• Vyacheslav Dubeyko's avatar
    nilfs2: fix fix very long mount time issue · a9bae189
    Vyacheslav Dubeyko authored
    There exists a situation when GC can work in background alone without
    any other filesystem activity during significant time.
    
    The nilfs_clean_segments() method calls nilfs_segctor_construct() that
    updates superblocks in the case of NILFS_SC_SUPER_ROOT and
    THE_NILFS_DISCONTINUED flags are set.  But when GC is working alone the
    nilfs_clean_segments() is called with unset THE_NILFS_DISCONTINUED flag.
    As a result, the update of superblocks doesn't occurred all this time
    and in the case of SPOR superblocks keep very old values of last super
    root placement.
    
    SYMPTOMS:
    
    Trying to mount a NILFS2 volume after SPOR in such environment ends with
    very long mounting time (it can achieve about several hours in some
    cases).
    
    REPRODUCING PATH:
    
    1. It needs to use external USB HDD, disable automount and doesn't
       make any additional filesystem activity on the NILFS2 volume.
    
    2. Generate temporary file with size about 100 - 500 GB (for example,
       dd if=/dev/zero of=<file_name> bs=1073741824 count=200).  The size of
       file defines duration of GC working.
    
    3. Then it needs to delete file.
    
    4. Start GC manually by means of command "nilfs-clean -p 0".  When you
       start GC by means of such way then, at the end, superblocks is updated
       by once.  So, for simulation of SPOR, it needs to wait sometime (15 -
       40 minutes) and simply switch off USB HDD manually.
    
    5. Switch on USB HDD again and try to mount NILFS2 volume.  As a
       result, NILFS2 volume will mount during very long time.
    
    REPRODUCIBILITY: 100%
    
    FIX:
    
    This patch adds checking that superblocks need to update and set
    THE_NILFS_DISCONTINUED flag before nilfs_clean_segments() call.
    Reported-by: default avatarSergey Alexandrov <splavgm@gmail.com>
    Signed-off-by: default avatarVyacheslav Dubeyko <slava@dubeyko.com>
    Tested-by: default avatarVyacheslav Dubeyko <slava@dubeyko.com>
    Acked-by: default avatarRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
    Tested-by: default avatarRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
    Cc: <stable@vger.kernel.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    a9bae189
ioctl.c 21.3 KB