[Qemu-devel] [PULL 37/42] sheepdog: fix vdi object update after live snapshot

[Stefan Hajnoczi <stefanha@redhat.com>]

From: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>

sheepdog driver should decide a write request is COW or not based on inode
object which is active when the write request is issued.

Example of wrong inode update path in the previous driver:
1. drier issues an ordinal write request to an existing object
2. user creates a snapshot of the VDI before the write request is completed
3. the respones for the request is RDONLY, because the VDI is already a snapshot
4. the driver reload an inode object of the new active VDI, then issues a write
   request again
5. the second write request can be completed
6. driver decide the request is COW or not with the below conditional branch:
   	  if (s->inode.data_vdi_id[idx] != s->inode.vdi_id) {
7. the ID of the written object and VID of the new active VDI is different, so
   the driver updates data_vdi_id[idx] and writes inode object
8. the existing object cannot be seen by the new active VDI, it results object
   leaking

Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Liu Yuan <namei.unix@gmail.com>
Cc: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Signed-off-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 block/sheepdog.c | 40 +++++++++++++++++++++++-----------------
 1 file changed, 23 insertions(+), 17 deletions(-)

diff --git a/block/sheepdog.c b/block/sheepdog.c
index 9175cc2..5f7e025 100644
--- a/block/sheepdog.c
+++ b/block/sheepdog.c
@@ -282,6 +282,7 @@ typedef struct AIOReq {
     unsigned int data_len;
     uint8_t flags;
     uint32_t id;
+    bool create;
 
     QLIST_ENTRY(AIOReq) aio_siblings;
 } AIOReq;
@@ -405,7 +406,7 @@ static const char * sd_strerror(int err)
 
 static inline AIOReq *alloc_aio_req(BDRVSheepdogState *s, SheepdogAIOCB *acb,
                                     uint64_t oid, unsigned int data_len,
-                                    uint64_t offset, uint8_t flags,
+                                    uint64_t offset, uint8_t flags, bool create,
                                     uint64_t base_oid, unsigned int iov_offset)
 {
     AIOReq *aio_req;
@@ -419,6 +420,7 @@ static inline AIOReq *alloc_aio_req(BDRVSheepdogState *s, SheepdogAIOCB *acb,
     aio_req->data_len = data_len;
     aio_req->flags = flags;
     aio_req->id = s->aioreq_seq_num++;
+    aio_req->create = create;
 
     acb->nr_pending++;
     return aio_req;
@@ -667,8 +669,8 @@ static int do_req(int sockfd, AioContext *aio_context, SheepdogReq *hdr,
 }
 
 static void coroutine_fn add_aio_request(BDRVSheepdogState *s, AIOReq *aio_req,
-                           struct iovec *iov, int niov, bool create,
-                           enum AIOCBState aiocb_type);
+                                         struct iovec *iov, int niov,
+                                         enum AIOCBState aiocb_type);
 static void coroutine_fn resend_aioreq(BDRVSheepdogState *s, AIOReq *aio_req);
 static int reload_inode(BDRVSheepdogState *s, uint32_t snapid, const char *tag);
 static int get_sheep_fd(BDRVSheepdogState *s, Error **errp);
@@ -701,7 +703,7 @@ static void coroutine_fn send_pending_req(BDRVSheepdogState *s, uint64_t oid)
         /* move aio_req from pending list to inflight one */
         QLIST_REMOVE(aio_req, aio_siblings);
         QLIST_INSERT_HEAD(&s->inflight_aio_head, aio_req, aio_siblings);
-        add_aio_request(s, aio_req, acb->qiov->iov, acb->qiov->niov, false,
+        add_aio_request(s, aio_req, acb->qiov->iov, acb->qiov->niov,
                         acb->aiocb_type);
     }
 }
@@ -800,7 +802,7 @@ static void coroutine_fn aio_read_response(void *opaque)
         }
         idx = data_oid_to_idx(aio_req->oid);
 
-        if (s->inode.data_vdi_id[idx] != s->inode.vdi_id) {
+        if (aio_req->create) {
             /*
              * If the object is newly created one, we need to update
              * the vdi object (metadata object).  min_dirty_data_idx
@@ -1120,8 +1122,8 @@ out:
 }
 
 static void coroutine_fn add_aio_request(BDRVSheepdogState *s, AIOReq *aio_req,
-                           struct iovec *iov, int niov, bool create,
-                           enum AIOCBState aiocb_type)
+                                         struct iovec *iov, int niov,
+                                         enum AIOCBState aiocb_type)
 {
     int nr_copies = s->inode.nr_copies;
     SheepdogObjReq hdr;
@@ -1132,6 +1134,7 @@ static void coroutine_fn add_aio_request(BDRVSheepdogState *s, AIOReq *aio_req,
     uint64_t offset = aio_req->offset;
     uint8_t flags = aio_req->flags;
     uint64_t old_oid = aio_req->base_oid;
+    bool create = aio_req->create;
 
