On Wed, Sep 26, 2018 at 11:24:55AM -0700, Bart Van Assche wrote:

On Wed, 2018-09-26 at 17:06 +0200, Johannes Thumshirn wrote:

quoted

On Wed, Sep 26, 2018 at 04:57:32PM +0200, Christoph Hellwig wrote:

quoted

I don't think this actually works given that rpm_status only exists
if CONFIG_PM is set.

I think it'll work as GCC does constant propagation. There are
actually some places in the kernel that follow this pattern.

This is what gcc on my development system thinks about that proposal:

In file included from ./arch/x86/include/asm/bug.h:83:0,
                 from ./include/linux/bug.h:5,
                 from ./include/linux/thread_info.h:12,
                 from ./arch/x86/include/asm/preempt.h:7,
                 from ./include/linux/preempt.h:81,
                 from ./include/linux/spinlock.h:51,
                 from ./include/linux/seqlock.h:36,
                 from ./include/linux/time.h:6,
                 from ./include/linux/stat.h:19,
                 from ./include/linux/module.h:10,
                 from block/blk-core.c:15:
block/blk-core.c: In function ‘elv_next_request’:
block/blk-core.c:2795:44: error: ‘struct request_queue’ has no member named ‘rpm_status’; did you mean ‘stats’?
                            WARN_ON_ONCE(q->rpm_status == RPM_SUSPENDED);
                                            ^
./include/asm-generic/bug.h:69:25: note: in definition of macro ‘WARN_ON_ONCE’
  int __ret_warn_on = !!(condition);   \
                         ^~~~~~~~~
scripts/Makefile.build:305: recipe for target 'block/blk-core.o' failed

Aparently this only works for functions and not struct members, my
bad.

	Johannes
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Johannes Thumshirn                                          Storage
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