vitastor/osd_primary.cpp

#include "osd.h"
#include "osd_rmw.h"

// read: read directly or read paired stripe(s), reconstruct, return
// write: read paired stripe(s), modify, write
//
// nuance: take care to read the same version from paired stripes!
// to do so, we remember "last readable" version until a write request completes
// and we postpone other write requests to the same stripe until completion of previous ones
//
// sync: sync peers, get unstable versions from somewhere, stabilize them

struct osd_primary_op_data_t
{
    pg_num_t pg_num;
    object_id oid;
    uint64_t target_ver;
    int n_subops = 0, done = 0, errors = 0;
    int degraded = 0, pg_size, pg_minsize;
    osd_rmw_stripe_t *stripes;
    osd_op_t *subops = NULL;
    void *rmw_buf = NULL;

    bool should_read_version = false;
};

void osd_t::finish_primary_op(osd_op_t *cur_op, int retval)
{
    // FIXME add separate magics
    cur_op->reply.hdr.magic = SECONDARY_OSD_REPLY_MAGIC;
    cur_op->reply.hdr.id = cur_op->req.hdr.id;
    cur_op->reply.hdr.opcode = cur_op->req.hdr.opcode;
    cur_op->reply.hdr.retval = retval;
    outbox_push(this->clients[cur_op->peer_fd], cur_op);
}

bool osd_t::prepare_primary_rw(osd_op_t *cur_op)
{
    // PG number is calculated from the offset
    // Our EC scheme stores data in fixed chunks equal to (K*block size)
    // But we must not use K in the process of calculating the PG number
    // So we calculate the PG number using a separate setting which should be per-inode (FIXME)
    // FIXME Real pg_num should equal the below expression + 1
    pg_num_t pg_num = (cur_op->req.rw.inode + cur_op->req.rw.offset / parity_block_size) % pg_count;
    // FIXME: Postpone operations in inactive PGs
    if (pg_num > pgs.size() || !(pgs[pg_num].state & PG_ACTIVE))
    {
        finish_primary_op(cur_op, -EINVAL);
        return false;
    }
    uint64_t pg_parity_size = bs_block_size * pgs[pg_num].pg_minsize;
    object_id oid = {
        .inode = cur_op->req.rw.inode,
        // oid.stripe = starting offset of the parity stripe, so it can be mapped back to the PG
        .stripe = (cur_op->req.rw.offset / parity_block_size) * parity_block_size +
            ((cur_op->req.rw.offset % parity_block_size) / pg_parity_size) * pg_parity_size
    };
    if ((cur_op->req.rw.offset + cur_op->req.rw.len) > (oid.stripe + pg_parity_size) ||
        (cur_op->req.rw.offset % bs_disk_alignment) != 0 ||
        (cur_op->req.rw.len % bs_disk_alignment) != 0)
    {
        finish_primary_op(cur_op, -EINVAL);
        return false;
    }
    osd_primary_op_data_t *op_data = (osd_primary_op_data_t*)calloc(
        sizeof(osd_primary_op_data_t) + sizeof(osd_rmw_stripe_t) * pgs[pg_num].pg_size, 1
    );
    op_data->pg_num = pg_num;
    op_data->oid = oid;
    op_data->stripes = ((osd_rmw_stripe_t*)(op_data+1));
    cur_op->op_data = op_data;
    split_stripes(pgs[pg_num].pg_minsize, bs_block_size, (uint32_t)(cur_op->req.rw.offset - oid.stripe), cur_op->req.rw.len, op_data->stripes);
    return true;
}

void osd_t::exec_primary_read(osd_op_t *cur_op)
{
    if (!prepare_primary_rw(cur_op))
    {
        return;
    }
    osd_primary_op_data_t *op_data = (osd_primary_op_data_t*)cur_op->op_data;
    auto & pg = pgs[op_data->pg_num];
    for (int role = 0; role < pg.pg_minsize; role++)
    {
        op_data->stripes[role].read_start = op_data->stripes[role].req_start;
        op_data->stripes[role].read_end = op_data->stripes[role].req_end;
    }
    // Determine version
    auto vo_it = pg.ver_override.find(op_data->oid);
    op_data->target_ver = vo_it != pg.ver_override.end() ? vo_it->second : UINT64_MAX;
    if (pg.state == PG_ACTIVE)
    {
        // Fast happy-path
        cur_op->buf = alloc_read_buffer(op_data->stripes, pg.pg_minsize, 0);
        submit_read_subops(pg.pg_minsize, pg.cur_set.data(), cur_op);
        cur_op->send_list.push_back(cur_op->buf, cur_op->req.rw.len);
    }
    else
    {
        // PG may be degraded or have misplaced objects
        auto st_it = pg.obj_states.find(op_data->oid);
        uint64_t* cur_set = (st_it != pg.obj_states.end()
            ? st_it->second->read_target.data()
            : pg.cur_set.data());
        if (extend_missing_stripes(op_data->stripes, cur_set, pg.pg_minsize, pg.pg_size) < 0)
        {
            free(op_data);
            finish_primary_op(cur_op, -EIO);
            return;
        }
        // Submit reads
        cur_op->buf = alloc_read_buffer(op_data->stripes, pg.pg_size, 0);
        submit_read_subops(pg.pg_size, cur_set, cur_op);
        op_data->pg_minsize = pg.pg_minsize;
        op_data->pg_size = pg.pg_size;
        op_data->degraded = 1;
    }
}

