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Commit ea0dda14 authored by David Anderson's avatar David Anderson
Browse files

libdm: Add LoopControl helpers for enabling direct IO. 

Bug: 134536978
Test: manual test
Change-Id: Iae25434ac54186fd6006b56eeb7a7f577a880053
parent d106f1e2

fs_mgr/libdm/include/libdm/loop_control.h

+3 −0
Original line number Diff line number Diff line
@@ -35,6 +35,9 @@ class LoopControl final { 
    // Detach the loop device given by 'loopdev' from the attached backing file.

    bool Detach(const std::string& loopdev) const;



    // Enable Direct I/O on a loop device. This requires kernel 4.9+.

    static bool EnableDirectIo(int fd);



    LoopControl(const LoopControl&) = delete;

    LoopControl& operator=(const LoopControl&) = delete;

    LoopControl& operator=(LoopControl&&) = default;

fs_mgr/libdm/loop_control.cpp

+21 −0
Original line number Diff line number Diff line
@@ -91,6 +91,27 @@ bool LoopControl::FindFreeLoopDevice(std::string* loopdev) const { 
    return true;

}



bool LoopControl::EnableDirectIo(int fd) {

#if !defined(LOOP_SET_BLOCK_SIZE)

    static constexpr int LOOP_SET_BLOCK_SIZE = 0x4C09;

#endif

#if !defined(LOOP_SET_DIRECT_IO)

    static constexpr int LOOP_SET_DIRECT_IO = 0x4C08;

#endif



    // Note: the block size has to be >= the logical block size of the underlying

    // block device, *not* the filesystem block size.

    if (ioctl(fd, LOOP_SET_BLOCK_SIZE, 4096)) {

        PLOG(ERROR) << "Could not set loop device block size";

        return false;

    }

    if (ioctl(fd, LOOP_SET_DIRECT_IO, 1)) {

        PLOG(ERROR) << "Could not set loop direct IO";

        return false;

    }

    return true;

}



LoopDevice::LoopDevice(int fd, bool auto_close) : fd_(fd), owns_fd_(auto_close) {

    Init();

}