i'm having real problems on space simple dissapearing on my flash
 partition on Routerboard 450 and a pretty recent trunk version (r40867)

 steps to build and install:

 1) svn'ed openwrt trunk, revision 40867
 2) 'make menuconfig' with no .config present, edited the default one and
 made just two changes: changed subtarget to 'Mikrotik devices with NAND
 flash' and also checked root .tar.gz target image, so i could netboot AND
 install this built
 3) built the images
 4) netbooted the image
 5) installed it on the flash using wget2nand
 6) rebooted from NAND

 everything works fine, no problem until here.

 To test the dissapearing space problem, right after this first boot from
 NAND, that means, a completly fresh OpenWRT install, I run dd to create a
 5Mb file from random data, excluded the file and do everything again.
 Between runs, a counter was being displayed just to let me know how many
 times it has already run.

 i=1; while true; do echo "run # $i"; rm -f /teste; dd if=/dev/urandom
 of=/teste bs=1M count=5; rm -f /teste; df | head -2; i=$(($i + 1)); done



 After running a lot of times, everything SEEMS to be OK, used and
 available spaces are the exact ones i had before starting the test:


 run # 210
 Filesystem           1K-blocks      Used Available Use% Mounted on
 rootfs                   61440      3060     58380   5% /


 However, after stopping the test (CTRL+C), manually excluded the last
 remaining /teste file and rebooted the RB450, i had:


 root@OpenWrt:/# df
 Filesystem           1K-blocks      Used Available Use% Mounted on
 rootfs                   61440     46292     15148  75% /


 My 'used' space went from 3060 to 46292 by simply rebooting !!!

 I ran the dd test for some extra times and space APPEARS unaffected
 between dd runs:


 run # 150
 Filesystem           1K-blocks      Used Available Use% Mounted on
 rootfs                   61440     46292     15148  75% /


 another manually removal of any /teste left, reboot and ...


 root@OpenWrt:/# df
 Filesystem           1K-blocks      Used Available Use% Mounted on
 rootfs                   61440     61424        16 100% /


 and from now on, it's game over ... system really cannot write anything on
 the partition anymore, as i'm really out of space. Listing files from /
 shows that i'm not actually using that much space, which makes me believe,
 somehow, my space is really getting lost, as i stated on the summary of
 this ticket.


 root@OpenWrt:/# dd if=/dev/urandom of=/teste bs=1M count=5
 dd: writing '/teste': No space left on device


 one curious note: during boot, as i'm watching boot from the serial
 console, there's a pause between these lines:


 yaffs: dev is 32505862 name is "mtdblock6" ro
 yaffs: passed flags ""
 ---  pause here ---
 VFS: Mounted root (yaffs filesystem) readonly on device 31:6.
 Freeing unused kernel memory: 228K (802e7000 - 80320000


 On the freshly installed OpenWRT, this pause is pretty short, less than 1
 second. And as space is getting lost, this pause gets bigger, reaching
 almost 7-8 seconds when i have the disk full problem on the RB450 (64Mb
 NAND flash). Dont know if this matters, but i noticed it.

 On RB450G, things are a little different, as space seems to get lost
 DURING dd runs as well:


 run # 7
 Filesystem           1K-blocks      Used Available Use% Mounted on
 rootfs                  520192      7224    512968   1% /

 run # 8
 Filesystem           1K-blocks      Used Available Use% Mounted on
 rootfs                  520192      7264    512928   1% /

 ...

 run # 27
 Filesystem           1K-blocks      Used Available Use% Mounted on
 rootfs                  520192      8032    512160   2% /

 run # 28
 Filesystem           1K-blocks      Used Available Use% Mounted on
 rootfs                  520192      8072    512120   2% /

 ...

 run # 37 (last run i waited)
 Filesystem           1K-blocks      Used Available Use% Mounted on
 rootfs                  520192      8444    511748   2% /


 and after manually excluded any /teste left and rebooted:


 root@OpenWrt:/# df
 Filesystem           1K-blocks      Used Available Use% Mounted on
 rootfs                  520192      8520    511672   2% /



 So, i can reproduce this weird and apparently buggy behavior on RB450 as
 well on RB450G. The two boards behaves a little different, RB450 losing
 space during reboots and RB450G losing space during normal operations of
 write/delete files and reboot as well.

 I had already opened a ticket, three years ago, regarding weird space
 usage on RB450, #9818 [https://dev.openwrt.org/ticket/9818]. It was closed
 with 'not a bug, wont fix'. I must confess that, at that time, i hadn't
 noticed if space was being lost during reboots as i noticed now.

 I have also found, on the forums, users complaining about space
 dissapearing on their yaffs2 partition as well. Curiously enough, both
 complaints are from users running on Routerboards

 [https://forum.openwrt.org/viewtopic.php?id=47352]

 [https://forum.openwrt.org/viewtopic.php?id=44940]

 I know lots of OpenWRT users wont do any kind of writing on the flash
 memory, just config files, so this will probably not be a real problem for
 them or, maybe, it will simply take too long for becaming a problem in
 fact. By the other side, i run squid on these boxes and need to have
 logging enabled. Of course, i have a closely watched log rotation script,
 given the low available flash space available. Anyway, that's completly
 fine to me, as these are deployed on small networks.

 For those that, somehow, uses writing on the partitions, this is certainly
 a critical bug because after reaching the 'disk full' condition, only a
 reflash will restore the box usable again. I could not find a way of
 'recovering' that space, so just a new flashing will get that box
 operational again.

-- 


	Atenciosamente / Sincerily,
	Leonardo Rodrigues
	Solutti Tecnologia
	http://www.solutti.com.br

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