Re: [PATCH] dax: Arrange for dax_supported check to span multiple devices

From: Jan Kara
Date: Wed May 15 2019 - 03:32:22 EST

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Next in thread: Pankaj Gupta: "Re: [PATCH] dax: Arrange for dax_supported check to span multiple devices"
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On Tue 14-05-19 20:48:49, Dan Williams wrote:
> Pankaj reports that starting with commit ad428cdb525a "dax: Check the
> end of the block-device capacity with dax_direct_access()" device-mapper
> no longer allows dax operation. This results from the stricter checks in
> __bdev_dax_supported() that validate that the start and end of a
> block-device map to the same 'pagemap' instance.
>
> Teach the dax-core and device-mapper to validate the 'pagemap' on a
> per-target basis. This is accomplished by refactoring the
> bdev_dax_supported() internals into generic_fsdax_supported() which
> takes a sector range to validate. Consequently generic_fsdax_supported()
> is suitable to be used in a device-mapper ->iterate_devices() callback.
> A new ->dax_supported() operation is added to allow composite devices to
> split and route upper-level bdev_dax_supported() requests.
>
> Fixes: ad428cdb525a ("dax: Check the end of the block-device...")
> Cc: <stable@xxxxxxxxxxxxxxx>
> Cc: Jan Kara <jack@xxxxxxx>
> Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
> Cc: Dave Jiang <dave.jiang@xxxxxxxxx>
> Cc: Mike Snitzer <snitzer@xxxxxxxxxx>
> Cc: Keith Busch <keith.busch@xxxxxxxxx>
> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
> Cc: Vishal Verma <vishal.l.verma@xxxxxxxxx>
> Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
> Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
> Reported-by: Pankaj Gupta <pagupta@xxxxxxxxxx>
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>

Thanks for the fix. The patch looks good to me so feel free to add:

