CoW changes the share state of a dax page, but the share count of the
page isn't updated. The next time access this page, it should have been
a newly accessed, but old association exists. So, we need to clear the
share state when CoW happens, in both dax_iomap_rw() and
dax_zero_iter().
Signed-off-by: Shiyang Ruan <ruansy.fnst@xxxxxxxxxxx>
---
fs/dax.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)
diff --git a/fs/dax.c b/fs/dax.c
index 85b81963ea31..482dda85ccaf 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1264,6 +1264,15 @@ static s64 dax_zero_iter(struct iomap_iter *iter, bool *did_zero)
if (srcmap->type == IOMAP_HOLE || srcmap->type == IOMAP_UNWRITTEN)
return length;
+ /*
+ * invalidate the pages whose sharing state is to be changed
+ * because of CoW.
+ */
+ if (iomap->flags & IOMAP_F_SHARED)
+ invalidate_inode_pages2_range(iter->inode->i_mapping,
+ pos >> PAGE_SHIFT,
+ (pos + length - 1) >> PAGE_SHIFT);
+
do {
unsigned offset = offset_in_page(pos);
unsigned size = min_t(u64, PAGE_SIZE - offset, length);
@@ -1324,12 +1333,13 @@ static loff_t dax_iomap_iter(const struct iomap_iter *iomi,
struct iov_iter *iter)
{
const struct iomap *iomap = &iomi->iomap;
- const struct iomap *srcmap = &iomi->srcmap;
+ const struct iomap *srcmap = iomap_iter_srcmap(iomi);
loff_t length = iomap_length(iomi);
loff_t pos = iomi->pos;
struct dax_device *dax_dev = iomap->dax_dev;
loff_t end = pos + length, done = 0;
bool write = iov_iter_rw(iter) == WRITE;
+ bool cow = write && iomap->flags & IOMAP_F_SHARED;
ssize_t ret = 0;
size_t xfer;
int id;
@@ -1356,7 +1366,7 @@ static loff_t dax_iomap_iter(const struct iomap_iter *iomi,
* into page tables. We have to tear down these mappings so that data
* written by write(2) is visible in mmap.
*/
- if (iomap->flags & IOMAP_F_NEW) {
+ if (iomap->flags & IOMAP_F_NEW || cow) {
invalidate_inode_pages2_range(iomi->inode->i_mapping,
pos >> PAGE_SHIFT,
(end - 1) >> PAGE_SHIFT);
@@ -1390,8 +1400,7 @@ static loff_t dax_iomap_iter(const struct iomap_iter *iomi,
break;
}
- if (write &&
- srcmap->type != IOMAP_HOLE && srcmap->addr != iomap->addr) {
+ if (cow) {
ret = dax_iomap_cow_copy(pos, length, PAGE_SIZE, srcmap,
kaddr);
if (ret)
--
2.38.1
