[PATCH 0/4] introduce new put_getdisk() call

[PATCH 0/4] introduce new put_getdisk() call

[Roman Pen]

Hello.

In this patchset in the first patch I fixed module reference leak inside
blk-cgroup.c.  In other patches I switched to a new put_getdisk() call,
which should be used if the disk was received by get_disk() or get_gendisk()
functions, which internally increase module reference.

The idea is to avoid confusion in the future and to have symmetric calls:

	alloc_disk() -> put_disk() [as it is done in all the block drivers]

and

	get_gendisk() -> put_gendisk() [if you need to find a disk by minor,major]

The second sequence internally increases disk owner module reference on
get and decreases it on put.

Roman Pen (4):
  block: fix module reference leak on put_disk() call for cgroups
    throttle
  block: introduce new call put_gendisk() in genhd.c
  block,fs: switch to a new put_gendisk() call
  hibernate: fix disk and module leak on successfull resume

 block/blk-cgroup.c       |  6 ++---
 block/genhd.c            | 59 +++++++++++++++++++++++++++++++++++++++++++++---
 fs/block_dev.c           | 24 ++++++--------------
 include/linux/genhd.h    |  1 +
 kernel/power/hibernate.c |  5 +++-
 5 files changed, 71 insertions(+), 24 deletions(-)

Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Gi-Oh Kim <gi-oh.kim@profitbricks.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Len Brown <len.brown@intel.com>
Cc: Ming Lei <tom.leiming@gmail.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Sagi Grimberg <sagig@mellanox.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: linux-block@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-pm@vger.kernel.org

-- 
2.6.2

[PATCH 0/4] introduce new put_getdisk() call

[Roman Pen]

Hello.

In this patchset in the first patch I fixed module reference leak inside
blk-cgroup.c.  In other patches I switched to a new put_getdisk() call,
which should be used if the disk was received by get_disk() or get_gendisk()
functions, which internally increase module reference.

The idea is to avoid confusion in the future and to have symmetric calls:

	alloc_disk() -> put_disk() [as it is done in all the block drivers]

and

	get_gendisk() -> put_gendisk() [if you need to find a disk by minor,major]

The second sequence internally increases disk owner module reference on
get and decreases it on put.

Roman Pen (4):
  block: fix module reference leak on put_disk() call for cgroups
    throttle
  block: introduce new call put_gendisk() in genhd.c
  block,fs: switch to a new put_gendisk() call
  hibernate: fix disk and module leak on successfull resume

 block/blk-cgroup.c       |  6 ++---
 block/genhd.c            | 59 +++++++++++++++++++++++++++++++++++++++++++++---
 fs/block_dev.c           | 24 ++++++--------------
 include/linux/genhd.h    |  1 +
 kernel/power/hibernate.c |  5 +++-
 5 files changed, 71 insertions(+), 24 deletions(-)

Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Gi-Oh Kim <gi-oh.kim@profitbricks.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Len Brown <len.brown@intel.com>
Cc: Ming Lei <tom.leiming@gmail.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Sagi Grimberg <sagig@mellanox.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: linux-block@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-pm@vger.kernel.org

-- 
2.6.2

[PATCH 1/4] block: fix module reference leak on put_disk() call for cgroups throttle

[Roman Pen]

get_disk(),get_gendisk() calls have non explicit side effect: they
increase the reference on the disk owner module.

The following is the correct sequence how to get a disk reference and
to put it:

    disk = get_gendisk(...);

    /* use disk */

    owner = disk->fops->owner;
    put_disk(disk);
    module_put(owner);

fs/block_dev.c is aware of this required module_put() call, but f.e.
blkg_conf_finish(), which is located in block/blk-cgroup.c, does not put
a module reference.  To see a leakage in action cgroups throttle config
can be used.  In the following script I'm removing throttle for /dev/ram0
(actually this is NOP, because throttle was never set for this device):

    # lsmod | grep brd
    brd                     5175  0
    # i=100; while [ $i -gt 0 ]; do echo "1:0 0" > \
        /sys/fs/cgroup/blkio/blkio.throttle.read_bps_device; i=$(($i - 1)); \
    done
    # lsmod | grep brd
    brd                     5175  100

Now brd module has 100 references.

