Compiling kernel version >= 2.6.34 on CentOS 5: RAID set "ddf1_foo" was not activated?

Why are you using a ddf format raid array in the first place? You appear to be trying to activate it with dmraid, which hasn't seen any development for several years and is more or less depreciated. mdadm is much better supported, and recent versions do support the ddf format, though it's native format is preferred.

Make sure you have loaded the dm-log module.

Thanks to all the help of my friend, the problem is solved.

On the first attempt, he commented out the line ti->error = "Error creating mirror dirty log"; in the dm-raid1.c, and inserted some debugging lines into dm-log.c to determine what caused the above error:

    log = kmalloc(sizeof(*log), GFP_KERNEL);
    if (!log)
        ti->error = "kmalloc error";
        return NULL;

    type = get_type(type_name);
    if (!type) {
        kfree(log);
        ti->error = "get_type error";
        return NULL;
    }

    log->flush_callback_fn = flush_callback_fn;
    log->type = type;
    if (type->ctr(log, ti, argc, argv)) {
        kfree(log);
        put_type(type);
        ti->error = "ctr error";
        return NULL;
    }

then recompiled the kernel and we get:

On the second attempt, he want to get the value of type_name:

if (type->ctr(log, ti, argc, argv)) {
    kfree(log);
    put_type(type);
    char* typeN = kmalloc(1000, GFP_KERNEL);
    char* pTypeN = typeN;
    char* ptype_name = type_name;
    while (*ptype_name != '\0') {
        *pTypeN = *ptype_name;
        ++pTypeN;
        ++ptype_name;
    }
    ti->error = typeN;
    return NULL;
}

Continue tracing to the core_ctr and the create_log_context by using the above method:

static int create_log_context(struct dm_dirty_log *log, struct dm_target *ti,
                  unsigned int argc, char **argv,
                  struct dm_dev *dev)
{
    enum sync sync = DEFAULTSYNC;

    struct log_c *lc;
    uint32_t region_size;
    unsigned int region_count;
    size_t bitset_size, buf_size;
    int r;

    if (argc < 1 || argc > 2) {
        DMWARN("wrong number of arguments to dirty region log");
        ti->error = "argc < 1 or > 2";
        return -EINVAL;
    }

    if (argc > 1) {
        if (!strcmp(argv[1], "sync"))
            sync = FORCESYNC;
        else if (!strcmp(argv[1], "nosync"))
            sync = NOSYNC;
        else {
            DMWARN("unrecognised sync argument to "
                   "dirty region log: %s", argv[1]);
            ti->error = "unrecognised sync argument to";
            return -EINVAL;
        }
    }

if (argc < 1 || argc > 2) {
    DMWARN("wrong number of arguments to dirty region log");
    char* argcStr = kmalloc(1000, GFP_KERNEL);
    char* pArgc = argcStr;
    unsigned int temp = argc;
    do {
        *pArgc = temp % 10;
        ++pArgc;
        temp = temp / 10;
    } while (temp > 0);
    *pArgc = ' ';
    ++pArgc;
    //copy argv;
    int i = 0;
    for (i; i < argc; ++i) {
        char* pArgv = argv[i];
        while (*pArgv != '\0') {
            *pArgc = *pArgv;
            ++pArgc;
            ++pArgv;
        }
        *pArgc = ' ';
        ++pArgc;
    }
    *pArgc = '\0';
    ti->error = argcStr;
    return -EINVAL;
}

Notice that the ASCII code of the black heart symbol is... 3.

Don't know why the author is mixing up the core_ctr with the disk_ctr. The type_name is core but the number of arguments is 3, so he trim the last argument (block_on_error) by inserting the following into the dm_dirty_log_create struct:

struct dm_dirty_log *dm_dirty_log_create(const char *type_name,
            struct dm_target *ti,
            int (*flush_callback_fn)(struct dm_target *ti),
            unsigned int argc, char **argv)
{
    struct dm_dirty_log_type *type;
    struct dm_dirty_log *log;

    log = kmalloc(sizeof(*log), GFP_KERNEL);
    if (!log) {
        ti->error = "kmalloc error";
        return NULL;
    }

    char* core = "core";
    char* pCore = core;
    int is_core = 1;

    char* ptype_name = type_name;
    while (*ptype_name != '\0') {
        if (*pCore != *ptype_name) {
            is_core = 0;
        }
        ++pCore;
        ++ptype_name;
    }

    if (is_core && *pCore == *ptype_name && argc == 3) {
        --argc;
    }
    type = get_type(type_name);

Let's see what happens:

# uname -r
2.6.34.14

# dmraid -s
*** Group superset .ddf1_disks
--> Active Subset
name   : ddf1_VCBOOT
size   : 489971712
stride : 128
type   : mirror
status : ok
subsets: 0
devs   : 2
spares : 0

# modprobe ceph

# lsmod | grep ceph
ceph                  176676  0 

# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/ddf1_VCBOOTp3
                      219G   17G  191G   8% /
/dev/mapper/ddf1_VCBOOTp1
                       99M   64M   30M  69% /boot
tmpfs                  48G   16M   48G   1% /dev/shm
192.168.2.13:6789,192.168.2.14:6789,192.168.2.15:6789:/
                       72T   28T   45T  39% /mnt/ceph

According to Ceph bug 4286, FUSE needs at least kernel 2.6.24 for atomic_o_trunc. I found an RPM for 2.6.25. This kernel appears to be for an HPC cluster.

I think your above issue is due to the heavy modification that Red Hat does to their kernel releases. It makes trying newer kernels much more difficult depending on your hardware configuration and software requirement.