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[84.16.102.26]) by smtp.gmail.com with ESMTPSA id l83sm10250121wmf.43.2020.03.25.12.13.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Mar 2020 12:13:57 -0700 (PDT) Date: Wed, 25 Mar 2020 20:13:56 +0100 From: Jiri Pirko To: Jakub Kicinski Cc: Jacob Keller , netdev@vger.kernel.org, Jiri Pirko Subject: Re: [PATCH 06/10] devlink: convert snapshot id getter to return an error Message-ID: <20200325191356.GF11304@nanopsycho.orion> References: <20200324223445.2077900-1-jacob.e.keller@intel.com> <20200324223445.2077900-7-jacob.e.keller@intel.com> <20200325110425.6fdf6cb3@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200325110425.6fdf6cb3@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Wed, Mar 25, 2020 at 07:04:25PM CET, kuba@kernel.org wrote: >On Tue, 24 Mar 2020 15:34:41 -0700 Jacob Keller wrote: >> diff --git a/drivers/net/netdevsim/dev.c b/drivers/net/netdevsim/dev.c >> index f7621ccb7b88..f9420b77e5fd 100644 >> --- a/drivers/net/netdevsim/dev.c >> +++ b/drivers/net/netdevsim/dev.c >> @@ -45,8 +45,7 @@ static ssize_t nsim_dev_take_snapshot_write(struct file *file, >> { >> struct nsim_dev *nsim_dev = file->private_data; >> void *dummy_data; >> - int err; >> - u32 id; >> + int err, id; >> >> dummy_data = kmalloc(NSIM_DEV_DUMMY_REGION_SIZE, GFP_KERNEL); >> if (!dummy_data) >> @@ -55,6 +54,10 @@ static ssize_t nsim_dev_take_snapshot_write(struct file *file, >> get_random_bytes(dummy_data, NSIM_DEV_DUMMY_REGION_SIZE); >> >> id = devlink_region_snapshot_id_get(priv_to_devlink(nsim_dev)); >> + if (id < 0) { >> + pr_err("Failed to get snapshot id\n"); >> + return id; >> + } >> err = devlink_region_snapshot_create(nsim_dev->dummy_region, >> dummy_data, id); >> if (err) { > >Hmm... next patch introduces some ref counting on the ID AFAICT, >should there be some form of snapshot_id_put(), once the driver is >done creating the regions it wants? > >First what if driver wants to create two snapshots with the same ID but >user space manages to delete the first one before second one is created. > >Second what if create fails, won't the snapshot ID just stay in XA with >count of 0 forever? Yeah, that seems like a race condition this is introducing.