dm: teach dm-targets to use a dax_device + dax_operations

Arrange for dm to lookup the dax services available from member devices.
Update the dax-capable targets, linear and stripe, to route dax
operations to the underlying device. Changes the target-internal
->direct_access() method to more closely align with the dax_operations
->direct_access() calling convention.

Cc: Toshi Kani <toshi.kani@hpe.com>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

6 files changed, 43 insertions, 48 deletions

diff --git a/drivers/md/dm-linear.c b/drivers/md/dm-linear.c
index 4788b0b989a9..c5a52f4dae81 100644
--- a/drivers/md/dm-linear.c
+++ b/drivers/md/dm-linear.c
@@ -9,6 +9,7 @@
 #include <linux/init.h>
 #include <linux/blkdev.h>
 #include <linux/bio.h>
+#include <linux/dax.h>
 #include <linux/slab.h>
 #include <linux/device-mapper.h>
 
@@ -141,22 +142,20 @@ static int linear_iterate_devices(struct dm_target *ti,
         return fn(ti, lc->dev, lc->start, ti->len, data);
 }
 
-static long linear_direct_access(struct dm_target *ti, sector_t sector,
-                                 void **kaddr, pfn_t *pfn, long size)
+static long linear_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
+                long nr_pages, void **kaddr, pfn_t *pfn)
 {
+        long ret;
         struct linear_c *lc = ti->private;
         struct block_device *bdev = lc->dev->bdev;
-        struct blk_dax_ctl dax = {
-                .sector = linear_map_sector(ti, sector),
-                .size = size,
-        };
-        long ret;
-
-        ret = bdev_direct_access(bdev, &dax);
-        *kaddr = dax.addr;
-        *pfn = dax.pfn;
-
-        return ret;
+        struct dax_device *dax_dev = lc->dev->dax_dev;
+        sector_t dev_sector, sector = pgoff * PAGE_SECTORS;
+
+        dev_sector = linear_map_sector(ti, sector);
+        ret = bdev_dax_pgoff(bdev, dev_sector, nr_pages * PAGE_SIZE, &pgoff);
+        if (ret)
+                return ret;
+        return dax_direct_access(dax_dev, pgoff, nr_pages, kaddr, pfn);
 }
 
 static struct target_type linear_target = {
@@ -169,7 +168,7 @@ static struct target_type linear_target = {
         .status = linear_status,
         .prepare_ioctl = linear_prepare_ioctl,
         .iterate_devices = linear_iterate_devices,
-        .direct_access = linear_direct_access,
+        .direct_access = linear_dax_direct_access,
 };
 
 int __init dm_linear_init(void)
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index c65feeada864..e152d9817c81 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -2302,8 +2302,8 @@ static int origin_map(struct dm_target *ti, struct bio *bio)
         return do_origin(o->dev, bio);
 }
 
-static long origin_direct_access(struct dm_target *ti, sector_t sector,
-                void **kaddr, pfn_t *pfn, long size)
+static long origin_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
+                long nr_pages, void **kaddr, pfn_t *pfn)
 {
         DMWARN("device does not support dax.");
         return -EIO;
@@ -2368,7 +2368,7 @@ static struct target_type origin_target = {
         .postsuspend = origin_postsuspend,
         .status  = origin_status,
         .iterate_devices = origin_iterate_devices,
-        .direct_access = origin_direct_access,
+        .direct_access = origin_dax_direct_access,
 };
 
 static struct target_type snapshot_target = {
diff --git a/drivers/md/dm-stripe.c b/drivers/md/dm-stripe.c
index 28193a57bf47..cb4b1e9e16ab 100644
--- a/drivers/md/dm-stripe.c
+++ b/drivers/md/dm-stripe.c
@@ -11,6 +11,7 @@
 #include <linux/init.h>
 #include <linux/blkdev.h>
 #include <linux/bio.h>
+#include <linux/dax.h>
 #include <linux/slab.h>
 #include <linux/log2.h>
 
@@ -308,27 +309,25 @@ static int stripe_map(struct dm_target *ti, struct bio *bio)
         return DM_MAPIO_REMAPPED;
 }
 
-static long stripe_direct_access(struct dm_target *ti, sector_t sector,
-                                 void **kaddr, pfn_t *pfn, long size)
+static long stripe_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
+                long nr_pages, void **kaddr, pfn_t *pfn)
 {
+        sector_t dev_sector, sector = pgoff * PAGE_SECTORS;
         struct stripe_c *sc = ti->private;
-        uint32_t stripe;
+        struct dax_device *dax_dev;
         struct block_device *bdev;
-        struct blk_dax_ctl dax = {
-                .size = size,
-        };
+        uint32_t stripe;
         long ret;
 
