Messages in this thread |  | | Subject | Re: [SOLVED + PATCH]: documented Oops running big-endian reiserfs on parisc architecture | From | "Ulrich Weigand" <> | Date | Tue, 4 Sep 2001 16:34:28 +0200 |
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Jeff Mahoney wrote:
> Are the S/390 asm/unaligned.h versions broken, or is the ReiserFS code doing > something not planned for? It's a 16-bit member, at a 16-bit alignment > in the structure. The structure itself need not be aligned in any > particular manner as it is read directly from disk, and is a packed structure.
The S/390 unaligned.h macros are just direct assignments because the S/390 hardware normally *allows* unaligned accesses just fine.
It is only *atomic* accesses (those implemented using the S/390 compare-and-swap instruction) that need to be word aligned; this includes the atomic bit operations that reiserfs appears to be using.
If these instructions really *need* to be atomic, then reiserfs should ensure they are performed on properly aligned data, or else there might be subtle bugs even on Intel, because the operations will not actually be atomic (even though they don't trap).
If you say that reiserfs doesn't really need these operations to be atomic because they run under other locks anyway, then they should not be using atomic operations in the first place; this will only cause unnecessary slowdown even on Intel.
Mit freundlichen Gruessen / Best Regards
Ulrich Weigand
-- Dr. Ulrich Weigand Linux for S/390 Design & Development IBM Deutschland Entwicklung GmbH, Schoenaicher Str. 220, 71032 Boeblingen Phone: +49-7031/16-3727 --- Email: Ulrich.Weigand@de.ibm.com
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