The patch below does not apply to the 4.14-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From c1fd0abee0d52eb7e2871194b6c79d54792f515f Mon Sep 17 00:00:00 2001
From: Mike Snitzer <snitzer@xxxxxxxxxx>
Date: Thu, 7 Dec 2017 22:42:27 -0500
Subject: [PATCH] dm mpath: fix bio-based multipath queue_if_no_path handling
Commit ca5beb76 ("dm mpath: micro-optimize the hot path relative to
MPATHF_QUEUE_IF_NO_PATH") caused bio-based DM-multipath to fail mptest's
"test_02_sdev_delete".
Restoring the logic that existed prior to commit ca5beb76 fixes this
bio-based DM-multipath regression. Also verified all mptest tests pass
with request-based DM-multipath.
This commit effectively reverts commit ca5beb76 -- but it does so
without reintroducing the need to take the m->lock spinlock in
must_push_back_{rq,bio}.
Fixes: ca5beb76 ("dm mpath: micro-optimize the hot path relative to MPATHF_QUEUE_IF_NO_PATH")
Cc: stable@xxxxxxxxxxxxxxx # 4.12+
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index 35a2a2fa477f..f7810cc869ac 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -457,6 +457,38 @@ do { \
dm_noflush_suspending((m)->ti)); \
} while (0)
+/*
+ * Check whether bios must be queued in the device-mapper core rather
+ * than here in the target.
+ *
+ * If MPATHF_QUEUE_IF_NO_PATH and MPATHF_SAVED_QUEUE_IF_NO_PATH hold
+ * the same value then we are not between multipath_presuspend()
+ * and multipath_resume() calls and we have no need to check
+ * for the DMF_NOFLUSH_SUSPENDING flag.
+ */
+static bool __must_push_back(struct multipath *m, unsigned long flags)
+{
+ return ((test_bit(MPATHF_QUEUE_IF_NO_PATH, &flags) !=
+ test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &flags)) &&
+ dm_noflush_suspending(m->ti));
+}
+
+/*
+ * Following functions use READ_ONCE to get atomic access to
+ * all m->flags to avoid taking spinlock
+ */
+static bool must_push_back_rq(struct multipath *m)
+{
+ unsigned long flags = READ_ONCE(m->flags);
+ return test_bit(MPATHF_QUEUE_IF_NO_PATH, &flags) || __must_push_back(m, flags);
+}
+
+static bool must_push_back_bio(struct multipath *m)
+{
+ unsigned long flags = READ_ONCE(m->flags);
+ return __must_push_back(m, flags);
+}
+
/*
* Map cloned requests (request-based multipath)
*/
@@ -478,7 +510,7 @@ static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
pgpath = choose_pgpath(m, nr_bytes);
if (!pgpath) {
- if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
+ if (must_push_back_rq(m))
return DM_MAPIO_DELAY_REQUEUE;
dm_report_EIO(m); /* Failed */
return DM_MAPIO_KILL;
@@ -553,7 +585,7 @@ static int __multipath_map_bio(struct multipath *m, struct bio *bio, struct dm_m
}
if (!pgpath) {
- if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
+ if (must_push_back_bio(m))
return DM_MAPIO_REQUEUE;
dm_report_EIO(m);
return DM_MAPIO_KILL;
@@ -651,8 +683,7 @@ static int queue_if_no_path(struct multipath *m, bool queue_if_no_path,
assign_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags,
(save_old_value && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) ||
(!save_old_value && queue_if_no_path));
- assign_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags,
- queue_if_no_path || dm_noflush_suspending(m->ti));
+ assign_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags, queue_if_no_path);
spin_unlock_irqrestore(&m->lock, flags);
if (!queue_if_no_path) {
@@ -1486,7 +1517,7 @@ static int multipath_end_io(struct dm_target *ti, struct request *clone,
fail_path(pgpath);
if (atomic_read(&m->nr_valid_paths) == 0 &&
- !test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
+ !must_push_back_rq(m)) {
if (error == BLK_STS_IOERR)
dm_report_EIO(m);
/* complete with the original error */
@@ -1521,8 +1552,12 @@ static int multipath_end_io_bio(struct dm_target *ti, struct bio *clone,
if (atomic_read(&m->nr_valid_paths) == 0 &&
!test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
- dm_report_EIO(m);
- *error = BLK_STS_IOERR;
+ if (must_push_back_bio(m)) {
+ r = DM_ENDIO_REQUEUE;
+ } else {
+ dm_report_EIO(m);
+ *error = BLK_STS_IOERR;
+ }
goto done;
}