On Wed, May 12, 2021 at 01:37:24AM +0000, ruansy.fnst@fujitsu.com wrote:

quoted

-----Original Message-----
From: Darrick J. Wong <djwong@kernel.org>
Subject: Re: [PATCH v5 3/7] fsdax: Add dax_iomap_cow_copy() for
dax_iomap_zero

On Tue, May 11, 2021 at 11:09:29AM +0800, Shiyang Ruan wrote:

quoted

Punch hole on a reflinked file needs dax_copy_edge() too.  Otherwise,
data in not aligned area will be not correct.  So, add the srcmap to
dax_iomap_zero() and replace memset() as dax_copy_edge().

Signed-off-by: Shiyang Ruan <redacted>
Reviewed-by: Ritesh Harjani <redacted>
---
 fs/dax.c               | 25 +++++++++++++++----------
 fs/iomap/buffered-io.c |  2 +-
 include/linux/dax.h    |  3 ++-
 3 files changed, 18 insertions(+), 12 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index ef0e564e7904..ee9d28a79bfb 100644
--- a/fs/dax.c
+++ b/fs/dax.c

@@ -1186,7 +1186,8 @@ static vm_fault_t dax_pmd_load_hole(struct

xa_state *xas, struct vm_fault *vmf,  }  #endif /* CONFIG_FS_DAX_PMD
*/

-s64 dax_iomap_zero(loff_t pos, u64 length, struct iomap *iomap)
+s64 dax_iomap_zero(loff_t pos, u64 length, struct iomap *iomap,
+		struct iomap *srcmap)
 {
 	sector_t sector = iomap_sector(iomap, pos & PAGE_MASK);
 	pgoff_t pgoff;

@@ -1208,19 +1209,23 @@ s64 dax_iomap_zero(loff_t pos, u64 length,

struct iomap *iomap)

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

Why isn't this "if (srcmap->type != IOMAP_HOLE)" ?

I suppose it has the same effect, since @iomap should never be a hole and we
should never have a @srcmap that's the same as @iomap, but still, we use
IOMAP_HOLE checks in most other parts of fs/iomap/.

According to its caller `iomap_zero_range_actor()`, whether
srcmap->type is IOMAP_HOLE has already been checked before
`dax_iomap_zero()`.  So the check you suggested will always be true...

Ah right, so it is.  I'll go review the newest version of this patch.

--D

--
Thanks,
Ruan Shiyang.

quoted

Other than that, the logic looks decent to me.

--D

quoted

+			rc = dax_iomap_cow_copy(offset, size, PAGE_SIZE, srcmap,
+						kaddr);
+			if (rc < 0)
+				goto out;
+		} else
+			memset(kaddr + offset, 0, size);
 		dax_flush(iomap->dax_dev, kaddr + offset, size);
 	}
+
+out:
 	dax_read_unlock(id);
-	return size;
+	return rc < 0 ? rc : size;
 }

 static loff_t

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c index

f2cd2034a87b..2734955ea67f 100644

--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c

@@ -933,7 +933,7 @@ static loff_t iomap_zero_range_actor(struct inode

*inode, loff_t pos,

quoted

 		s64 bytes;

 		if (IS_DAX(inode))
-			bytes = dax_iomap_zero(pos, length, iomap);
+			bytes = dax_iomap_zero(pos, length, iomap, srcmap);
 		else
 			bytes = iomap_zero(inode, pos, length, iomap, srcmap);
 		if (bytes < 0)

diff --git a/include/linux/dax.h b/include/linux/dax.h index

b52f084aa643..3275e01ed33d 100644

--- a/include/linux/dax.h
+++ b/include/linux/dax.h

@@ -237,7 +237,8 @@ vm_fault_t dax_finish_sync_fault(struct vm_fault

*vmf,  int dax_delete_mapping_entry(struct address_space *mapping,
pgoff_t index);  int dax_invalidate_mapping_entry_sync(struct

address_space *mapping,

quoted

 				      pgoff_t index);
-s64 dax_iomap_zero(loff_t pos, u64 length, struct iomap *iomap);
+s64 dax_iomap_zero(loff_t pos, u64 length, struct iomap *iomap,
+		struct iomap *srcmap);
 static inline bool dax_mapping(struct address_space *mapping)  {
 	return mapping->host && IS_DAX(mapping->host);
--
2.31.1