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From: Chaitanya Kulkarni <Chaitanya.Kulkarni@wdc.com>
To: Christoph Hellwig <hch@lst.de>, Daniel Wagner <dwagner@suse.de>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Sagi Grimberg <sagi@grimberg.me>,
	"linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>,
	Johannes Thumshirn <jthumshirn@suse.de>
Subject: Re: [RFC] nvmet: Always remove processed AER elements from list
Date: Sun, 3 Nov 2019 18:55:14 +0000	[thread overview]
Message-ID: <BYAPR04MB574907EE2666D6DA48DE30AD867C0@BYAPR04MB5749.namprd04.prod.outlook.com> (raw)
In-Reply-To: <20191031145127.GC6024@lst.de>

On 10/31/2019 07:51 AM, Christoph Hellwig wrote:
> On Wed, Oct 30, 2019 at 04:24:18PM +0100, Daniel Wagner wrote:
>> All async events are enqueued via nvmet_add_async_event() which
>> updates the ctrl->async_event_cmds[] array and additionally an struct
>> nvmet_async_event is added to the ctrl->async_events list.
>>
>> Under normal operations the nvmet_async_event_work() updates again the
>> ctrl->async_event_cmds and removes the corresponding struct
>> nvmet_async_event from the list again. Though nvmet_sq_destroy() could
>> be called which calles nvmet_async_events_free() which only updates
>> the ctrl->async_event_cmds[] array.
>>
>> Add a new function nvmet_async_events_process() which processes the
>> async events and updates both array and the list. With this we avoid
>> having two places where the array and list are modified.
>
> I don't think this patch is correct.  We can have AEN commands pending
> that aren't used - that is the host sent the command, but the target
> did not have even event yet.  That means the command sits in
> async_event_cmds, but there is no entry in >async_events for it yet.
>
> That being said I think what we want is to do the loop in your new
> nvmet_async_events_free first, but after that still call the loop in
> the existing nvmet_async_events_free after that.  That ensures we first
> flush out everything in ->async_events, and then also return any
> potential remaining entry.
>
Something like following on the top of this patch ?
(compile tested only).

diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
index b1b9dc58c3b4..36a859082846 100644
--- a/drivers/nvme/target/core.c
+++ b/drivers/nvme/target/core.c
@@ -153,6 +153,18 @@ static void nvmet_async_events_process(struct 
nvmet_ctrl *ctrl, u16 status)
                 mutex_unlock(&ctrl->lock);
                 nvmet_req_complete(req, status);
         }
+
+       while (1) {
+               mutex_lock(&ctrl->lock);
+               if (!ctrl->nr_async_event_cmds) {
+                       mutex_unlock(&ctrl->lock);
+                       return;
+               }
+
+               req = ctrl->async_event_cmds[--ctrl->nr_async_event_cmds];
+               mutex_unlock(&ctrl->lock);
+               nvmet_req_complete(req, NVME_SC_INTERNAL | NVME_SC_DNR);
+       }
  }

  static void nvmet_async_events_free(struct nvmet_ctrl *ctrl)

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  reply	other threads:[~2019-11-03 18:55 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-30 15:24 Daniel Wagner
2019-10-30 19:58 ` Chaitanya Kulkarni
2019-10-31  7:06   ` Johannes Thumshirn
2019-10-31 14:51 ` Christoph Hellwig
2019-11-03 18:55   ` Chaitanya Kulkarni [this message]
2019-11-03 19:48     ` Chaitanya Kulkarni
2019-11-03 20:14       ` Chaitanya Kulkarni

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