[PATCH v4 19/21] erofs: implement fscache-based data read for data blobs

[Jeffle Xu <jefflexu@xxxxxxxxxxxxxxxxx>]

This patch implements the data plane of reading data from data blob file
over fscache.

Signed-off-by: Jeffle Xu <jefflexu@xxxxxxxxxxxxxxxxx>
---
 fs/erofs/data.c     |  3 +++
 fs/erofs/fscache.c  | 16 +++++++++++++---
 fs/erofs/internal.h |  1 +
 3 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/fs/erofs/data.c b/fs/erofs/data.c
index 1bff99576883..c5ccf55c050c 100644
--- a/fs/erofs/data.c
+++ b/fs/erofs/data.c
@@ -200,6 +200,7 @@ int erofs_map_dev(struct super_block *sb, struct erofs_map_dev *map)
 	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;
+	map->m_ctx = EROFS_SB(sb)->bootstrap;
 
 	if (map->m_deviceid) {
 		down_read(&devs->rwsem);
@@ -211,6 +212,7 @@ 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;
+		map->m_ctx = dif->ctx;
 		up_read(&devs->rwsem);
 	} else if (devs->extra_devices) {
 		down_read(&devs->rwsem);
@@ -228,6 +230,7 @@ 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;
+				map->m_ctx = dif->ctx;
 				break;
 			}
 		}
diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index 4da148cc4484..89c533ad965e 100644
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -70,11 +70,21 @@ static inline int erofs_fscache_get_map(struct erofs_fscache_map *fsmap,
 					struct erofs_map_blocks *map,
 					struct super_block *sb)
 {
-	struct erofs_sb_info *sbi = EROFS_SB(sb);
+	struct erofs_map_dev mdev;
+	int ret;
+
+	mdev = (struct erofs_map_dev) {
+		.m_deviceid = map->m_deviceid,
+		.m_pa = map->m_pa,
+	};
+
+	ret = erofs_map_dev(sb, &mdev);
+	if (ret)
+		return ret;
 
-	fsmap->m_ctx  = sbi->bootstrap;
+	fsmap->m_ctx  = mdev.m_ctx;
+	fsmap->m_pa   = mdev.m_pa;
 	fsmap->m_la   = map->m_la;
-	fsmap->m_pa   = map->m_pa;
 	fsmap->m_llen = map->m_llen;
 
 	return 0;
diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index 5d514c7b73cc..6ccf14952b2d 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -486,6 +486,7 @@ struct erofs_map_dev {
 	struct block_device *m_bdev;
 	struct dax_device *m_daxdev;
 	u64 m_dax_part_off;
+	struct erofs_fscache_context *m_ctx;
 
 	erofs_off_t m_pa;
 	unsigned int m_deviceid;
-- 
2.27.0