On 4/19/20 12:45 PM, Luis Chamberlain wrote:
+/**
+ * blk_put_queue - decrement the request_queue refcount
+ *
+ * @q: the request_queue structure to decrement the refcount for
+ *
How about following the example from
Documentation/doc-guide/kernel-doc.rst and not leaving a blank line
above the function argument documentation?
+ * Decrements the refcount to the request_queue kobject, when this reaches
^^
of?
+ * 0 we'll have blk_release_queue() called. You should avoid calling
+ * this function in atomic context but if you really have to ensure you
+ * first refcount the block device with bdgrab() / bdput() so that the
+ * last decrement happens in blk_cleanup_queue().
+ */
Is calling bdgrab() and bdput() an option from a context in which it is
not guaranteed that the block device is open?
Does every context that calls blk_put_queue() also call blk_cleanup_queue()?
How about avoiding confusion by changing the last sentence of that
comment into something like the following: "The last reference must not
be dropped from atomic context. If it is necessary to call
blk_put_queue() from atomic context, make sure that that call does not
decrease the request queue refcount to zero."
/**
* blk_cleanup_queue - shutdown a request queue
+ *
* @q: request queue to shutdown
*
How about following the example from
Documentation/doc-guide/kernel-doc.rst and not leaving a blank line
above the function argument documentation?
* Mark @q DYING, drain all pending requests, mark @q DEAD, destroy and
* put it. All future requests will be failed immediately with -ENODEV.
+ *
+ * You should not call this function in atomic context. If you need to
+ * refcount a request_queue in atomic context, instead refcount the
+ * block device with bdgrab() / bdput().
Surrounding blk_cleanup_queue() with bdgrab() / bdput() does not help.
This blk_cleanup_queue() must not be called from atomic context.
/**
- * __blk_release_queue - release a request queue
- * @work: pointer to the release_work member of the request queue to be released
+ * blk_release_queue - release a request queue
+ *
+ * This function is called as part of the process when a block device is being
+ * unregistered. Releasing a request queue starts with blk_cleanup_queue(),
+ * which set the appropriate flags and then calls blk_put_queue() as the last
+ * step. blk_put_queue() decrements the reference counter of the request queue
+ * and once the reference counter reaches zero, this function is called to
+ * release all allocated resources of the request queue.
*
- * Description:
- * This function is called when a block device is being unregistered. The
- * process of releasing a request queue starts with blk_cleanup_queue, which
- * set the appropriate flags and then calls blk_put_queue, that decrements
- * the reference counter of the request queue. Once the reference counter
- * of the request queue reaches zero, blk_release_queue is called to release
- * all allocated resources of the request queue.
+ * This function can sleep, and so we must ensure that the very last
+ * blk_put_queue() is never called from atomic context.
+ *
+ * @kobj: pointer to a kobject, who's container is a request_queue
*/
Please follow the style used elsewhere in the kernel and move function
argument documentation just below the line with the function name.
Thanks,
Bart.
