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Message-Id: <20170419173138.06621e66@thinkpad>
Date: Wed, 19 Apr 2017 17:31:38 +0200
From: Gerald Schaefer <gerald.schaefer@...ibm.com>
To: Dan Williams <dan.j.williams@...el.com>
Cc: linux-nvdimm@...ts.01.org, linux-kernel@...r.kernel.org,
linux-block@...r.kernel.org, dm-devel@...hat.com,
linux-fsdevel@...r.kernel.org, hch@....de
Subject: Re: [resend PATCH v2 08/33] dcssblk: add dax_operations support
On Mon, 17 Apr 2017 12:09:32 -0700
Dan Williams <dan.j.williams@...el.com> wrote:
> Setup a dax_dev to have the same lifetime as the dcssblk block device
> and add a ->direct_access() method that is equivalent to
> dcssblk_direct_access(). Once fs/dax.c has been converted to use
> dax_operations the old dcssblk_direct_access() will be removed.
>
> Cc: Gerald Schaefer <gerald.schaefer@...ibm.com>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> ---
> drivers/s390/block/Kconfig | 1 +
> drivers/s390/block/dcssblk.c | 54 +++++++++++++++++++++++++++++++++++-------
> 2 files changed, 46 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/s390/block/Kconfig b/drivers/s390/block/Kconfig
> index 4a3b62326183..0acb8c2f9475 100644
> --- a/drivers/s390/block/Kconfig
> +++ b/drivers/s390/block/Kconfig
> @@ -14,6 +14,7 @@ config BLK_DEV_XPRAM
>
> config DCSSBLK
> def_tristate m
> + select DAX
> prompt "DCSSBLK support"
> depends on S390 && BLOCK
> help
> diff --git a/drivers/s390/block/dcssblk.c b/drivers/s390/block/dcssblk.c
> index 415d10a67b7a..682a9eb4934d 100644
> --- a/drivers/s390/block/dcssblk.c
> +++ b/drivers/s390/block/dcssblk.c
> @@ -18,6 +18,7 @@
> #include <linux/interrupt.h>
> #include <linux/platform_device.h>
> #include <linux/pfn_t.h>
> +#include <linux/dax.h>
> #include <asm/extmem.h>
> #include <asm/io.h>
>
> @@ -30,8 +31,10 @@ static int dcssblk_open(struct block_device *bdev, fmode_t mode);
> static void dcssblk_release(struct gendisk *disk, fmode_t mode);
> static blk_qc_t dcssblk_make_request(struct request_queue *q,
> struct bio *bio);
> -static long dcssblk_direct_access(struct block_device *bdev, sector_t secnum,
> +static long dcssblk_blk_direct_access(struct block_device *bdev, sector_t secnum,
> void **kaddr, pfn_t *pfn, long size);
> +static long dcssblk_dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff,
> + long nr_pages, void **kaddr, pfn_t *pfn);
>
> static char dcssblk_segments[DCSSBLK_PARM_LEN] = "\0";
>
> @@ -40,7 +43,11 @@ static const struct block_device_operations dcssblk_devops = {
> .owner = THIS_MODULE,
> .open = dcssblk_open,
> .release = dcssblk_release,
> - .direct_access = dcssblk_direct_access,
> + .direct_access = dcssblk_blk_direct_access,
> +};
> +
> +static const struct dax_operations dcssblk_dax_ops = {
> + .direct_access = dcssblk_dax_direct_access,
> };
>
> struct dcssblk_dev_info {
> @@ -57,6 +64,7 @@ struct dcssblk_dev_info {
> struct request_queue *dcssblk_queue;
> int num_of_segments;
> struct list_head seg_list;
> + struct dax_device *dax_dev;
> };
>
> struct segment_info {
> @@ -389,6 +397,8 @@ dcssblk_shared_store(struct device *dev, struct device_attribute *attr, const ch
> }
> list_del(&dev_info->lh);
>
> + kill_dax(dev_info->dax_dev);
> + put_dax(dev_info->dax_dev);
> del_gendisk(dev_info->gd);
> blk_cleanup_queue(dev_info->dcssblk_queue);
> dev_info->gd->queue = NULL;
> @@ -525,6 +535,7 @@ dcssblk_add_store(struct device *dev, struct device_attribute *attr, const char
> int rc, i, j, num_of_segments;
> struct dcssblk_dev_info *dev_info;
> struct segment_info *seg_info, *temp;
> + struct dax_device *dax_dev;
> char *local_buf;
> unsigned long seg_byte_size;
>
> @@ -654,6 +665,11 @@ dcssblk_add_store(struct device *dev, struct device_attribute *attr, const char
> if (rc)
> goto put_dev;
>
> + dax_dev = alloc_dax(dev_info, dev_info->gd->disk_name,
> + &dcssblk_dax_ops);
> + if (!dax_dev)
> + goto put_dev;
> +
The returned dax_dev should be stored into dev_info->dax_dev, for later use
by kill/put_dax(). This can also be done directly, so that we don't need the
local dax_dev variable here.
