[PATCH 4.19 76/88] dm writecache: handle DAX to partitions on persistent memory correctly

Greg Kroah-Hartman
2020-09-08T18:07:08Z

From: Mikulas Patocka <mpatocka@redhat.com>

commit f9e040efcc28309e5c592f7e79085a9a52e31f58 upstream.

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: 48debafe4f2f ("dm: add writecache target")
Cc: stable@vger.kernel.org # 4.18+
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/md/dm-writecache.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

--- a/drivers/md/dm-writecache.c
+++ b/drivers/md/dm-writecache.c
@@ -226,6 +226,7 @@ static int persistent_memory_claim(struc
pfn_t pfn;
int id;
struct page **pages;
+ sector_t offset;

wc->memory_vmapped = false;

@@ -244,9 +245,16 @@ static int persistent_memory_claim(struc
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;
@@ -268,7 +276,7 @@ static int persistent_memory_claim(struc
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;