The issue is fixed by calling module_put() just right away put_disk().

Signed-off-by: Roman Pen <roman.penyaev@profitbricks.com>
Cc: Gi-Oh Kim <gi-oh.kim@profitbricks.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
 block/blk-cgroup.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 5a37188..66e6f1a 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -788,6 +788,7 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
 {
 	struct gendisk *disk;
 	struct blkcg_gq *blkg;
+	struct module *owner;
 	unsigned int major, minor;
 	int key_len, part, ret;
 	char *body;
@@ -804,7 +805,9 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
 	if (!disk)
 		return -ENODEV;
 	if (part) {
+		owner = disk->fops->owner;
 		put_disk(disk);
+		module_put(owner);
 		return -ENODEV;
 	}
 
@@ -820,7 +823,9 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
 		ret = PTR_ERR(blkg);
 		rcu_read_unlock();
 		spin_unlock_irq(disk->queue->queue_lock);
+		owner = disk->fops->owner;
 		put_disk(disk);
+		module_put(owner);
 		/*
 		 * If queue was bypassing, we should retry.  Do so after a
 		 * short msleep().  It isn't strictly necessary but queue
@@ -851,9 +856,13 @@ EXPORT_SYMBOL_GPL(blkg_conf_prep);
 void blkg_conf_finish(struct blkg_conf_ctx *ctx)
 	__releases(ctx->disk->queue->queue_lock) __releases(rcu)
 {
+	struct module *owner;
+
 	spin_unlock_irq(ctx->disk->queue->queue_lock);
 	rcu_read_unlock();
+	owner = ctx->disk->fops->owner;
 	put_disk(ctx->disk);
+	module_put(owner);
 }
 EXPORT_SYMBOL_GPL(blkg_conf_finish);
 
-- 
2.6.2

[PATCH 2/4] block: introduce new call put_gendisk() in genhd.c

[Roman Pen]

The confusion comes from the fact, that if disk was get using

    get_disk()
    get_gendisk()

calls, you also have to put a disk owner module reference, so the sequence
is the following:

    disk = get_gendisk(...);

    /* use disk */

    owner = disk->fops->owner;
    put_disk(disk);
    module_put(owner);

The disk, which was allocated using alloc_disk() requires only the opposite
put_disk() call, without puting the module reference.

That's error prone.

Here in this patch new call is introduced put_gendisk(), which is aimed to
put a disk reference and also a disk owner reference.

The expected usage for the block drivers has not been changed and is the
following:

    disk = alloc_disk(...);

    /* use */

    put_disk(disk);

The expected usage for those who did get_gendisk():

    disk = get_gendisk();

    /* use */

    put_gendisk(disk);

That should help to get rid of modules references leak, which happens if
disk was received by get_gendisk() call, but then was put by put_disk(),
without corresponding module_put().

Also function description is updated.

Signed-off-by: Roman Pen <roman.penyaev@profitbricks.com>
Cc: Gi-Oh Kim <gi-oh.kim@profitbricks.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Sagi Grimberg <sagig@mellanox.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Ming Lei <tom.leiming@gmail.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: linux-block@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
 block/genhd.c         | 59 ++++++++++++++++++++++++++++++++++++++++++++++++---
 include/linux/genhd.h |  1 +
 2 files changed, 57 insertions(+), 3 deletions(-)

diff --git a/block/genhd.c b/block/genhd.c
index 0f566a5..66c8278 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -722,7 +722,13 @@ static ssize_t disk_badblocks_store(struct device *dev,
  * @partno: returned partition index
  *
  * This function gets the structure containing partitioning
- * information for the given device @devt.
+ * information for the given device @devt and increases the kobj
+ * and disk owner module references.
+ *
+ * RETURNS:
+ * Resulting gendisk on success, NULL in case of failure. After usage
+ * disk must be put with put_gendisk() call, which also puts the module
+ * reference.
  */
 struct gendisk *get_gendisk(dev_t devt, int *partno)
 {
@@ -1305,6 +1311,17 @@ struct gendisk *alloc_disk(int minors)
 }
 EXPORT_SYMBOL(alloc_disk);
 
