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From: Matteo Croce <mcroce@linux.microsoft.com>
To: linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	Jens Axboe <axboe@kernel.dk>
Cc: linux-kernel@vger.kernel.org,
	"Lennart Poettering" <lennart@poettering.net>,
	"Luca Boccassi" <bluca@debian.org>,
	"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>,
	"Matthew Wilcox" <willy@infradead.org>,
	"Christoph Hellwig" <hch@infradead.org>,
	JeffleXu <jefflexu@linux.alibaba.com>
Subject: [PATCH v3 4/6] block: export diskseq in sysfs
Date: Wed, 23 Jun 2021 12:58:56 +0200	[thread overview]
Message-ID: <20210623105858.6978-5-mcroce@linux.microsoft.com> (raw)
In-Reply-To: <20210623105858.6978-1-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.

    $ grep . /sys/class/block/*/diskseq
    /sys/class/block/loop0/diskseq:13
    /sys/class/block/loop1/diskseq:14
    /sys/class/block/loop2/diskseq:5
    /sys/class/block/loop3/diskseq:6
    /sys/class/block/ram0/diskseq:1
    /sys/class/block/ram1/diskseq:2
    /sys/class/block/vda/diskseq:7

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 610dd86fd4b6..768d8d5d1eca 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1680,6 +1680,7 @@ 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)
 {
@@ -1750,16 +1751,26 @@ 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,
 };
 
-- 
2.31.1


  parent reply	other threads:[~2021-06-23 11:00 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-23 10:58 [PATCH v3 0/6] block: add a sequence number to disks Matteo Croce
2021-06-23 10:58 ` [PATCH v3 1/6] block: add disk sequence number Matteo Croce
2021-06-23 11:48   ` Christoph Hellwig
2021-06-23 13:10     ` Matteo Croce
2021-06-23 13:51       ` Lennart Poettering
2021-06-23 14:01         ` Hannes Reinecke
2021-06-23 14:07           ` Luca Boccassi
2021-06-23 14:21             ` Hannes Reinecke
2021-06-23 14:34               ` Luca Boccassi
2021-06-23 14:55               ` Lennart Poettering
2021-06-23 14:12           ` Lennart Poettering
2021-06-23 15:02             ` Hannes Reinecke
2021-06-23 15:34               ` Luca Boccassi
2021-06-23 15:48               ` Lennart Poettering
2021-06-23 14:28       ` Christoph Hellwig
2021-06-23 10:58 ` [PATCH v3 2/6] block: add ioctl to read the " Matteo Croce
2021-06-23 10:58 ` [PATCH v3 3/6] block: refactor sysfs code Matteo Croce
2021-06-23 11:52   ` Christoph Hellwig
2021-06-23 19:03     ` Matteo Croce
2021-06-24  6:12       ` Christoph Hellwig
2021-06-23 10:58 ` Matteo Croce [this message]
2021-06-23 10:58 ` [PATCH v3 5/6] block: increment sequence number Matteo Croce
2021-06-23 10:58 ` [PATCH v3 6/6] loop: " Matteo Croce
2021-06-23 11:57   ` Christoph Hellwig
2021-06-23 13:13     ` Luca Boccassi
2021-06-23 14:25       ` Christoph Hellwig
2021-06-23 15:29         ` Lennart Poettering
2021-06-24  6:11           ` Christoph Hellwig
2021-06-23 12:03 ` [PATCH v3 0/6] block: add a sequence number to disks Hannes Reinecke
2021-06-23 12:46   ` Luca Boccassi
2021-06-23 14:07   ` Lennart Poettering

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