[sheepdog] [PATCH v9 01/19] sheep: introduce generational reference counting for object reclaim
Hitoshi Mitake
mitake.hitoshi at gmail.com
Thu May 22 16:30:19 CEST 2014
Generational reference counting is an algorithm to reclaim data
efficiently without race conditions on distributed system. This
extends vdi objects structure to store generational reference counts,
and increments the counts when creating snapshots.
Cc: MORITA Kazutaka <morita.kazutaka at lab.ntt.co.jp>
Cc: Alessandro Bolgia <alessandro at extensys.it>
Tested-by: Valerio Pachera <sirio81 at gmail.com>
Signed-off-by: Hitoshi Mitake <mitake.hitoshi at lab.ntt.co.jp>
---
v7:
- fix invalid inheritance of reference count
v6:
- update store format in another patch, not in this one
v5:
- update store version and break compatibility explicitly
- rename data_ref -> gref
v4:
- remove a bug in snapshot_vdi(), storing an invalid number of references
include/sheepdog_proto.h | 6 ++++
sheep/vdi.c | 88 ++++++++++++++++++++++++++++++++++++++++--------
2 files changed, 80 insertions(+), 14 deletions(-)
diff --git a/include/sheepdog_proto.h b/include/sheepdog_proto.h
index 9361bad..9937497 100644
--- a/include/sheepdog_proto.h
+++ b/include/sheepdog_proto.h
@@ -212,6 +212,11 @@ struct sd_rsp {
};
};
+struct generation_reference {
+ int32_t generation;
+ int32_t count;
+};
+
struct sd_inode {
char name[SD_MAX_VDI_LEN];
char tag[SD_MAX_VDI_TAG_LEN];
@@ -230,6 +235,7 @@ struct sd_inode {
uint32_t child_vdi_id[MAX_CHILDREN];
uint32_t data_vdi_id[SD_INODE_DATA_INDEX];
uint32_t btree_counter;
+ struct generation_reference gref[SD_INODE_DATA_INDEX];
};
struct sd_index {
diff --git a/sheep/vdi.c b/sheep/vdi.c
index baac2f9..4a8c4f7 100644
--- a/sheep/vdi.c
+++ b/sheep/vdi.c
@@ -224,7 +224,8 @@ out:
static struct sd_inode *alloc_inode(const struct vdi_iocb *iocb,
uint32_t new_snapid, uint32_t new_vid,
- uint32_t *data_vdi_id)
+ uint32_t *data_vdi_id,
+ struct generation_reference *gref)
{
struct sd_inode *new = xzalloc(sizeof(*new));
unsigned long block_size = SD_DATA_OBJ_SIZE;
@@ -246,6 +247,17 @@ static struct sd_inode *alloc_inode(const struct vdi_iocb *iocb,
else if (new->store_policy)
sd_inode_init(new->data_vdi_id, 1);
+ if (gref) {
+ assert(data_vdi_id);
+
+ for (int i = 0; i < SD_INODE_DATA_INDEX; i++) {
+ if (!data_vdi_id[i])
+ continue;
+
+ new->gref[i].generation = gref[i].generation + 1;
+ }
+ }
+
return new;
}
@@ -264,7 +276,8 @@ static int find_free_idx(uint32_t *vdi_id, size_t max_idx)
static int create_vdi(const struct vdi_iocb *iocb, uint32_t new_snapid,
uint32_t new_vid)
{
- struct sd_inode *new = alloc_inode(iocb, new_snapid, new_vid, NULL);
+ struct sd_inode *new = alloc_inode(iocb, new_snapid, new_vid, NULL,
+ NULL);
int ret;
sd_debug("%s: size %" PRIu64 ", new_vid %" PRIx32 ", copies %d, "
@@ -323,18 +336,22 @@ static int clone_vdi(const struct vdi_iocb *iocb, uint32_t new_snapid,
/* TODO: multiple sd_write_object should be performed atomically */
- /* update a base vdi */
- ret = sd_write_object(vid_to_vdi_oid(base_vid), (char *)&new_vid,
- sizeof(new_vid),
- offsetof(struct sd_inode, child_vdi_id[idx]),
- false);
+ for (int i = 0; i < ARRAY_SIZE(base->gref); i++) {
+ if (base->data_vdi_id[i])
+ base->gref[i].count++;
+ }
+
+ ret = sd_write_object(vid_to_vdi_oid(base_vid), (char *)base->gref,
+ sizeof(base->gref),
+ offsetof(struct sd_inode, gref), false);
