f2fs: implement iomap operations

Implement 'struct iomap_ops' for f2fs, in preparation for making f2fs
use iomap for direct I/O.

Note that this may be used for other things besides direct I/O in the
future; however, for now I've only tested it for direct I/O.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/Kconfig

@@ -7,6 +7,7 @@ config F2FS_FS
 	select CRYPTO_CRC32
 	select F2FS_FS_XATTR if FS_ENCRYPTION
 	select FS_ENCRYPTION_ALGS if FS_ENCRYPTION
+	select FS_IOMAP
 	select LZ4_COMPRESS if F2FS_FS_LZ4
 	select LZ4_DECOMPRESS if F2FS_FS_LZ4
 	select LZ4HC_COMPRESS if F2FS_FS_LZ4HC

fs/f2fs/data.c

@@ -21,6 +21,7 @@
 #include <linux/cleancache.h>
 #include <linux/sched/signal.h>
 #include <linux/fiemap.h>
+#include <linux/iomap.h>
 
 #include "f2fs.h"
 #include "node.h"
@@ -4237,3 +4238,58 @@ void f2fs_destroy_bio_entry_cache(void)
 {
 	kmem_cache_destroy(bio_entry_slab);
 }
+
+static int f2fs_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
+			    unsigned int flags, struct iomap *iomap,
+			    struct iomap *srcmap)
+{
+	struct f2fs_map_blocks map = {};
+	pgoff_t next_pgofs = 0;
+	int err;
+
+	map.m_lblk = bytes_to_blks(inode, offset);
+	map.m_len = bytes_to_blks(inode, offset + length - 1) - map.m_lblk + 1;
+	map.m_next_pgofs = &next_pgofs;
+	map.m_seg_type = f2fs_rw_hint_to_seg_type(inode->i_write_hint);
+	if (flags & IOMAP_WRITE)
+		map.m_may_create = true;
+
+	err = f2fs_map_blocks(inode, &map, flags & IOMAP_WRITE,
+			      F2FS_GET_BLOCK_DIO);
+	if (err)
+		return err;
+
+	iomap->offset = blks_to_bytes(inode, map.m_lblk);
+
+	if (map.m_flags & (F2FS_MAP_MAPPED | F2FS_MAP_UNWRITTEN)) {
+		iomap->length = blks_to_bytes(inode, map.m_len);
+		if (map.m_flags & F2FS_MAP_MAPPED) {
+			iomap->type = IOMAP_MAPPED;
+			iomap->flags |= IOMAP_F_MERGED;
+		} else {
+			iomap->type = IOMAP_UNWRITTEN;
+		}
+		if (WARN_ON_ONCE(!__is_valid_data_blkaddr(map.m_pblk)))
+			return -EINVAL;
+
+		iomap->bdev = map.m_bdev;
+		iomap->addr = blks_to_bytes(inode, map.m_pblk);
+	} else {
+		iomap->length = blks_to_bytes(inode, next_pgofs) -
+				iomap->offset;
+		iomap->type = IOMAP_HOLE;
+		iomap->addr = IOMAP_NULL_ADDR;
+	}
+
+	if (map.m_flags & F2FS_MAP_NEW)
+		iomap->flags |= IOMAP_F_NEW;
+	if ((inode->i_state & I_DIRTY_DATASYNC) ||
+	    offset + length > i_size_read(inode))
+		iomap->flags |= IOMAP_F_DIRTY;
+
+	return 0;
+}
+
+const struct iomap_ops f2fs_iomap_ops = {
+	.iomap_begin	= f2fs_iomap_begin,
+};

fs/f2fs/f2fs.h

@@ -3655,6 +3655,7 @@ int f2fs_init_post_read_processing(void);
 void f2fs_destroy_post_read_processing(void);
 int f2fs_init_post_read_wq(struct f2fs_sb_info *sbi);
 void f2fs_destroy_post_read_wq(struct f2fs_sb_info *sbi);
+extern const struct iomap_ops f2fs_iomap_ops;
 
 /*
  * gc.c