Memory leak problem with JFFS2

[Frederic Giasson]

Hi all,

I discovered what looks like a memory leak in JFFS2.
I setup a test in which a script does the following operations in order:
	1- mount JFFS2;
	2- sync;
	3- Erase linux kernel file from JFFS2; 
	4- sync;	
	5- Copy a new file to JFFS2 partition ( gzip-compressed linux kernel
)
	6- sync;
	7- umount JFFS2;
	8- vmstat;
	9- Goto step 1.

After numerous loops of this test script (between 110 and 470, it is never
the same), the system hangs at mount command.  Looking at the log, each time
vmstat is called I observe that free memory has gone down 8KB after each
loop of the script.  This is very likely to mean that there is a memory leak
related to JFFS2's memory usage ( free/dirty/very dirty lists and so forth
maybe ).  I did not dig into the code yet, I though that maybe someone else
encountered the problem and had already investigated it.

So a setup a second test script which is:

	1- mount JFFS2;
	2- sync;
	3- umount JFFS2;
	4- vmstat;
	5- goto step 1;

And I observed that free memory was going down 8KB each loop, same as in
first test.  

So to confirm that the leak comes from the fact of doing repeated
mount/umount, I setup a third test which is exactly like the first test,
except that I removed mount and umount commands. That time free memory usage
remained constant, which make me think that the leak is probably related to
memory incorrectly freed at umount time.  Nevertheless, the third test also
hanged, after 170 loops, at copy command.		

Between, note that the sync command sprinkled in the test loops are there to
speed up the process.  In fact, I observed that doing a sync after a file
erasure triggers the gc and wait for it to complete its task, so when I
write data to JFFS2 after it does not need to garbage collect in the mean
time.  This makes write times to JFFS2 much more deterministic.

I am using linux kernel 2.4.19 pre 7, and JFFS2 code from CVS as per May
14th, 2002.  By the way, does anybody can tell me if there is some sorts of
branches or labels in JFFS2 CVS, other that time stamps?  Is there a label
per linux release, for instance?

Thanks in advance,

Frédéric Giasson