From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Thu, 9 Nov 2017 13:52:15 +0100 From: Christoph Hellwig To: Sagi Grimberg Cc: Christoph Hellwig , Keith Busch , Jens Axboe , Hannes Reinecke , Johannes Thumshirn , linux-nvme@lists.infradead.org, linux-block@vger.kernel.org Subject: Re: [PATCH 3/5] nvme: track shared namespaces Message-ID: <20171109125214.GA21795@lst.de> References: <20171102183034.9320-1-hch@lst.de> <20171102183034.9320-4-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: List-ID: On Thu, Nov 09, 2017 at 01:37:43PM +0200, Sagi Grimberg wrote: > >> To allow lockless path lookup the list of nvme_ns structures per >> nvme_ns_head is protected by SRCU, which requires freeing the nvme_ns >> structure through call_srcu. > > Can you remind me why isn't rcu sufficient? Can looking up a > path (ns from head->list) block? blk_mq_make_request can block. From mboxrd@z Thu Jan 1 00:00:00 1970 From: hch@lst.de (Christoph Hellwig) Date: Thu, 9 Nov 2017 13:52:15 +0100 Subject: [PATCH 3/5] nvme: track shared namespaces In-Reply-To: References: <20171102183034.9320-1-hch@lst.de> <20171102183034.9320-4-hch@lst.de> Message-ID: <20171109125214.GA21795@lst.de> On Thu, Nov 09, 2017@01:37:43PM +0200, Sagi Grimberg wrote: > >> To allow lockless path lookup the list of nvme_ns structures per >> nvme_ns_head is protected by SRCU, which requires freeing the nvme_ns >> structure through call_srcu. > > Can you remind me why isn't rcu sufficient? Can looking up a > path (ns from head->list) block? blk_mq_make_request can block.