JFFS2 Garbage collection issue

[Albrecht, Harald]

Hi all,

we are currently facing a problem with the Garbage-collection on a JFFS2 
file system.

We have an embedded linux system based on an ARM9 AT91RM9200 processor 
with an Intel / Micron JS28F256 NOR-flash of 32MB in size.
The Flash holds the U-Boot loader and its environment and in the main 
part (30MB) of the chip a JFFS2-based root-file-system.
Our Linux kernel version is 2.6.24.3

Some minutes after startup of the system, the garbage collector (gc.c) 
does a scan of the file system, gathering information for the garbage 
collection procedures that may be initiated based upon that data.
On some file systems, especially such with long runtime and therefore 
many file operations, this scan consumes a lot of time. On some systems 
it stays in that scan for more that 10 minutes. The problem with this 
behaviour is the fact, that during the scan the file system is locked, 
and therefore all file operations are suspended. This leads to a crash 
of the system, when the application program hangs for a long time, 
waiting for a file operation to return from a system call, and the 
watchdog is not triggered.

In a test system without watchdog, after the scan, the system runs normally.
The flash chip itself shows no errors, so it seems to be a problem of 
the file system.

Any idea or suggestion to solve the problem would be very welcome!

Harald Albrecht