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c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=st0YQO+9N+wj1Bpy5FgTMDvwfrDYYhxnz84DaeIYHvE=; b=EruQW9zwAZrBnGYCYleK8hDa46oaoorAPHjC+od9PKKQxfU8n0fRvRdj6E4yB2cKxy w3rnRAKmAvLpmcQaHuaxtGwNb5SHFFIMxN+mPfyNsr/n2MGmYZN1z+npnpdmrNn4QXUC JTT29+yD2eLxVHSjMIJ7czMag6fk9YQbr57uy95YsG5ku4enMTbBkuhMnUUhIY/voB3c 4nvAKOM/O0oTJKcfmLeVy0+nR5ooHgf+TIgyfTmM3pqDImancQ2bRlIeSra7rYPBBQhI rcaryG2s5xOUimmP6qditFQJuHeVKCVoZ4fznugepG1/95sy1PRh9Biw21x+L9xqlyi8 HKTw== X-Gm-Message-State: AOAM532Y8On7KSsAtwLrlduCI1VgoafWsNzaRMaRaF3w6CwndUKQwSTO a7PBEI9+MU1R1/ijnSWramMz0lxcmFSnoNoA2nywbA== X-Google-Smtp-Source: ABdhPJxKT8AjTlortJSpv1MwycxURB5wVgMFtwFPFUW2XppCLIraO4Bs/8ibaYUjNpKiTvsmpR6qSMA5TwM2NTNsvFQ= X-Received: by 2002:a17:907:20af:: with SMTP id pw15mr66148379ejb.204.1594428447936; Fri, 10 Jul 2020 17:47:27 -0700 (PDT) MIME-Version: 1.0 References: <158500767138.2088294.17131646259803932461.stgit@dwillia2-desk3.amr.corp.intel.com> <158500773552.2088294.8756587190550753100.stgit@dwillia2-desk3.amr.corp.intel.com> <23742bb8-831f-29ff-1463-75427eec57c7@oracle.com> In-Reply-To: From: Dan Williams Date: Fri, 10 Jul 2020 17:47:17 -0700 Message-ID: Subject: Re: [PATCH 11/12] device-dax: Add dis-contiguous resource support To: Joao Martins Cc: Linux MM , Dave Hansen , Christoph Hellwig , linux-nvdimm , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: BA5F018140B69 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam04 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Apr 6, 2020 at 1:22 PM Dan Williams wrote: > > On Mon, Apr 6, 2020 at 3:46 AM 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); > > > - 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); > > > > You might be missing: > > > > first = region_res->child; > > > > (...) right after returning from __alloc_dev_dax_range(). Alternatively, perhaps > > even moving the 'retry' label to right before the @first initialization. > > > > In the case that you pick space from the beginning, the child resource of the > > dax region will point to first occupied region, and that changes after you pick > > this space. So, IIUC, you want to adjust where you start searching free space > > otherwise you end up wrongly picking that same space twice. > > > > If it helps, the bug can be reproduced in this unit test below, see > > daxctl_test3() test: > > It definitely will, thanks. I'll be circling back to this now that > I've settled my tree for the v5.7 window. s/v5.7/v5.9/ whats a couple of kernel release cycles between friends? I went ahead and moved the retry loop above the assignment of first as you suggested.