On Thu, 2016-09-08 at 07:48 -0600, Kani, Toshimitsu wrote:
> On Thu, 2016-09-08 at 13:57 +0300, Kirill A. Shutemov wrote:
> >
> > On Mon, Aug 29, 2016 at 10:00:43PM +0000, Kani, Toshimitsu wrote:
:
> > >
> > > Looking further, these shmem_huge handlings only check pre-
> > > conditions. So, we should be able to make shmem_get_unmapped_are
> > > a() as a wrapper, which checks such shmem-specific conitions, and
> > > then call __thp_get_unmapped_area() for the actual work. All
> > > DAX-specific checks are performed in thp_get_unmapped_area() as
> > > well. We can make __thp_get_unmapped_area() as a common
> > > function.
> > >
> > > I'd prefer to make such change as a separate item,
> >
> > Do you have plan to submit such change?
>
> Yes, I will submit the change once I finish testing.
I found a bug in the current code, and need some clarification. The
if-statement below is reverted.
===
diff --git a/mm/shmem.c b/mm/shmem.c
index fd8b2b5..aec5b49 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1980,7 +1980,7 @@ unsigned long shmem_get_unmapped_area(struct file
*file,
return addr;
sb = shm_mnt->mnt_sb;
}
- if (SHMEM_SB(sb)->huge != SHMEM_HUGE_NEVER)
+ if (SHMEM_SB(sb)->huge == SHMEM_HUGE_NEVER)
return addr;
}
===
Because of this bug, mounting tmpfs with "huge=never" enables huge page
mappings, and "huge=always" or others disables it...
The above simple change will change the default behavior, though. When
"huge=" option is not specified, SHMEM_SB(sb)->huge is set to zero,
which is SHMEM_HUGE_NEVER. Therefore, huge page mappings are enabled
by default because of this bug.
What's the intended default behavior of this feature?
Thanks,
-Toshi
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