Reviewed-by: Jan Kara <jack@xxxxxxx>

Honza

> ---
> Hi Mike,
>
> Another day another new dax operation to allow device-mapper to better
> scope dax operations.
>
> Let me know if the device-mapper changes look sane. This passes a new
> unit test that indeed fails on current mainline.
>
> https://github.com/pmem/ndctl/blob/device-mapper-pending/test/dm.sh
>
> drivers/dax/super.c | 88 +++++++++++++++++++++++++++---------------
> drivers/md/dm-table.c | 17 +++++---
> drivers/md/dm.c | 20 ++++++++++
> drivers/md/dm.h | 1
> drivers/nvdimm/pmem.c | 1
> drivers/s390/block/dcssblk.c | 1
> include/linux/dax.h | 19 +++++++++
> 7 files changed, 110 insertions(+), 37 deletions(-)
>
> diff --git a/drivers/dax/super.c b/drivers/dax/super.c
> index 0a339b85133e..ec2f2262e3a9 100644
> --- a/drivers/dax/super.c
> +++ b/drivers/dax/super.c
> @@ -73,22 +73,12 @@ struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev)
> EXPORT_SYMBOL_GPL(fs_dax_get_by_bdev);
> #endif
>
> -/**
> - * __bdev_dax_supported() - Check if the device supports dax for filesystem
> - * @bdev: block device to check
> - * @blocksize: The block size of the device
> - *
> - * This is a library function for filesystems to check if the block device
> - * can be mounted with dax option.
> - *
> - * Return: true if supported, false if unsupported
> - */
> -bool __bdev_dax_supported(struct block_device *bdev, int blocksize)
> +bool generic_fsdax_supported(struct dax_device *dax_dev,
> + struct block_device *bdev, int blocksize, sector_t start,
> + sector_t sectors)
> {
> - struct dax_device *dax_dev;
> bool dax_enabled = false;
> pgoff_t pgoff, pgoff_end;
> - struct request_queue *q;
> char buf[BDEVNAME_SIZE];
> void *kaddr, *end_kaddr;
> pfn_t pfn, end_pfn;
> @@ -102,21 +92,14 @@ bool __bdev_dax_supported(struct block_device *bdev, int blocksize)
> return false;
> }
>
> - q = bdev_get_queue(bdev);
> - if (!q || !blk_queue_dax(q)) {
> - pr_debug("%s: error: request queue doesn't support dax\n",
> - bdevname(bdev, buf));
> - return false;
> - }
> -
> - err = bdev_dax_pgoff(bdev, 0, PAGE_SIZE, &pgoff);
> + err = bdev_dax_pgoff(bdev, start, PAGE_SIZE, &pgoff);
> if (err) {
> pr_debug("%s: error: unaligned partition for dax\n",
> bdevname(bdev, buf));
> return false;
> }
>
> - last_page = PFN_DOWN(i_size_read(bdev->bd_inode) - 1) * 8;
> + last_page = PFN_DOWN((start + sectors - 1) * 512) * PAGE_SIZE / 512;
> err = bdev_dax_pgoff(bdev, last_page, PAGE_SIZE, &pgoff_end);
> if (err) {
> pr_debug("%s: error: unaligned partition for dax\n",
> @@ -124,20 +107,11 @@ bool __bdev_dax_supported(struct block_device *bdev, int blocksize)
> return false;
> }
>
> - dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
> - if (!dax_dev) {
> - pr_debug("%s: error: device does not support dax\n",
> - bdevname(bdev, buf));
> - return false;
> - }
> -
> id = dax_read_lock();
> len = dax_direct_access(dax_dev, pgoff, 1, &kaddr, &pfn);
> len2 = dax_direct_access(dax_dev, pgoff_end, 1, &end_kaddr, &end_pfn);
> dax_read_unlock(id);
>
> - put_dax(dax_dev);
> -
> if (len < 1 || len2 < 1) {
> pr_debug("%s: error: dax access failed (%ld)\n",
> bdevname(bdev, buf), len < 1 ? len : len2);
> @@ -178,6 +152,49 @@ bool __bdev_dax_supported(struct block_device *bdev, int blocksize)
> }
> return true;
> }
> +EXPORT_SYMBOL_GPL(generic_fsdax_supported);
> +
> +/**
> + * __bdev_dax_supported() - Check if the device supports dax for filesystem
> + * @bdev: block device to check
> + * @blocksize: The block size of the device
> + *
> + * This is a library function for filesystems to check if the block device
> + * can be mounted with dax option.
> + *
> + * Return: true if supported, false if unsupported
> + */
> +bool __bdev_dax_supported(struct block_device *bdev, int blocksize)
> +{
> + struct dax_device *dax_dev;
> + struct request_queue *q;
> + char buf[BDEVNAME_SIZE];
> + bool ret;
> + int id;
> +
> + q = bdev_get_queue(bdev);
> + if (!q || !blk_queue_dax(q)) {
> + pr_debug("%s: error: request queue doesn't support dax\n",
