netfs: Add retry stat counters

Add stat counters to count the number of request and subrequest retries and
display them in /proc/fs/netfs/stats.

Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/20250212222402.3618494-3-dhowells@redhat.com
cc: Jeff Layton <jlayton@kernel.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: dhowells

fs/netfs/internal.h

@@ -135,6 +135,8 @@ extern atomic_t netfs_n_rh_write_begin;
 extern atomic_t netfs_n_rh_write_done;
 extern atomic_t netfs_n_rh_write_failed;
 extern atomic_t netfs_n_rh_write_zskip;
+extern atomic_t netfs_n_rh_retry_read_req;
+extern atomic_t netfs_n_rh_retry_read_subreq;
 extern atomic_t netfs_n_wh_buffered_write;
 extern atomic_t netfs_n_wh_writethrough;
 extern atomic_t netfs_n_wh_dio_write;
@@ -147,6 +149,8 @@ extern atomic_t netfs_n_wh_upload_failed;
 extern atomic_t netfs_n_wh_write;
 extern atomic_t netfs_n_wh_write_done;
 extern atomic_t netfs_n_wh_write_failed;
+extern atomic_t netfs_n_wh_retry_write_req;
+extern atomic_t netfs_n_wh_retry_write_subreq;
 extern atomic_t netfs_n_wb_lock_skip;
 extern atomic_t netfs_n_wb_lock_wait;
 extern atomic_t netfs_n_folioq;

fs/netfs/read_retry.c

@@ -14,6 +14,7 @@ static void netfs_reissue_read(struct netfs_io_request *rreq,
 {
 	__clear_bit(NETFS_SREQ_MADE_PROGRESS, &subreq->flags);
 	__set_bit(NETFS_SREQ_IN_PROGRESS, &subreq->flags);
+	netfs_stat(&netfs_n_rh_retry_read_subreq);
 	subreq->rreq->netfs_ops->issue_read(subreq);
 }
 
@@ -260,6 +261,8 @@ void netfs_retry_reads(struct netfs_io_request *rreq)
 	struct netfs_io_stream *stream = &rreq->io_streams[0];
 	DEFINE_WAIT(myself);
 
+	netfs_stat(&netfs_n_rh_retry_read_req);
+
 	set_bit(NETFS_RREQ_RETRYING, &rreq->flags);
 
 	/* Wait for all outstanding I/O to quiesce before performing retries as

fs/netfs/stats.c

@@ -29,6 +29,8 @@ atomic_t netfs_n_rh_write_begin;
 atomic_t netfs_n_rh_write_done;
 atomic_t netfs_n_rh_write_failed;
 atomic_t netfs_n_rh_write_zskip;
+atomic_t netfs_n_rh_retry_read_req;
+atomic_t netfs_n_rh_retry_read_subreq;
 atomic_t netfs_n_wh_buffered_write;
 atomic_t netfs_n_wh_writethrough;
 atomic_t netfs_n_wh_dio_write;
@@ -41,6 +43,8 @@ atomic_t netfs_n_wh_upload_failed;
 atomic_t netfs_n_wh_write;
 atomic_t netfs_n_wh_write_done;
 atomic_t netfs_n_wh_write_failed;
+atomic_t netfs_n_wh_retry_write_req;
+atomic_t netfs_n_wh_retry_write_subreq;
 atomic_t netfs_n_wb_lock_skip;
 atomic_t netfs_n_wb_lock_wait;
 atomic_t netfs_n_folioq;
@@ -81,6 +85,11 @@ int netfs_stats_show(struct seq_file *m, void *v)
 		   atomic_read(&netfs_n_wh_write),
 		   atomic_read(&netfs_n_wh_write_done),
 		   atomic_read(&netfs_n_wh_write_failed));
+	seq_printf(m, "Retries: rq=%u rs=%u wq=%u ws=%u\n",
+		   atomic_read(&netfs_n_rh_retry_read_req),
+		   atomic_read(&netfs_n_rh_retry_read_subreq),
+		   atomic_read(&netfs_n_wh_retry_write_req),
+		   atomic_read(&netfs_n_wh_retry_write_subreq));
 	seq_printf(m, "Objs   : rr=%u sr=%u foq=%u wsc=%u\n",
 		   atomic_read(&netfs_n_rh_rreq),
 		   atomic_read(&netfs_n_rh_sreq),

fs/netfs/write_issue.c

@@ -253,6 +253,7 @@ void netfs_reissue_write(struct netfs_io_stream *stream,
 	subreq->retry_count++;
 	__clear_bit(NETFS_SREQ_MADE_PROGRESS, &subreq->flags);
 	__set_bit(NETFS_SREQ_IN_PROGRESS, &subreq->flags);
+	netfs_stat(&netfs_n_wh_retry_write_subreq);
 	netfs_do_issue_write(stream, subreq);
 }
 

fs/netfs/write_retry.c

@@ -203,6 +203,8 @@ void netfs_retry_writes(struct netfs_io_request *wreq)
 	struct netfs_io_stream *stream;
 	int s;
 
+	netfs_stat(&netfs_n_wh_retry_write_req);
+
 	/* Wait for all outstanding I/O to quiesce before performing retries as
 	 * we may need to renegotiate the I/O sizes.
 	 */