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From: Jan Kara <jack@suse.cz>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	virtio-fs@redhat.com, miklos@szeredi.hu, stefanha@redhat.com,
	dgilbert@redhat.com, Christoph Hellwig <hch@infradead.org>,
	Dan Williams <dan.j.williams@intel.com>,
	linux-nvdimm@lists.01.org
Subject: Re: [PATCH v2 01/20] dax: Modify bdev_dax_pgoff() to handle NULL bdev
Date: Mon, 17 Aug 2020 18:57:31 +0200	[thread overview]
Message-ID: <20200817165731.GB22500@quack2.suse.cz> (raw)
In-Reply-To: <20200807195526.426056-2-vgoyal@redhat.com>

On Fri 07-08-20 15:55:07, Vivek Goyal wrote:
> virtiofs does not have a block device but it has dax device.
> Modify bdev_dax_pgoff() to be able to handle that.
> 
> If there is no bdev, that means dax offset is 0. (It can't be a partition
> block device starting at an offset in dax device).
> 
> This is little hackish. There have been discussions about getting rid
> of dax not supporting partitions.
> 
> https://lore.kernel.org/linux-fsdevel/20200107125159.GA15745@infradead.org/
> 
> IMHO, this path can easily break exisitng users. For example
> ioctl(BLKPG_ADD_PARTITION) will start breaking on block devices
> supporting DAX. Also, I personally find it very useful to be able to
> partition dax devices and still be able to use DAX.
> 
> Alternatively, I tried to store offset into dax device information in iomap
> interface, but that got NACKed.
> 
> https://lore.kernel.org/linux-fsdevel/20200217133117.GB20444@infradead.org/
> 
> I can't think of a good path to solve this issue properly. So to make
> progress, it seems this patch is least bad option for now and I hope
> we can take it.
> 
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
> Cc: Christoph Hellwig <hch@infradead.org>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: linux-nvdimm@lists.01.org

This patch looks OK to me. You can add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  drivers/dax/super.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/dax/super.c b/drivers/dax/super.c
> index 8e32345be0f7..c4bec437e88b 100644
> --- a/drivers/dax/super.c
> +++ b/drivers/dax/super.c
> @@ -46,7 +46,8 @@ EXPORT_SYMBOL_GPL(dax_read_unlock);
>  int bdev_dax_pgoff(struct block_device *bdev, sector_t sector, size_t size,
>  		pgoff_t *pgoff)
>  {
> -	phys_addr_t phys_off = (get_start_sect(bdev) + sector) * 512;
> +	sector_t start_sect = bdev ? get_start_sect(bdev) : 0;
> +	phys_addr_t phys_off = (start_sect + sector) * 512;
>  
>  	if (pgoff)
>  		*pgoff = PHYS_PFN(phys_off);
> -- 
> 2.25.4
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

  reply	other threads:[~2020-08-17 17:32 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-07 19:55 [PATCH v2 00/20] virtiofs: Add DAX support Vivek Goyal
2020-08-07 19:55 ` [PATCH v2 01/20] dax: Modify bdev_dax_pgoff() to handle NULL bdev Vivek Goyal
2020-08-17 16:57   ` Jan Kara [this message]
2020-08-07 19:55 ` [PATCH v2 02/20] dax: Create a range version of dax_layout_busy_page() Vivek Goyal
2020-08-17 16:53   ` Jan Kara
2020-08-17 17:22     ` Vivek Goyal
2020-08-07 19:55 ` [PATCH v2 03/20] virtio: Add get_shm_region method Vivek Goyal
2020-08-10 13:47   ` Michael S. Tsirkin
2020-08-10 13:54     ` Vivek Goyal
2020-08-10 14:02   ` Michael S. Tsirkin
2020-08-10 14:06   ` Michael S. Tsirkin
2020-08-07 19:55 ` [PATCH v2 04/20] virtio: Implement get_shm_region for PCI transport Vivek Goyal
2020-08-10 14:05   ` Michael S. Tsirkin
2020-08-10 14:50     ` Vivek Goyal
     [not found]       ` <CAAfnVBk+Hmcm2ftd3wOK-P2NyYQ7z4Wrf1JKhLJaNkCZBLoo6g@mail.gmail.com>
2020-08-17 20:29         ` Vivek Goyal
2020-08-07 19:55 ` [PATCH v2 05/20] virtio: Implement get_shm_region for MMIO transport Vivek Goyal
2020-08-10 14:03   ` Michael S. Tsirkin
2020-08-07 19:55 ` [PATCH v2 06/20] virtiofs: Provide a helper function for virtqueue initialization Vivek Goyal
2020-08-07 19:55 ` [PATCH v2 07/20] fuse: Get rid of no_mount_options Vivek Goyal
2020-08-07 19:55 ` [PATCH v2 08/20] fuse,virtiofs: Add a mount option to enable dax Vivek Goyal
2020-08-07 19:55 ` [PATCH v2 09/20] virtio_fs, dax: Set up virtio_fs dax_device Vivek Goyal
2020-08-07 19:55 ` [PATCH v2 10/20] fuse,virtiofs: Keep a list of free dax memory ranges Vivek Goyal
2020-08-07 19:55 ` [PATCH v2 11/20] fuse: implement FUSE_INIT map_alignment field Vivek Goyal
2020-08-07 19:55 ` [PATCH v2 12/20] fuse: Introduce setupmapping/removemapping commands Vivek Goyal
2020-08-07 19:55 ` [PATCH v2 13/20] fuse, dax: Implement dax read/write operations Vivek Goyal
2020-08-10 22:06   ` Dave Chinner
2020-08-11 17:44     ` Vivek Goyal
2020-08-07 19:55 ` [PATCH v2 14/20] fuse,dax: add DAX mmap support Vivek Goyal
2020-08-07 19:55 ` [PATCH v2 15/20] fuse, dax: Take ->i_mmap_sem lock during dax page fault Vivek Goyal
2020-08-10 22:22   ` Dave Chinner
2020-08-11 17:55     ` Vivek Goyal
2020-08-12  1:23       ` Dave Chinner
2020-08-12 21:10         ` Vivek Goyal
2020-08-13  5:12           ` Dave Chinner
2020-08-07 19:55 ` [PATCH v2 16/20] fuse,virtiofs: Define dax address space operations Vivek Goyal
2020-08-07 19:55 ` [PATCH v2 17/20] fuse,virtiofs: Maintain a list of busy elements Vivek Goyal
2020-08-07 19:55 ` [PATCH v2 18/20] fuse: Release file in process context Vivek Goyal
2020-08-10  8:29   ` Miklos Szeredi
2020-08-10 15:48     ` Vivek Goyal
2020-08-10 19:37     ` Vivek Goyal
2020-08-10 19:39       ` Miklos Szeredi
2020-08-07 19:55 ` [PATCH v2 19/20] fuse: Take inode lock for dax inode truncation Vivek Goyal
2020-08-07 19:55 ` [PATCH v2 20/20] fuse,virtiofs: Add logic to free up a memory range Vivek Goyal
2020-08-10  7:29 ` [PATCH v2 00/20] virtiofs: Add DAX support Miklos Szeredi
2020-08-10 13:08   ` Vivek Goyal

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