5f2720ef4d605e3f6372dd718b6e29a17c0b7adb
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
9 losetup /dev/loop1 test.img
10 mdadm --assemble md /dev/loop1
13 https://raid.wiki.kernel.org/index.php/RAID_superblock_formats#Sub-versions_of_the_version-1_superblock
14 https://docs.huihoo.com/doxygen/linux/kernel/3.7/md__p_8h_source.html
23 #include <linux/raid/md_p.h>
25 void random_uuid(__u8
*buf
)
28 for (int i
= 0; i
< 4; i
++)
33 static unsigned int calc_sb_1_csum(struct mdp_superblock_1
* sb
)
35 unsigned int disk_csum
, csum
;
36 unsigned long long newcsum
;
37 int size
= sizeof(*sb
) + __le32_to_cpu(sb
->max_dev
)*2;
38 unsigned int *isuper
= (unsigned int*)sb
;
40 /* make sure I can count... (needs include cstddef) */
42 if (offsetof(struct mdp_superblock_1,data_offset) != 128 ||
43 offsetof(struct mdp_superblock_1, utime) != 192 ||
44 sizeof(struct mdp_superblock_1) != 256) {
45 fprintf(stderr, "WARNING - superblock isn't sized correctly\n");
49 disk_csum
= sb
->sb_csum
;
52 for (; size
>=4; size
-= 4 ) {
53 newcsum
+= __le32_to_cpu(*isuper
);
58 newcsum
+= __le16_to_cpu(*(unsigned short*) isuper
);
60 csum
= (newcsum
& 0xffffffff) + (newcsum
>> 32);
61 sb
->sb_csum
= disk_csum
;
62 return __cpu_to_le32(csum
);
66 //printf("Superblock\n");
68 size_t data_size
= 8192; //512B sectors (should be divisible by 8 sectors to keep 4kB alignment)
70 srand(time(NULL
)); //FIXME: Seed UUID properly
72 struct mdp_superblock_1 sb
= {0};
74 /* constant array information - 128 bytes */
75 sb
.magic
= 0xa92b4efc; /* MD_SB_MAGIC: 0xa92b4efc - little endian */
76 sb
.major_version
= 1; /* 1 */
77 sb
.feature_map
= 0; //MD_FEATURE_BITMAP_OFFSET; /* bit 0 set if 'bitmap_offset' is meaningful */ //FIXME: internal bitmap bit is not seen by mdadm????
78 sb
.pad0
= 0; /* always set to 0 when writing */
81 random_uuid(sb
.set_uuid
); /* user-space generated. U8[16]*/
82 memcpy(sb
.set_name
, "localhost:7", 12); /* set and interpreted by user-space. CHAR[32] */
83 sb
.ctime
=0; /* lo 40 bits are seconds, top 24 are microseconds or 0*/
85 sb
.level
=1; /* -4 (multipath), -1 (linear), 0,1,4,5 */
86 //sb.layout=2; /* only for raid5 and raid10 currently */
87 sb
.size
=data_size
; /* used size of component devices, in 512byte sectors */
89 sb
.chunksize
=0; /* in 512byte sectors - not used in raid 1 */
91 sb
.bitmap_offset
=8; /* sectors after start of superblock that bitmap starts
92 * NOTE: signed, so bitmap can be before superblock
93 * only meaningful of feature_map[0] is set.
96 /* constant this-device information - 64 bytes */
97 sb
.data_offset
=2048; /* sector start of data, often 0 */
98 sb
.data_size
=data_size
; /* sectors in this device that can be used for data */
99 sb
.super_offset
=8; /* sector start of this superblock */
101 sb
.dev_number
=0; /* permanent identifier of this device - not role in raid */
102 sb
.cnt_corrected_read
=0; /* number of read errors that were corrected by re-writing */
103 random_uuid(sb
.device_uuid
); /* user-space setable, ignored by kernel U8[16] */
104 sb
.devflags
=0; /* per-device flags. Only two defined...*/
105 //#define WriteMostly1 1 /* mask for writemostly flag in above */
106 //#define FailFast1 2 /* Should avoid retries and fixups and just fail */
108 /* Bad block log. If there are any bad blocks the feature flag is set.
109 * If offset and size are non-zero, that space is reserved and available
111 sb
.bblog_shift
=9; /* shift from sectors to block size */ //FIXME: not sure with this!
112 sb
.bblog_size
=8; /* number of sectors reserved for list */
113 sb
.bblog_offset
=16; /* sector offset from superblock to bblog,
114 * signed - not unsigned */
116 /* array state information - 64 bytes */
117 sb
.utime
=0; /* 40 bits second, 24 bits microseconds */
118 sb
.events
=0; /* incremented when superblock updated */
119 sb
.resync_offset
=0; /* data before this offset (from data_offset) known to be in sync */
120 sb
.max_dev
=sb
.raid_disks
; /* size of devs[] array to consider */
121 //__u8 pad3[64-32]; /* set to 0 when writing */
123 /* device state information. Indexed by dev_number.
125 * Note there are no per-device state flags. State information is rolled
126 * into the 'roles' value. If a device is spare or faulty, then it doesn't
127 * have a meaningful role.
129 //__le16 dev_roles[]; /* role in array, or 0xffff for a spare, or 0xfffe for faulty */
133 sb
.sb_csum
=calc_sb_1_csum(&sb
);
135 //Empty space before metadata (sector 0 - 7)
136 for(int i
=0;i
<(sb
.super_offset
*512);i
++) putc(0, stdout
);
138 //Superblock and padding (sector 8 - 2048)
139 fwrite(&sb
, sizeof(sb
), 1, stdout
);
140 for(int i
=0;i
<(((sb
.data_offset
-sb
.super_offset
)*512)-sizeof(sb
));i
++) putc(0, stdout
);
143 for(int i
=0;i
<(data_size
*512);i
++) putc(0, stdout
);
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