[dm-devel] [PATCH] dm-writecache: add cond_resched

[Mikulas Patocka]

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

Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>
Cc: stable at vger.kernel.org	# v4.18+

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

Index: linux-2.6/drivers/md/dm-writecache.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-writecache.c	2020-03-24 18:05:34.000000000 +0100
+++ linux-2.6/drivers/md/dm-writecache.c	2020-03-27 09:27:02.000000000 +0100
@@ -923,6 +923,7 @@ 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;
@@ -977,6 +978,7 @@ 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++) {
@@ -1883,8 +1885,10 @@ 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);