> + bdevname(bdev, buf));
> + return false;
> + }
> +
> + dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
> + if (!dax_dev) {
> + pr_debug("%s: error: device does not support dax\n",
> + bdevname(bdev, buf));
> + return false;
> + }
> +
> + id = dax_read_lock();
> + ret = dax_supported(dax_dev, bdev, blocksize, 0,
> + i_size_read(bdev->bd_inode) / 512);
> + dax_read_unlock(id);
> +
> + put_dax(dax_dev);
> +
> + return ret;
> +}
> EXPORT_SYMBOL_GPL(__bdev_dax_supported);
> #endif
>
> @@ -303,6 +320,15 @@ long dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff, long nr_pages,
> }
> EXPORT_SYMBOL_GPL(dax_direct_access);
>
> +bool dax_supported(struct dax_device *dax_dev, struct block_device *bdev,
> + int blocksize, sector_t start, sector_t len)
> +{
> + if (!dax_alive(dax_dev))
> + return false;
> +
> + return dax_dev->ops->dax_supported(dax_dev, bdev, blocksize, start, len);
> +}
> +
> size_t dax_copy_from_iter(struct dax_device *dax_dev, pgoff_t pgoff, void *addr,
> size_t bytes, struct iov_iter *i)
> {
> diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
> index cde3b49b2a91..350cf0451456 100644
> --- a/drivers/md/dm-table.c
> +++ b/drivers/md/dm-table.c
> @@ -880,13 +880,17 @@ void dm_table_set_type(struct dm_table *t, enum dm_queue_mode type)
> }
> EXPORT_SYMBOL_GPL(dm_table_set_type);
>
> +/* validate the dax capability of the target device span */
> static int device_supports_dax(struct dm_target *ti, struct dm_dev *dev,
> - sector_t start, sector_t len, void *data)
> + sector_t start, sector_t len, void *data)
> {
> - return bdev_dax_supported(dev->bdev, PAGE_SIZE);
> + int blocksize = *(int *) data;
> +
> + return generic_fsdax_supported(dev->dax_dev, dev->bdev, blocksize,
> + start, len);
> }
>
> -static bool dm_table_supports_dax(struct dm_table *t)
> +bool dm_table_supports_dax(struct dm_table *t, int blocksize)
> {
> struct dm_target *ti;
> unsigned i;
> @@ -899,7 +903,8 @@ static bool dm_table_supports_dax(struct dm_table *t)
> return false;
>
> if (!ti->type->iterate_devices ||
> - !ti->type->iterate_devices(ti, device_supports_dax, NULL))
> + !ti->type->iterate_devices(ti, device_supports_dax,
> + &blocksize))
> return false;
> }
>
> @@ -979,7 +984,7 @@ static int dm_table_determine_type(struct dm_table *t)
> verify_bio_based:
> /* We must use this table as bio-based */
> t->type = DM_TYPE_BIO_BASED;
> - if (dm_table_supports_dax(t) ||
> + if (dm_table_supports_dax(t, PAGE_SIZE) ||
> (list_empty(devices) && live_md_type == DM_TYPE_DAX_BIO_BASED)) {
> t->type = DM_TYPE_DAX_BIO_BASED;
> } else {
> @@ -1905,7 +1910,7 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
> }
> blk_queue_write_cache(q, wc, fua);
>
> - if (dm_table_supports_dax(t))
> + if (dm_table_supports_dax(t, PAGE_SIZE))
> blk_queue_flag_set(QUEUE_FLAG_DAX, q);
> else
> blk_queue_flag_clear(QUEUE_FLAG_DAX, q);
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index 043f0761e4a0..c28787f5357b 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -1105,6 +1105,25 @@ static long dm_dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff,
> return ret;
> }
>
> +static bool dm_dax_supported(struct dax_device *dax_dev, struct block_device *bdev,
> + int blocksize, sector_t start, sector_t len)
> +{
> + struct mapped_device *md = dax_get_private(dax_dev);
> + struct dm_table *map;
> + int srcu_idx;
> + bool ret;
> +
> + map = dm_get_live_table(md, &srcu_idx);
> + if (!map)
> + return false;
> +
> + ret = dm_table_supports_dax(map, blocksize);
> +
> + dm_put_live_table(md, srcu_idx);
> +
> + return ret;
> +}
> +
> static size_t dm_dax_copy_from_iter(struct dax_device *dax_dev, pgoff_t pgoff,
> void *addr, size_t bytes, struct iov_iter *i)
> {
> @@ -3192,6 +3211,7 @@ static const struct block_device_operations dm_blk_dops = {
>
> static const struct dax_operations dm_dax_ops = {
> .direct_access = dm_dax_direct_access,
> + .dax_supported = dm_dax_supported,
> .copy_from_iter = dm_dax_copy_from_iter,
> .copy_to_iter = dm_dax_copy_to_iter,
> };
> diff --git a/drivers/md/dm.h b/drivers/md/dm.h
