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From: Matteo Croce <mcroce@linux.microsoft.com>
To: linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org
Cc: linux-kernel@vger.kernel.org,
	"Lennart Poettering" <lennart@poettering.net>,
	"Luca Boccassi" <bluca@debian.org>,
	"Jens Axboe" <axboe@kernel.dk>,
	"Alexander Viro" <viro@zeniv.linux.org.uk>,
	"Damien Le Moal" <damien.lemoal@wdc.com>,
	"Tejun Heo" <tj@kernel.org>,
	"Javier González" <javier@javigon.com>,
	"Niklas Cassel" <niklas.cassel@wdc.com>,
	"Johannes Thumshirn" <johannes.thumshirn@wdc.com>,
	"Hannes Reinecke" <hare@suse.de>
Subject: [PATCH -next 4/5] block: export diskseq in sysfs
Date: Mon, 15 Mar 2021 21:02:41 +0100
Message-ID: <20210315200242.67355-5-mcroce@linux.microsoft.com> (raw)
In-Reply-To: <20210315200242.67355-1-mcroce@linux.microsoft.com>

From: Matteo Croce <mcroce@microsoft.com>

Add a new sysfs handle to export the new diskseq value.
Place it in <sysfs>/block/<disk>/diskseq and document it.

Signed-off-by: Matteo Croce <mcroce@microsoft.com>
---
 Documentation/ABI/testing/sysfs-block | 12 ++++++++++++
 block/genhd.c                         | 11 +++++++++++
 2 files changed, 23 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-block b/Documentation/ABI/testing/sysfs-block
index e34cdeeeb9d4..a0ed87386639 100644
--- a/Documentation/ABI/testing/sysfs-block
+++ b/Documentation/ABI/testing/sysfs-block
@@ -28,6 +28,18 @@ Description:
 		For more details refer Documentation/admin-guide/iostats.rst
 
 
+What:		/sys/block/<disk>/diskseq
+Date:		February 2021
+Contact:	Matteo Croce <mcroce@microsoft.com>
+Description:
+		The /sys/block/<disk>/diskseq files reports the disk
+		sequence number, which is a monotonically increasing
+		number assigned to every drive.
+		Some devices, like the loop device, refresh such number
+		every time the backing file is changed.
+		The value type is 64 bit unsigned.
+
+
 What:		/sys/block/<disk>/<part>/stat
 Date:		February 2008
 Contact:	Jerome Marchand <jmarchan@redhat.com>
diff --git a/block/genhd.c b/block/genhd.c
index 57d92ea7ae05..6a7ed426def0 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1764,6 +1764,7 @@ static void disk_check_events(struct disk_events *ev,
  * events_async		: list of events which can be detected w/o polling
  *			  (always empty, only for backwards compatibility)
  * events_poll_msecs	: polling interval, 0: disable, -1: system default
+ * diskseq		: disk sequence number, since boot
  */
 static ssize_t __disk_events_show(unsigned int events, char *buf)
 {
@@ -1834,16 +1835,26 @@ static ssize_t disk_events_poll_msecs_store(struct device *dev,
 	return count;
 }
 
+static ssize_t diskseq_show(struct device *dev,
+			    struct device_attribute *attr, char *buf)
+{
+	struct gendisk *disk = dev_to_disk(dev);
+
+	return sprintf(buf, "%llu\n", disk->diskseq);
+}
+
 static const DEVICE_ATTR(events, 0444, disk_events_show, NULL);
 static const DEVICE_ATTR(events_async, 0444, disk_events_async_show, NULL);
 static const DEVICE_ATTR(events_poll_msecs, 0644,
 			 disk_events_poll_msecs_show,
 			 disk_events_poll_msecs_store);
+static const DEVICE_ATTR(diskseq, 0444, diskseq_show, NULL);
 
 static const struct attribute *disk_sysfs_attrs[] = {
 	&dev_attr_events.attr,
 	&dev_attr_events_async.attr,
 	&dev_attr_events_poll_msecs.attr,
+	&dev_attr_diskseq.attr,
 	NULL,
 };
 
-- 
2.30.2


  parent reply index

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-15 20:02 [PATCH -next 0/5] block: add a sequence number to disks Matteo Croce
2021-03-15 20:02 ` [PATCH -next 1/5] block: add disk sequence number Matteo Croce
2021-03-15 20:18   ` Matthew Wilcox
2021-03-15 21:04     ` Matthew Wilcox
2021-03-15 21:32       ` Lennart Poettering
2021-03-25 17:29       ` Matteo Croce
2021-03-26  8:00         ` Hannes Reinecke
2021-03-25 20:58       ` Lennart Poettering
2021-03-16 14:13     ` Christoph Hellwig
2021-04-20 20:12       ` Lennart Poettering
2021-03-25 20:52     ` Lennart Poettering
2021-03-16  1:44   ` JeffleXu
2021-03-23 17:43     ` Matteo Croce
2021-03-15 20:02 ` [PATCH -next 2/5] block: add ioctl to read the " Matteo Croce
2021-03-15 20:13   ` Matthew Wilcox
2021-03-15 20:17     ` Damien Le Moal
2021-03-15 20:34     ` Matteo Croce
2021-03-15 20:02 ` [PATCH -next 3/5] block: refactor sysfs code Matteo Croce
2021-03-15 20:02 ` Matteo Croce [this message]
2021-03-15 20:02 ` [PATCH -next 5/5] loop: increment sequence number Matteo Croce

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