+/**
+ * alloc_disk_node - allocates disk for specified minors and node id.
+ *
+ * @minors: how many minors are expected for that disk before switching
+ *          to extended block range
+ * @node_id: memory node from which to allocate
+ *
+ * RETURNS:
+ * Resulting disk on success, NULL in case of failure.
+ * alloc_disk() and alloc_disk_node() are paired with put_disk() call.
+ */
 struct gendisk *alloc_disk_node(int minors, int node_id)
 {
 	struct gendisk *disk;
@@ -1349,6 +1366,16 @@ struct gendisk *alloc_disk_node(int minors, int node_id)
 }
 EXPORT_SYMBOL(alloc_disk_node);
 
+/**
+ * get_disk - increases the kobj and module references.
+ *
+ * @disk: disk for which references should be increased
+ *
+ * RETURNS:
+ * Resulting kobj of the disk on success, NULL in case of failure.
+ * After usage disk must be put with put_gendisk() call, which also
+ * puts the module reference.
+ */
 struct kobject *get_disk(struct gendisk *disk)
 {
 	struct module *owner;
@@ -1367,17 +1394,43 @@ struct kobject *get_disk(struct gendisk *disk)
 	return kobj;
 
 }
-
 EXPORT_SYMBOL(get_disk);
 
+/**
+ * put_disk - puts only kobj reference.
+ *
+ * @disk: disk to put
+ *
+ * This put_disk() is paired with alloc_disk().  Never call this
+ * if you get a disk using get_gendisk() or get_disk() calls.
+ */
 void put_disk(struct gendisk *disk)
 {
 	if (disk)
 		kobject_put(&disk_to_dev(disk)->kobj);
 }
-
 EXPORT_SYMBOL(put_disk);
 
+/**
+ * put_gendisk - puts kobj and disk owner module references.
+ *
+ * @disk: disk to put
+ *
+ * This put_gendisk() is paired with get_gendisk() and get_disk() calls.
+ * Never use this call if you just have allocated a disk using alloc_disk(),
+ * use put_disk() instead.
+ */
+void put_gendisk(struct gendisk *disk)
+{
+	if (disk) {
+		struct module *owner = disk->fops->owner;
+
+		put_disk(disk);
+		module_put(owner);
+	}
+}
+EXPORT_SYMBOL(put_gendisk);
+
 static void set_disk_ro_uevent(struct gendisk *gd, int ro)
 {
 	char event[] = "DISK_RO=1";
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 9e4e547..f84efbf 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -635,6 +635,7 @@ extern struct gendisk *alloc_disk_node(int minors, int node_id);
 extern struct gendisk *alloc_disk(int minors);
 extern struct kobject *get_disk(struct gendisk *disk);
 extern void put_disk(struct gendisk *disk);
+extern void put_gendisk(struct gendisk *disk);
 extern void blk_register_region(dev_t devt, unsigned long range,
 			struct module *module,
 			struct kobject *(*probe)(dev_t, int *, void *),
-- 
2.6.2

[PATCH 3/4] block,fs: switch to a new put_gendisk() call

[Roman Pen]

In previous patch a new put_gendisk() call was introduced, which puts the
disk and the disk owner module references.

This new call should help not to forget about required module_put() after
receiving a disk pointer using get_disk() or get_gendisk() calls.

In this patch disk_put(),module_put() sequences are replaced with a single
put_gendisk() call.

