreq->subreq_counter);
 
 		switch (subreq->source) {
 		case NETFS_UPLOAD_TO_SERVER:

include/linux/netfs.h

@@ -202,7 +202,7 @@ struct netfs_io_request {
 	unsigned int		debug_id;
 	unsigned int		rsize;		/* Maximum read size (0 for none) */
 	unsigned int		wsize;		/* Maximum write size (0 for none) */
-	unsigned int		subreq_counter;	/* Next subreq->debug_index */
+	atomic_t		subreq_counter;	/* Next subreq->debug_index */
 	atomic_t		nr_outstanding;	/* Number of ops in progress */
 	atomic_t		nr_copy_ops;	/* Number of copy-to-cache ops in progress */
 	size_t			submitted;	/* Amount submitted for I/O so far */