/*
 * Copyright (C) 2018 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <libfiemap_writer/fiemap_writer.h>

#include <dirent.h>
#include <fcntl.h>
#include <linux/fs.h>
#include <stdio.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/sysmacros.h>
#include <sys/types.h>
#include <sys/vfs.h>
#include <unistd.h>

#include <limits>
#include <string>
#include <utility>
#include <vector>

#include <android-base/file.h>
#include <android-base/logging.h>
#include <android-base/stringprintf.h>
#include <android-base/strings.h>
#include <android-base/unique_fd.h>

namespace android {
namespace fiemap_writer {

// We are expecting no more than 512 extents in a fiemap of the file we create.
// If we find more, then it is treated as error for now.
static constexpr const uint32_t kMaxExtents = 512;

// TODO: Fallback to using fibmap if FIEMAP_EXTENT_MERGED is set.
static constexpr const uint32_t kUnsupportedExtentFlags =
        FIEMAP_EXTENT_UNKNOWN | FIEMAP_EXTENT_UNWRITTEN | FIEMAP_EXTENT_DELALLOC |
        FIEMAP_EXTENT_NOT_ALIGNED | FIEMAP_EXTENT_DATA_INLINE | FIEMAP_EXTENT_DATA_TAIL |
        FIEMAP_EXTENT_UNWRITTEN | FIEMAP_EXTENT_SHARED | FIEMAP_EXTENT_MERGED;

// Large file support must be enabled.
static_assert(sizeof(off_t) == sizeof(uint64_t));

static inline void cleanup(const std::string& file_path, bool created) {
    if (created) {
        unlink(file_path.c_str());
    }
}

static bool BlockDeviceToName(uint32_t major, uint32_t minor, std::string* bdev_name) {
    // The symlinks in /sys/dev/block point to the block device node under /sys/device/..
    // The directory name in the target corresponds to the name of the block device. We use
    // that to extract the block device name.
    // e.g for block device name 'ram0', there exists a symlink named '1:0' in /sys/dev/block as
    // follows.
    //    1:0 -> ../../devices/virtual/block/ram0
    std::string sysfs_path = ::android::base::StringPrintf("/sys/dev/block/%u:%u", major, minor);
    std::string sysfs_bdev;

    if (!::android::base::Readlink(sysfs_path, &sysfs_bdev)) {
        PLOG(ERROR) << "Failed to read link at: " << sysfs_path;
        return false;
    }

    *bdev_name = ::android::base::Basename(sysfs_bdev);
    // Paranoid sanity check to make sure we just didn't get the
    // input in return as-is.
    if (sysfs_bdev == *bdev_name) {
        LOG(ERROR) << "Malformed symlink for block device: " << sysfs_bdev;
        return false;
    }

    return true;
}

static bool DeviceMapperStackPop(const std::string& bdev, std::string* bdev_raw) {
    // TODO: Stop popping the device mapper stack if dm-linear target is found
    if (!::android::base::StartsWith(bdev, "dm-")) {
        // We are at the bottom of the device mapper stack.
        *bdev_raw = bdev;
        return true;
    }

    std::string dm_leaf_dir = ::android::base::StringPrintf("/sys/block/%s/slaves", bdev.c_str());
    auto d = std::unique_ptr<DIR, decltype(&closedir)>(opendir(dm_leaf_dir.c_str()), closedir);
    if (d == nullptr) {
        PLOG(ERROR) << "Failed to open: " << dm_leaf_dir;
        return false;
    }

    struct dirent* de;
    uint32_t num_leaves = 0;
    std::string bdev_next = "";
    while ((de = readdir(d.get())) != nullptr) {
        if (!strcmp(de->d_name, ".") || !strcmp(de->d_name, "..")) {
            continue;
        }

        // We set the first name we find here
        if (bdev_next.empty()) {
            bdev_next = de->d_name;
        }
        num_leaves++;
    }

    // if we have more than one leaves, we return immediately. We can't continue to create the
    // file since we don't know how to write it out using fiemap, so it will be readable via the
    // underlying block devices later. The reader will also have to construct the same device mapper
    // target in order read the file out.
    if (num_leaves > 1) {
        LOG(ERROR) << "Found " << num_leaves << " leaf block devices under device mapper device "
                   << bdev;
        return false;
    }

