File xfs_repair-add-prefetch-trace-calls-to-debug-thread-creation-failures.patch of Package xfsprogs.6453

From: Jeff Mahoney <jeffm@suse.com>
Subject: xfs_repair: add prefetch trace calls to debug thread creation failures
Git-commit: e8ff6275b3559c276df39f17377c46a58243ccb3
Patch-mainline: v4.13.0
References: bsc#1019938

When debugging prefetch failures, it's useful to have thread creation
failure messages that are output as warnings on stderr in the trace
log as well.  It's also helpful to see when an AG gets queued behind
another one rather than having the thread started directly, which
has a separate trace line.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
---
 repair/prefetch.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/repair/prefetch.c b/repair/prefetch.c
index 044fab2e..37d60d67 100644
--- a/repair/prefetch.c
+++ b/repair/prefetch.c
@@ -703,6 +703,8 @@ pf_queuing_worker(
 		if (err != 0) {
 			do_warn(_("failed to create prefetch thread: %s\n"),
 				strerror(err));
+			pftrace("failed to create prefetch thread for AG %d: %s",
+				args->agno, strerror(err));
 			args->io_threads[i] = 0;
 			if (i == 0) {
 				pf_start_processing(args);
@@ -817,6 +819,8 @@ pf_create_prefetch_thread(
 	if (err != 0) {
 		do_warn(_("failed to create prefetch thread: %s\n"),
 			strerror(err));
+		pftrace("failed to create prefetch thread for AG %d: %s",
+			args->agno, strerror(err));
 		args->queuing_thread = 0;
 		cleanup_inode_prefetch(args);
 	}
@@ -882,8 +886,11 @@ start_inode_prefetch(
 		if (prev_args->prefetch_done) {
 			if (!pf_create_prefetch_thread(args))
 				args = NULL;
-		} else
+		} else {
 			prev_args->next_args = args;
+			pftrace("queued AG %d after AG %d",
+				args->agno, prev_args->agno);
+		}
 		pthread_mutex_unlock(&prev_args->lock);
 	}