Android媒体应用下不能将两个U盘间文件复制

一、现象

复制时提示只读文件。

二、原因

1.错误

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shell@coconut:/mnt/usb $ ls -l  
drwxrwxr-x media_rw media_rw          1970-01-01 08:00 1214-9D53  
drwxrwxr-x media_rw media_rw          1970-01-01 08:00 4256-0C90  

shell@coconut:/mnt/usb $ ls -l
drwxrwxr-x media_rw media_rw          1970-01-01 08:00 1214-9D53
drwxrwxr-x media_rw media_rw          1970-01-01 08:00 4256-0C90

2.正确

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130|shell@coconut:/mnt/usb $ ls -l  
drwxrwxr-x system   sdcard_rw          2015-03-26 19:51 1214-9D53  
drwxrwxr-x system   sdcard_rw          2015-03-26 19:50 4256-0C90  

130|shell@coconut:/mnt/usb $ ls -l
drwxrwxr-x system   sdcard_rw          2015-03-26 19:51 1214-9D53
drwxrwxr-x system   sdcard_rw          2015-03-26 19:50 4256-0C90

三、问题解决
在挂载参数上做改动

system/vold/Volume.cpp

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int Volume::mountVol() {  
  if (isFatFs) {  
    if (Fat::doMount(devicePath, getMountpoint(), false, false, false,  
                /*AID_MEDIA_RW*/AID_SYSTEM, /*AID_MEDIA_RW*/AID_SDCARD_RW, /*permMask*/0002, true)) { //modify by tank  
      SLOGE("%s failed to mount via VFAT (%s)\n", devicePath, strerror(errno));  
      isFatFs = false;  
    } else {  
      isExtFs = false;  
      isExfatFs = false;  
    }  
  }  
}  

int Volume::mountVol() {
if (isFatFs) {
if (Fat::doMount(devicePath, getMountpoint(), false, false, false,
/*AID_MEDIA_RW*/AID_SYSTEM, /*AID_MEDIA_RW*/AID_SDCARD_RW, /*permMask*/0002, true)) { //modify by tank
SLOGE("%s failed to mount via VFAT (%s)\n", devicePath, strerror(errno));
isFatFs = false;
} else {
isExtFs = false;
isExfatFs = false;
}
}
}

过滤log方法：logcat -s Vold MountService DirectVolume