Re: UBI memory leak after creating and removing volumes

["John Smith" <john.smith@pace.com>]

Previously I said:

> On Tue, 2009-02-17 at 12:01 +0000, John.Smith@pace.com wrote:
> > I am using a 2.6.18 Kernel, patched with MTD from Kernel 2.6.21, and
> > UBI from the mainline kernel a few days later on 1 May 2007.  The
> > whole is running on an embedded MIPS device.
> >

The problem is still present on current versions of Linux. I have
tested on 2.6.28.6 using QEMU to make a virtual x86.

With these settings in the kernel .config file:
   CONFIG_MTD=y
   CONFIG_MTD_BLKDEVS=y
   CONFIG_MTD_MTDRAM=y
   CONFIG_MTD_UBI=y

then a sequence of calls of the form

for ((i=0; i<100; i++)) ; do
   ubimkvol -d 0 -n 2 -N vol2 -s 1000
   ubimkvol -d 0 -n 3 -N vol3 -s 1000
   ubirmvol -d 0 -n 3
   ubirmvol -d 0 -n 2
done
cat /proc/meminfo | grep Slab

shows Slab increasing by about 1.6kB per iteration

The problem can also be demonstrated using MTD modules,
without using UBI. If I build two MTD simulated devices
as kernel modules using these settings in .config:
   CONFIG_MTD_MTDRAM=m
   CONFIG_MTD_NAND_NANDSIM=m

then

   insmod mtdram.ko
   insmod nandsim.ko
   rmmod  nandsim.ko
   rmmod  mtdram.ko

shows a similar leak of about 1.6kB.


The leak does not happen if the calls are not nested. So
   insmod mtdram.ko
   rmmod  mtdram.ko
   insmod nandsim.ko
   rmmod  nandsim.ko
and
   ubimkvol -d 0 -n 2 -N vol2 -s 1000
   ubirmvol -d 0 -n 2
   ubimkvol -d 0 -n 3 -N vol3 -s 1000
   ubirmvol -d 0 -n 3
do not leak.

The leak does not happen if
# CONFIG_MTD_BLKDEVS is not set.

 From /proc/slabinfo it seems that we are leaking sysfs_dir_cache
objects.

John

John Smith

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