[PATCH 1/2] fsdax,xfs: fix warning messages at dax_[dis]associate_entry()

[Shiyang Ruan]

This patch fixes the warning message reported in dax_associate_entry()
and dax_disassociate_entry().
1. reset page->mapping and ->index when refcount counting down to 0.
2. set IOMAP_F_SHARED flag when iomap read to allow one dax page to be
associated more than once for not only write but also read.
3. should zero the edge (when not aligned) if srcmap is HOLE or
UNWRITTEN.
4. iterator of two files in dedupe should be executed side by side, not
nested.
5. use xfs_dax_write_iomap_ops for xfs zero and truncate. 

Signed-off-by: Shiyang Ruan <ruansy.fnst@xxxxxxxxxxx>
---
 fs/dax.c           | 114 ++++++++++++++++++++++++++-------------------
 fs/xfs/xfs_iomap.c |   6 +--
 2 files changed, 69 insertions(+), 51 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 1c6867810cbd..5ea7c0926b7f 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -398,7 +398,7 @@ static void dax_disassociate_entry(void *entry, struct address_space *mapping,
 		WARN_ON_ONCE(trunc && page_ref_count(page) > 1);
 		if (dax_mapping_is_cow(page->mapping)) {
 			/* keep the CoW flag if this page is still shared */
-			if (page->index-- > 0)
+			if (page->index-- > 1)
 				continue;
 		} else
 			WARN_ON_ONCE(page->mapping && page->mapping != mapping);
@@ -840,12 +840,6 @@ static bool dax_fault_is_synchronous(const struct iomap_iter *iter,
 		(iter->iomap.flags & IOMAP_F_DIRTY);
 }
 
-static bool dax_fault_is_cow(const struct iomap_iter *iter)
-{
-	return (iter->flags & IOMAP_WRITE) &&
-		(iter->iomap.flags & IOMAP_F_SHARED);
-}
-
 /*
  * By this point grab_mapping_entry() has ensured that we have a locked entry
  * of the appropriate size so we don't have to worry about downgrading PMDs to
@@ -859,13 +853,14 @@ static void *dax_insert_entry(struct xa_state *xas, struct vm_fault *vmf,
 {
 	struct address_space *mapping = vmf->vma->vm_file->f_mapping;
 	void *new_entry = dax_make_entry(pfn, flags);
-	bool dirty = !dax_fault_is_synchronous(iter, vmf->vma);
-	bool cow = dax_fault_is_cow(iter);
+	bool write = iter->flags & IOMAP_WRITE;
+	bool dirty = write && !dax_fault_is_synchronous(iter, vmf->vma);
+	bool shared = iter->iomap.flags & IOMAP_F_SHARED;
 
 	if (dirty)
 		__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
 
-	if (cow || (dax_is_zero_entry(entry) && !(flags & DAX_ZERO_PAGE))) {
+	if (shared || (dax_is_zero_entry(entry) && !(flags & DAX_ZERO_PAGE))) {
 		unsigned long index = xas->xa_index;
 		/* we are replacing a zero page with block mapping */
 		if (dax_is_pmd_entry(entry))
@@ -877,12 +872,12 @@ static void *dax_insert_entry(struct xa_state *xas, struct vm_fault *vmf,
 
 	xas_reset(xas);
 	xas_lock_irq(xas);
-	if (cow || dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
+	if (shared || dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
 		void *old;
 
 		dax_disassociate_entry(entry, mapping, false);
 		dax_associate_entry(new_entry, mapping, vmf->vma, vmf->address,
-				cow);
+				shared);
 		/*
 		 * Only swap our new entry into the page cache if the current
 		 * entry is a zero page or an empty entry.  If a normal PTE or
@@ -902,7 +897,7 @@ static void *dax_insert_entry(struct xa_state *xas, struct vm_fault *vmf,
 	if (dirty)
 		xas_set_mark(xas, PAGECACHE_TAG_DIRTY);
 
-	if (cow)
+	if (write && shared)
 		xas_set_mark(xas, PAGECACHE_TAG_TOWRITE);
 
 	xas_unlock_irq(xas);
@@ -1107,23 +1102,35 @@ static int dax_iomap_cow_copy(loff_t pos, uint64_t length, size_t align_size,
 	loff_t end = pos + length;
 	loff_t pg_end = round_up(end, align_size);
 	bool copy_all = head_off == 0 && end == pg_end;
+	/* write zero at edge if srcmap is a HOLE or IOMAP_UNWRITTEN */
+	bool zero_edge = srcmap->flags & IOMAP_F_SHARED ||
+			 srcmap->type == IOMAP_UNWRITTEN;
 	void *saddr = 0;
 	int ret = 0;
 
-	ret = dax_iomap_direct_access(srcmap, pos, size, &saddr, NULL);
-	if (ret)
-		return ret;
+	if (!zero_edge) {
+		ret = dax_iomap_direct_access(srcmap, pos, size, &saddr, NULL);
+		if (ret)
+			return ret;
+	}
 
 	if (copy_all) {
-		ret = copy_mc_to_kernel(daddr, saddr, length);
-		return ret ? -EIO : 0;
+		if (zero_edge)
+			memset(daddr, 0, size);
+		else
+			ret = copy_mc_to_kernel(daddr, saddr, length);
+		goto out;
 	}
 
 	/* Copy the head part of the range */
 	if (head_off) {
-		ret = copy_mc_to_kernel(daddr, saddr, head_off);
-		if (ret)
-			return -EIO;
+		if (zero_edge)
+			memset(daddr, 0, head_off);
+		else {
+			ret = copy_mc_to_kernel(daddr, saddr, head_off);
+			if (ret)
+				return -EIO;
+		}
 	}
 
