3 files changed, 21 insertions, 8 deletions

diff --git a/fs/erofs/data.c b/fs/erofs/data.c
index e18476c85fa2..fa7ddb7ad980 100644
--- a/fs/erofs/data.c
+++ b/fs/erofs/data.c
@@ -192,6 +192,7 @@ int erofs_map_dev(struct super_block *sb, struct erofs_map_dev *map)
 	/* primary device by default */
 	map->m_bdev = sb->s_bdev;
 	map->m_daxdev = EROFS_SB(sb)->dax_dev;
+	map->m_dax_part_off = EROFS_SB(sb)->dax_part_off;
 
 	if (map->m_deviceid) {
 		down_read(&devs->rwsem);
@@ -202,6 +203,7 @@ int erofs_map_dev(struct super_block *sb, struct erofs_map_dev *map)
 		}
 		map->m_bdev = dif->bdev;
 		map->m_daxdev = dif->dax_dev;
+		map->m_dax_part_off = dif->dax_part_off;
 		up_read(&devs->rwsem);
 	} else if (devs->extra_devices) {
 		down_read(&devs->rwsem);
@@ -218,6 +220,7 @@ int erofs_map_dev(struct super_block *sb, struct erofs_map_dev *map)
 				map->m_pa -= startoff;
 				map->m_bdev = dif->bdev;
 				map->m_daxdev = dif->dax_dev;
+				map->m_dax_part_off = dif->dax_part_off;
 				break;
 			}
 		}
@@ -248,9 +251,13 @@ static int erofs_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
 	if (ret)
 		return ret;
 
-	iomap->bdev = mdev.m_bdev;
-	iomap->dax_dev = mdev.m_daxdev;
 	iomap->offset = map.m_la;
+	if (flags & IOMAP_DAX) {
+		iomap->dax_dev = mdev.m_daxdev;
+		iomap->offset += mdev.m_dax_part_off;
+	} else {
+		iomap->bdev = mdev.m_bdev;
+	}
 	iomap->length = map.m_llen;
 	iomap->flags = 0;
 	iomap->private = NULL;
diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index 3db494a398b2..b8272fb95fd6 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -51,6 +51,7 @@ struct erofs_device_info {
 	char *path;
 	struct block_device *bdev;
 	struct dax_device *dax_dev;
+	u64 dax_part_off;
 
 	u32 blocks;
 	u32 mapped_blkaddr;
@@ -115,6 +116,7 @@ struct erofs_sb_info {
 #endif	/* CONFIG_EROFS_FS_ZIP */
 	struct erofs_dev_context *devs;
 	struct dax_device *dax_dev;
+	u64 dax_part_off;
 	u64 total_blocks;
 	u32 primarydevice_blocks;
 
@@ -467,6 +469,7 @@ static inline int z_erofs_map_blocks_iter(struct inode *inode,
 struct erofs_map_dev {
 	struct block_device *m_bdev;
 	struct dax_device *m_daxdev;
+	u64 m_dax_part_off;
 
 	erofs_off_t m_pa;
 	unsigned int m_deviceid;
diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index 5c137647fa8a..915eefe0d7e2 100644
--- a/fs/erofs/super.c
+++ b/fs/erofs/super.c
@@ -267,7 +267,7 @@ static int erofs_init_devices(struct super_block *sb,
 			break;
 		}
 		dif->bdev = bdev;
-		dif->dax_dev = fs_dax_get_by_bdev(bdev);
+		dif->dax_dev = fs_dax_get_by_bdev(bdev, &dif->dax_part_off);
 		dif->blocks = le32_to_cpu(dis->blocks);
 		dif->mapped_blkaddr = le32_to_cpu(dis->mapped_blkaddr);
 		sbi->total_blocks += dif->blocks;
@@ -597,7 +597,7 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
 
 	sb->s_fs_info = sbi;
 	sbi->opt = ctx->opt;
-	sbi->dax_dev = fs_dax_get_by_bdev(sb->s_bdev);
+	sbi->dax_dev = fs_dax_get_by_bdev(sb->s_bdev, &sbi->dax_part_off);
 	sbi->devs = ctx->devs;
 	ctx->devs = NULL;
 
@@ -605,10 +605,13 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
 	if (err)
 		return err;
 
-	if (test_opt(&sbi->opt, DAX_ALWAYS) &&
-	    !dax_supported(sbi->dax_dev, sb->s_bdev, EROFS_BLKSIZ, 0, bdev_nr_sectors(sb->s_bdev))) {
-		errorfc(fc, "DAX unsupported by block device. Turning off DAX.");
-		clear_opt(&sbi->opt, DAX_ALWAYS);
+	if (test_opt(&sbi->opt, DAX_ALWAYS)) {
+		BUILD_BUG_ON(EROFS_BLKSIZ != PAGE_SIZE);
+
+		if (!sbi->dax_dev) {
+			errorfc(fc, "DAX unsupported by block device. Turning off DAX.");
+			clear_opt(&sbi->opt, DAX_ALWAYS);
+		}
 	}
 	sb->s_flags |= SB_RDONLY | SB_NOATIME;
 	sb->s_maxbytes = MAX_LFS_FILESIZE;