Signed-off-by: Roman Pen <roman.penyaev@profitbricks.com>
Cc: Gi-Oh Kim <gi-oh.kim@profitbricks.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-block@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org
---
 block/blk-cgroup.c | 15 +++------------
 fs/block_dev.c     | 24 +++++++-----------------
 2 files changed, 10 insertions(+), 29 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 66e6f1a..2ed9636 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -788,7 +788,6 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
 {
 	struct gendisk *disk;
 	struct blkcg_gq *blkg;
-	struct module *owner;
 	unsigned int major, minor;
 	int key_len, part, ret;
 	char *body;
@@ -805,9 +804,7 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
 	if (!disk)
 		return -ENODEV;
 	if (part) {
-		owner = disk->fops->owner;
-		put_disk(disk);
-		module_put(owner);
+		put_gendisk(disk);
 		return -ENODEV;
 	}
 
@@ -823,9 +820,7 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
 		ret = PTR_ERR(blkg);
 		rcu_read_unlock();
 		spin_unlock_irq(disk->queue->queue_lock);
-		owner = disk->fops->owner;
-		put_disk(disk);
-		module_put(owner);
+		put_gendisk(disk);
 		/*
 		 * If queue was bypassing, we should retry.  Do so after a
 		 * short msleep().  It isn't strictly necessary but queue
@@ -856,13 +851,9 @@ EXPORT_SYMBOL_GPL(blkg_conf_prep);
 void blkg_conf_finish(struct blkg_conf_ctx *ctx)
 	__releases(ctx->disk->queue->queue_lock) __releases(rcu)
 {
-	struct module *owner;
-
 	spin_unlock_irq(ctx->disk->queue->queue_lock);
 	rcu_read_unlock();
-	owner = ctx->disk->fops->owner;
-	put_disk(ctx->disk);
-	module_put(owner);
+	put_gendisk(ctx->disk);
 }
 EXPORT_SYMBOL_GPL(blkg_conf_finish);
 
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 7b9cd49..dc2ea76 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -15,7 +15,6 @@
 #include <linux/highmem.h>
 #include <linux/blkdev.h>
 #include <linux/backing-dev.h>
-#include <linux/module.h>
 #include <linux/blkpg.h>
 #include <linux/magic.h>
 #include <linux/buffer_head.h>
@@ -870,8 +869,7 @@ static struct block_device *bd_start_claiming(struct block_device *bdev,
 	else
 		whole = bdgrab(bdev);
 
-	module_put(disk->fops->owner);
-	put_disk(disk);
+	put_gendisk(disk);
 	if (!whole)
 		return ERR_PTR(-ENOMEM);
 
@@ -1167,7 +1165,6 @@ static void __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part);
 static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
 {
 	struct gendisk *disk;
-	struct module *owner;
 	int ret;
 	int partno;
 	int perm = 0;
@@ -1193,7 +1190,6 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
 	disk = get_gendisk(bdev->bd_dev, &partno);
 	if (!disk)
 		goto out;
-	owner = disk->fops->owner;
 
 	disk_block_events(disk);
 	mutex_lock_nested(&bdev->bd_mutex, for_part);
@@ -1222,8 +1218,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
 					bdev->bd_queue = NULL;
 					mutex_unlock(&bdev->bd_mutex);
 					disk_unblock_events(disk);
-					put_disk(disk);
-					module_put(owner);
+					put_gendisk(disk);
 					goto restart;
 				}
 			}
@@ -1285,9 +1280,8 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
 			if (ret)
 				goto out_unlock_bdev;
 		}
-		/* only one opener holds refs to the module and disk */
-		put_disk(disk);
-		module_put(owner);
+		/* only one opener holds refs to the disk */
+		put_gendisk(disk);
 	}
 	bdev->bd_openers++;
 	if (for_part)
@@ -1307,8 +1301,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
  out_unlock_bdev:
 	mutex_unlock(&bdev->bd_mutex);
 	disk_unblock_events(disk);
-	put_disk(disk);
-	module_put(owner);
+	put_gendisk(disk);
  out:
 	bdput(bdev);
 