     if (!nr_copies) {
         error_report("bug");
@@ -1324,6 +1327,7 @@ static bool check_simultaneous_create(BDRVSheepdogState *s, AIOReq *aio_req)
             DPRINTF("simultaneous create to %" PRIx64 "\n", aio_req->oid);
             aio_req->flags = 0;
             aio_req->base_oid = 0;
+            aio_req->create = false;
             QLIST_REMOVE(aio_req, aio_siblings);
             QLIST_INSERT_HEAD(&s->pending_aio_head, aio_req, aio_siblings);
             return true;
@@ -1336,7 +1340,8 @@ static bool check_simultaneous_create(BDRVSheepdogState *s, AIOReq *aio_req)
 static void coroutine_fn resend_aioreq(BDRVSheepdogState *s, AIOReq *aio_req)
 {
     SheepdogAIOCB *acb = aio_req->aiocb;
-    bool create = false;
+
+    aio_req->create = false;
 
     /* check whether this request becomes a CoW one */
     if (acb->aiocb_type == AIOCB_WRITE_UDATA && is_data_obj(aio_req->oid)) {
@@ -1354,17 +1359,17 @@ static void coroutine_fn resend_aioreq(BDRVSheepdogState *s, AIOReq *aio_req)
             aio_req->base_oid = vid_to_data_oid(s->inode.data_vdi_id[idx], idx);
             aio_req->flags |= SD_FLAG_CMD_COW;
         }
-        create = true;
+        aio_req->create = true;
     }
 out:
     if (is_data_obj(aio_req->oid)) {
-        add_aio_request(s, aio_req, acb->qiov->iov, acb->qiov->niov, create,
+        add_aio_request(s, aio_req, acb->qiov->iov, acb->qiov->niov,
                         acb->aiocb_type);
     } else {
         struct iovec iov;
         iov.iov_base = &s->inode;
         iov.iov_len = sizeof(s->inode);
-        add_aio_request(s, aio_req, &iov, 1, false, AIOCB_WRITE_UDATA);
+        add_aio_request(s, aio_req, &iov, 1, AIOCB_WRITE_UDATA);
     }
 }
 
@@ -1877,9 +1882,9 @@ static void coroutine_fn sd_write_done(SheepdogAIOCB *acb)
         iov.iov_base = &s->inode;
         iov.iov_len = sizeof(s->inode);
         aio_req = alloc_aio_req(s, acb, vid_to_vdi_oid(s->inode.vdi_id),
-                                data_len, offset, 0, 0, offset);
+                                data_len, offset, 0, false, 0, offset);
         QLIST_INSERT_HEAD(&s->inflight_aio_head, aio_req, aio_siblings);
-        add_aio_request(s, aio_req, &iov, 1, false, AIOCB_WRITE_UDATA);
+        add_aio_request(s, aio_req, &iov, 1, AIOCB_WRITE_UDATA);
 
         acb->aio_done_func = sd_finish_aiocb;
         acb->aiocb_type = AIOCB_WRITE_UDATA;
@@ -2078,7 +2083,8 @@ static int coroutine_fn sd_co_rw_vector(void *p)
             DPRINTF("new oid %" PRIx64 "\n", oid);
         }
 
-        aio_req = alloc_aio_req(s, acb, oid, len, offset, flags, old_oid, done);
+        aio_req = alloc_aio_req(s, acb, oid, len, offset, flags, create,
+                                old_oid, done);
         QLIST_INSERT_HEAD(&s->inflight_aio_head, aio_req, aio_siblings);
 
         if (create) {
@@ -2087,7 +2093,7 @@ static int coroutine_fn sd_co_rw_vector(void *p)
             }
         }
 
-        add_aio_request(s, aio_req, acb->qiov->iov, acb->qiov->niov, create,
+        add_aio_request(s, aio_req, acb->qiov->iov, acb->qiov->niov,
                         acb->aiocb_type);
     done:
         offset = 0;
@@ -2167,9 +2173,9 @@ static int coroutine_fn sd_co_flush_to_disk(BlockDriverState *bs)
     acb->aio_done_func = sd_finish_aiocb;
 
     aio_req = alloc_aio_req(s, acb, vid_to_vdi_oid(s->inode.vdi_id),
-                            0, 0, 0, 0, 0);
+                            0, 0, 0, false, 0, 0);
     QLIST_INSERT_HEAD(&s->inflight_aio_head, aio_req, aio_siblings);
-    add_aio_request(s, aio_req, NULL, 0, false, acb->aiocb_type);
+    add_aio_request(s, aio_req, NULL, 0, acb->aiocb_type);
 
     qemu_coroutine_yield();
     return acb->ret;
-- 
1.9.3