iomap: rework unshare flag

Instead of another internal flags namespace inside of buffered-io.c,
just pass a UNSHARE hint in the main iomap flags field.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>

fs/iomap/buffered-io.c

@@ -508,10 +508,6 @@ iomap_migrate_page(struct address_space *mapping, struct page *newpage,
 EXPORT_SYMBOL_GPL(iomap_migrate_page);
 #endif /* CONFIG_MIGRATION */
 
-enum {
-	IOMAP_WRITE_F_UNSHARE		= (1 << 0),
-};
-
 static void
 iomap_write_failed(struct inode *inode, loff_t pos, unsigned len)
 {
@@ -541,7 +537,7 @@ iomap_read_page_sync(loff_t block_start, struct page *page, unsigned poff,
 }
 
 static int __iomap_write_begin(struct iomap_iter *iter, loff_t pos,
-		unsigned len, int flags, struct page *page)
+		unsigned len, struct page *page)
 {
 	struct iomap *srcmap = iomap_iter_srcmap(iter);
 	struct iomap_page *iop = iomap_page_create(iter->inode, page);
@@ -560,13 +556,13 @@ static int __iomap_write_begin(struct iomap_iter *iter, loff_t pos,
 		if (plen == 0)
 			break;
 
-		if (!(flags & IOMAP_WRITE_F_UNSHARE) &&
+		if (!(iter->flags & IOMAP_UNSHARE) &&
 		    (from <= poff || from >= poff + plen) &&
 		    (to <= poff || to >= poff + plen))
 			continue;
 
 		if (iomap_block_needs_zeroing(iter, block_start)) {
-			if (WARN_ON_ONCE(flags & IOMAP_WRITE_F_UNSHARE))
+			if (WARN_ON_ONCE(iter->flags & IOMAP_UNSHARE))
 				return -EIO;
 			zero_user_segments(page, poff, from, to, poff + plen);
 		} else {
@@ -596,7 +592,7 @@ static int iomap_write_begin_inline(struct iomap_iter *iter,
 }
 
 static int iomap_write_begin(struct iomap_iter *iter, loff_t pos, unsigned len,
-		unsigned flags, struct page **pagep)
+		struct page **pagep)
 {
 	const struct iomap_page_ops *page_ops = iter->iomap.page_ops;
 	struct iomap *srcmap = iomap_iter_srcmap(iter);
@@ -628,7 +624,7 @@ static int iomap_write_begin(struct iomap_iter *iter, loff_t pos, unsigned len,
 	else if (srcmap->flags & IOMAP_F_BUFFER_HEAD)
 		status = __block_write_begin_int(page, pos, len, NULL, srcmap);
 	else
-		status = __iomap_write_begin(iter, pos, len, flags, page);
+		status = __iomap_write_begin(iter, pos, len, page);
 
 	if (unlikely(status))
 		goto out_unlock;
@@ -759,7 +755,7 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 			break;
 		}
 
-		status = iomap_write_begin(iter, pos, bytes, 0, &page);
+		status = iomap_write_begin(iter, pos, bytes, &page);
 		if (unlikely(status))
 			break;
 
@@ -836,8 +832,7 @@ static loff_t iomap_unshare_iter(struct iomap_iter *iter)
 		unsigned long bytes = min_t(loff_t, PAGE_SIZE - offset, length);
 		struct page *page;
 
-		status = iomap_write_begin(iter, pos, bytes,
-				IOMAP_WRITE_F_UNSHARE, &page);
+		status = iomap_write_begin(iter, pos, bytes, &page);
 		if (unlikely(status))
 			return status;
 
@@ -865,7 +860,7 @@ iomap_file_unshare(struct inode *inode, loff_t pos, loff_t len,
 		.inode		= inode,
 		.pos		= pos,
 		.len		= len,
-		.flags		= IOMAP_WRITE,
+		.flags		= IOMAP_WRITE | IOMAP_UNSHARE,
 	};
 	int ret;
 
@@ -882,7 +877,7 @@ static s64 __iomap_zero_iter(struct iomap_iter *iter, loff_t pos, u64 length)
 	unsigned offset = offset_in_page(pos);
 	unsigned bytes = min_t(u64, PAGE_SIZE - offset, length);
 
-	status = iomap_write_begin(iter, pos, bytes, 0, &page);
+	status = iomap_write_begin(iter, pos, bytes, &page);
 	if (status)
 		return status;
 

include/linux/iomap.h

@@ -140,6 +140,7 @@ struct iomap_page_ops {
 #define IOMAP_DIRECT		(1 << 4) /* direct I/O */
 #define IOMAP_NOWAIT		(1 << 5) /* do not block */
 #define IOMAP_OVERWRITE_ONLY	(1 << 6) /* only pure overwrites allowed */
+#define IOMAP_UNSHARE		(1 << 7) /* unshare_file_range */
 
 struct iomap_ops {
 	/*