zircon/system/ulib/fs/block-txn.cpp

// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <zircon/device/block.h>
#include <fbl/algorithm.h>
#include <fbl/macros.h>
#include <fbl/vector.h>

#include <fs/block-txn.h>
#include <fs/vfs.h>

#include <utility>

namespace fs {

BlockTxn::BlockTxn(TransactionHandler* handler) : handler_(handler) {}

BlockTxn::~BlockTxn() {
    Transact();
}

#ifdef __Fuchsia__

void BlockTxn::EnqueueOperation(uint32_t op, vmoid_t id, uint64_t vmo_offset,
                                uint64_t dev_offset, uint64_t nblocks) {
    // TODO(ZX-2253): Remove this assertion.
    ZX_ASSERT_MSG(nblocks < UINT32_MAX, "Too many blocks");
    uint32_t blocks = static_cast<uint32_t>(nblocks);
    for (size_t i = 0; i < requests_.size(); i++) {
        if (requests_[i].vmoid != id || requests_[i].opcode != op) {
            continue;
        }

        if (requests_[i].vmo_offset == vmo_offset) {
            // Take the longer of the operations (if operating on the same
            // blocks).
            if (requests_[i].length <= blocks) {
                requests_[i].length = blocks;
            }
            return;
        } else if ((requests_[i].vmo_offset + requests_[i].length == vmo_offset) &&
                   (requests_[i].dev_offset + requests_[i].length == dev_offset)) {
            // Combine with the previous request, if immediately following.
            requests_[i].length += blocks;
            return;
        }
    }

    block_fifo_request_t request;
    request.opcode = op;
    request.group = handler_->BlockGroupID();
    request.vmoid = id;
    // NOTE: It's easier to compare everything when dealing
    // with blocks (not offsets!) so the following are described in
    // terms of blocks until we Transact().
    request.length = blocks;
    request.vmo_offset = vmo_offset;
    request.dev_offset = dev_offset;
    requests_.push_back(std::move(request));
}

zx_status_t BlockTxn::Transact() {
    // Fast-path for already completed transactions.
    if (requests_.is_empty()) {
        return ZX_OK;
    }
    // Convert 'filesystem block' units to 'disk block' units.
    const size_t kBlockFactor = handler_->FsBlockSize() / handler_->DeviceBlockSize();
    for (size_t i = 0; i < requests_.size(); i++) {
        requests_[i].vmo_offset *= kBlockFactor;
        requests_[i].dev_offset *= kBlockFactor;
        // TODO(ZX-2253): Remove this assertion.
        uint64_t length = requests_[i].length * kBlockFactor;
        ZX_ASSERT_MSG(length < UINT32_MAX, "Too many blocks");
        requests_[i].length = static_cast<uint32_t>(length);
    }
    zx_status_t status = ZX_OK;
    if (requests_.size() != 0) {
        status = handler_->Transaction(requests_.get(), requests_.size());
    }
    requests_.reset();
    return status;
}

#else

void BlockTxn::EnqueueOperation(uint32_t op, const void* id, uint64_t vmo_offset,
                                uint64_t dev_offset, uint64_t nblocks) {
    for (size_t b = 0; b < nblocks; b++) {
        void* data = GetBlock(handler_->FsBlockSize(), id, vmo_offset + b);
        if (op == BLOCKIO_WRITE) {
            handler_->Writeblk(static_cast<uint32_t>(dev_offset + b), data);
        } else if (op == BLOCKIO_READ) {
            handler_->Readblk(static_cast<uint32_t>(dev_offset + b), data);
        } else if (op == BLOCKIO_FLUSH) {
            // No-op.
        } else {
            ZX_ASSERT(false); // Invalid operation.
        }
    }
}

// Activate the transaction (do nothing)
zx_status_t BlockTxn::Transact() {
    return ZX_OK;
}

#endif

} // namespace fs