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From: Luis Chamberlain <mcgrof@kernel.org>
To: axboe@kernel.dk, viro@zeniv.linux.org.uk, bvanassche@acm.org,
	gregkh@linuxfoundation.org, rostedt@goodmis.org,
	mingo@redhat.com, jack@suse.cz, ming.lei@redhat.com,
	nstange@suse.de, akpm@linux-foundation.org
Cc: mhocko@suse.com, yukuai3@huawei.com, martin.petersen@oracle.com,
	jejb@linux.ibm.com, linux-block@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org,
	Luis Chamberlain <mcgrof@kernel.org>,
	Christoph Hellwig <hch@lst.de>
Subject: [PATCH v6 1/6] block: add docs for gendisk / request_queue refcount helpers
Date: Mon,  8 Jun 2020 17:01:21 +0000	[thread overview]
Message-ID: <20200608170127.20419-2-mcgrof@kernel.org> (raw)
In-Reply-To: <20200608170127.20419-1-mcgrof@kernel.org>

This adds documentation for the gendisk / request_queue refcount
helpers.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
---
 block/blk-core.c | 13 +++++++++++++
 block/genhd.c    | 50 +++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 62 insertions(+), 1 deletion(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 62a4904db921..a0760aac110a 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -321,6 +321,13 @@ void blk_clear_pm_only(struct request_queue *q)
 }
 EXPORT_SYMBOL_GPL(blk_clear_pm_only);
 
+/**
+ * blk_put_queue - decrement the request_queue refcount
+ * @q: the request_queue structure to decrement the refcount for
+ *
+ * Decrements the refcount of the request_queue kobject. When this reaches 0
+ * we'll have blk_release_queue() called.
+ */
 void blk_put_queue(struct request_queue *q)
 {
 	kobject_put(&q->kobj);
@@ -598,6 +605,12 @@ struct request_queue *blk_alloc_queue(make_request_fn make_request, int node_id)
 }
 EXPORT_SYMBOL(blk_alloc_queue);
 
+/**
+ * blk_get_queue - increment the request_queue refcount
+ * @q: the request_queue structure to increment the refcount for
+ *
+ * Increment the refcount of the request_queue kobject.
+ */
 bool blk_get_queue(struct request_queue *q)
 {
 	if (likely(!blk_queue_dying(q))) {
diff --git a/block/genhd.c b/block/genhd.c
index 1a7659327664..f741613d731f 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -876,6 +876,20 @@ static void invalidate_partition(struct gendisk *disk, int partno)
 	bdput(bdev);
 }
 
+/**
+ * del_gendisk - remove the gendisk
+ * @disk: the struct gendisk to remove
+ *
+ * Removes the gendisk and all its associated resources. This deletes the
+ * partitions associated with the gendisk, and unregisters the associated
+ * request_queue.
+ *
+ * This is the counter to the respective __device_add_disk() call.
+ *
+ * The final removal of the struct gendisk happens when its refcount reaches 0
+ * with put_disk(), which should be called after del_gendisk(), if
+ * __device_add_disk() was used.
+ */
 void del_gendisk(struct gendisk *disk)
 {
 	struct disk_part_iter piter;
@@ -1514,6 +1528,23 @@ int disk_expand_part_tbl(struct gendisk *disk, int partno)
 	return 0;
 }
 
+/**
+ * disk_release - releases all allocated resources of the gendisk
+ * @dev: the device representing this disk
+ *
+ * This function releases all allocated resources of the gendisk.
+ *
+ * The struct gendisk refcount is incremented with get_gendisk() or
+ * get_disk_and_module(), and its refcount is decremented with
+ * put_disk_and_module() or put_disk(). Once the refcount reaches 0 this
+ * function is called.
+ *
+ * Drivers which used __device_add_disk() have a gendisk with a request_queue
+ * assigned. Since the request_queue sits on top of the gendisk for these
+ * drivers we also call blk_put_queue() for them, and we expect the
+ * request_queue refcount to reach 0 at this point, and so the request_queue
+ * will also be freed prior to the disk.
+ */
 static void disk_release(struct device *dev)
 {
 	struct gendisk *disk = dev_to_disk(dev);
@@ -1727,6 +1758,13 @@ struct gendisk *__alloc_disk_node(int minors, int node_id)
 }
 EXPORT_SYMBOL(__alloc_disk_node);
 
+/**
+ * get_disk_and_module - increments the gendisk and gendisk fops module refcount
+ * @disk: the struct gendisk to to increment the refcount for
+ *
+ * This increments the refcount for the struct gendisk, and the gendisk's
+ * fops module owner.
+ */
 struct kobject *get_disk_and_module(struct gendisk *disk)
 {
 	struct module *owner;
@@ -1747,6 +1785,13 @@ struct kobject *get_disk_and_module(struct gendisk *disk)
 }
 EXPORT_SYMBOL(get_disk_and_module);
 
+/**
+ * put_disk - decrements the gendisk refcount
+ * @disk: the struct gendisk to to decrement the refcount for
+ *
+ * This decrements the refcount for the struct gendisk. When this reaches 0
+ * we'll have disk_release() called.
+ */
 void put_disk(struct gendisk *disk)
 {
 	if (disk)
@@ -1754,7 +1799,10 @@ void put_disk(struct gendisk *disk)
 }
 EXPORT_SYMBOL(put_disk);
 
-/*
+/**
+ * put_disk_and_module - decrements the module and gendisk refcount
+ * @disk: the struct gendisk to to decrement the refcount for
+ *
  * This is a counterpart of get_disk_and_module() and thus also of
  * get_gendisk().
  */
-- 
2.26.2



  reply	other threads:[~2020-06-08 17:01 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-08 17:01 [PATCH v6 0/8] block: fix blktrace debugfs use after free Luis Chamberlain
2020-06-08 17:01 ` Luis Chamberlain [this message]
2020-06-08 17:01 ` [PATCH v6 2/6] block: clarify context for refcount increment helpers Luis Chamberlain
2020-06-08 17:01 ` [PATCH v6 3/6] block: revert back to synchronous request_queue removal Luis Chamberlain
2020-06-13  1:53   ` Bart Van Assche
2020-06-19 20:23     ` Luis Chamberlain
2020-06-08 17:01 ` [PATCH v6 4/6] blktrace: annotate required lock on do_blk_trace_setup() Luis Chamberlain
2020-06-09 14:18   ` Christoph Hellwig
2020-06-13  1:54   ` Bart Van Assche
2020-06-08 17:01 ` [PATCH v6 5/6] loop: be paranoid on exit and prevent new additions / removals Luis Chamberlain
2020-06-08 17:01 ` [PATCH v6 6/6] blktrace: fix debugfs use after free Luis Chamberlain
2020-06-09 15:06   ` Christoph Hellwig
2020-06-09 17:29     ` Luis Chamberlain
2020-06-09 17:32       ` Christoph Hellwig
2020-06-09 17:53         ` Luis Chamberlain
2020-06-10  6:42           ` Christoph Hellwig
2020-06-10 21:09             ` Luis Chamberlain
2020-06-10 21:52               ` Luis Chamberlain
2020-06-10 23:31                 ` Luis Chamberlain
2020-06-11  5:40                   ` Christoph Hellwig
2020-06-13  2:42   ` Bart Van Assche
2020-06-19 15:36     ` Luis Chamberlain

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