Re: [PATCH 10/11] dm-stripe: add a stripe_dax_pgoff helper

all subsystems

On Sun, Oct 17, 2021 at 9:41 PM Christoph Hellwig [off-list ref] wrote:
Add a helper to perform the entire remapping for DAX accesses.  This
helper open codes bdev_dax_pgoff given that the alignment checks have
already been done by the submitting file system and don't need to be
repeated.
Again, looks good. Kind of embarrassing when the open-coded version is
less LOC than using the helper.

Mike, ack?

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/md/dm-stripe.c | 63 ++++++++++--------------------------------
 1 file changed, 15 insertions(+), 48 deletions(-)

diff --git a/drivers/md/dm-stripe.c b/drivers/md/dm-stripe.c
index f084607220293..50dba3f39274c 100644
--- a/drivers/md/dm-stripe.c
+++ b/drivers/md/dm-stripe.c
@@ -301,83 +301,50 @@ static int stripe_map(struct dm_target *ti, struct bio *bio)
 }

 #if IS_ENABLED(CONFIG_FS_DAX)
-static long stripe_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
-               long nr_pages, void **kaddr, pfn_t *pfn)
+static struct dax_device *stripe_dax_pgoff(struct dm_target *ti, pgoff_t *pgoff)
 {
-       sector_t dev_sector, sector = pgoff * PAGE_SECTORS;
        struct stripe_c *sc = ti->private;
-       struct dax_device *dax_dev;
        struct block_device *bdev;
+       sector_t dev_sector;
        uint32_t stripe;
-       long ret;

-       stripe_map_sector(sc, sector, &stripe, &dev_sector);
+       stripe_map_sector(sc, *pgoff * PAGE_SECTORS, &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_dax_pgoff(bdev, dev_sector, nr_pages * PAGE_SIZE, &pgoff);
-       if (ret)
-               return ret;
+       *pgoff = (get_start_sect(bdev) + dev_sector) >> PAGE_SECTORS_SHIFT;
+       return sc->stripe[stripe].dev->dax_dev;
+}
+
+static long stripe_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
+               long nr_pages, void **kaddr, pfn_t *pfn)
+{
+       struct dax_device *dax_dev = stripe_dax_pgoff(ti, &pgoff);
+
        return dax_direct_access(dax_dev, pgoff, nr_pages, kaddr, pfn);
 }

 static size_t stripe_dax_copy_from_iter(struct dm_target *ti, pgoff_t pgoff,
                void *addr, size_t bytes, struct iov_iter *i)
 {
-       sector_t dev_sector, sector = pgoff * PAGE_SECTORS;
-       struct stripe_c *sc = ti->private;
-       struct dax_device *dax_dev;
-       struct block_device *bdev;
-       uint32_t stripe;
-
-       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;
+       struct dax_device *dax_dev = stripe_dax_pgoff(ti, &pgoff);

-       if (bdev_dax_pgoff(bdev, dev_sector, ALIGN(bytes, PAGE_SIZE), &pgoff))
-               return 0;
        return dax_copy_from_iter(dax_dev, pgoff, addr, bytes, i);
 }

 static size_t stripe_dax_copy_to_iter(struct dm_target *ti, pgoff_t pgoff,
                void *addr, size_t bytes, struct iov_iter *i)
 {
-       sector_t dev_sector, sector = pgoff * PAGE_SECTORS;
-       struct stripe_c *sc = ti->private;
-       struct dax_device *dax_dev;
-       struct block_device *bdev;
-       uint32_t stripe;
-
-       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;
+       struct dax_device *dax_dev = stripe_dax_pgoff(ti, &pgoff);

-       if (bdev_dax_pgoff(bdev, dev_sector, ALIGN(bytes, PAGE_SIZE), &pgoff))
-               return 0;
        return dax_copy_to_iter(dax_dev, pgoff, addr, bytes, i);
 }

 static int stripe_dax_zero_page_range(struct dm_target *ti, pgoff_t pgoff,
                                      size_t nr_pages)
 {
-       int ret;
-       sector_t dev_sector, sector = pgoff * PAGE_SECTORS;
-       struct stripe_c *sc = ti->private;
-       struct dax_device *dax_dev;
-       struct block_device *bdev;
-       uint32_t stripe;
+       struct dax_device *dax_dev = stripe_dax_pgoff(ti, &pgoff);

-       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_dax_pgoff(bdev, dev_sector, nr_pages << PAGE_SHIFT, &pgoff);
-       if (ret)
-               return ret;
        return dax_zero_page_range(dax_dev, pgoff, nr_pages);
 }

--
2.30.2
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