Re: [Qemu-devel] [PATCH v2 1/2] sheepdog: fix vdi object update after live snapshot

[Liu Yuan]

On Tue, Jun 03, 2014 at 11:58:21PM +0900, Hitoshi Mitake wrote:
> On Tue, Jun 3, 2014 at 9:41 PM, Liu Yuan <address@hidden> wrote:
> > On Tue, Jun 03, 2014 at 01:54:21PM +0900, Hitoshi Mitake wrote:
> >> sheepdog driver should decide a write request is COW or not based on
> >> inode object which is active when the write request is issued.
> >>
> >> Cc: Kevin Wolf <address@hidden>
> >> Cc: Stefan Hajnoczi <address@hidden>
> >> Cc: Liu Yuan <address@hidden>
> >> Cc: MORITA Kazutaka <address@hidden>
> >> Signed-off-by: Hitoshi Mitake <address@hidden>
> >> ---
> >>  block/sheepdog.c |   40 +++++++++++++++++++++++-----------------
> >>  1 files changed, 23 insertions(+), 17 deletions(-)
> >>
> >> diff --git a/block/sheepdog.c b/block/sheepdog.c
> >> index 4ecbf5f..637e57f 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;
> >> @@ -404,7 +405,7 @@ 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;
> >> @@ -418,6 +419,7 @@ 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;
> >> @@ -664,8 +666,8 @@ static int do_req(int sockfd, SheepdogReq *hdr, void 
> >> *data,
> >>  }
> >>
> >>  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);
> >> @@ -698,7 +700,7 @@ 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);
> >>      }
> >>  }
> >> @@ -797,7 +799,7 @@ 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
> >> @@ -1117,8 +1119,8 @@ 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;
> >> @@ -1129,6 +1131,7 @@ 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");
> >> @@ -1315,6 +1318,7 @@ 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;
> >> @@ -1327,7 +1331,8 @@ 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)) {
> >> @@ -1345,17 +1350,17 @@ 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);
> >>      }
> >>  }
> >>
> >> @@ -1849,9 +1854,9 @@ 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;
> >> @@ -2049,7 +2054,8 @@ 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) {
> >> @@ -2058,7 +2064,7 @@ 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;
> >> @@ -2138,9 +2144,9 @@ 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;
> >> --
> >> 1.7.1
> >>
> >
> > Which line is the problem and which line fixes it? Seems not easy to find 
> > it out.
> > I just saw some restructuring of 'create' field.
> >
> 
> The below line in aio_read_response() is the problem:
> 
> > @@ -797,7 +799,7 @@ 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) {

Seems it is not very obvious and to be honest I still don't get the catch why it
is buggy. Could you please describe it in the commit log why this line is
problematic and we have to use ->create to fix it.

Thanks
Yuan