hello everyone!
when bluestore is overwrite ,it will use wal.
and i think it is like journal. IO divided into submit and apply.
When i look at the code, i find _wal_apply().
But i can not find wal submit.
I only found the following code :
---------------------------------------------------------------------------------------------------------------------
// chunk-aligned wal overwrite?
if (b->get_blob().get_ondisk_length() >= b_off + b_len &&
b_off % chunk_size == 0 &&
b_len % chunk_size == 0 &&
b->get_blob().is_allocated(b_off, b_len)) {
bluestore_wal_op_t *op = _get_wal_op(txc, o);
op->op = bluestore_wal_op_t::OP_WRITE;
_buffer_cache_write(txc, b, b_off, padded,
wctx->buffered ? 0 : Buffer::FLAG_NOCACHE);
int r = b->get_blob().map(
b_off, b_len,
[&](uint64_t offset, uint64_t length) {
op->extents.emplace_back(bluestore_pextent_t(offset, length));
return 0;
});
assert(r == 0);
if (b->get_blob().csum_type) {
b->dirty_blob().calc_csum(b_off, padded);
}
op->data.claim(padded);
dout(20) << __func__ << " wal write 0x" << std::hex << b_off << "~"
<< b_len << std::dec << " of mutable " << *b
<< " at " << op->extents << dendl;
Extent *le = o->extent_map.set_lextent(offset, offset - bstart, length,
b, &wctx->old_extents);
b->dirty_blob().mark_used(le->blob_offset, le->length);
txc->statfs_delta.stored() += le->length;
dout(20) << __func__ << " lex " << *le << dendl;
logger->inc(l_bluestore_write_small_wal);
return;
-------------------------------------------------------------------------------------------------------------------
but these code does not write Block device partition of wal.
how does Bluestore submit IO to Block device partition of wal ?
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