erofs: add fiemap support with iomap

This adds fiemap support for both uncompressed files and compressed
files by using iomap infrastructure.

Link: https://lore.kernel.org/r/[e-mail]
Reviewed-by: Chao Yu <[e-mail]>
Signed-off-by: Gao Xiang <[e-mail]>

fs/erofs/data.c

···
  */
 #include "internal.h"
 #include <linux/prefetch.h>
-#include <linux/iomap.h>
 #include <linux/dax.h>
 #include <trace/events/erofs.h>
 
···
 	.iomap_begin = erofs_iomap_begin,
 	.iomap_end = erofs_iomap_end,
 };
+
+int erofs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
+		 u64 start, u64 len)
+{
+	if (erofs_inode_is_data_compressed(EROFS_I(inode)->datalayout)) {
+#ifdef CONFIG_EROFS_FS_ZIP
+		return iomap_fiemap(inode, fieinfo, start, len,
+				    &z_erofs_iomap_report_ops);
+#else
+		return -EOPNOTSUPP;
+#endif
+	}
+	return iomap_fiemap(inode, fieinfo, start, len, &erofs_iomap_ops);
+}
 
 /*
  * since we dont have write or truncate flows, so no inode

fs/erofs/inode.c

···
 	.getattr = erofs_getattr,
 	.listxattr = erofs_listxattr,
 	.get_acl = erofs_get_acl,
+	.fiemap = erofs_fiemap,
 };
 
 const struct inode_operations erofs_symlink_iops = {

fs/erofs/internal.h

···
 #include <linux/magic.h>
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
+#include <linux/iomap.h>
 #include "erofs_fs.h"
 
 /* redefine pr_fmt "erofs: " */
···
 #define EROFS_GET_BLOCKS_FIEMAP	0x0002
 
 /* zmap.c */
+extern const struct iomap_ops z_erofs_iomap_report_ops;
+
 #ifdef CONFIG_EROFS_FS_ZIP
 int z_erofs_fill_inode(struct inode *inode);
 int z_erofs_map_blocks_iter(struct inode *inode,
···
 /* data.c */
 extern const struct file_operations erofs_file_fops;
 struct page *erofs_get_meta_page(struct super_block *sb, erofs_blk_t blkaddr);
+int erofs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
+		 u64 start, u64 len);
 
 /* inode.c */
 static inline unsigned long erofs_inode_hash(erofs_nid_t nid)

fs/erofs/namei.c

···
 	.getattr = erofs_getattr,
 	.listxattr = erofs_listxattr,
 	.get_acl = erofs_get_acl,
+	.fiemap = erofs_fiemap,
 };

fs/erofs/zmap.c

···
 	DBG_BUGON(err < 0 && err != -ENOMEM);
 	return err;
 }
+
+static int z_erofs_iomap_begin_report(struct inode *inode, loff_t offset,
+				loff_t length, unsigned int flags,
+				struct iomap *iomap, struct iomap *srcmap)
+{
+	int ret;
+	struct erofs_map_blocks map = { .m_la = offset };
+
+	ret = z_erofs_map_blocks_iter(inode, &map, EROFS_GET_BLOCKS_FIEMAP);
+	if (map.mpage)
+		put_page(map.mpage);
+	if (ret < 0)
+		return ret;
+
+	iomap->bdev = inode->i_sb->s_bdev;
+	iomap->offset = map.m_la;
+	iomap->length = map.m_llen;
+	if (map.m_flags & EROFS_MAP_MAPPED) {
+		iomap->type = IOMAP_MAPPED;
+		iomap->addr = map.m_pa;
+	} else {
+		iomap->type = IOMAP_HOLE;
+		iomap->addr = IOMAP_NULL_ADDR;
+		/*
+		 * No strict rule how to describe extents for post EOF, yet
+		 * we need do like below. Otherwise, iomap itself will get
+		 * into an endless loop on post EOF.
+		 */
+		if (iomap->offset >= inode->i_size)
+			iomap->length = length + map.m_la - offset;
+	}
+	iomap->flags = 0;
+	return 0;
+}
+
+const struct iomap_ops z_erofs_iomap_report_ops = {
+	.iomap_begin = z_erofs_iomap_begin_report,
+};