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Fri, 2 Feb 2024 11:31:58 -0500 (EST) Message-ID: Date: Fri, 2 Feb 2024 11:32:00 -0500 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v3 2/4] dax: Check for data cache aliasing at runtime Content-Language: en-US From: Mathieu Desnoyers To: Dan Williams , Arnd Bergmann , Dave Chinner Cc: linux-kernel@vger.kernel.org, Andrew Morton , Linus Torvalds , linux-mm@kvack.org, linux-arch@vger.kernel.org, Vishal Verma , Dave Jiang , Matthew Wilcox , Russell King , nvdimm@lists.linux.dev, linux-cxl@vger.kernel.org, linux-fsdevel@vger.kernel.org, dm-devel@lists.linux.dev References: <20240131162533.247710-1-mathieu.desnoyers@efficios.com> <20240131162533.247710-3-mathieu.desnoyers@efficios.com> <65bab567665f3_37ad2943c@dwillia2-xfh.jf.intel.com.notmuch> <0a38176b-c453-4be0-be83-f3e1bb897973@efficios.com> <65bac71a9659b_37ad29428@dwillia2-xfh.jf.intel.com.notmuch> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 3DEB2180005 X-Rspam-User: X-Stat-Signature: 44ix3ozqfbsdpzyziz4ioffkhwcycmy7 X-Rspamd-Server: rspam03 X-HE-Tag: 1706891520-17406 X-HE-Meta: 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 hXnaAERK 3XaeYo/Gs27nJYqPw9nuXVoZR1zkL5RTps4lHJf6G2oTumeMBBAfXbjZwh/w40e4Fd2kU5ywyrP2dFGsFgrXNGw+LUgmXrsIwrenebb4yR3TOT+/Bg/ToPPp+7YwWBYF1bp9jcVzGxR51YGIu4fdBe1aq9B7UnVwWBUk4c8cfqDw5v8LMnH4P+dJh70bC5m3fhtmV87Zjt4sJz2Nqf37o/EE2BSnI0O0QSaXEJJQ67MXZSp6i7AMNsshQWIy9dOvx3mHQk7D8TILlstEbLnngVvDVtlvlHa9Ewk6LU5RJLzs1deX9/q4Xpjjq+Uo6qjzrJIk4t4fbWfiU6rWhNHZ6Vwjb1Oit7NC5pgLvMoOQku8f7xs= 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: List-Subscribe: List-Unsubscribe: On 2024-02-01 10:44, Mathieu Desnoyers wrote: > On 2024-01-31 17:18, Dan Williams wrote: [...] >> diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c >> index 5f1be1da92ce..11053a70f5ab 100644 >> --- a/fs/fuse/virtio_fs.c >> +++ b/fs/fuse/virtio_fs.c >> @@ -16,6 +16,7 @@ >>   #include >>   #include >>   #include >> +#include >>   #include >>   #include "fuse_i.h" >> @@ -795,8 +796,11 @@ static void virtio_fs_cleanup_dax(void *data) >>       put_dax(dax_dev); >>   } >> +DEFINE_FREE(cleanup_dax, struct dax_dev *, if (!IS_ERR_OR_NULL(_T)) >> virtio_fs_cleanup_dax(_T)) >> + >>   static int virtio_fs_setup_dax(struct virtio_device *vdev, struct >> virtio_fs *fs) > > So either I'm completely missing how ownership works in this function, or > we should be really concerned about the fact that it does no actual > cleanup of anything on any error. [...] > > Here what I'm seeing so far: > > - devm_release_mem_region() is never called after > devm_request_mem_region(). Not >   on error, neither on teardown, > - pgmap is never freed on error after devm_kzalloc. I was indeed missing something: the devm_ family of functions keeps ownership at the device level, so we would not need explicit teardown. > >>   { >> +    struct dax_device *dax_dev __free(cleanup_dax) = NULL; >>       struct virtio_shm_region cache_reg; >>       struct dev_pagemap *pgmap; >>       bool have_cache; >> @@ -804,6 +808,15 @@ static int virtio_fs_setup_dax(struct >> virtio_device *vdev, struct virtio_fs *fs) >>       if (!IS_ENABLED(CONFIG_FUSE_DAX)) >>           return 0; >> +    dax_dev = alloc_dax(fs, &virtio_fs_dax_ops); >> +    if (IS_ERR(dax_dev)) { >> +        int rc = PTR_ERR(dax_dev); >> + >> +        if (rc == -EOPNOTSUPP) >> +            return 0; >> +        return rc; >> +    } > > What is gained by moving this allocation here ? I'm still concerned about moving the call to alloc_dax() before the setup of the memory region it will use. Are those completely independent ? > >> + >>       /* Get cache region */ >>       have_cache = virtio_get_shm_region(vdev, &cache_reg, >>                          (u8)VIRTIO_FS_SHMCAP_ID_CACHE); >> @@ -849,10 +862,7 @@ static int virtio_fs_setup_dax(struct >> virtio_device *vdev, struct virtio_fs *fs) >>       dev_dbg(&vdev->dev, "%s: window kaddr 0x%px phys_addr 0x%llx len >> 0x%llx\n", >>           __func__, fs->window_kaddr, cache_reg.addr, cache_reg.len); >> -    fs->dax_dev = alloc_dax(fs, &virtio_fs_dax_ops); >> -    if (IS_ERR(fs->dax_dev)) >> -        return PTR_ERR(fs->dax_dev); >> - >> +    fs->dax_dev = no_free_ptr(dax_dev); >>       return devm_add_action_or_reset(&vdev->dev, virtio_fs_cleanup_dax, >>                       fs->dax_dev); >>   } > [...] Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com