Android5.0挂载NTFS为只读问题

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一、问题描述

连接两个u盘；一个为NTFS，一个为FAT32；从NTFS可以向FAT32拷贝，反之报错“只读文件系统”。

二、问题原因

mount

/dev/block/vold/8:1 /mnt/usb/843E1E3A3E1E2628 ntfs ro,dirsync,nosuid,nodev,noexec,relatime,uid=1023,gid=1023,umask=02,nls=utf8,errors=continue,mft_zone_multiplier=1 0 0

ll /mnt/usb/

dr-xr-xr-x media_rw media_rw          2015-04-03 14:23 843E1E3A3E1E2628

问题有两个：

1.NTFS格式U盘挂载为READONLY；

2.挂载点目录权限问题

三、问题解决

1.修复问题1

移植fstype_support/android_external_ntfs-3g，使用ntfs-3g挂载。

NTFS_3G文件系统支持包

system/vold/Ntfs.cpp

#define  NTFS_3G_PATH  "/system/bin/ntfs-3g" //add by tankint Ntfs::doMount(const char *fsPath, const char *mountPoint,                 bool ro, bool remount, int ownerUid, int ownerGid,                 int permMask) {    int rc;    unsigned long flags;    char mountData[255];    flags = MS_NODEV | MS_NOEXEC | MS_NOSUID | MS_DIRSYNC;    flags |= (ro ? MS_RDONLY : 0);    flags |= (remount ? MS_REMOUNT : 0);#if 0    char value[PROPERTY_VALUE_MAX];    property_get("persist.sampling_profiler", value, "");    if (value[0] == '1') {        SLOGW("The SD card is world-writable because the"            " 'persist.sampling_profiler' system property is set to '1'.");        permMask = 0;    }    sprintf(mountData,            "uid=%d,gid=%d,fmask=%o,dmask=%o,nls=utf8",            ownerUid, ownerGid, permMask, permMask);    rc = mount(fsPath, mountPoint, "ntfs3g", flags, mountData);#else    SLOGI("mount ntfs block device by tcl ntfs ntfs-3g");    sprintf(mountData,"locale=utf8,uid=%d,gid=%d,fmask=%o,dmask=%o,inherit, atime",\                        ownerUid, ownerGid, permMask, permMask);    const char *args[16];    args[0] = NTFS_3G_PATH;    args[1] = fsPath;    args[2] = mountPoint;    args[3] = "-o";    args[4] = mountData;    args[5] = NULL;    rc = logwrap(5, args, 1);#endif    if (rc) {        SLOGE("%s appears to be a read only filesystem - retrying mount RO", fsPath);        flags |= MS_RDONLY;        rc = mount(fsPath, mountPoint, "ntfs", flags, mountData);    }    return rc;}

2.修复问题2

system/vold/Volume.cpp

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;    }  }}

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