debian/patches/rbd-add-an-asynchronous-flush.patch

   1 From dc7588c1eb3008bda53dde1d6b890cd299758155 Mon Sep 17 00:00:00 2001
   2 From: Josh Durgin <josh.durgin@inktank.com>
   3 Date: Fri, 29 Mar 2013 13:03:23 -0700
   4 Subject: [PATCH] rbd: add an asynchronous flush
   5
   6 The existing bdrv_co_flush_to_disk implementation uses rbd_flush(),
   7 which is sychronous and causes the main qemu thread to block until it
   8 is complete. This results in unresponsiveness and extra latency for
   9 the guest.
  10
  11 Fix this by using an asynchronous version of flush.  This was added to
  12 librbd with a special #define to indicate its presence, since it will
  13 be backported to stable versions. Thus, there is no need to check the
  14 version of librbd.
  15
  16 Implement this as bdrv_aio_flush, since it matches other aio functions
  17 in the rbd block driver, and leave out bdrv_co_flush_to_disk when the
  18 asynchronous version is available.
  19
  20 Reported-by: Oliver Francke <oliver@filoo.de>
  21 Signed-off-by: Josh Durgin <josh.durgin@inktank.com>
  22 Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
  23 ---
  24  block/rbd.c |   37 +++++++++++++++++++++++++++++++++----
  25  1 files changed, 33 insertions(+), 4 deletions(-)
  26
  27 diff --git a/block/rbd.c b/block/rbd.c
  28 index 1a8ea6d..141b488 100644
  29 --- a/block/rbd.c
  30 +++ b/block/rbd.c
  31 @@ -63,7 +63,8 @@
  32  typedef enum {
  33      RBD_AIO_READ,
  34      RBD_AIO_WRITE,
  35 -    RBD_AIO_DISCARD
  36 +    RBD_AIO_DISCARD,
  37 +    RBD_AIO_FLUSH
  38  } RBDAIOCmd;
  39
  40  typedef struct RBDAIOCB {
  41 @@ -379,8 +380,7 @@ static void qemu_rbd_complete_aio(RADOSCB *rcb)
  42
  43      r = rcb->ret;
  44
  45 -    if (acb->cmd == RBD_AIO_WRITE ||
  46 -        acb->cmd == RBD_AIO_DISCARD) {
  47 +    if (acb->cmd != RBD_AIO_READ) {
  48          if (r < 0) {
  49              acb->ret = r;
  50              acb->error = 1;
  51 @@ -659,6 +659,16 @@ static int rbd_aio_discard_wrapper(rbd_image_t image,
  52  #endif
  53  }
  54
  55 +static int rbd_aio_flush_wrapper(rbd_image_t image,
  56 +                                 rbd_completion_t comp)
  57 +{
  58 +#ifdef LIBRBD_SUPPORTS_AIO_FLUSH
  59 +    return rbd_aio_flush(image, comp);
  60 +#else
  61 +    return -ENOTSUP;
  62 +#endif
  63 +}
  64 +
  65  static BlockDriverAIOCB *rbd_start_aio(BlockDriverState *bs,
  66                                         int64_t sector_num,
  67                                         QEMUIOVector *qiov,
  68 @@ -679,7 +689,7 @@ static BlockDriverAIOCB *rbd_start_aio(BlockDriverState *bs,
  69      acb = qemu_aio_get(&rbd_aiocb_info, bs, cb, opaque);
  70      acb->cmd = cmd;
  71      acb->qiov = qiov;
  72 -    if (cmd == RBD_AIO_DISCARD) {
  73 +    if (cmd == RBD_AIO_DISCARD || cmd == RBD_AIO_FLUSH) {
  74          acb->bounce = NULL;
  75      } else {
  76          acb->bounce = qemu_blockalign(bs, qiov->size);
  77 @@ -723,6 +733,9 @@ static BlockDriverAIOCB *rbd_start_aio(BlockDriverState *bs,
  78      case RBD_AIO_DISCARD:
  79          r = rbd_aio_discard_wrapper(s->image, off, size, c);
  80          break;
  81 +    case RBD_AIO_FLUSH:
  82 +        r = rbd_aio_flush_wrapper(s->image, c);
  83 +        break;
  84      default:
  85          r = -EINVAL;
  86      }
  87 @@ -762,6 +775,16 @@ static BlockDriverAIOCB *qemu_rbd_aio_writev(BlockDriverState *bs,
  88                           RBD_AIO_WRITE);
  89  }
  90
  91 +#ifdef LIBRBD_SUPPORTS_AIO_FLUSH
  92 +static BlockDriverAIOCB *qemu_rbd_aio_flush(BlockDriverState *bs,
  93 +                                            BlockDriverCompletionFunc *cb,
  94 +                                            void *opaque)
  95 +{
  96 +    return rbd_start_aio(bs, 0, NULL, 0, cb, opaque, RBD_AIO_FLUSH);
  97 +}
  98 +
  99 +#else
 100 +
 101  static int qemu_rbd_co_flush(BlockDriverState *bs)
 102  {
 103  #if LIBRBD_VERSION_CODE >= LIBRBD_VERSION(0, 1, 1)
 104 @@ -772,6 +795,7 @@ static int qemu_rbd_co_flush(BlockDriverState *bs)
 105      return 0;
 106  #endif
 107  }
 108 +#endif
 109
 110  static int qemu_rbd_getinfo(BlockDriverState *bs, BlockDriverInfo *bdi)
 111  {
 112 @@ -949,7 +973,12 @@ static BlockDriver bdrv_rbd = {
 113
 114      .bdrv_aio_readv         = qemu_rbd_aio_readv,
 115      .bdrv_aio_writev        = qemu_rbd_aio_writev,
 116 +
 117 +#ifdef LIBRBD_SUPPORTS_AIO_FLUSH
 118 +    .bdrv_aio_flush         = qemu_rbd_aio_flush,
 119 +#else
 120      .bdrv_co_flush_to_disk  = qemu_rbd_co_flush,
 121 +#endif
 122
 123  #ifdef LIBRBD_SUPPORTS_DISCARD
 124      .bdrv_aio_discard       = qemu_rbd_aio_discard,
 125 --
 126 1.7.0.4
 127