if (ret != SD_RES_SUCCESS) {
ret = SD_RES_BASE_VDI_WRITE;
goto out;
}
/* create a new vdi */
- new = alloc_inode(iocb, new_snapid, new_vid, base->data_vdi_id);
+ new = alloc_inode(iocb, new_snapid, new_vid, base->data_vdi_id,
+ base->gref);
ret = sd_write_object(vid_to_vdi_oid(new_vid), (char *)new,
sizeof(*new), 0, true);
if (ret != SD_RES_SUCCESS)
@@ -373,7 +390,7 @@ static int snapshot_vdi(const struct vdi_iocb *iocb, uint32_t new_snapid,
base_vid, iocb->nr_copies, new_snapid);
ret = sd_read_object(vid_to_vdi_oid(base_vid), (char *)base,
- sizeof(*base), 0);
+ SD_INODE_HEADER_SIZE, 0);
if (ret != SD_RES_SUCCESS) {
ret = SD_RES_BASE_VDI_READ;
goto out;
@@ -390,15 +407,47 @@ static int snapshot_vdi(const struct vdi_iocb *iocb, uint32_t new_snapid,
/* update a base vdi */
base->snap_ctime = iocb->time;
base->child_vdi_id[idx] = new_vid;
+
+ /* TODO: multiple sd_write_object should be performed atomically */
+
ret = sd_write_object(vid_to_vdi_oid(base_vid), (char *)base,
SD_INODE_HEADER_SIZE, 0, false);
if (ret != SD_RES_SUCCESS) {
+ sd_err("updating header of VDI %" PRIx32 "failed", base_vid);
+ ret = SD_RES_BASE_VDI_WRITE;
+ goto out;
+ }
+
+ ret = sd_read_object(vid_to_vdi_oid(base_vid), (char *)base,
+ sizeof(*base), 0);
+ if (ret != SD_RES_SUCCESS) {
+ ret = SD_RES_BASE_VDI_READ;
+ goto out;
+ }
+
+ for (int i = 0; i < ARRAY_SIZE(base->gref); i++) {
+ if (!base->data_vdi_id[i])
+ continue;
+
+ base->gref[i].count++;
+ }
+
+ ret = sd_write_object(vid_to_vdi_oid(base_vid), (char *)base,
+ sizeof(*base), 0, false);
+ if (ret != SD_RES_SUCCESS) {
+ sd_err("updating gref of VDI %" PRIx32 "failed", base_vid);
ret = SD_RES_BASE_VDI_WRITE;
goto out;
}
/* create a new vdi */
- new = alloc_inode(iocb, new_snapid, new_vid, base->data_vdi_id);
+ new = alloc_inode(iocb, new_snapid, new_vid, base->data_vdi_id, NULL);
+ for (int i = 0; i < ARRAY_SIZE(base->gref); i++) {
+ if (!base->data_vdi_id[i])
+ continue;
+
+ new->gref[i].generation = base->gref[i].generation + 1;
+ }
ret = sd_write_object(vid_to_vdi_oid(new_vid), (char *)new,
sizeof(*new), 0, true);
if (ret != SD_RES_SUCCESS)
@@ -456,10 +505,20 @@ static int rebase_vdi(const struct vdi_iocb *iocb, uint32_t new_snapid,
/* TODO: multiple sd_write_object should be performed atomically */
+ ret = sd_write_object(vid_to_vdi_oid(cur_vid), (char *)&iocb->time,
+ sizeof(iocb->time),
+ offsetof(struct sd_inode, snap_ctime), false);
+ if (ret != SD_RES_SUCCESS) {
+ ret = SD_RES_VDI_WRITE;
+ goto out;
+ }
+
+ for (int i = 0; i < ARRAY_SIZE(base->gref); i++)
+ base->gref[i].count++;
/* update current working vdi */
- ret = sd_write_object(vid_to_vdi_oid(cur_vid), (char *)&iocb->time,
- sizeof(iocb->time),
- offsetof(struct sd_inode, snap_ctime), false);
+ ret = sd_write_object(vid_to_vdi_oid(base_vid), (char *)base->gref,
+ sizeof(base->gref),
+ offsetof(struct sd_inode, gref), false);
if (ret != SD_RES_SUCCESS) {
ret = SD_RES_VDI_WRITE;
goto out;
@@ -476,7 +535,8 @@ static int rebase_vdi(const struct vdi_iocb *iocb, uint32_t new_snapid,
}
/* create a new vdi */
- new = alloc_inode(iocb, new_snapid, new_vid, base->data_vdi_id);
+ new = alloc_inode(iocb, new_snapid, new_vid, base->data_vdi_id,
+ base->gref);
ret = sd_write_object(vid_to_vdi_oid(new_vid), (char *)new,
sizeof(*new), 0, true);
if (ret != SD_RES_SUCCESS)
--
1.9.1
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