Re: [Qemu-devel] [PATCH v4] sheepdog: selectable object size support

[Liu Yuan <namei.unix@gmail.com>]

On Tue, Feb 10, 2015 at 11:10:51AM +0800, Liu Yuan wrote:
> On Tue, Jan 27, 2015 at 05:35:27PM +0900, Teruaki Ishizaki wrote:
> > Previously, qemu block driver of sheepdog used hard-coded VDI object size.
> > This patch enables users to handle "block_size_shift" value for
> > calculating VDI object size.
> > 
> > When you start qemu, you don't need to specify additional command option.
> > 
> > But when you create the VDI which doesn't have default object size
> > with qemu-img command, you specify block_size_shift option.
> > 
> > If you want to create a VDI of 8MB(1 << 23) object size,
> > you need to specify following command option.
> > 
> >  # qemu-img create -o block_size_shift=23 sheepdog:test1 100M
> > 
> > In addition, when you don't specify qemu-img command option,
> > a default value of sheepdog cluster is used for creating VDI.
> > 
> >  # qemu-img create sheepdog:test2 100M
> > 
> > Signed-off-by: Teruaki Ishizaki <ishizaki.teruaki@lab.ntt.co.jp>
> > ---
> > V4:
> >  - Limit a read/write buffer size for creating a preallocated VDI.
> >  - Replace a parse function for the block_size_shift option.
> >  - Fix an error message.
> > 
> > V3:
> >  - Delete the needless operation of buffer.
> >  - Delete the needless operations of request header.
> >    for SD_OP_GET_CLUSTER_DEFAULT.
> >  - Fix coding style problems.
> > 
> > V2:
> >  - Fix coding style problem (white space).
> >  - Add members, store_policy and block_size_shift to struct SheepdogVdiReq.
> >  - Initialize request header to use block_size_shift specified by user.
> > ---
> >  block/sheepdog.c          |  138 ++++++++++++++++++++++++++++++++++++++-------
> >  include/block/block_int.h |    1 +
> >  2 files changed, 119 insertions(+), 20 deletions(-)
> > 
> > diff --git a/block/sheepdog.c b/block/sheepdog.c
> > index be3176f..a43b947 100644
> > --- a/block/sheepdog.c
> > +++ b/block/sheepdog.c
> > @@ -37,6 +37,7 @@
> >  #define SD_OP_READ_VDIS      0x15
> >  #define SD_OP_FLUSH_VDI      0x16
> >  #define SD_OP_DEL_VDI        0x17
> > +#define SD_OP_GET_CLUSTER_DEFAULT   0x18
> >  
> >  #define SD_FLAG_CMD_WRITE    0x01
> >  #define SD_FLAG_CMD_COW      0x02
> > @@ -167,7 +168,8 @@ typedef struct SheepdogVdiReq {
> >      uint32_t base_vdi_id;
> >      uint8_t copies;
> >      uint8_t copy_policy;
> > -    uint8_t reserved[2];
> > +    uint8_t store_policy;
> > +    uint8_t block_size_shift;
> >      uint32_t snapid;
> >      uint32_t type;
> >      uint32_t pad[2];
> > @@ -186,6 +188,21 @@ typedef struct SheepdogVdiRsp {
> >      uint32_t pad[5];
> >  } SheepdogVdiRsp;
> >  
> > +typedef struct SheepdogClusterRsp {
> > +    uint8_t proto_ver;
> > +    uint8_t opcode;
> > +    uint16_t flags;
> > +    uint32_t epoch;
> > +    uint32_t id;
> > +    uint32_t data_length;
> > +    uint32_t result;
> > +    uint8_t nr_copies;
> > +    uint8_t copy_policy;
> > +    uint8_t block_size_shift;
> > +    uint8_t __pad1;
> > +    uint32_t __pad2[6];
> > +} SheepdogClusterRsp;
> > +
> >  typedef struct SheepdogInode {
> >      char name[SD_MAX_VDI_LEN];
> >      char tag[SD_MAX_VDI_TAG_LEN];
> > @@ -1544,6 +1561,7 @@ static int do_sd_create(BDRVSheepdogState *s, uint32_t *vdi_id, int snapshot,
> >      hdr.vdi_size = s->inode.vdi_size;
> >      hdr.copy_policy = s->inode.copy_policy;
> >      hdr.copies = s->inode.nr_copies;
> > +    hdr.block_size_shift = s->inode.block_size_shift;
> >  
> >      ret = do_req(fd, s->aio_context, (SheepdogReq *)&hdr, buf, &wlen, &rlen);
> >  
> > @@ -1569,9 +1587,12 @@ static int do_sd_create(BDRVSheepdogState *s, uint32_t *vdi_id, int snapshot,
> >  static int sd_prealloc(const char *filename, Error **errp)
> >  {
> >      BlockDriverState *bs = NULL;
> > +    BDRVSheepdogState *base = NULL;
> > +    unsigned long buf_size;
> >      uint32_t idx, max_idx;
