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Wed, 25 Mar 2020 10:35:37 +0000 Received: from pps.filterd (aserp3020.oracle.com [127.0.0.1]) by aserp3020.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 02PAQZkc054609; Wed, 25 Mar 2020 10:35:36 GMT Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by aserp3020.oracle.com with ESMTP id 3003q01df5-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 25 Mar 2020 10:35:36 +0000 Received: from abhmp0005.oracle.com (abhmp0005.oracle.com [141.146.116.11]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 02PAZZ1p020169; Wed, 25 Mar 2020 10:35:35 GMT Received: from [10.175.203.78] (/10.175.203.78) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Wed, 25 Mar 2020 03:35:35 -0700 Subject: Re: [PATCH 11/12] device-dax: Add dis-contiguous resource support From: Joao Martins To: Dan Williams Cc: linux-mm@kvack.org, dave.hansen@linux.intel.com, hch@lst.de, linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org References: <158500767138.2088294.17131646259803932461.stgit@dwillia2-desk3.amr.corp.intel.com> <158500773552.2088294.8756587190550753100.stgit@dwillia2-desk3.amr.corp.intel.com> <9a6ff83f-095c-0689-d6d1-693a6e9c07e6@oracle.com> Message-ID: Date: Wed, 25 Mar 2020 10:35:31 +0000 MIME-Version: 1.0 In-Reply-To: <9a6ff83f-095c-0689-d6d1-693a6e9c07e6@oracle.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9570 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 adultscore=0 bulkscore=0 suspectscore=5 spamscore=0 phishscore=0 mlxlogscore=999 malwarescore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2003250090 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9570 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 malwarescore=0 bulkscore=0 phishscore=0 suspectscore=5 impostorscore=0 spamscore=0 adultscore=0 priorityscore=1501 mlxlogscore=999 lowpriorityscore=0 mlxscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2003250090 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/24/20 4:12 PM, Joao Martins wrote: > On 3/23/20 11:55 PM, Dan Williams wrote: >> static ssize_t dev_dax_resize(struct dax_region *dax_region, >> struct dev_dax *dev_dax, resource_size_t size) >> { >> resource_size_t avail = dax_region_avail_size(dax_region), to_alloc; >> - resource_size_t dev_size = range_len(&dev_dax->range); >> + resource_size_t dev_size = dev_dax_size(dev_dax); >> struct resource *region_res = &dax_region->res; >> struct device *dev = &dev_dax->dev; >> - const char *name = dev_name(dev); >> struct resource *res, *first; >> + resource_size_t alloc = 0; >> + int rc; >> >> if (dev->driver) >> return -EBUSY; >> @@ -684,38 +766,47 @@ static ssize_t dev_dax_resize(struct dax_region *dax_region, >> * allocating a new resource. >> */ >> first = region_res->child; >> - if (!first) >> - return __alloc_dev_dax_range(dev_dax, dax_region->res.start, >> - to_alloc); > > You probably want to retain the condition above? > > Otherwise it removes the ability to create new devices or resizing it , once we > have zero-ed the last one. > A quick unit test that I had stashed here to help explain what I mean: cd /sys/bus/dax/devices # dax0.0 is the only dax device in the corresponding dax_region echo dax0.0 > dax0.0/driver/unbind echo 0 > dax0.0/size # Shouldn't fail but returns -ENOSPC despite having # the full region available cat $(readlink -f dax0.0/../dax_region/available_size) > dax0.0/size >> - for (res = first; to_alloc && res; res = res->sibling) { >> +retry: >> + rc = -ENOSPC; >> + for (res = first; res; res = res->sibling) { >> struct resource *next = res->sibling; >> - resource_size_t free; >> >> /* space at the beginning of the region */ >> - free = 0; >> - if (res == first && res->start > dax_region->res.start) >> - free = res->start - dax_region->res.start; >> - if (free >= to_alloc && dev_size == 0) >> - return __alloc_dev_dax_range(dev_dax, >> - dax_region->res.start, to_alloc); >> - >> - free = 0; >> + if (res == first && res->start > dax_region->res.start) { >> + alloc = min(res->start - dax_region->res.start, >> + to_alloc); >> + rc = __alloc_dev_dax_range(dev_dax, >> + dax_region->res.start, alloc); >> + break; >> + } >> + >> + alloc = 0; >> /* space between allocations */ >> if (next && next->start > res->end + 1) >> - free = next->start - res->end + 1; >> + alloc = min(next->start - (res->end + 1), to_alloc); >> >> /* space at the end of the region */ >> - if (free < to_alloc && !next && res->end < region_res->end) >> - free = region_res->end - res->end; >> - >> - if (free >= to_alloc && strcmp(name, res->name) == 0) >> - return __adjust_dev_dax_range(dev_dax, res, >> - resource_size(res) + to_alloc); >> - else if (free >= to_alloc && dev_size == 0) >> - return __alloc_dev_dax_range(dev_dax, res->end + 1, >> - to_alloc); >> + if (!alloc && !next && res->end < region_res->end) >> + alloc = min(region_res->end - res->end, to_alloc); >> + >> + if (!alloc) >> + continue; >> + >> + if (adjust_ok(dev_dax, res)) { >> + rc = __adjust_dev_dax_range(dev_dax, res, >> + resource_size(res) + alloc); >> + break; >> + } >> + rc = __alloc_dev_dax_range(dev_dax, res->end + 1, >> + alloc); > > I am wondering if we should switch to: > > if (adjust_ok(...)) > rc = __adjust_dev_dax_range(...); > else > rc = __alloc_dev_dax_range(...); > > And then a debug print at the end depicting whether and how did we grabbed > space? Something like: > > dev_dbg(&dev_dax->dev, "%s(%d) %d", action, location, rc); > > Assuming we set @location to its values when we allocate space at the end, > beginning or middle; and @action to whether we adjusted up/down or allocated new > range. > > Essentially, something similar to namespaces scan_allocate() just to help > troubleshoot? > > Regards, > Joao >