This change doesn't affect behavior of sheepdog driver. Just for
documentation purpose.
Signed-off-by: Hitoshi Mitake <mitake.hitoshi@xxxxxxxxxxxxx>
---
usr/bs_sheepdog.c | 21 +++++++++++++++++++--
1 file changed, 19 insertions(+), 2 deletions(-)
diff --git a/usr/bs_sheepdog.c b/usr/bs_sheepdog.c
index a333675..15f44d8 100644
--- a/usr/bs_sheepdog.c
+++ b/usr/bs_sheepdog.c
@@ -193,6 +193,19 @@ struct sheepdog_vdi_rsp {
uint32_t pad[5];
};
+/*
+ * Historical notes: previous version of sheepdog (< v0.9.0) has a limit of
+ * maximum number of children which can be created from single VDI. So the inode
+ * object has an array for storing the IDs of the child VDIs. The constant
+ * OLD_MAX_CHILDREN represents it. Current sheepdog doesn't have the limitation,
+ * so we are recycling the area (4 * OLD_MAX_CHILDREN = 4KB) for storing new
+ * metadata.
+ *
+ * users of the released area:
+ * - uint32_t btree_counter
+ */
+#define OLD_MAX_CHILDREN 1024U
+
struct sheepdog_inode {
char name[SD_MAX_VDI_LEN];
char tag[SD_MAX_VDI_TAG_LEN];
@@ -201,13 +214,17 @@ struct sheepdog_inode {
uint64_t vm_clock_nsec;
uint64_t vdi_size;
uint64_t vm_state_size;
- uint16_t copy_policy;
+ uint8_t copy_policy;
+ uint8_t store_policy;
uint8_t nr_copies;
uint8_t block_size_shift;
uint32_t snap_id;
uint32_t vdi_id;
uint32_t parent_vdi_id;
- uint32_t child_vdi_id[MAX_CHILDREN];
+
+ uint32_t btree_counter;
+ uint32_t __unused[OLD_MAX_CHILDREN - 1];
+
uint32_t data_vdi_id[MAX_DATA_OBJS];
};
--
1.9.1
--
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