* Urs Beyerle ([log in to unmask]) [20061115 11:13]:

> As written in
> ftp://ftp.scientificlinux.org/linux/scientific/44/i386/contrib/RPMS/xfs/README,
> XFS is not recommended on SL4 32bit kernels.

Correct.

> What kind of problems where observed?

Starting with RHEL4, the 4KSTACKS option is enabled when the
kernel is compiled.  This limits each process' kernel stack to
4K with separate stack for interrupts.  XFS can have deep call
chains (it's a complex filesystem doing complex stuff) and the
codebase included in SL4 has not been updated to take this reduced
stackspace into consideration (it's effectively the XFS codebase
from the 2.6.9 times).  As a result, it is possible to load the
machine so that XFS overflows its stack and then the game is
over.  It can be easily triggered by stacking several software
layers (SCSI+LVM/MD+XFS+NFS) on top of each other but it has
been demonstrated that the stack overflow can be triggered with
sufficient load on plain SCSI+XFS systems as well.

> Is somebody working on a solution, which does not require to
> recompile the standard SL4 kernel?

The proper solution would be to backport stack-usage reducing XFS
patches from newer vanilla kernels to the SL4 kernel.  AFAICT
nobody is working on it actively as we speak.  There are some
garage projects here and there (hint-hint ;) but no ETA and
certainly no commitment.  Your best bet is to move to 64-bit
platform (practically any CPU you can buy nowadays would qualify).

Peter

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