dm writecache: handle DAX to partitions on persistent memory correctly

The function dax_direct_access doesn't take partitions into account,
it always maps pages from the beginning of the device. Therefore,
persistent_memory_claim() must get the partition offset using
get_start_sect() and add it to the page offsets passed to
dax_direct_access().

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Fixes: 27be8d954730 ("dm: add writecache target")
Cc: stable@vger.kernel.org # 4.18+
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm-writecache.c b/drivers/md/dm-writecache.c
index 86dbe0c8b45c60314b1d5113b4ab7c38d6b6e788..6271d1e741cf7a478abaf691d7b4f115e2c9a678 100644 (file)
--- a/drivers/md/dm-writecache.c
+++ b/drivers/md/dm-writecache.c
@@ -231,6 +231,7 @@ static int persistent_memory_claim(struct dm_writecache *wc)
        pfn_t pfn;
        int id;
        struct page **pages;
+       sector_t offset;
 
        wc->memory_vmapped = false;
 
@@ -245,9 +246,16 @@ static int persistent_memory_claim(struct dm_writecache *wc)
                goto err1;
        }
 
+       offset = get_start_sect(wc->ssd_dev->bdev);
+       if (offset & (PAGE_SIZE / 512 - 1)) {
+               r = -EINVAL;
+               goto err1;
+       }
+       offset >>= PAGE_SHIFT - 9;
+
        id = dax_read_lock();
 
-       da = dax_direct_access(wc->ssd_dev->dax_dev, 0, p, &wc->memory_map, &pfn);
+       da = dax_direct_access(wc->ssd_dev->dax_dev, offset, p, &wc->memory_map, &pfn);
        if (da < 0) {
                wc->memory_map = NULL;
                r = da;
@@ -269,7 +277,7 @@ static int persistent_memory_claim(struct dm_writecache *wc)
                i = 0;
                do {
                        long daa;
-                       daa = dax_direct_access(wc->ssd_dev->dax_dev, i, p - i,
+                       daa = dax_direct_access(wc->ssd_dev->dax_dev, offset + i, p - i,
                                                NULL, &pfn);
                        if (daa <= 0) {
                                r = daa ? daa : -EINVAL;