Method pwrite

fs/cache/cached_fs.cpp:222–225

pwrite* need to be aligned to 4KB for avoiding write padding.

    //  pwrite* need to be aligned to 4KB for avoiding write padding.
    ssize_t pwrite(const void *buf, size_t count, off_t offset) override {
        struct iovec v { const_cast<void *>(buf), count };
        return pwritev(&v, 1, offset);
    }

    ssize_t pwritev(const struct iovec *iov, int iovcnt, off_t offset) override {
        return pwritev2(iov, iovcnt, offset, 0);