Convert minix regular file and symlink address space operations from
buffer_head to iomap. The new minix_aops uses iomap_dirty_folio,
iomap_invalidate_folio, iomap_bio_read_folio, iomap_bio_readahead,
iomap_writepages, iomap_bmap, and related iomap helpers.
The write_begin/write_end callbacks are removed since buffered writes
now go through iomap_file_buffered_write in file.c.

Directories keep using buffer_heads via a new minix_dir_aops, which
retains the old block_dirty_folio, block_read_full_folio,
block_write_begin, generic_write_end, and mpage_writepages. This is
necessary because directory entry manipulation (minix_prepare_chunk,
minix_write_begin) still uses the buffer_head chunk protocol.

minix_bmap is converted from generic_block_bmap to iomap_bmap.

The minix_get_block function is exported (non-static) so the
directory aops can still use it for block_write_begin and
mpage_writepages.

Signed-off-by: Jeremy Bingham <jbingham@gmail.com>
---
 fs/minix/inode.c | 86 +++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 78 insertions(+), 8 deletions(-)

diff --git a/fs/minix/inode.c b/fs/minix/inode.c
index c30cc590698d..2ba6766fce51 100644
--- a/fs/minix/inode.c
+++ b/fs/minix/inode.c
@@ -436,7 +436,32 @@ static int minix_statfs(struct dentry *dentry, struct kstatfs *buf)
 	return 0;
 }
 
-static int minix_get_block(struct inode *inode, sector_t block,
+static ssize_t minix_writeback_range(struct iomap_writepage_ctx *wpc,
+	struct folio *folio, u64 pos, unsigned int len, u64 end_pos)
+{
+	int error;
+
+	if (pos < wpc->iomap.offset ||
+			pos >= wpc->iomap.offset + wpc->iomap.length) {
+		if (INODE_VERSION(wpc->inode) == MINIX_V1)
+			error = V1_minix_iomap_begin(wpc->inode, pos, len, IOMAP_WRITE,
+				&wpc->iomap, NULL);
+		else
+			error = V2_minix_iomap_begin(wpc->inode, pos, len, IOMAP_WRITE,
+				&wpc->iomap, NULL);
+		if (error)
+			return error;
+	}
+
+	return iomap_add_to_ioend(wpc, folio, pos, end_pos, len);
+}
+
+static const struct iomap_writeback_ops minix_writeback_ops = {
+	.writeback_range = minix_writeback_range,
+	.writeback_submit = iomap_ioend_writeback_submit,
+};
+
+int minix_get_block(struct inode *inode, sector_t block,
 		    struct buffer_head *bh_result, int create)
 {
 	if (INODE_VERSION(inode) == MINIX_V1)
@@ -445,17 +470,45 @@ static int minix_get_block(struct inode *inode, sector_t block,
 		return V2_minix_get_block(inode, block, bh_result, create);
 }
 
-static int minix_writepages(struct address_space *mapping,
+/* The old minix_writepages, preserved for directory operations. */
+static int minix_block_writepages(struct address_space *mapping,
 		struct writeback_control *wbc)
 {
 	return mpage_writepages(mapping, wbc, minix_get_block);
 }
 
+static int minix_writepages(struct address_space *mapping,
+		struct writeback_control *wbc)
+{
+	struct iomap_writepage_ctx wpc = {
+		.inode = mapping->host,
+		.wbc = wbc,
+		.ops = &minix_writeback_ops,
+	};
+	return iomap_writepages(&wpc);
+}
+
 static int minix_read_folio(struct file *file, struct folio *folio)
+{
+	const struct iomap_ops *ops = minix_iomap_ops_ver(folio->mapping->host);
+
+	iomap_bio_read_folio(folio, ops);
+	return 0;
+}
+
+/* The old minix_read_folio, preserved for directory operations. */
+static int minix_block_read_folio(struct file *file, struct folio *folio)
 {
 	return block_read_full_folio(folio, minix_get_block);
 }
 
+static void minix_readahead(struct readahead_control *rac)
+{
+	const struct iomap_ops *ops = minix_iomap_ops_ver(rac->mapping->host);
+
+	iomap_bio_readahead(rac, ops);
+}
+
 int minix_prepare_chunk(struct folio *folio, loff_t pos, unsigned len)
 {
 	return __block_write_begin(folio, pos, len, minix_get_block);
@@ -487,19 +540,36 @@ static int minix_write_begin(const struct kiocb *iocb,
 
 static sector_t minix_bmap(struct address_space *mapping, sector_t block)
 {
-	return generic_block_bmap(mapping,block,minix_get_block);
+	const struct iomap_ops *ops = minix_iomap_ops_ver(mapping->host);
+
+	return iomap_bmap(mapping, block, ops);
 }
 
-static const struct address_space_operations minix_aops = {
-	.dirty_folio	= block_dirty_folio,
-	.invalidate_folio = block_invalidate_folio,
+const struct address_space_operations minix_aops = {
+	.dirty_folio	= iomap_dirty_folio,
+	.invalidate_folio = iomap_invalidate_folio,
 	.read_folio = minix_read_folio,
+	.readahead = minix_readahead,
 	.writepages = minix_writepages,
+	.migrate_folio = filemap_migrate_folio,
+	.bmap = minix_bmap,
+	.is_partially_uptodate = iomap_is_partially_uptodate,
+	.release_folio = iomap_release_folio,
+	.error_remove_folio = generic_error_remove_folio,
+};
+
+/* A special aops for directories that keeps using the buffer head chunks, at
+ * least for the time being.
+ */
+static const struct address_space_operations minix_dir_aops = {
+	.dirty_folio = block_dirty_folio,
+	.invalidate_folio = block_invalidate_folio,
+	.read_folio = minix_block_read_folio,
 	.write_begin = minix_write_begin,
 	.write_end = generic_write_end,
 	.migrate_folio = buffer_migrate_folio,
 	.bmap = minix_bmap,
-	.direct_IO = noop_direct_IO
+	.writepages = minix_block_writepages,
 };
 
 static const struct inode_operations minix_symlink_inode_operations = {
@@ -516,7 +586,7 @@ void minix_set_inode(struct inode *inode, dev_t rdev)
 	} else if (S_ISDIR(inode->i_mode)) {
 		inode->i_op = &minix_dir_inode_operations;
 		inode->i_fop = &minix_dir_operations;
-		inode->i_mapping->a_ops = &minix_aops;
+		inode->i_mapping->a_ops = &minix_dir_aops;
 	} else if (S_ISLNK(inode->i_mode)) {
 		inode->i_op = &minix_symlink_inode_operations;
 		inode_nohighmem(inode);
-- 
2.47.3