    // recursively call with the block device we found in order to pop the device mapper stack.
    return DeviceMapperStackPop(bdev_next, bdev_raw);
}

bool FiemapWriter::GetBlockDeviceForFile(const std::string& file_path, std::string* bdev_path,
                                         bool* uses_dm) {
    struct stat sb;
    if (stat(file_path.c_str(), &sb)) {
        PLOG(ERROR) << "Failed to get stat for: " << file_path;
        return false;
    }

    std::string bdev;
    if (!BlockDeviceToName(major(sb.st_dev), minor(sb.st_dev), &bdev)) {
        LOG(ERROR) << "Failed to get block device name for " << major(sb.st_dev) << ":"
                   << minor(sb.st_dev);
        return false;
    }

    std::string bdev_raw;
    if (!DeviceMapperStackPop(bdev, &bdev_raw)) {
        LOG(ERROR) << "Failed to get the bottom of the device mapper stack for device: " << bdev;
        return false;
    }

    if (uses_dm) {
        *uses_dm = (bdev_raw != bdev);
    }

    LOG(DEBUG) << "Popped device (" << bdev_raw << ") from device mapper stack starting with ("
               << bdev << ")";

    *bdev_path = ::android::base::StringPrintf("/dev/block/%s", bdev_raw.c_str());

    // Make sure we are talking to a block device before calling it a success.
    if (stat(bdev_path->c_str(), &sb)) {
        PLOG(ERROR) << "Failed to get stat for block device: " << *bdev_path;
        return false;
    }

    if ((sb.st_mode & S_IFMT) != S_IFBLK) {
        PLOG(ERROR) << "File: " << *bdev_path << " is not a block device";
        return false;
    }

    return true;
}

static bool GetBlockDeviceSize(int bdev_fd, const std::string& bdev_path, uint64_t* bdev_size) {
    uint64_t size_in_bytes = 0;
    if (ioctl(bdev_fd, BLKGETSIZE64, &size_in_bytes)) {
        PLOG(ERROR) << "Failed to get total size for: " << bdev_path;
        return false;
    }

    *bdev_size = size_in_bytes;

    return true;
}

static uint64_t GetFileSize(const std::string& file_path) {
    struct stat sb;
    if (stat(file_path.c_str(), &sb)) {
        PLOG(ERROR) << "Failed to get size for file: " << file_path;
        return 0;
    }

    return sb.st_size;
}

static bool PerformFileChecks(const std::string& file_path, uint64_t file_size, uint64_t* blocksz,
                              uint32_t* fs_type) {
    struct statfs64 sfs;
    if (statfs64(file_path.c_str(), &sfs)) {
        PLOG(ERROR) << "Failed to read file system status at: " << file_path;
        return false;
    }

    if (!sfs.f_bsize) {
        LOG(ERROR) << "Unsupported block size: " << sfs.f_bsize;
        return false;
    }

    // Check if the filesystem is of supported types.
    // Only ext4, f2fs, and vfat are tested and supported.
    switch (sfs.f_type) {
        case EXT4_SUPER_MAGIC:
        case F2FS_SUPER_MAGIC:
        case MSDOS_SUPER_MAGIC:
            break;
        default:
            LOG(ERROR) << "Unsupported file system type: 0x" << std::hex << sfs.f_type;
            return false;
    }

    uint64_t available_bytes = sfs.f_bsize * sfs.f_bavail;
    if (available_bytes <= file_size) {
        LOG(ERROR) << "Not enough free space in file system to create file of size : " << file_size;
        return false;
    }

    *blocksz = sfs.f_bsize;
    *fs_type = sfs.f_type;
    return true;
}

static bool FallocateFallback(int file_fd, uint64_t block_size, uint64_t file_size,
                              const std::string& file_path,
                              const std::function<bool(uint64_t, uint64_t)>& on_progress) {
    // Even though this is much faster than writing zeroes, it is still slow
    // enough that we need to fire the progress callback periodically. To
    // easily achieve this, we seek in chunks. We use 1000 chunks since
    // normally we only fire the callback on 1/1000th increments.
    uint64_t bytes_per_chunk = std::max(file_size / 1000, block_size);