Also, in the error case, a proper rc should be set before going to put_dev,
probably -ENOMEM.
I took a quick look at the patches for the other affected drivers, and it
looks like axonram also has the "missing rc" issue, and brd the "missing
brd->dax_dev init" issue, pmem seems to be fine.
> get_device(&dev_info->dev);
> device_add_disk(&dev_info->dev, dev_info->gd);
>
> @@ -752,6 +768,8 @@ dcssblk_remove_store(struct device *dev, struct device_attribute *attr, const ch
> }
>
> list_del(&dev_info->lh);
> + kill_dax(dev_info->dax_dev);
> + put_dax(dev_info->dax_dev);
> del_gendisk(dev_info->gd);
> blk_cleanup_queue(dev_info->dcssblk_queue);
> dev_info->gd->queue = NULL;
> @@ -883,21 +901,39 @@ dcssblk_make_request(struct request_queue *q, struct bio *bio)
> }
>
> static long
> -dcssblk_direct_access (struct block_device *bdev, sector_t secnum,
> +__dcssblk_direct_access(struct dcssblk_dev_info *dev_info, pgoff_t pgoff,
> + long nr_pages, void **kaddr, pfn_t *pfn)
> +{
> + resource_size_t offset = pgoff * PAGE_SIZE;
> + unsigned long dev_sz;
> +
> + dev_sz = dev_info->end - dev_info->start + 1;
> + *kaddr = (void *) dev_info->start + offset;
> + *pfn = __pfn_to_pfn_t(PFN_DOWN(dev_info->start + offset), PFN_DEV);
> +
> + return (dev_sz - offset) / PAGE_SIZE;
> +}
> +
> +static long
> +dcssblk_blk_direct_access(struct block_device *bdev, sector_t secnum,
> void **kaddr, pfn_t *pfn, long size)
> {
> struct dcssblk_dev_info *dev_info;
> - unsigned long offset, dev_sz;
>
> dev_info = bdev->bd_disk->private_data;
> if (!dev_info)
> return -ENODEV;
> - dev_sz = dev_info->end - dev_info->start + 1;
> - offset = secnum * 512;
> - *kaddr = (void *) dev_info->start + offset;
> - *pfn = __pfn_to_pfn_t(PFN_DOWN(dev_info->start + offset), PFN_DEV);
> + return __dcssblk_direct_access(dev_info, PHYS_PFN(secnum * 512),
> + PHYS_PFN(size), kaddr, pfn) * PAGE_SIZE;
> +}
> +
> +static long
> +dcssblk_dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff,
> + long nr_pages, void **kaddr, pfn_t *pfn)
> +{
> + struct dcssblk_dev_info *dev_info = dax_get_private(dax_dev);
>
> - return dev_sz - offset;
> + return __dcssblk_direct_access(dev_info, pgoff, nr_pages, kaddr, pfn);
> }
>
> static void
>
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