[Galaxy S 4 Mini Q&A, Help & Troubleshooting] MaChiMiB:
Check your external sdcards f2fs file system and repair it

All you need is already on your phone.

Preperation

- Use "Terminal Emulator" on the phone or adb shell commands

- Get root by entering "su"

[*] Find the device your SD card is bound to

- Tpye "mount" to get a list with very likely "/dev/block/vold/179:33 on /mnt/media_rw/sdcard1" or simillar in it

- /dev/block/vold/179:33 is your external sdcard

[*] Leave MTP mode

- Go to Settings -> Storage -> Menue (3 dots) -> USB computer connection: select Mass Storage (MTP prevents the work with the sdcard).

- You won't see "/dev/block/vold/179:33" anymore in the mount list.

[*] Execute fsck.f2fs to check and repair

- "cd /system/bin" to change directory

- execute "fsck.f2fs -f /dev/block/vold/179:33"

- it takes a while to check/repair the sdcard

other fsck.f2fs options:

https://bbs.archlinux.org/viewtopic.php?id=190239

Posts that helped me:

http://android.stackexchange.com/questions/38745/check-and-fix-sd-card-errors-within-android-itself

http://ubuntuforums.org/showthread.php?t=2086313&page=4&p=12382119#post12382119

Example for the mount list 1):

C:\Minimal ADB and Fastboot>adb shell mount
rootfs on / type rootfs (ro,seclabel,relatime)
tmpfs on /dev type tmpfs (rw,seclabel,nosuid,relatime,mode=755)
devpts on /dev/pts type devpts (rw,seclabel,relatime,mode=600)
proc on /proc type proc (rw,relatime)
sysfs on /sys type sysfs (rw,seclabel,relatime)
selinuxfs on /sys/fs/selinux type selinuxfs (rw,relatime)
debugfs on /sys/kernel/debug type debugfs (rw,seclabel,relatime)
none on /acct type cgroup (rw,relatime,cpuacct)
none on /sys/fs/cgroup type tmpfs (rw,seclabel,relatime,mode=750,gid=1000)
none on /sys/fs/cgroup/memory type cgroup (rw,relatime,memory)
tmpfs on /mnt/asec type tmpfs (rw,seclabel,relatime,mode=755,gid=1000)
tmpfs on /mnt/obb type tmpfs (rw,seclabel,relatime,mode=755,gid=1000)
none on /dev/memcg type cgroup (rw,relatime,memory)
none on /dev/cpuctl type cgroup (rw,relatime,cpu)
/dev/block/platform/msm_sdcc.1/by-name/system on /system type ext4 (rw,seclabel,relatime,errors=panic,data=ordered)
/dev/block/platform/msm_sdcc.1/by-name/userdata on /data type f2fs (rw,seclabel,nosuid,nodev,noatime,nodiratime,background_gc=on,discard,user_xattr,inline_xattr,acl,flush_merge,active_logs=6)
/dev/block/platform/msm_sdcc.1/by-name/cache on /cache type f2fs (rw,seclabel,nosuid,nodev,noatime,nodiratime,background_gc=on,discard,user_xattr,inline_xattr,acl,flush_merge,active_logs=6)
/dev/block/platform/msm_sdcc.1/by-name/efs on /efs type ext4 (rw,seclabel,nosuid,nodev,noatime,journal_checksum,journal_async_commit,noauto_da_alloc,data=ordered)
/dev/block/platform/msm_sdcc.1/by-name/persist on /persist type ext4 (rw,seclabel,nosuid,nodev,relatime,nodelalloc,data=ordered)
/dev/block/platform/msm_sdcc.1/by-name/modem on /firmware type vfat (ro,context=u:object_r:firmware_file:s0,relatime,uid=1000,gid=1000,fmask=0337,dmask=0227,codepage=cp437,iocharset=iso8859-1,shortname=lower,errors=remount-ro)
/dev/fuse on /mnt/shell/emulated type fuse (rw,nosuid,nodev,noexec,relatime,user_id=1023,group_id=1023,default_permissions,allow_other)
[COLOR=red]/dev/block/vold/179:33 on /mnt/media_rw/sdcard1 type f2fs [/COLOR](rw,dirsync,context=u:object_r:sdcard_posix:s0,nosuid,nodev,noexec,noatime,background_gc=off,user_xattr,inline_xattr,acl,active_logs=2)
/dev/block/vold/179:33 on /mnt/secure/asec type f2fs (rw,dirsync,context=u:object_r:sdcard_posix:s0,nosuid,nodev,noexec,noatime,background_gc=off,user_xattr,inline_xattr,acl,active_logs=2)
/dev/fuse on /storage/sdcard1 type fuse (rw,nosuid,nodev,noexec,relatime,user_id=1023,group_id=1023,default_permissions,allow_other)