Messages in this thread | | | Subject | Re: [PATCH v2 04/10] block: revert back to synchronous request_queue removal | From | Bart Van Assche <> | Date | Sun, 19 Apr 2020 15:23:31 -0700 |
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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.
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