linux-ext4 - [PATCH 08/11] dm-linear: add a linear_dax

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Date:   Mon, 18 Oct 2021 06:40:51 +0200
From:   Christoph Hellwig <hch@....de>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Dan Williams <dan.j.williams@...el.com>,
        Mike Snitzer <snitzer@...hat.com>,
        Ira Weiny <ira.weiny@...el.com>, dm-devel@...hat.com,
        linux-xfs@...r.kernel.org, nvdimm@...ts.linux.dev,
        linux-s390@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-erofs@...ts.ozlabs.org, linux-ext4@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: [PATCH 08/11] dm-linear: add a linear_dax_pgoff helper

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.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 drivers/md/dm-linear.c | 49 +++++++++++++-----------------------------
 1 file changed, 15 insertions(+), 34 deletions(-)

diff --git a/drivers/md/dm-linear.c b/drivers/md/dm-linear.c
index 32fbab11bf90c..bf03f73fd0f36 100644
--- a/drivers/md/dm-linear.c
+++ b/drivers/md/dm-linear.c
@@ -164,63 +164,44 @@ static int linear_iterate_devices(struct dm_target *ti,
 }
 
 #if IS_ENABLED(CONFIG_FS_DAX)
+static struct dax_device *linear_dax_pgoff(struct dm_target *ti, pgoff_t *pgoff)
+{
+	struct linear_c *lc = ti->private;
+	sector_t sector = linear_map_sector(ti, *pgoff << PAGE_SECTORS_SHIFT);
+
+	*pgoff = (get_start_sect(lc->dev->bdev) + sector) >> PAGE_SECTORS_SHIFT;
+	return lc->dev->dax_dev;
+}
+
 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 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;
+	struct dax_device *dax_dev = linear_dax_pgoff(ti, &pgoff);
+
 	return dax_direct_access(dax_dev, pgoff, nr_pages, kaddr, pfn);
 }
 
 static size_t linear_dax_copy_from_iter(struct dm_target *ti, pgoff_t pgoff,
 		void *addr, size_t bytes, struct iov_iter *i)
 {
-	struct linear_c *lc = ti->private;
-	struct block_device *bdev = lc->dev->bdev;
-	struct dax_device *dax_dev = lc->dev->dax_dev;
-	sector_t dev_sector, sector = pgoff * PAGE_SECTORS;
+	struct dax_device *dax_dev = linear_dax_pgoff(ti, &pgoff);
 
-	dev_sector = linear_map_sector(ti, sector);
-	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 linear_dax_copy_to_iter(struct dm_target *ti, pgoff_t pgoff,
 		void *addr, size_t bytes, struct iov_iter *i)
 {
-	struct linear_c *lc = ti->private;
-	struct block_device *bdev = lc->dev->bdev;
-	struct dax_device *dax_dev = lc->dev->dax_dev;
-	sector_t dev_sector, sector = pgoff * PAGE_SECTORS;
+	struct dax_device *dax_dev = linear_dax_pgoff(ti, &pgoff);
 
-	dev_sector = linear_map_sector(ti, sector);
-	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 linear_dax_zero_page_range(struct dm_target *ti, pgoff_t pgoff,
 				      size_t nr_pages)
 {
-	int ret;
-	struct linear_c *lc = ti->private;
-	struct block_device *bdev = lc->dev->bdev;
-	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_SHIFT, &pgoff);
-	if (ret)
-		return ret;
+	struct dax_device *dax_dev = linear_dax_pgoff(ti, &pgoff);
+
 	return dax_zero_page_range(dax_dev, pgoff, nr_pages);
 }
 
-- 
2.30.2