7c946ca8b48de87b10a721b5c30bc6d9b9b17ea5
1 /* MDRAID Superblock generator
2 This should create valid mdraid superblock for raid1 with 1 device.
3 It is still work in progress, but following seems to be recognized:
7 mdadm --examine test.img
16 #include <linux/raid/md_p.h>
18 void random_uuid(__u8
*buf
)
21 for (int i
= 0; i
< 4; i
++)
26 static unsigned int calc_sb_1_csum(struct mdp_superblock_1
* sb
)
28 unsigned int disk_csum
, csum
;
29 unsigned long long newcsum
;
30 int size
= sizeof(*sb
) + __le32_to_cpu(sb
->max_dev
)*2;
31 unsigned int *isuper
= (unsigned int*)sb
;
33 /* make sure I can count... (needs include cstddef) */
35 if (offsetof(struct mdp_superblock_1,data_offset) != 128 ||
36 offsetof(struct mdp_superblock_1, utime) != 192 ||
37 sizeof(struct mdp_superblock_1) != 256) {
38 fprintf(stderr, "WARNING - superblock isn't sized correctly\n");
42 disk_csum
= sb
->sb_csum
;
45 for (; size
>=4; size
-= 4 ) {
46 newcsum
+= __le32_to_cpu(*isuper
);
51 newcsum
+= __le16_to_cpu(*(unsigned short*) isuper
);
53 csum
= (newcsum
& 0xffffffff) + (newcsum
>> 32);
54 sb
->sb_csum
= disk_csum
;
55 return __cpu_to_le32(csum
);
59 srand(time(NULL
)); //FIXME: Seed UUID properly
61 struct mdp_superblock_1 sb
= {0};
63 /* constant array information - 128 bytes */
64 sb
.magic
= 0xa92b4efc; /* MD_SB_MAGIC: 0xa92b4efc - little endian */
65 sb
.major_version
= 1; /* 1 */
66 sb
.feature_map
= 0; /* bit 0 set if 'bitmap_offset' is meaningful */
67 sb
.pad0
= 0; /* always set to 0 when writing */
70 random_uuid(sb
.set_uuid
); /* user-space generated. U8[16]*/
71 memcpy(sb
.set_name
, "localhost:777", 6); /* set and interpreted by user-space. CHAR[32] */
72 sb
.ctime
=0; /* lo 40 bits are seconds, top 24 are microseconds or 0*/
74 sb
.level
=1; /* -4 (multipath), -1 (linear), 0,1,4,5 */
75 sb
.layout
=2; /* only for raid5 and raid10 currently */
76 sb
.size
; /* used size of component devices, in 512byte sectors */
78 sb
.chunksize
=0; /* in 512byte sectors - not used in raid 1 */
80 sb
.bitmap_offset
=0; /* sectors after start of superblock that bitmap starts
81 * NOTE: signed, so bitmap can be before superblock
82 * only meaningful of feature_map[0] is set.
85 /* constant this-device information - 64 bytes */
86 sb
.data_offset
=4096+sizeof(sb
); /* sector start of data, often 0 */
87 sb
.data_size
; /* sectors in this device that can be used for data */
88 sb
.super_offset
=8; /* sector start of this superblock */
90 sb
.dev_number
=0; /* permanent identifier of this device - not role in raid */
91 sb
.cnt_corrected_read
=0; /* number of read errors that were corrected by re-writing */
92 random_uuid(sb
.device_uuid
); /* user-space setable, ignored by kernel U8[16] */
93 sb
.devflags
=0; /* per-device flags. Only two defined...*/
94 //#define WriteMostly1 1 /* mask for writemostly flag in above */
95 //#define FailFast1 2 /* Should avoid retries and fixups and just fail */
97 /* array state information - 64 bytes */
98 sb
.utime
=0; /* 40 bits second, 24 bits microseconds */
99 sb
.events
=0; /* incremented when superblock updated */
100 sb
.resync_offset
=0; /* data before this offset (from data_offset) known to be in sync */
101 sb
.max_dev
=1; /* size of devs[] array to consider */
102 //__u8 pad3[64-32]; /* set to 0 when writing */
104 /* device state information. Indexed by dev_number.
106 * Note there are no per-device state flags. State information is rolled
107 * into the 'roles' value. If a device is spare or faulty, then it doesn't
108 * have a meaningful role.
110 //__le16 dev_roles[]; /* role in array, or 0xffff for a spare, or 0xfffe for faulty */
113 sb
.sb_csum
=calc_sb_1_csum(&sb
);
115 //printf("Superblock\n");
116 for(int i
=0;i
<4096;i
++) putc(0, stdout
);
117 fwrite(&sb
, sizeof(sb
), 1, stdout
);
118 for(int i
=0;i
<40960;i
++) putc(0, stdout
);
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