iomap: make iomap_write_end() return a boolean

For now, we can make sure iomap_write_end() always return 0 or copied
bytes, so instead of return written bytes, convert to return a boolean
to indicate the copied bytes have been written to the pagecache.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Link: https://lore.kernel.org/r/20240320110548.2200662-9-yi.zhang@huaweicloud.com
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

fs/iomap/buffered-io.c

@@ -828,7 +828,7 @@ static int iomap_write_begin(struct iomap_iter *iter, loff_t pos,
 	return status;
 }
 
-static size_t __iomap_write_end(struct inode *inode, loff_t pos, size_t len,
+static bool __iomap_write_end(struct inode *inode, loff_t pos, size_t len,
 		size_t copied, struct folio *folio)
 {
 	flush_dcache_folio(folio);
@@ -845,14 +845,14 @@ static size_t __iomap_write_end(struct inode *inode, loff_t pos, size_t len,
 	 * redo the whole thing.
 	 */
 	if (unlikely(copied < len && !folio_test_uptodate(folio)))
-		return 0;
+		return false;
 	iomap_set_range_uptodate(folio, offset_in_folio(folio, pos), len);
 	iomap_set_range_dirty(folio, offset_in_folio(folio, pos), copied);
 	filemap_dirty_folio(inode->i_mapping, folio);
-	return copied;
+	return true;
 }
 
-static size_t iomap_write_end_inline(const struct iomap_iter *iter,
+static void iomap_write_end_inline(const struct iomap_iter *iter,
 		struct folio *folio, loff_t pos, size_t copied)
 {
 	const struct iomap *iomap = &iter->iomap;
@@ -867,20 +867,31 @@ static size_t iomap_write_end_inline(const struct iomap_iter *iter,
 	kunmap_local(addr);
 
 	mark_inode_dirty(iter->inode);
-	return copied;
 }
 
-/* Returns the number of bytes copied.  May be 0.  Cannot be an errno. */
-static size_t iomap_write_end(struct iomap_iter *iter, loff_t pos, size_t len,
+/*
+ * Returns true if all copied bytes have been written to the pagecache,
+ * otherwise return false.
+ */
+static bool iomap_write_end(struct iomap_iter *iter, loff_t pos, size_t len,
 		size_t copied, struct folio *folio)
 {
 	const struct iomap *srcmap = iomap_iter_srcmap(iter);
 
-	if (srcmap->type == IOMAP_INLINE)
-		return iomap_write_end_inline(iter, folio, pos, copied);
-	if (srcmap->flags & IOMAP_F_BUFFER_HEAD)
-		return block_write_end(NULL, iter->inode->i_mapping, pos, len,
-				       copied, &folio->page, NULL);
+	if (srcmap->type == IOMAP_INLINE) {
+		iomap_write_end_inline(iter, folio, pos, copied);
+		return true;
+	}
+
+	if (srcmap->flags & IOMAP_F_BUFFER_HEAD) {
+		size_t bh_written;
+
+		bh_written = block_write_end(NULL, iter->inode->i_mapping, pos,
+					len, copied, &folio->page, NULL);
+		WARN_ON_ONCE(bh_written != copied && bh_written != 0);
+		return bh_written == copied;
+	}
+
 	return __iomap_write_end(iter->inode, pos, len, copied, folio);
 }
 
@@ -945,7 +956,8 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 			flush_dcache_folio(folio);
 
 		copied = copy_folio_from_iter_atomic(folio, offset, bytes, i);
-		written = iomap_write_end(iter, pos, bytes, copied, folio);
+		written = iomap_write_end(iter, pos, bytes, copied, folio) ?
+			  copied : 0;
 
 		/*
 		 * Update the in-memory inode size after copying the data into
@@ -1323,6 +1335,7 @@ static loff_t iomap_unshare_iter(struct iomap_iter *iter)
 		int status;
 		size_t offset;
 		size_t bytes = min_t(u64, SIZE_MAX, length);
+		bool ret;
 
 		status = iomap_write_begin(iter, pos, bytes, &folio);
 		if (unlikely(status))
@@ -1334,9 +1347,9 @@ static loff_t iomap_unshare_iter(struct iomap_iter *iter)
 		if (bytes > folio_size(folio) - offset)
 			bytes = folio_size(folio) - offset;
 
-		bytes = iomap_write_end(iter, pos, bytes, bytes, folio);
+		ret = iomap_write_end(iter, pos, bytes, bytes, folio);
 		__iomap_put_folio(iter, pos, bytes, folio);
-		if (WARN_ON_ONCE(bytes == 0))
+		if (WARN_ON_ONCE(!ret))
 			return -EIO;
 
 		cond_resched();
@@ -1385,6 +1398,7 @@ static loff_t iomap_zero_iter(struct iomap_iter *iter, bool *did_zero)
 		int status;
 		size_t offset;
 		size_t bytes = min_t(u64, SIZE_MAX, length);
+		bool ret;
 
 		status = iomap_write_begin(iter, pos, bytes, &folio);
 		if (status)
@@ -1399,9 +1413,9 @@ static loff_t iomap_zero_iter(struct iomap_iter *iter, bool *did_zero)
 		folio_zero_range(folio, offset, bytes);
 		folio_mark_accessed(folio);
 
-		bytes = iomap_write_end(iter, pos, bytes, bytes, folio);
+		ret = iomap_write_end(iter, pos, bytes, bytes, folio);
 		__iomap_put_folio(iter, pos, bytes, folio);
-		if (WARN_ON_ONCE(bytes == 0))
+		if (WARN_ON_ONCE(!ret))
 			return -EIO;
 
 		pos += bytes;