void osd_t::handle_primary_read_subop(osd_op_t *cur_op, int ok)
{
    osd_primary_op_data_t *op_data = (osd_primary_op_data_t*)cur_op->op_data;
    if (!ok)
        op_data->errors++;
    else
        op_data->done++;
    if ((op_data->errors + op_data->done) >= op_data->n_subops)
    {
        delete[] op_data->subops;
        op_data->subops = NULL;
        if (op_data->errors > 0)
        {
            free(op_data);
            cur_op->op_data = NULL;
            finish_primary_op(cur_op, -EIO);
            return;
        }
        if (op_data->degraded)
        {
            // Reconstruct missing stripes
            // FIXME: Always EC(k+1) by now. Add different coding schemes
            osd_rmw_stripe_t *stripes = op_data->stripes;
            for (int role = 0; role < op_data->pg_minsize; role++)
            {
                if (stripes[role].read_end != 0 && stripes[role].missing)
                {
                    reconstruct_stripe(stripes, op_data->pg_size, role);
                }
                if (stripes[role].req_end != 0)
                {
                    // Send buffer in parts to avoid copying
                    cur_op->send_list.push_back(
                        stripes[role].read_buf + (stripes[role].read_start - stripes[role].req_start), stripes[role].req_end
                    );
                }
            }
        }
        free(op_data);
        cur_op->op_data = NULL;
        finish_primary_op(cur_op, cur_op->req.rw.len);
    }
}

void osd_t::submit_read_subops(int read_pg_size, const uint64_t* osd_set, osd_op_t *cur_op)
{
    osd_primary_op_data_t *op_data = (osd_primary_op_data_t*)cur_op->op_data;
    osd_rmw_stripe_t *stripes = op_data->stripes;
    // Allocate subops
    int n_subops = 0, force_read = -1;
    for (int role = 0; role < read_pg_size; role++)
    {
        if (osd_set[role] == this->osd_num || osd_set[role] != 0 && force_read == -1)
        {
            force_read = role;
        }
        if (osd_set[role] != 0 && stripes[role].read_end != 0)
        {
            n_subops++;
        }
    }
    if (!n_subops && op_data->should_read_version)
    {
        n_subops = 1;
    }
    else
    {
        force_read = -1;
    }
    osd_op_t *subops = new osd_op_t[n_subops];
    op_data->n_subops = n_subops;
    op_data->subops = subops;
    int subop = 0;
    for (int role = 0; role < read_pg_size; role++)
    {
        if (stripes[role].read_end == 0 && force_read != role)
        {
            continue;
        }
        auto role_osd_num = osd_set[role];
        if (role_osd_num != 0)
        {
            if (role_osd_num == this->osd_num)
            {
                subops[subop].bs_op = {
                    .opcode = BS_OP_READ,
                    .callback = [cur_op, this](blockstore_op_t *subop)
                    {
                        handle_primary_read_subop(cur_op, subop->retval == subop->len);
                    },
                    .oid = {
                        .inode = op_data->oid.inode,
                        .stripe = op_data->oid.stripe | role,
                    },
                    .version = op_data->target_ver,
                    .offset = stripes[role].read_start,
                    .len = stripes[role].read_end - stripes[role].read_start,
                    .buf = stripes[role].read_buf,
                };
                bs->enqueue_op(&subops[subop].bs_op);
            }
            else
            {
                subops[subop].op_type = OSD_OP_OUT;
                subops[subop].peer_fd = this->osd_peer_fds.at(role_osd_num);
                subops[subop].req.sec_rw = {
                    .header = {
                        .magic = SECONDARY_OSD_OP_MAGIC,
                        .id = this->next_subop_id++,
                        .opcode = OSD_OP_SECONDARY_READ,
                    },
                    .oid = {
                        .inode = op_data->oid.inode,
                        .stripe = op_data->oid.stripe | role,
                    },
                    .version = op_data->target_ver,
                    .offset = stripes[role].read_start,
                    .len = stripes[role].read_end - stripes[role].read_start,
                };
                subops[subop].buf = stripes[role].read_buf;
                subops[subop].callback = [cur_op, this](osd_op_t *subop)
                {
                    // so it doesn't get freed. FIXME: do it better
                    subop->buf = NULL;
                    handle_primary_read_subop(cur_op, subop->reply.hdr.retval == subop->req.sec_rw.len);
                };
                outbox_push(clients[subops[subop].peer_fd], &subops[subop]);
            }
            subop++;
        }
    }
}

void osd_t::exec_primary_write(osd_op_t *cur_op)
{
    if (!prepare_primary_rw(cur_op))
    {
        return;
    }
    osd_primary_op_data_t *op_data = (osd_primary_op_data_t*)cur_op->op_data;
    auto & pg = pgs[op_data->pg_num];
    // Check if actions are pending for this object
    auto act_it = pg.obj_stab_actions.lower_bound((obj_piece_id_t){
        .oid = op_data->oid,
        .osd_num = 0,
    });
    if (act_it != pg.obj_stab_actions.end() &&
        act_it->first.oid.inode == op_data->oid.inode &&
        (act_it->first.oid.stripe & ~STRIPE_MASK) == op_data->oid.stripe)
    {
        // FIXME postpone the request until actions are done
        free(op_data);
        finish_primary_op(cur_op, -EIO);
        return;
    }
    // Check if there are other write requests to the same object
    
    // Determine blocks to read
    op_data->rmw_buf = calc_rmw_reads(cur_op->buf, op_data->stripes, pg.cur_set.data(), pg.pg_size, pg.pg_minsize, pg.pg_cursize);
    op_data->should_read_version = true;
    // Read required blocks
    submit_read_subops(pg.pg_size, pg.cur_set.data(), cur_op);
    // ->>>>> Continue from the callback
    // Calculate parity
    calc_rmw_parity(op_data->stripes, op_data->pg_size);
    // Save version override if degraded
    
    // Send writes
    
    // ->>>>> Continue from the callback
    // Remember version as unstable
    
    // Remove version override if degraded
    
}

void osd_t::exec_primary_sync(osd_op_t *cur_op)
{
    
}