ubifs became broken on contigous power-fails

[Alexander Pazdnikov]

Artem, thank you very much, now applying your patches and making new stress-tests :-)

Also last holidays have caught another issue.

We've modified our program to primary mount ubi2:dbfs in RO, then sleep 3 secs, then remount in RW.
Today have found half (5/10) of devices with the error : No space left on device
If mount by hands this stalled fs primary in RW mode, then everything goes OK.
If drop down mount "mount ubi2:dbfs in RO, then sleep 3 secs", leave only mount in RW, everything also goes OK.

[    6.576168] UBIFS: recovery needed
[    6.665035] UBIFS: recovery deferred
[    6.668941] UBIFS: mounted UBI device 2, volume 0, name "dbfs"
[    6.674801] UBIFS: mounted read-only
[    6.678707] UBIFS: file system size:   189407232 bytes (184968 KiB, 180 MiB, 1468 LEBs)
[    6.687496] UBIFS: journal size:       9418752 bytes (9198 KiB, 8 MiB, 73 LEBs)
[    6.694332] UBIFS: media format:       w4/r0 (latest is w4/r0)
[    6.700191] UBIFS: default compressor: lzo
[    6.705074] UBIFS: reserved for root:  4952683 bytes (4836 KiB)
[    9.787104] UBIFS: completing deferred recovery
Remounting ubi2:dbfs on /usr/local/ecom/db failed: No space left on device

# df
Filesystem                Size      Used Available Use% Mounted on
ubi0:rootfs              13.2M      7.2M      6.0M  55% /
tmpfs                     4.0K         0      4.0K   0% /dev
shm                       1.0M         0      1.0M   0% /dev/shm
tmpfs                     1.0M     12.0K   1012.0K   1% /tmp
tmpfs                     1.0M      4.0K   1020.0K   0% /root
ubi1:logs                11.5M      2.4M      8.4M  22% /var/log
ubi1:tmp                 13.4M     16.0K     12.7M   0% /usr/local/ecom/tmp
ubi0:local                2.1M     44.0K      1.9M   2% /var/local
ubi:config                2.0M     68.0K      1.9M   3% /usr/local/ecom/conf
ubi2:dbfs               169.2M     18.7M    145.8M  11% /usr/local/ecom/db

-- 
Best regards,
Sasha