@@ -1525,7 +1518,7 @@ static void __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part)
 		/*
 		 * Detaching bdev inode from its wb in __destroy_inode()
 		 * is too late: the queue which embeds its bdi (along with
-		 * root wb) can be gone as soon as we put_disk() below.
+		 * root wb) can be gone as soon as we put_gendisk() below.
 		 */
 		inode_detach_wb(bdev->bd_inode);
 	}
@@ -1534,8 +1527,6 @@ static void __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part)
 			disk->fops->release(disk, mode);
 	}
 	if (!bdev->bd_openers) {
-		struct module *owner = disk->fops->owner;
-
 		disk_put_part(bdev->bd_part);
 		bdev->bd_part = NULL;
 		bdev->bd_disk = NULL;
@@ -1543,8 +1534,7 @@ static void __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part)
 			victim = bdev->bd_contains;
 		bdev->bd_contains = NULL;
 
-		put_disk(disk);
-		module_put(owner);
+		put_gendisk(disk);
 	}
 	mutex_unlock(&bdev->bd_mutex);
 	bdput(bdev);
-- 
2.6.2

[PATCH 4/4] hibernate: fix disk and module leak on successfull resume

[Roman Pen]

Do not forget to put the disk back.

Signed-off-by: Roman Pen <roman.penyaev@profitbricks.com>
Cc: Gi-Oh Kim <gi-oh.kim@profitbricks.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Len Brown <len.brown@intel.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: linux-pm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
 kernel/power/hibernate.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index b7342a2..1f53dc2 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -785,8 +785,11 @@ static int software_resume(void)
 	 */
 	if (isdigit(resume_file[0]) && resume_wait) {
 		int partno;
-		while (!get_gendisk(swsusp_resume_device, &partno))
+		struct gendisk *disk;
+
+		while (!(disk = get_gendisk(swsusp_resume_device, &partno)))
 			msleep(10);
+		put_gendisk(disk);
 	}
 
 	if (!swsusp_resume_device) {
-- 
2.6.2

[PATCH 4/4] hibernate: fix disk and module leak on successfull resume

[Roman Pen]

Do not forget to put the disk back.

Signed-off-by: Roman Pen <roman.penyaev@profitbricks.com>
Cc: Gi-Oh Kim <gi-oh.kim@profitbricks.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Len Brown <len.brown@intel.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: linux-pm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
 kernel/power/hibernate.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index b7342a2..1f53dc2 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -785,8 +785,11 @@ static int software_resume(void)
 	 */
 	if (isdigit(resume_file[0]) && resume_wait) {
 		int partno;
-		while (!get_gendisk(swsusp_resume_device, &partno))
+		struct gendisk *disk;
+
+		while (!(disk = get_gendisk(swsusp_resume_device, &partno)))
 			msleep(10);
+		put_gendisk(disk);
 	}
 
 	if (!swsusp_resume_device) {
-- 
2.6.2

Re: [PATCH 0/4] introduce new put_getdisk() call

[Tejun Heo]

On Mon, Feb 01, 2016 at 03:51:51PM +0100, Roman Pen wrote:
> Hello.
> 
> In this patchset in the first patch I fixed module reference leak inside
> blk-cgroup.c.  In other patches I switched to a new put_getdisk() call,
> which should be used if the disk was received by get_disk() or get_gendisk()
> functions, which internally increase module reference.
> 
> The idea is to avoid confusion in the future and to have symmetric calls:
> 
> 	alloc_disk() -> put_disk() [as it is done in all the block drivers]
> 
> and
> 
> 	get_gendisk() -> put_gendisk() [if you need to find a disk by minor,major]
> 
> The second sequence internally increases disk owner module reference on
> get and decreases it on put.

For the entire series,

 Acked-by: Tejun Heo <tj@kernel.org>

Nice catch, thanks!