    // Seek just to the end of each chunk and write a single byte, causing
    // the filesystem to allocate blocks.
    off_t cursor = 0;
    off_t end = static_cast<off_t>(file_size);
    while (cursor < end) {
        cursor = std::min(static_cast<off_t>(cursor + bytes_per_chunk), end);
        auto rv = TEMP_FAILURE_RETRY(lseek(file_fd, cursor - 1, SEEK_SET));
        if (rv < 0) {
            PLOG(ERROR) << "Failed to lseek " << file_path;
            return false;
        }
        if (rv != cursor - 1) {
            LOG(ERROR) << "Seek returned wrong offset " << rv << " for file " << file_path;
            return false;
        }
        char buffer[] = {0};
        if (!android::base::WriteFully(file_fd, buffer, 1)) {
            PLOG(ERROR) << "Write failed: " << file_path;
            return false;
        }
        if (on_progress && !on_progress(cursor, file_size)) {
            return false;
        }
    }
    return true;
}

static bool AllocateFile(int file_fd, const std::string& file_path, uint64_t blocksz,
                         uint64_t file_size, unsigned int fs_type,
                         std::function<bool(uint64_t, uint64_t)> on_progress) {
    // Reserve space for the file on the file system and write it out to make sure the extents
    // don't come back unwritten. Return from this function with the kernel file offset set to 0.
    // If the filesystem is f2fs, then we also PIN the file on disk to make sure the blocks
    // aren't moved around.
    switch (fs_type) {
        case EXT4_SUPER_MAGIC:
        case F2FS_SUPER_MAGIC:
            if (fallocate(file_fd, FALLOC_FL_ZERO_RANGE, 0, file_size)) {
                PLOG(ERROR) << "Failed to allocate space for file: " << file_path
                            << " size: " << file_size;
                return false;
            }
            break;
        case MSDOS_SUPER_MAGIC:
            // fallocate() is not supported, and not needed, since VFAT does not support holes.
            // Instead we can perform a much faster allocation.
            return FallocateFallback(file_fd, blocksz, file_size, file_path, on_progress);
        default:
            LOG(ERROR) << "Missing fallocate() support for file system " << fs_type;
            return false;
    }

    // write zeroes in 'blocksz' byte increments until we reach file_size to make sure the data
    // blocks are actually written to by the file system and thus getting rid of the holes in the
    // file.
    auto buffer = std::unique_ptr<void, decltype(&free)>(calloc(1, blocksz), free);
    if (buffer == nullptr) {
        LOG(ERROR) << "failed to allocate memory for writing file";
        return false;
    }

    off64_t offset = lseek64(file_fd, 0, SEEK_SET);
    if (offset < 0) {
        PLOG(ERROR) << "Failed to seek at the beginning of : " << file_path;
        return false;
    }

    int permille = -1;
    while (offset < file_size) {
        if (!::android::base::WriteFully(file_fd, buffer.get(), blocksz)) {
            PLOG(ERROR) << "Failed to write" << blocksz << " bytes at offset" << offset
                        << " in file " << file_path;
            return false;
        }

        offset += blocksz;

        // Don't invoke the callback every iteration - wait until a significant
        // chunk (here, 1/1000th) of the data has been processed.
        int new_permille = (static_cast<uint64_t>(offset) * 1000) / file_size;
        if (new_permille != permille && static_cast<uint64_t>(offset) != file_size) {
            if (on_progress && !on_progress(offset, file_size)) {
                return false;
            }
            permille = new_permille;
        }
    }

    if (lseek64(file_fd, 0, SEEK_SET) < 0) {
        PLOG(ERROR) << "Failed to reset offset at the beginning of : " << file_path;
        return false;
    }

    // flush all writes here ..
    if (fsync(file_fd)) {
        PLOG(ERROR) << "Failed to synchronize written file:" << file_path;
        return false;
    }