> index 2d539b82ec08..e5e240bfa2d0 100644
> --- a/drivers/md/dm.h
> +++ b/drivers/md/dm.h
> @@ -78,6 +78,7 @@ void dm_unlock_md_type(struct mapped_device *md);
> void dm_set_md_type(struct mapped_device *md, enum dm_queue_mode type);
> enum dm_queue_mode dm_get_md_type(struct mapped_device *md);
> struct target_type *dm_get_immutable_target_type(struct mapped_device *md);
> +bool dm_table_supports_dax(struct dm_table *t, int blocksize);
>
> int dm_setup_md_queue(struct mapped_device *md, struct dm_table *t);
>
> diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
> index 0279eb1da3ef..845c5b430cdd 100644
> --- a/drivers/nvdimm/pmem.c
> +++ b/drivers/nvdimm/pmem.c
> @@ -295,6 +295,7 @@ static size_t pmem_copy_to_iter(struct dax_device *dax_dev, pgoff_t pgoff,
>
> static const struct dax_operations pmem_dax_ops = {
> .direct_access = pmem_dax_direct_access,
> + .dax_supported = generic_fsdax_supported,
> .copy_from_iter = pmem_copy_from_iter,
> .copy_to_iter = pmem_copy_to_iter,
> };
> diff --git a/drivers/s390/block/dcssblk.c b/drivers/s390/block/dcssblk.c
> index 4e8aedd50cb0..d04d4378ca50 100644
> --- a/drivers/s390/block/dcssblk.c
> +++ b/drivers/s390/block/dcssblk.c
> @@ -59,6 +59,7 @@ static size_t dcssblk_dax_copy_to_iter(struct dax_device *dax_dev,
>
> static const struct dax_operations dcssblk_dax_ops = {
> .direct_access = dcssblk_dax_direct_access,
> + .dax_supported = generic_fsdax_supported,
> .copy_from_iter = dcssblk_dax_copy_from_iter,
> .copy_to_iter = dcssblk_dax_copy_to_iter,
> };
> diff --git a/include/linux/dax.h b/include/linux/dax.h
> index 0dd316a74a29..f5544fc62319 100644
> --- a/include/linux/dax.h
> +++ b/include/linux/dax.h
> @@ -19,6 +19,12 @@ struct dax_operations {
> */
> long (*direct_access)(struct dax_device *, pgoff_t, long,
> void **, pfn_t *);
> + /*
> + * Validate whether this device is usable as an fsdax backing
> + * device.
> + */
> + bool (*dax_supported)(struct dax_device *, struct block_device *, int,
> + sector_t, sector_t);
> /* copy_from_iter: required operation for fs-dax direct-i/o */
> size_t (*copy_from_iter)(struct dax_device *, pgoff_t, void *, size_t,
> struct iov_iter *);
> @@ -75,6 +81,10 @@ static inline bool bdev_dax_supported(struct block_device *bdev, int blocksize)
> return __bdev_dax_supported(bdev, blocksize);
> }
>
> +bool generic_fsdax_supported(struct dax_device *dax_dev,
> + struct block_device *bdev, int blocksize, sector_t start,
> + sector_t sectors);
> +
> static inline struct dax_device *fs_dax_get_by_host(const char *host)
> {
> return dax_get_by_host(host);
> @@ -99,6 +109,13 @@ static inline bool bdev_dax_supported(struct block_device *bdev,
> return false;
> }
>
> +static inline bool generic_fsdax_supported(struct dax_device *dax_dev,
> + struct block_device *bdev, int blocksize, sector_t start,
> + sector_t sectors)
> +{
> + return false;
> +}
> +
> static inline struct dax_device *fs_dax_get_by_host(const char *host)
> {
> return NULL;
> @@ -142,6 +159,8 @@ bool dax_alive(struct dax_device *dax_dev);
> void *dax_get_private(struct dax_device *dax_dev);
> long dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff, long nr_pages,
> void **kaddr, pfn_t *pfn);
> +bool dax_supported(struct dax_device *dax_dev, struct block_device *bdev,
> + int blocksize, sector_t start, sector_t len);
> size_t dax_copy_from_iter(struct dax_device *dax_dev, pgoff_t pgoff, void *addr,
> size_t bytes, struct iov_iter *i);
> size_t dax_copy_to_iter(struct dax_device *dax_dev, pgoff_t pgoff, void *addr,
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR

Next message: Geert Uytterhoeven: "Re: [PATCH] clk: Remove io.h from clk-provider.h"
Previous message: Justin Piszcz: "RE: 5.1 kernel: khugepaged stuck at 100%"
In reply to: Dan Williams: "[PATCH] dax: Arrange for dax_supported check to span multiple devices"
Next in thread: Pankaj Gupta: "Re: [PATCH] dax: Arrange for dax_supported check to span multiple devices"
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