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    SubjectRe: [PATCH v2 2/3] genhd, efi: add efi partition metadata to hd_structs
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    On Wed, Aug 4, 2010 at 4:00 AM, Karel Zak <kzak@redhat.com> wrote:
    > On Tue, Aug 03, 2010 at 09:04:42PM -0500, Will Drewry wrote:
    >> This change extends the partition_meta_info structure to
    >> support EFI GPT-specific metadata and ensures that data
    >> is copied in on partition scanning.
    >
    > Why do want to store GPT-specific data (efi_guid_t) to
    > partition_meta_info? I think it would be better to use label and uuid
    > in a generic format (e.g. string or u8 uuid[16]) -- then you don't
    > have to use things like union, disklabel specific code to compare
    > uuids, etc.  IMHO your current code is too complicated.
    >
    >> +             info = alloc_part_info(NULL);
    >> +             if (!info) {
    >> +                     printk(KERN_WARNING
    >> +                            "unable to allocate memory for part->info\n");
    >> +                     continue;
    >> +             }
    >> +             info->format = PARTITION_META_INFO_FORMAT_EFI;
    >> +             memcpy(info->efi.uuid.b, ptes[i].unique_partition_guid.b,
    >> +                     sizeof(info->efi.uuid.b));
    >> +             memcpy(info->efi.type.b, ptes[i].partition_type_guid.b,
    >> +                     sizeof(info->efi.type.b));
    >
    > why do you need to partition type?

    For GPT, at least, the partition type isn't directly encoded anywhere
    else and it can be vendor specific. For instance, if a vendor wants
    to make an auto-configuring, they could reserve a
    VENDOR-ROOT-PRI0-PART-TYPE-GUID then easily create a mount path for
    it. Of course, that could easily be kludged by reusing a UUID.


    >
    >> +             memcpy(info->efi.label, ptes[i].partition_name,
    >> +                     sizeof(info->efi.label));
    >
    > the partition name is in UTF8LE, is it correct to use it in raw
    > format?

    Since the type was partition specific, I left the data untouched. It
    sounds like it'd be more useful to expose the data in a generic way
    which would mean converting it, I guess?

    >> +             state->parts[i + 1].info = info;
    >>       }
    >>       kfree(ptes);
    >>       kfree(gpt);
    >> diff --git a/include/linux/genhd.h b/include/linux/genhd.h
    >> index 7b6644a..beb98e3 100644
    >> --- a/include/linux/genhd.h
    >> +++ b/include/linux/genhd.h
    >> @@ -91,11 +91,25 @@ struct disk_stats {
    >>  enum partition_meta_info_format_t {
    >>       /* Partition info format */
    >>       PARTITION_META_INFO_FORMAT_NONE = 0,
    >> +     PARTITION_META_INFO_FORMAT_EFI,
    >> +     /* Place additional formats here. */
    >> +     PARTITION_META_INFO_FORMAT_MAX,
    >>  };
    >>
    >> +#ifdef CONFIG_EFI_PARTITION
    >> +#include <linux/efi.h>
    >> +#endif
    >> +
    >>  struct partition_meta_info {
    >>       enum partition_meta_info_format_t format;
    >>       union {
    >> +#ifdef CONFIG_EFI_PARTITION
    >> +             struct {
    >> +                     efi_guid_t uuid;
    >> +                     efi_guid_t type;
    >> +                     efi_char16_t label[72 / sizeof(efi_char16_t)];
    >> +             } efi;
    >> +#endif
    >>       };
    >>  };
    >>
    >> --
    >> 1.7.0.4
    >>
    >
    > --
    >  Karel Zak  <kzak@redhat.com>
    >  http://karelzak.blogspot.com
    >
    --
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