Messages in this thread Patch in this message | | | From | Roman Pen <> | Subject | [PATCH 2/4] block: introduce new call put_gendisk() in genhd.c | Date | Mon, 1 Feb 2016 15:51:53 +0100 |
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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
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