[PATCH v9 5/8] fsdax: Add dax_iomap_cow_copy() for dax_iomap_zero

From: Shiyang Ruan
Date: Wed Sep 15 2021 - 06:46:00 EST


Punch hole on a reflinked file needs dax_iomap_cow_copy() too.
Otherwise, data in not aligned area will be not correct. So, add the
CoW operation for not aligned case in dax_iomap_zero().

Signed-off-by: Shiyang Ruan <ruansy.fnst@xxxxxxxxxxx>
Reviewed-by: Ritesh Harjani <riteshh@xxxxxxxxxxxxx>
Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx>
---
fs/dax.c | 27 +++++++++++++++++----------
1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 4f346e25e488..ca4308c85988 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1212,6 +1212,7 @@ static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault *vmf,
s64 dax_iomap_zero(struct iomap_iter *iter, loff_t pos, u64 length)
{
const struct iomap *iomap = &iter->iomap;
+ const struct iomap *srcmap = &iter->srcmap;
sector_t sector = iomap_sector(iomap, pos & PAGE_MASK);
pgoff_t pgoff;
long rc, id;
@@ -1230,21 +1231,27 @@ s64 dax_iomap_zero(struct iomap_iter *iter, loff_t pos, u64 length)

id = dax_read_lock();

- if (page_aligned)
+ if (page_aligned) {
rc = dax_zero_page_range(iomap->dax_dev, pgoff, 1);
- else
- rc = dax_direct_access(iomap->dax_dev, pgoff, 1, &kaddr, NULL);
- if (rc < 0) {
- dax_read_unlock(id);
- return rc;
+ goto out;
}

- if (!page_aligned) {
- memset(kaddr + offset, 0, size);
+ rc = dax_direct_access(iomap->dax_dev, pgoff, 1, &kaddr, NULL);
+ if (rc < 0)
+ goto out;
+ memset(kaddr + offset, 0, size);
+ if (srcmap->addr != IOMAP_HOLE && srcmap->addr != iomap->addr) {
+ rc = dax_iomap_cow_copy(pos, size, PAGE_SIZE, srcmap,
+ kaddr);
+ if (rc < 0)
+ goto out;
+ dax_flush(iomap->dax_dev, kaddr, PAGE_SIZE);
+ } else
dax_flush(iomap->dax_dev, kaddr + offset, size);
- }
+
+out:
dax_read_unlock(id);
- return size;
+ return rc < 0 ? rc : size;
}

static loff_t dax_iomap_iter(const struct iomap_iter *iomi,
--
2.33.0