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[GIT,PULL,11/37] lightnvm: pblk: prevent race in pblk_rb_flush_point_set

Message ID 20180329220524.30363-12-mb@lightnvm.io (mailing list archive)
State New, archived
Headers show

Commit Message

Matias Bjorling March 29, 2018, 10:04 p.m. UTC 
From: Hans Holmberg <hans.holmberg@cnexlabs.com>

Make sure that we are not advancing the sync pointer while
we're adding bios to the write buffer entry completion list.

This race condition results in bios not completing and was identified
by a hang when running xfstest generic/113.

Signed-off-by: Hans Holmberg <hans.holmberg@cnexlabs.com>
Reviewed-by: Javier González <javier@cnexlabs.com>
Signed-off-by: Matias Bjørling <mb@lightnvm.io>
---
 drivers/lightnvm/pblk-rb.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)
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Patch

diff --git a/drivers/lightnvm/pblk-rb.c b/drivers/lightnvm/pblk-rb.c
index 8b1434060fb3..52fdd85dbc97 100644
--- a/drivers/lightnvm/pblk-rb.c
+++ b/drivers/lightnvm/pblk-rb.c
@@ -355,10 +355,13 @@  static int pblk_rb_flush_point_set(struct pblk_rb *rb, struct bio *bio,
 	struct pblk_rb_entry *entry;
 	unsigned int sync, flush_point;
 
+	pblk_rb_sync_init(rb, NULL);
 	sync = READ_ONCE(rb->sync);
 
-	if (pos == sync)
+	if (pos == sync) {
+		pblk_rb_sync_end(rb, NULL);
 		return 0;
+	}
 
 #ifdef CONFIG_NVM_DEBUG
 	atomic_inc(&rb->inflight_flush_point);
@@ -367,8 +370,6 @@  static int pblk_rb_flush_point_set(struct pblk_rb *rb, struct bio *bio,
 	flush_point = (pos == 0) ? (rb->nr_entries - 1) : (pos - 1);
 	entry = &rb->entries[flush_point];
 
-	pblk_rb_sync_init(rb, NULL);
-
 	/* Protect flush points */
 	smp_store_release(&rb->flush_point, flush_point);