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Re: [Qemu-devel] [PATCH v3] sheepdog: selectable object size support


From: Kevin Wolf
Subject: Re: [Qemu-devel] [PATCH v3] sheepdog: selectable object size support
Date: Fri, 23 Jan 2015 14:53:19 +0100
User-agent: Mutt/1.5.21 (2010-09-15)

Am 23.01.2015 um 09:24 hat Teruaki Ishizaki geschrieben:
> 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 <address@hidden>
> ---
> 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          |  140 
> ++++++++++++++++++++++++++++++++++++++-------
>  include/block/block_int.h |    1 +
>  2 files changed, 119 insertions(+), 22 deletions(-)
> 
> diff --git a/block/sheepdog.c b/block/sheepdog.c
> index be3176f..c9f06db 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 +1587,11 @@ 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;
>      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 +1605,23 @@ 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 = g_malloc0(object_size);

If I understand correctly, block_size_shift can be up to 31, i.e. this
is a 2 GB allocation. Do you really think this is a good idea?

At least use g_try_malloc0() here, so that a memory allocation failure
doesn't crash qemu. (Same goes for all potentially huge allocations that
you make in the whole codebase.)

> +    max_idx = DIV_ROUND_UP(vdi_size, object_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 * object_size, buf, object_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 * object_size, buf, object_size);
>          if (ret < 0) {
>              goto out;
>          }
> @@ -1610,7 +1635,9 @@ out_with_err_set:
>      if (bs) {
>          bdrv_unref(bs);
>      }
> -    g_free(buf);
> +    if (buf) {
> +        g_free(buf);
> +    }

This is unnecessary. g_free(NULL) is valid, it does nothing.

>      return ret;
>  }
> @@ -1669,6 +1696,17 @@ static int parse_redundancy(BDRVSheepdogState *s, 
> const char *opt)
>      return 0;
>  }
>  
> +static int parse_block_size_shift(BDRVSheepdogState *s, const char *opt)
> +{
> +    struct SheepdogInode *inode = &s->inode;
> +    inode->block_size_shift = (uint8_t)atoi(opt);

atoi() is best avoided, it has poor error handling.

But I think you don't need this parse function at all, see below.

> +    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 +1717,7 @@ 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);
> @@ -1718,10 +1757,15 @@ 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;
> -        goto out;
> +    g_free(buf);
> +    buf = qemu_opt_get_del(opts, BLOCK_OPT_BLOCK_SIZE_SHIFT);
> +    if (buf) {
> +        ret = parse_block_size_shift(s, buf);
> +        if (ret < 0) {
> +            error_setg(errp, "Invalid block_size_shift:"
> +                             " '%s'. please use 20-31", buf);
> +            goto out;
> +        }
>      }

You could use qemu_opt_get_number_del() here and get a number directly
from QemuOpts that you don't have to parse any more, if you defined the
option as QEMU_OPT_NUMBER instead of QEMU_OPT_STRING.

>      if (backing_file) {
> @@ -1757,6 +1801,45 @@ 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) {
> +        SheepdogVdiReq hdr;
> +        SheepdogClusterRsp *rsp = (SheepdogClusterRsp *)&hdr;
> +        Error *local_err = NULL;
> +        int fd;
> +        unsigned int wlen = 0, rlen = 0;
> +
> +        fd = connect_to_sdog(s, &local_err);
> +        if (fd < 0) {
> +            error_report("%s", error_get_pretty(local_err));
> +            error_free(local_err);
> +            ret = -EIO;
> +            goto out;
> +        }
> +
> +        memset(&hdr, 0, sizeof(hdr));
> +        hdr.opcode = SD_OP_GET_CLUSTER_DEFAULT;
> +        hdr.proto_ver = SD_PROTO_VER;
> +
> +        ret = do_req(fd, s->aio_context, (SheepdogReq *)&hdr,
> +                     NULL, &wlen, &rlen);
> +        closesocket(fd);
> +        if (ret) {
> +            error_setg_errno(errp, -ret, "failed to get cluster default");
> +            goto out;
> +        }
> +        s->inode.block_size_shift = rsp->block_size_shift;
> +    }
> +
> +    max_vdi_size = (UINT64_C(1) << s->inode.block_size_shift) * 
> MAX_DATA_OBJS;
> +
> +    if (s->inode.vdi_size > max_vdi_size) {
> +        error_setg(errp, "too big image size");

Please capitalise the first word in an error messages, i.e. "Too big
image size".

> +        ret = -EINVAL;
> +        goto out;
> +    }
> +
>      ret = do_sd_create(s, &vid, 0, errp);
>      if (ret) {
>          goto out;

Kevin



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