    // Send one last progress notification.
    if (on_progress && !on_progress(file_size, file_size)) {
        return false;
    }
    return true;
}

static bool PinFile(int file_fd, const std::string& file_path, uint32_t fs_type) {
    if (fs_type != F2FS_SUPER_MAGIC) {
        // No pinning necessary for ext4/msdos. The blocks, once allocated, are
        // expected to be fixed.
        return true;
    }

// F2FS-specific ioctl
// It requires the below kernel commit merged in v4.16-rc1.
//   1ad71a27124c ("f2fs: add an ioctl to disable GC for specific file")
// In android-4.4,
//   56ee1e817908 ("f2fs: updates on v4.16-rc1")
// In android-4.9,
//   2f17e34672a8 ("f2fs: updates on v4.16-rc1")
// In android-4.14,
//   ce767d9a55bc ("f2fs: updates on v4.16-rc1")
#ifndef F2FS_IOC_SET_PIN_FILE
#ifndef F2FS_IOCTL_MAGIC
#define F2FS_IOCTL_MAGIC 0xf5
#endif
#define F2FS_IOC_SET_PIN_FILE _IOW(F2FS_IOCTL_MAGIC, 13, __u32)
#endif

    uint32_t pin_status = 1;
    int error = ioctl(file_fd, F2FS_IOC_SET_PIN_FILE, &pin_status);
    if (error < 0) {
        if ((errno == ENOTTY) || (errno == ENOTSUP)) {
            PLOG(ERROR) << "Failed to pin file, not supported by kernel: " << file_path;
        } else {
            PLOG(ERROR) << "Failed to pin file: " << file_path;
        }
        return false;
    }

    return true;
}

static bool IsFilePinned(int file_fd, const std::string& file_path, uint32_t fs_type) {
    if (fs_type != F2FS_SUPER_MAGIC) {
        // No pinning necessary for ext4 or vfat. The blocks, once allocated,
        // are expected to be fixed.
        return true;
    }

// F2FS-specific ioctl
// It requires the below kernel commit merged in v4.16-rc1.
//   1ad71a27124c ("f2fs: add an ioctl to disable GC for specific file")
// In android-4.4,
//   56ee1e817908 ("f2fs: updates on v4.16-rc1")
// In android-4.9,
//   2f17e34672a8 ("f2fs: updates on v4.16-rc1")
// In android-4.14,
//   ce767d9a55bc ("f2fs: updates on v4.16-rc1")
#ifndef F2FS_IOC_GET_PIN_FILE
#ifndef F2FS_IOCTL_MAGIC
#define F2FS_IOCTL_MAGIC 0xf5
#endif
#define F2FS_IOC_GET_PIN_FILE _IOR(F2FS_IOCTL_MAGIC, 14, __u32)
#endif

    // F2FS_IOC_GET_PIN_FILE returns the number of blocks moved.
    uint32_t moved_blocks_nr;
    int error = ioctl(file_fd, F2FS_IOC_GET_PIN_FILE, &moved_blocks_nr);
    if (error < 0) {
        if ((errno == ENOTTY) || (errno == ENOTSUP)) {
            PLOG(ERROR) << "Failed to get file pin status, not supported by kernel: " << file_path;
        } else {
            PLOG(ERROR) << "Failed to get file pin status: " << file_path;
        }
        return false;
    }

    if (moved_blocks_nr) {
        LOG(ERROR) << moved_blocks_nr << " blocks moved in file " << file_path;
    }
    return moved_blocks_nr == 0;
}

bool FiemapWriter::HasPinnedExtents(const std::string& file_path) {
    android::base::unique_fd fd(open(file_path.c_str(), O_NOFOLLOW | O_CLOEXEC | O_RDONLY));
    if (fd < 0) {
        PLOG(ERROR) << "open: " << file_path;
        return false;
    }

    struct statfs64 sfs;
    if (fstatfs64(fd, &sfs)) {
        PLOG(ERROR) << "fstatfs64: " << file_path;
        return false;
    }
    return IsFilePinned(fd, file_path, sfs.f_type);
}