-- 
tejun

Re: [PATCH 4/4] hibernate: fix disk and module leak on successfull resume

[Rafael J. Wysocki]

On Monday, February 01, 2016 03:51:55 PM Roman Pen wrote:
> Do not forget to put the disk back.
> 
> Signed-off-by: Roman Pen <roman.penyaev@profitbricks.com>
> Cc: Gi-Oh Kim <gi-oh.kim@profitbricks.com>
> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
> Cc: Len Brown <len.brown@intel.com>
> Cc: Pavel Machek <pavel@ucw.cz>
> Cc: linux-pm@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

> ---
>  kernel/power/hibernate.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
> index b7342a2..1f53dc2 100644
> --- a/kernel/power/hibernate.c
> +++ b/kernel/power/hibernate.c
> @@ -785,8 +785,11 @@ static int software_resume(void)
>  	 */
>  	if (isdigit(resume_file[0]) && resume_wait) {
>  		int partno;
> -		while (!get_gendisk(swsusp_resume_device, &partno))
> +		struct gendisk *disk;
> +
> +		while (!(disk = get_gendisk(swsusp_resume_device, &partno)))
>  			msleep(10);
> +		put_gendisk(disk);
>  	}
>  
>  	if (!swsusp_resume_device) {
> 

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.

Re: [PATCH 1/4] block: fix module reference leak on put_disk() call for cgroups throttle

[Gi-Oh Kim]

On 01.02.2016 15:51, Roman Pen wrote:
> get_disk(),get_gendisk() calls have non explicit side effect: they
> increase the reference on the disk owner module.
>
> The following is the correct sequence how to get a disk reference and
> to put it:
>
>      disk = get_gendisk(...);
>
>      /* use disk */
>
>      owner = disk->fops->owner;
>      put_disk(disk);
>      module_put(owner);
>
> fs/block_dev.c is aware of this required module_put() call, but f.e.
> blkg_conf_finish(), which is located in block/blk-cgroup.c, does not put
> a module reference.  To see a leakage in action cgroups throttle config
> can be used.  In the following script I'm removing throttle for /dev/ram0
> (actually this is NOP, because throttle was never set for this device):
>
>      # lsmod | grep brd
>      brd                     5175  0
>      # i=100; while [ $i -gt 0 ]; do echo "1:0 0" > \
>          /sys/fs/cgroup/blkio/blkio.throttle.read_bps_device; i=$(($i - 1)); \
>      done
>      # lsmod | grep brd
>      brd                     5175  100
>
> Now brd module has 100 references.

I hope this patch would be merged into stable versions.
I've tested the patch with v3.12.45 on my server.

Before apply the patch, reference count was leaked.
# lsmod | grep loop
loop                   16091  0
# echo "7:0 1048576" > /sys/fs/cgroup/blkio/blkio.throttle.read_bps_device
# lsmod | grep loop
loop                   16091  1
# echo "7:0 1048576" > /sys/fs/cgroup/blkio/blkio.throttle.read_bps_device
# lsmod | grep loop
loop                   16091  2
# echo "7:0 1048576" > /sys/fs/cgroup/blkio/blkio.throttle.read_bps_device
# lsmod | grep loop
loop                   16091  3
# echo "7:0 1048576" > /sys/fs/cgroup/blkio/blkio.throttle.read_bps_device
# lsmod | grep loop
loop                   16091  4

After apply the patch, reference count was still:
# lsmod | grep loop
loop                   19171  0
# echo "7:0 1048576" > /sys/fs/cgroup/blkio/blkio.throttle.read_bps_device
# lsmod | grep loop
loop                   19171  0
# echo "7:0 1048576" > /sys/fs/cgroup/blkio/blkio.throttle.read_bps_device
# lsmod | grep loop
loop                   19171  0
# echo "7:0 1048576" > /sys/fs/cgroup/blkio/blkio.throttle.read_bps_device
# lsmod | grep loop
loop                   19171  0


-- 
Best regards,
Gi-Oh Kim