Re: [RFC v4 3/9] file-posix: introduce get_sysfs_long_val for a block queue of sysfs attribute

[Damien Le Moal]

On 7/12/22 11:13, Sam Li wrote:
> Use sysfs attribute files to get the zoned device information in case
> that ioctl() commands of zone management interface won't work.
> 
> Signed-off-by: Sam Li <faithilikerun@gmail.com>
> ---
>  block/file-posix.c | 38 +++++++++++++++++++++++++++-----------
>  1 file changed, 27 insertions(+), 11 deletions(-)
> 
> diff --git a/block/file-posix.c b/block/file-posix.c
> index e7523ae2ed..3161d39ea4 100644
> --- a/block/file-posix.c
> +++ b/block/file-posix.c
> @@ -1218,15 +1218,19 @@ 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 zoned device information (chunk_sectors, zoned_append_max_bytes,
> + * max_open_zones, max_active_zones) through sysfs attribute files.
> + */
> +static long get_sysfs_long_val(int fd, struct stat *st,
> +                               const char *attribute) {
>  #ifdef CONFIG_LINUX
>      char buf[32];
>      const char *end;
>      char *sysfspath = NULL;
>      int ret;
>      int sysfd = -1;
> -    long max_segments;
> +    long val;
>  
>      if (S_ISCHR(st->st_mode)) {
>          if (ioctl(fd, SG_GET_SG_TABLESIZE, &ret) == 0) {
> @@ -1239,8 +1243,9 @@ static int hdev_get_max_segments(int fd, struct stat 
> *st)
>          return -ENOTSUP;
>      }
>  
> -    sysfspath = g_strdup_printf("/sys/dev/block/%u:%u/queue/max_segments",
> -                                major(st->st_rdev), minor(st->st_rdev));
> +    sysfspath = g_strdup_printf("/sys/dev/block/%u:%u/queue/%s",
> +                                major(st->st_rdev), minor(st->st_rdev),
> +                                attribute);
>      sysfd = open(sysfspath, O_RDONLY);
>      if (sysfd == -1) {
>          ret = -errno;
> @@ -1258,9 +1263,9 @@ static int hdev_get_max_segments(int fd, struct stat 
> *st)
>      }
>      buf[ret] = 0;
>      /* The file is ended with '\n', pass 'end' to accept that. */
> -    ret = qemu_strtol(buf, &end, 10, &max_segments);
> +    ret = qemu_strtol(buf, &end, 10, &val);
>      if (ret == 0 && end && *end == '\n') {
> -        ret = max_segments;
> +        ret = val;
>      }
>  
>  out:
> @@ -1274,6 +1279,10 @@ out:
>  #endif
>  }
>  
> +static int hdev_get_max_segments(int fd, struct stat *st) {
> +    return get_sysfs_long_val(fd, st, "max_segments");
> +}
> +
>  static void raw_refresh_limits(BlockDriverState *bs, Error **errp)
>  {
>      BDRVRawState *s = bs->opaque;
> @@ -1883,10 +1892,17 @@ static int handle_aiocb_zone_mgmt(void *opaque) {
>      int64_t zone_size_mask;
>      int ret;
>  
> -    g_autofree struct stat *file = NULL;
> -    file = g_new(struct stat, 1);
> -    stat(s->filename, file);
> -    zone_size = get_sysfs_long_val(fd, file, "chunk_sectors");
> +    struct stat file;
> +    if (fstat(fd, &file) < 0) {
> +        return -errno;
> +    }
> +    mod = get_sysfs_str_val(fd, &file);
> +    if (mod != BLK_Z_HM) {
> +        ret = -ENOTSUP;
> +        return ret;
> +    }
> +
> +    zone_size = get_sysfs_long_val(fd, &file, "chunk_sectors");
>      zone_size_mask = zone_size - 1;
>      if (offset & zone_size_mask) {
>          error_report("offset is not the start of a zone");

This hunk that modifies raw_refresh_limits() should go into another patch.
Likely, you want that as part of patch 1, so this patch to introduce the
get_sysfs_long_val() helper function should come before patch 1.


-- 
Damien Le Moal
Western Digital Research