static bool ReadFiemap(int file_fd, const std::string& file_path,
                       std::vector<struct fiemap_extent>* extents) {
    uint64_t fiemap_size =
            sizeof(struct fiemap_extent) + kMaxExtents * sizeof(struct fiemap_extent);
    auto buffer = std::unique_ptr<void, decltype(&free)>(calloc(1, fiemap_size), free);
    if (buffer == nullptr) {
        LOG(ERROR) << "Failed to allocate memory for fiemap";
        return false;
    }

    struct fiemap* fiemap = reinterpret_cast<struct fiemap*>(buffer.get());
    fiemap->fm_start = 0;
    fiemap->fm_length = UINT64_MAX;
    // make sure file is synced to disk before we read the fiemap
    fiemap->fm_flags = FIEMAP_FLAG_SYNC;
    fiemap->fm_extent_count = kMaxExtents;

    if (ioctl(file_fd, FS_IOC_FIEMAP, fiemap)) {
        PLOG(ERROR) << "Failed to get FIEMAP from the kernel for file: " << file_path;
        return false;
    }

    if (fiemap->fm_mapped_extents == 0) {
        LOG(ERROR) << "File " << file_path << " has zero extents";
        return false;
    }

    // Iterate through each extent read and make sure its valid before adding it to the vector
    bool last_extent_seen = false;
    struct fiemap_extent* extent = &fiemap->fm_extents[0];
    for (uint32_t i = 0; i < fiemap->fm_mapped_extents; i++, extent++) {
        // LogExtent(i + 1, *extent);
        if (extent->fe_flags & kUnsupportedExtentFlags) {
            LOG(ERROR) << "Extent " << i + 1 << " of file " << file_path
                       << " has unsupported flags";
            extents->clear();
            return false;
        }

        if (extent->fe_flags & FIEMAP_EXTENT_LAST) {
            last_extent_seen = true;
            if (i != (fiemap->fm_mapped_extents - 1)) {
                LOG(WARNING) << "Extents are being received out-of-order";
            }
        }
        extents->emplace_back(std::move(*extent));
    }

    if (!last_extent_seen) {
        // The file is possibly too fragmented.
        if (fiemap->fm_mapped_extents == kMaxExtents) {
            LOG(ERROR) << "File is too fragmented, needs more than " << kMaxExtents << " extents.";
        }
        extents->clear();
    }

    return last_extent_seen;
}

static bool ReadFibmap(int file_fd, const std::string& file_path,
                       std::vector<struct fiemap_extent>* extents) {
    struct stat s;
    if (fstat(file_fd, &s)) {
        PLOG(ERROR) << "Failed to stat " << file_path;
        return false;
    }

    unsigned int blksize;
    if (ioctl(file_fd, FIGETBSZ, &blksize) < 0) {
        PLOG(ERROR) << "Failed to get FIGETBSZ for " << file_path;
        return false;
    }
    if (!blksize) {
        LOG(ERROR) << "Invalid filesystem block size: " << blksize;
        return false;
    }

    uint64_t num_blocks = (s.st_size + blksize - 1) / blksize;
    if (num_blocks > std::numeric_limits<uint32_t>::max()) {
        LOG(ERROR) << "Too many blocks for FIBMAP (" << num_blocks << ")";
        return false;
    }

    for (uint32_t last_block, block_number = 0; block_number < num_blocks; block_number++) {
        uint32_t block = block_number;
        if (ioctl(file_fd, FIBMAP, &block)) {
            PLOG(ERROR) << "Failed to get FIBMAP for file " << file_path;
            return false;
        }
        if (!block) {
            LOG(ERROR) << "Logical block " << block_number << " is a hole, which is not supported";
            return false;
        }

        if (!extents->empty() && block == last_block + 1) {
            extents->back().fe_length += blksize;
        } else {
            extents->push_back(fiemap_extent{.fe_logical = block_number,
                                             .fe_physical = static_cast<uint64_t>(block) * blksize,
                                             .fe_length = static_cast<uint64_t>(blksize),
                                             .fe_flags = 0});
        }
        last_block = block;
    }
    return true;
}