> > +    uint32_t object_size;
> >      int64_t vdi_size;
> > -    void *buf = g_malloc0(SD_DATA_OBJ_SIZE);
> > +    void *buf = NULL;
> >      int ret;
> >  
> >      ret = bdrv_open(&bs, filename, NULL, NULL, BDRV_O_RDWR | BDRV_O_PROTOCOL,
> > @@ -1585,18 +1606,24 @@ static int sd_prealloc(const char *filename, Error **errp)
> >          ret = vdi_size;
> >          goto out;
> >      }
> > -    max_idx = DIV_ROUND_UP(vdi_size, SD_DATA_OBJ_SIZE);
> > +
> > +    base = bs->opaque;
> > +    object_size = (UINT32_C(1) << base->inode.block_size_shift);
> > +    buf_size = MIN(object_size, SD_DATA_OBJ_SIZE);
> > +    buf = g_malloc0(buf_size);
> > +
> > +    max_idx = DIV_ROUND_UP(vdi_size, buf_size);
> >  
> >      for (idx = 0; idx < max_idx; idx++) {
> >          /*
> >           * The created image can be a cloned image, so we need to read
> >           * a data from the source image.
> >           */
> > -        ret = bdrv_pread(bs, idx * SD_DATA_OBJ_SIZE, buf, SD_DATA_OBJ_SIZE);
> > +        ret = bdrv_pread(bs, idx * buf_size, buf, buf_size);
> >          if (ret < 0) {
> >              goto out;
> >          }
> > -        ret = bdrv_pwrite(bs, idx * SD_DATA_OBJ_SIZE, buf, SD_DATA_OBJ_SIZE);
> > +        ret = bdrv_pwrite(bs, idx * buf_size, buf, buf_size);
> >          if (ret < 0) {
> >              goto out;
> >          }
> > @@ -1669,6 +1696,21 @@ static int parse_redundancy(BDRVSheepdogState *s, const char *opt)
> >      return 0;
> >  }
> >  
> > +static int parse_block_size_shift(BDRVSheepdogState *s, QemuOpts *opt)
> > +{
> > +    struct SheepdogInode *inode = &s->inode;
> > +    inode->block_size_shift =
> > +        (uint8_t)qemu_opt_get_number_del(opt, "block_size_shift", 0);
> > +    if (inode->block_size_shift == 0) {
> > +        /* block_size_shift is set for cluster default value by sheepdog */
> > +        return 0;
> > +    } else if (inode->block_size_shift < 20 || inode->block_size_shift > 31) {
> > +        return -EINVAL;
> > +    }
> > +
> > +    return 0;
> > +}
> > +
> >  static int sd_create(const char *filename, QemuOpts *opts,
> >                       Error **errp)
> >  {
> > @@ -1679,6 +1721,7 @@ static int sd_create(const char *filename, QemuOpts *opts,
> >      BDRVSheepdogState *s;
> >      char tag[SD_MAX_VDI_TAG_LEN];
> >      uint32_t snapid;
> > +    uint64_t max_vdi_size;
> >      bool prealloc = false;
> >  
> >      s = g_new0(BDRVSheepdogState, 1);
> > @@ -1718,9 +1761,10 @@ static int sd_create(const char *filename, QemuOpts *opts,
> >          }
> >      }
> >  
> > -    if (s->inode.vdi_size > SD_MAX_VDI_SIZE) {
> > -        error_setg(errp, "too big image size");
> > -        ret = -EINVAL;
> > +    ret = parse_block_size_shift(s, opts);
> > +    if (ret < 0) {
> > +        error_setg(errp, "Invalid block_size_shift:"
> > +                         " '%s'. please use 20-31", buf);
> >          goto out;
> >      }
> >  
> > @@ -1757,6 +1801,47 @@ static int sd_create(const char *filename, QemuOpts *opts,
> >      }
> >  
> >      s->aio_context = qemu_get_aio_context();
> > +
> > +    /* if block_size_shift is not specified, get cluster default value */
> > +    if (s->inode.block_size_shift == 0) {
> 
> Seems that we don't keep backward compatibility for new QEMU and old sheep that
> doesn't support SD_OP_GET_CLUSTER_DEFAULT.
> 
> What will happen if old QEMU with new sheep that support block_size_shift? Most
> distributions will ship the old stable qemu that wouldn't be aware of
> block_size_shift.
> 
> I'd suggest we have 0 in block_size_shift represent 4MB to keep backward
> compatiblity.

How about make this additional field as the factor to multiply 4MB? that is,

(x + 1) * 4MB

qemu-img create -o object_size=8MB test 1G

will have x set as 1 and the formula will equal to 8MB.

-o object_size=4MB will set x as 0 and default value for x is 0 too to keep
backward compatiblity.

Thanks
Yuan