-        stripe_map_sector(sc, sector, &stripe, &dax.sector);
-
-        dax.sector += sc->stripe[stripe].physical_start;
+        stripe_map_sector(sc, sector, &stripe, &dev_sector);
+        dev_sector += sc->stripe[stripe].physical_start;
+        dax_dev = sc->stripe[stripe].dev->dax_dev;
         bdev = sc->stripe[stripe].dev->bdev;
 
-        ret = bdev_direct_access(bdev, &dax);
-        *kaddr = dax.addr;
-        *pfn = dax.pfn;
-
-        return ret;
+        ret = bdev_dax_pgoff(bdev, dev_sector, nr_pages * PAGE_SIZE, &pgoff);
+        if (ret)
+                return ret;
+        return dax_direct_access(dax_dev, pgoff, nr_pages, kaddr, pfn);
 }
 
 /*
@@ -448,7 +447,7 @@ static struct target_type stripe_target = {
         .status = stripe_status,
         .iterate_devices = stripe_iterate_devices,
         .io_hints = stripe_io_hints,
-        .direct_access = stripe_direct_access,
+        .direct_access = stripe_dax_direct_access,
 };
 
 int __init dm_stripe_init(void)
diff --git a/drivers/md/dm-target.c b/drivers/md/dm-target.c
index 43d3445b121d..6a7968f93f3c 100644
--- a/drivers/md/dm-target.c
+++ b/drivers/md/dm-target.c
@@ -142,8 +142,8 @@ static void io_err_release_clone_rq(struct request *clone)
 {
 }
 
-static long io_err_direct_access(struct dm_target *ti, sector_t sector,
-                                 void **kaddr, pfn_t *pfn, long size)
+static long io_err_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
+                long nr_pages, void **kaddr, pfn_t *pfn)
 {
         return -EIO;
 }
@@ -157,7 +157,7 @@ static struct target_type error_target = {
         .map  = io_err_map,
         .clone_and_map_rq = io_err_clone_and_map_rq,
         .release_clone_rq = io_err_release_clone_rq,
-        .direct_access = io_err_direct_access,
+        .direct_access = io_err_dax_direct_access,
 };
 
 int __init dm_target_init(void)
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index bd56dfe43a99..ef4c6f8cad47 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -630,6 +630,7 @@ static int open_table_device(struct table_device *td, dev_t dev,
         }
 
         td->dm_dev.bdev = bdev;
+        td->dm_dev.dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
         return 0;
 }
 
@@ -643,7 +644,9 @@ static void close_table_device(struct table_device *td, struct mapped_device *md
 
         bd_unlink_disk_holder(td->dm_dev.bdev, dm_disk(md));
         blkdev_put(td->dm_dev.bdev, td->dm_dev.mode | FMODE_EXCL);
+        put_dax(td->dm_dev.dax_dev);
         td->dm_dev.bdev = NULL;
+        td->dm_dev.dax_dev = NULL;
 }
 
 static struct table_device *find_table_device(struct list_head *l, dev_t dev,
@@ -945,16 +948,9 @@ static long dm_dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff,
         if (len < 1)
                 goto out;
         nr_pages = min(len, nr_pages);
-        if (ti->type->direct_access) {
-                ret = ti->type->direct_access(ti, sector, kaddr, pfn,
-                                nr_pages * PAGE_SIZE);
-                /*
-                 * FIXME: convert ti->type->direct_access to return
-                 * nr_pages directly.
-                 */
-                if (ret >= 0)
-                        ret /= PAGE_SIZE;
-        }
+        if (ti->type->direct_access)
+                ret = ti->type->direct_access(ti, pgoff, nr_pages, kaddr, pfn);
+
  out:
         dm_put_live_table(md, srcu_idx);
 
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index bcba4d89089c..df830d167892 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -128,14 +128,15 @@ typedef int (*dm_busy_fn) (struct dm_target *ti);
  *  < 0 : error
  * >= 0 : the number of bytes accessible at the address
  */
-typedef long (*dm_direct_access_fn) (struct dm_target *ti, sector_t sector,
-                                     void **kaddr, pfn_t *pfn, long size);
+typedef long (*dm_dax_direct_access_fn) (struct dm_target *ti, pgoff_t pgoff,
+                long nr_pages, void **kaddr, pfn_t *pfn);
 #define PAGE_SECTORS (PAGE_SIZE / 512)
 
 void dm_error(const char *message);
 
 struct dm_dev {
         struct block_device *bdev;
+        struct dax_device *dax_dev;
         fmode_t mode;
         char name[16];
 };
@@ -177,7 +178,7 @@ struct target_type {
         dm_busy_fn busy;
         dm_iterate_devices_fn iterate_devices;
         dm_io_hints_fn io_hints;
-        dm_direct_access_fn direct_access;
+        dm_dax_direct_access_fn direct_access;
 
         /* For internal device-mapper use. */
         struct list_head list;