FiemapUniquePtr FiemapWriter::Open(const std::string& file_path, uint64_t file_size, bool create,
                                   std::function<bool(uint64_t, uint64_t)> progress) {
    // if 'create' is false, open an existing file and do not truncate.
    int open_flags = O_RDWR | O_CLOEXEC;
    if (create) {
        if (access(file_path.c_str(), F_OK) == 0) {
            LOG(WARNING) << "File " << file_path << " already exists, truncating";
        }
        open_flags |= O_CREAT | O_TRUNC;
    }
    ::android::base::unique_fd file_fd(
            TEMP_FAILURE_RETRY(open(file_path.c_str(), open_flags, S_IRUSR | S_IWUSR)));
    if (file_fd < 0) {
        PLOG(ERROR) << "Failed to create file at: " << file_path;
        return nullptr;
    }

    std::string abs_path;
    if (!::android::base::Realpath(file_path, &abs_path)) {
        PLOG(ERROR) << "Invalid file path: " << file_path;
        cleanup(file_path, create);
        return nullptr;
    }

    std::string bdev_path;
    if (!GetBlockDeviceForFile(abs_path, &bdev_path)) {
        LOG(ERROR) << "Failed to get block dev path for file: " << file_path;
        cleanup(abs_path, create);
        return nullptr;
    }

    ::android::base::unique_fd bdev_fd(
            TEMP_FAILURE_RETRY(open(bdev_path.c_str(), O_RDONLY | O_CLOEXEC)));
    if (bdev_fd < 0) {
        PLOG(ERROR) << "Failed to open block device: " << bdev_path;
        cleanup(file_path, create);
        return nullptr;
    }

    uint64_t bdevsz;
    if (!GetBlockDeviceSize(bdev_fd, bdev_path, &bdevsz)) {
        LOG(ERROR) << "Failed to get block device size for : " << bdev_path;
        cleanup(file_path, create);
        return nullptr;
    }

    if (!create) {
        file_size = GetFileSize(abs_path);
        if (file_size == 0) {
            LOG(ERROR) << "Invalid file size of zero bytes for file: " << abs_path;
            return nullptr;
        }
    }

    uint64_t blocksz;
    uint32_t fs_type;
    if (!PerformFileChecks(abs_path, file_size, &blocksz, &fs_type)) {
        LOG(ERROR) << "Failed to validate file or file system for file:" << abs_path;
        cleanup(abs_path, create);
        return nullptr;
    }

    // Align up to the nearest block size.
    if (file_size % blocksz) {
        file_size += blocksz - (file_size % blocksz);
    }

    if (create) {
        if (!AllocateFile(file_fd, abs_path, blocksz, file_size, fs_type, std::move(progress))) {
            LOG(ERROR) << "Failed to allocate file: " << abs_path << " of size: " << file_size
                       << " bytes";
            cleanup(abs_path, create);
            return nullptr;
        }
    }

    // f2fs may move the file blocks around.
    if (!PinFile(file_fd, abs_path, fs_type)) {
        cleanup(abs_path, create);
        LOG(ERROR) << "Failed to pin the file in storage";
        return nullptr;
    }

    // now allocate the FiemapWriter and start setting it up
    FiemapUniquePtr fmap(new FiemapWriter());
    switch (fs_type) {
        case EXT4_SUPER_MAGIC:
        case F2FS_SUPER_MAGIC:
            if (!ReadFiemap(file_fd, abs_path, &fmap->extents_)) {
                LOG(ERROR) << "Failed to read fiemap of file: " << abs_path;
                cleanup(abs_path, create);
                return nullptr;
            }
            break;
        case MSDOS_SUPER_MAGIC:
            if (!ReadFibmap(file_fd, abs_path, &fmap->extents_)) {
                LOG(ERROR) << "Failed to read fibmap of file: " << abs_path;
                cleanup(abs_path, create);
                return nullptr;
            }
            break;
    }

    fmap->file_path_ = abs_path;
    fmap->bdev_path_ = bdev_path;
    fmap->file_size_ = file_size;
    fmap->bdev_size_ = bdevsz;
    fmap->fs_type_ = fs_type;
    fmap->block_size_ = blocksz;

    LOG(VERBOSE) << "Successfully created FiemapWriter for file " << abs_path << " on block device "
                 << bdev_path;
    return fmap;
}

}  // namespace fiemap_writer
}  // namespace android