direct i/o problem with 2.4.20 and 2.4.21rc7

From: Larry Auton (
Date: Sat Jun 14 2003 - 13:18:47 EST

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:

    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
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