 	/* Copy the tail part of the range */
@@ -1131,12 +1138,19 @@ static int dax_iomap_cow_copy(loff_t pos, uint64_t length, size_t align_size,
 		loff_t tail_off = head_off + length;
 		loff_t tail_len = pg_end - end;
 
-		ret = copy_mc_to_kernel(daddr + tail_off, saddr + tail_off,
-					tail_len);
-		if (ret)
-			return -EIO;
+		if (zero_edge)
+			memset(daddr + tail_off, 0, tail_len);
+		else {
+			ret = copy_mc_to_kernel(daddr + tail_off,
+						saddr + tail_off, tail_len);
+			if (ret)
+				return -EIO;
+		}
 	}
-	return 0;
+out:
+	if (zero_edge)
+		dax_flush(srcmap->dax_dev, daddr, size);
+	return ret ? -EIO : 0;
 }
 
 /*
@@ -1235,13 +1249,9 @@ static int dax_memzero(struct iomap_iter *iter, loff_t pos, size_t size)
 	if (ret < 0)
 		return ret;
 	memset(kaddr + offset, 0, size);
-	if (srcmap->addr != iomap->addr) {
-		ret = dax_iomap_cow_copy(pos, size, PAGE_SIZE, srcmap,
-					 kaddr);
-		if (ret < 0)
-			return ret;
-		dax_flush(iomap->dax_dev, kaddr, PAGE_SIZE);
-	} else
+	if (iomap->flags & IOMAP_F_SHARED)
+		ret = dax_iomap_cow_copy(pos, size, PAGE_SIZE, srcmap, kaddr);
+	else
 		dax_flush(iomap->dax_dev, kaddr + offset, size);
 	return ret;
 }
@@ -1258,6 +1268,15 @@ 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);
@@ -1318,12 +1337,13 @@ 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;
@@ -1350,7 +1370,7 @@ 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);
@@ -1384,8 +1404,7 @@ 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)
@@ -1532,7 +1551,7 @@ static vm_fault_t dax_fault_iter(struct vm_fault *vmf,
 		struct xa_state *xas, void **entry, bool pmd)
 {
 	const struct iomap *iomap = &iter->iomap;
-	const struct iomap *srcmap = &iter->srcmap;
+	const struct iomap *srcmap = iomap_iter_srcmap(iter);
 	size_t size = pmd ? PMD_SIZE : PAGE_SIZE;
 	loff_t pos = (loff_t)xas->xa_index << PAGE_SHIFT;
 	bool write = iter->flags & IOMAP_WRITE;
@@ -1563,8 +1582,7 @@ static vm_fault_t dax_fault_iter(struct vm_fault *vmf,
 
 	*entry = dax_insert_entry(xas, vmf, iter, *entry, pfn, entry_flags);
 
-	if (write &&
-	    srcmap->type != IOMAP_HOLE && srcmap->addr != iomap->addr) {
+	if (write && iomap->flags & IOMAP_F_SHARED) {
 		err = dax_iomap_cow_copy(pos, size, size, srcmap, kaddr);
 		if (err)
 			return dax_fault_return(err);
@@ -1936,15 +1954,15 @@ int dax_dedupe_file_range_compare(struct inode *src, loff_t srcoff,
 		.len		= len,
 		.flags		= IOMAP_DAX,
 	};
-	int ret;
+	int ret, compared = 0;
 
-	while ((ret = iomap_iter(&src_iter, ops)) > 0) {
-		while ((ret = iomap_iter(&dst_iter, ops)) > 0) {
-			dst_iter.processed = dax_range_compare_iter(&src_iter,
-						&dst_iter, len, same);
-		}
-		if (ret <= 0)
-			src_iter.processed = ret;
+	while ((ret = iomap_iter(&src_iter, ops)) > 0 &&
+	       (ret = iomap_iter(&dst_iter, ops)) > 0) {
+		compared = dax_range_compare_iter(&src_iter, &dst_iter, len,
+						  same);
+		if (compared < 0)
+			return ret;
+		src_iter.processed = dst_iter.processed = compared;
 	}
 	return ret;
 }
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 07da03976ec1..d9401d0300ad 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -1215,7 +1215,7 @@ xfs_read_iomap_begin(
 		return error;
 	error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb, &imap,
 			       &nimaps, 0);
-	if (!error && (flags & IOMAP_REPORT))
+	if (!error && ((flags & IOMAP_REPORT) || IS_DAX(inode)))
 		error = xfs_reflink_trim_around_shared(ip, &imap, &shared);
 	xfs_iunlock(ip, lockmode);
 
@@ -1370,7 +1370,7 @@ xfs_zero_range(
 
 	if (IS_DAX(inode))
 		return dax_zero_range(inode, pos, len, did_zero,
-				      &xfs_direct_write_iomap_ops);
+				      &xfs_dax_write_iomap_ops);
 	return iomap_zero_range(inode, pos, len, did_zero,
 				&xfs_buffered_write_iomap_ops);
 }
@@ -1385,7 +1385,7 @@ xfs_truncate_page(
 
 	if (IS_DAX(inode))
 		return dax_truncate_page(inode, pos, did_zero,
-					&xfs_direct_write_iomap_ops);
+					&xfs_dax_write_iomap_ops);
 	return iomap_truncate_page(inode, pos, did_zero,
 				   &xfs_buffered_write_iomap_ops);
 }
-- 
2.38.1