Denys Vlasenko wrote:
> Hi Al, Benjamin, David,
>
> struct kiocb is placed on stack by, for example, do_sync_write().
> Eventually it contributes to xfs writeout path's stack usage, among others.
> This is *the* path which causes 4k stack overflows on i386 with xfs.
>
> This patch trivially reorders fields of this structure,
> and makes some of them smaller.
Great, thanks for doing this. I see one fatal bug, though. Can you fix
it up and resubmit?
- unsigned long ki_flags;
+ unsigned short ki_flags; /* range: 0..2 */
Careful, ki_flags is used by the bitops routines which require an
unsigned long. I'd just leave ki_flags as is.
> ki_nr_segs: ulong -> uint: nobody uses 4 billion element writev's
> (and it would not work anyway)
Indeed. Maybe explicitly mention that it's safe 'cause we pass
ki_nbytes to rw_copy_check_uvector() for comparison against UIO_MAXIOV
before we store it in the kiocb.
+ /*unsigned short ki_opcode; - moved up for denser packing */
Don't bother commenting out fields that are moved, just move 'em.
Otherwise it looks great, thanks.
- z
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