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From: Dan Williams <dan.j.williams@intel.com>
To: vishal.l.verma@intel.com
Cc: Krzysztof Rusocki <krzysztof.rusocki@intel.com>, nvdimm@lists.linux.dev
Subject: [ndctl PATCH 2/2] ndctl/scrub: Reread scrub-engine status at start
Date: Wed, 26 May 2021 16:33:10 -0700	[thread overview]
Message-ID: <162207199057.3715490.2469820075085914776.stgit@dwillia2-desk3.amr.corp.intel.com> (raw)
In-Reply-To: <162207197868.3715490.6562405741837220139.stgit@dwillia2-desk3.amr.corp.intel.com>

Given that the kernel has exponential backoff to cover the lack of
interrupts for scrub completion status there is a reasonable likelihood
that 'ndctl start-scrub' is issued while the hardware/platform scrub-state
is idle, but the kernel engine poll timer has not fired.

Trigger at least one poll cycle for the kernel to re-read the scrub-state
before reporting that ARS is busy.

Reported-by: Krzysztof Rusocki <krzysztof.rusocki@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 ndctl/lib/libndctl.c |   12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/ndctl/lib/libndctl.c b/ndctl/lib/libndctl.c
index e5641feec23d..536e142cf6af 100644
--- a/ndctl/lib/libndctl.c
+++ b/ndctl/lib/libndctl.c
@@ -1354,8 +1354,18 @@ static int __ndctl_bus_get_scrub_state(struct ndctl_bus *bus,
 NDCTL_EXPORT int ndctl_bus_start_scrub(struct ndctl_bus *bus)
 {
 	struct ndctl_ctx *ctx = ndctl_bus_get_ctx(bus);
+	int rc;
+
+	rc = sysfs_write_attr(ctx, bus->scrub_path, "1\n");
 
-	return sysfs_write_attr(ctx, bus->scrub_path, "1\n");
+	/*
+	 * Try at least 1 poll cycle before reporting busy in case this
+	 * request hits the kernel's exponential backoff while the
+	 * hardware/platform scrub state is idle.
+	 */
+	if (rc == -EBUSY && ndctl_bus_poll_scrub_completion(bus, 1, 1) == 0)
+		return sysfs_write_attr(ctx, bus->scrub_path, "1\n");
+	return rc;
 }
 
 NDCTL_EXPORT int ndctl_bus_get_scrub_state(struct ndctl_bus *bus)


      parent reply	other threads:[~2021-05-26 23:33 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-26 23:32 [ndctl PATCH 0/2] ndctl/scrub: Fix start-scrub vs exponential backoff Dan Williams
2021-05-26 23:33 ` [ndctl PATCH 1/2] ndctl/scrub: Stop translating return values Dan Williams
2021-05-26 23:33 ` Dan Williams [this message]

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