linux-kernel - [PATCH 5.5 180/257] dm writecache: add cond

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Date:   Thu, 16 Apr 2020 15:23:51 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Mikulas Patocka <mpatocka@...hat.com>,
        Mike Snitzer <snitzer@...hat.com>
Subject: [PATCH 5.5 180/257] dm writecache: add cond_resched to avoid CPU hangs

From: Mikulas Patocka <mpatocka@...hat.com>

commit 1edaa447d958bec24c6a79685a5790d98976fd16 upstream.

Initializing a dm-writecache device can take a long time when the
persistent memory device is large.  Add cond_resched() to a few loops
to avoid warnings that the CPU is stuck.

Cc: stable@...r.kernel.org # v4.18+
Signed-off-by: Mikulas Patocka <mpatocka@...hat.com>
Signed-off-by: Mike Snitzer <snitzer@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/md/dm-writecache.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/drivers/md/dm-writecache.c
+++ b/drivers/md/dm-writecache.c
@@ -872,6 +872,7 @@ static int writecache_alloc_entries(stru
 		struct wc_entry *e = &wc->entries[b];
 		e->index = b;
 		e->write_in_progress = false;
+		cond_resched();
 	}
 
 	return 0;
@@ -926,6 +927,7 @@ static void writecache_resume(struct dm_
 			e->original_sector = le64_to_cpu(wme.original_sector);
 			e->seq_count = le64_to_cpu(wme.seq_count);
 		}
+		cond_resched();
 	}
 #endif
 	for (b = 0; b < wc->n_blocks; b++) {
@@ -1770,8 +1772,10 @@ static int init_memory(struct dm_writeca
 	pmem_assign(sb(wc)->n_blocks, cpu_to_le64(wc->n_blocks));
 	pmem_assign(sb(wc)->seq_count, cpu_to_le64(0));
 
-	for (b = 0; b < wc->n_blocks; b++)
+	for (b = 0; b < wc->n_blocks; b++) {
 		write_original_sector_seq_count(wc, &wc->entries[b], -1, -1);
+		cond_resched();
+	}
 
 	writecache_flush_all_metadata(wc);
 	writecache_commit_flushed(wc, false);