direct i/o problem with 2.4.20 and 2.4.21rc7

I have an application that requires direct i/o to thousands of files. On 2.4.19 the open's would eventually fail (at around 7200 files). On 2.4.20 and 2.4.21rc7 the machine hangs.

Here's a sample program to do the deed:

    wget http://www.skarven.net/lda/crashme.c
    cc -o crashme crashme.c	# compile it
    ./crashme 4000		# OK
    ./crashme 9999		# CRASH

It's a little obfuscated to eliminate the need for root privileges to mess with rlimit. It simply opens a bunch of files with O_DIRECT and, when enough files are open, the system will hang.

The system hangs when '/proc/slabinfo' reports that 'kiobuf' reaches just over 7230 active objects. I don't believe that this problem is specific to any particular file system as the failure occurs when using both ext2 and reiserfs.

Larry Auton