iomap: build the writeback code without CONFIG_BLOCK

JIRA: https://issues.redhat.com/browse/RHEL-121230

commit 5699b7e
Author: Christoph Hellwig <hch@lst.de>
Date:   Thu Jul 10 15:33:38 2025 +0200

    iomap: build the writeback code without CONFIG_BLOCK

    Allow fuse to use the iomap writeback code even when CONFIG_BLOCK is
    not enabled.  Do this with an ifdef instead of a separate file to keep
    the iomap_folio_state local to buffered-io.c.

    Signed-off-by: Christoph Hellwig <hch@lst.de>
    Link: https://lore.kernel.org/20250710133343.399917-15-hch@lst.de
    Reviewed-by: Darrick J. Wong <djwong@kernel.org>
    Reviewed-by: Joanne Koong <joannelkoong@gmail.com>
    Signed-off-by: Christian Brauner <brauner@kernel.org>

Signed-off-by: Brian Foster <bfoster@redhat.com>

Author: Brian Foster

fs/iomap/Makefile

@@ -9,9 +9,9 @@ ccflags-y += -I $(src)		# needed for trace events
 obj-$(CONFIG_FS_IOMAP)		+= iomap.o
 
 iomap-y				+= trace.o \
-				   iter.o
-iomap-$(CONFIG_BLOCK)		+= buffered-io.o \
-				   direct-io.o \
+				   iter.o \
+				   buffered-io.o
+iomap-$(CONFIG_BLOCK)		+= direct-io.o \
 				   ioend.o \
 				   fiemap.o \
 				   seek.o

fs/iomap/buffered-io.c

@@ -278,6 +278,46 @@ static void iomap_adjust_read_range(struct inode *inode, struct folio *folio,
 	*lenp = plen;
 }
 
+static inline bool iomap_block_needs_zeroing(const struct iomap_iter *iter,
+		loff_t pos)
+{
+	const struct iomap *srcmap = iomap_iter_srcmap(iter);
+
+	return srcmap->type != IOMAP_MAPPED ||
+		(srcmap->flags & IOMAP_F_NEW) ||
+		pos >= i_size_read(iter->inode);
+}
+
+/**
+ * iomap_read_inline_data - copy inline data into the page cache
+ * @iter: iteration structure
+ * @folio: folio to copy to
+ *
+ * Copy the inline data in @iter into @folio and zero out the rest of the folio.
+ * Only a single IOMAP_INLINE extent is allowed at the end of each file.
+ * Returns zero for success to complete the read, or the usual negative errno.
+ */
+static int iomap_read_inline_data(const struct iomap_iter *iter,
+		struct folio *folio)
+{
+	const struct iomap *iomap = iomap_iter_srcmap(iter);
+	size_t size = i_size_read(iter->inode) - iomap->offset;
+	size_t offset = offset_in_folio(folio, iomap->offset);
+
+	if (folio_test_uptodate(folio))
+		return 0;
+
+	if (WARN_ON_ONCE(size > iomap->length))
+		return -EIO;
+	if (offset > 0)
+		ifs_alloc(iter->inode, folio, iter->flags);
+
+	folio_fill_tail(folio, offset, iomap->inline_data, size);
+	iomap_set_range_uptodate(folio, offset, folio_size(folio) - offset);
+	return 0;
+}
+
+#ifdef CONFIG_BLOCK
 static void iomap_finish_folio_read(struct folio *folio, size_t off,
 		size_t len, int error)
 {
@@ -317,45 +357,6 @@ struct iomap_readpage_ctx {
 	struct readahead_control *rac;
 };
 
-/**
- * iomap_read_inline_data - copy inline data into the page cache
- * @iter: iteration structure
- * @folio: folio to copy to
- *
- * Copy the inline data in @iter into @folio and zero out the rest of the folio.
- * Only a single IOMAP_INLINE extent is allowed at the end of each file.
- * Returns zero for success to complete the read, or the usual negative errno.
- */
-static int iomap_read_inline_data(const struct iomap_iter *iter,
-		struct folio *folio)
-{
-	const struct iomap *iomap = iomap_iter_srcmap(iter);
-	size_t size = i_size_read(iter->inode) - iomap->offset;
-	size_t offset = offset_in_folio(folio, iomap->offset);
-
-	if (folio_test_uptodate(folio))
-		return 0;
-
-	if (WARN_ON_ONCE(size > iomap->length))
-		return -EIO;
-	if (offset > 0)
-		ifs_alloc(iter->inode, folio, iter->flags);
-
-	folio_fill_tail(folio, offset, iomap->inline_data, size);
-	iomap_set_range_uptodate(folio, offset, folio_size(folio) - offset);
-	return 0;
-}
-
-static inline bool iomap_block_needs_zeroing(const struct iomap_iter *iter,
-		loff_t pos)
-{
-	const struct iomap *srcmap = iomap_iter_srcmap(iter);
-
-	return srcmap->type != IOMAP_MAPPED ||
-		(srcmap->flags & IOMAP_F_NEW) ||
-		pos >= i_size_read(iter->inode);
-}
-
 static int iomap_readpage_iter(struct iomap_iter *iter,
 		struct iomap_readpage_ctx *ctx)
 {
@@ -548,6 +549,27 @@ void iomap_readahead(struct readahead_control *rac, const struct iomap_ops *ops)
 }
 EXPORT_SYMBOL_GPL(iomap_readahead);
 
+static int iomap_read_folio_range(const struct iomap_iter *iter,
+		struct folio *folio, loff_t pos, size_t len)
+{
+	const struct iomap *srcmap = iomap_iter_srcmap(iter);
+	struct bio_vec bvec;
+	struct bio bio;
+
+	bio_init(&bio, srcmap->bdev, &bvec, 1, REQ_OP_READ);
+	bio.bi_iter.bi_sector = iomap_sector(srcmap, pos);
+	bio_add_folio_nofail(&bio, folio, len, offset_in_folio(folio, pos));
+	return submit_bio_wait(&bio);
+}
+#else
+static int iomap_read_folio_range(const struct iomap_iter *iter,
+		struct folio *folio, loff_t pos, size_t len)
+{
+	WARN_ON_ONCE(1);
+	return -EIO;
+}
+#endif /* CONFIG_BLOCK */
+
 /*
  * iomap_is_partially_uptodate checks whether blocks within a folio are
  * uptodate or not.
@@ -659,19 +681,6 @@ iomap_write_failed(struct inode *inode, loff_t pos, unsigned len)
 					 pos + len - 1);
 }
 
-static int iomap_read_folio_range(const struct iomap_iter *iter,
-		struct folio *folio, loff_t pos, size_t len)
-{
-	const struct iomap *srcmap = iomap_iter_srcmap(iter);
-	struct bio_vec bvec;
-	struct bio bio;
-
-	bio_init(&bio, srcmap->bdev, &bvec, 1, REQ_OP_READ);
-	bio.bi_iter.bi_sector = iomap_sector(srcmap, pos);
-	bio_add_folio_nofail(&bio, folio, len, offset_in_folio(folio, pos));
-	return submit_bio_wait(&bio);
-}
-
 static int __iomap_write_begin(const struct iomap_iter *iter,
 		const struct iomap_write_ops *write_ops, size_t len,
 		struct folio *folio)