Re: [PATCH v9 2/7] file-posix: introduce helper functions for sysfs attributes

[Damien Le Moal <damien.lemoal@opensource.wdc.com>]

On 2022/09/10 14:27, Sam Li wrote:
> Use get_sysfs_str_val() to get the string value of device
> zoned model. Then get_sysfs_zoned_model() can convert it to
> BlockZoneModel type of QEMU.
> 
> Use get_sysfs_long_val() to get the long value of zoned device
> information.
> 
> Signed-off-by: Sam Li <faithilikerun@gmail.com>
> Reviewed-by: Hannes Reinecke <hare@suse.de>
> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

Looks good to me.

Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>

> ---
>  block/file-posix.c               | 121 ++++++++++++++++++++++---------
>  include/block/block_int-common.h |   3 +
>  2 files changed, 88 insertions(+), 36 deletions(-)
> 
> diff --git a/block/file-posix.c b/block/file-posix.c
> index 48cd096624..0a8b4b426e 100644
> --- a/block/file-posix.c
> +++ b/block/file-posix.c
> @@ -1210,66 +1210,109 @@ static int hdev_get_max_hw_transfer(int fd, struct stat *st)
>  #endif
>  }
>  
> -static int hdev_get_max_segments(int fd, struct stat *st)
> -{
> +/*
> + * Get a sysfs attribute value as character string.
> + */
> +static int get_sysfs_str_val(struct stat *st, const char *attribute,
> +                             char **val) {
>  #ifdef CONFIG_LINUX
> -    char buf[32];
> -    const char *end;
> -    char *sysfspath = NULL;
> +    g_autofree char *sysfspath = NULL;
>      int ret;
> -    int sysfd = -1;
> -    long max_segments;
> +    size_t len;
>  
> -    if (S_ISCHR(st->st_mode)) {
> -        if (ioctl(fd, SG_GET_SG_TABLESIZE, &ret) == 0) {
> -            return ret;
> -        }
> +    if (!S_ISBLK(st->st_mode)) {
>          return -ENOTSUP;
>      }
>  
> -    if (!S_ISBLK(st->st_mode)) {
> -        return -ENOTSUP;
> +    sysfspath = g_strdup_printf("/sys/dev/block/%u:%u/queue/%s",
> +                                major(st->st_rdev), minor(st->st_rdev),
> +                                attribute);
> +    ret = g_file_get_contents(sysfspath, val, &len, NULL);
> +    if (ret == -1) {
> +        return -ENOENT;
>      }
>  
> -    sysfspath = g_strdup_printf("/sys/dev/block/%u:%u/queue/max_segments",
> -                                major(st->st_rdev), minor(st->st_rdev));
> -    sysfd = open(sysfspath, O_RDONLY);
> -    if (sysfd == -1) {
> -        ret = -errno;
> -        goto out;
> +    /* The file is ended with '\n' */
> +    char *p;
> +    p = *val;
> +    if (*(p + len - 1) == '\n') {
> +        *(p + len - 1) = '\0';
>      }
> -    do {
> -        ret = read(sysfd, buf, sizeof(buf) - 1);
> -    } while (ret == -1 && errno == EINTR);
> +    return ret;
> +#else
> +    return -ENOTSUP;
> +#endif
> +}
> +
> +static int get_sysfs_zoned_model(struct stat *st, BlockZoneModel *zoned) {
> +    g_autofree char *val = NULL;
> +    int ret;
> +
> +    ret = get_sysfs_str_val(st, "zoned", &val);
>      if (ret < 0) {
> -        ret = -errno;
> -        goto out;
> -    } else if (ret == 0) {
> -        ret = -EIO;
> -        goto out;
> +        return ret;
>      }
> -    buf[ret] = 0;
> -    /* The file is ended with '\n', pass 'end' to accept that. */
> -    ret = qemu_strtol(buf, &end, 10, &max_segments);
> -    if (ret == 0 && end && *end == '\n') {
> -        ret = max_segments;
> +
> +    if (strcmp(val, "host-managed") == 0) {
> +        *zoned = BLK_Z_HM;
> +    } else if (strcmp(val, "host-aware") == 0) {
> +        *zoned = BLK_Z_HA;
> +    } else if (strcmp(val, "none") == 0) {
> +        *zoned = BLK_Z_NONE;
> +    } else {
> +        return -ENOTSUP;
>      }
> +    return 0;
> +}
>  
> -out:
> -    if (sysfd != -1) {
> -        close(sysfd);
> +/*
> + * Get a sysfs attribute value as a long integer.
> + */
> +static long get_sysfs_long_val(struct stat *st, const char *attribute) {
> +#ifdef CONFIG_LINUX
> +    g_autofree char *str = NULL;
> +    const char *end;
> +    long val;
> +    int ret;
> +
> +    ret = get_sysfs_str_val(st, attribute, &str);
> +    if (ret < 0) {
> +        return ret;
> +    }
> +
> +    /* The file is ended with '\n', pass 'end' to accept that. */
> +    ret = qemu_strtol(str, &end, 10, &val);
> +    if (ret == 0 && end && *end == '\0') {
> +        ret = val;
>      }
> -    g_free(sysfspath);
>      return ret;
>  #else
>      return -ENOTSUP;
>  #endif
>  }
>  
> +static int hdev_get_max_segments(int fd, struct stat *st) {
> +#ifdef CONFIG_LINUX
> +    int ret;
> +
> +    if (S_ISCHR(st->st_mode)) {
> +        if (ioctl(fd, SG_GET_SG_TABLESIZE, &ret) == 0) {
> +            return ret;
> +        }
> +        return -ENOTSUP;
> +    }
> +    return get_sysfs_long_val(st, "max_segments");
> +#else
> +    return -ENOTSUP;
> +#endif
> +}
> +
>  static void raw_refresh_limits(BlockDriverState *bs, Error **errp)
>  {
>      BDRVRawState *s = bs->opaque;
>      struct stat st;
> +    int ret;
> +    BlockZoneModel zoned;
>  
>      s->needs_alignment = raw_needs_alignment(bs);
>      raw_probe_alignment(bs, s->fd, errp);
> @@ -1307,6 +1350,12 @@ static void raw_refresh_limits(BlockDriverState *bs, Error **errp)
>              bs->bl.max_hw_iov = ret;
>          }
>      }
> +
> +    ret = get_sysfs_zoned_model(&st, &zoned);
> +    if (ret < 0) {
> +        zoned = BLK_Z_NONE;
> +    }
> +    bs->bl.zoned = zoned;
>  }
>  
>  static int check_for_dasd(int fd)
> diff --git a/include/block/block_int-common.h b/include/block/block_int-common.h
> index 8947abab76..7f7863cc9e 100644
> --- a/include/block/block_int-common.h
> +++ b/include/block/block_int-common.h
> @@ -825,6 +825,9 @@ typedef struct BlockLimits {
>  
>      /* maximum number of iovec elements */
>      int max_iov;
> +
> +    /* device zone model */
> +    BlockZoneModel zoned;
>  } BlockLimits;
>  
>  typedef struct BdrvOpBlocker BdrvOpBlocker;

-- 
Damien Le Moal
Western Digital Research