Hi all
The test for VM_CAN_NONLINEAR always fails
Signed-off-by: Yan Zheng<[email protected]>
----
diff -ur linux-2.6.23-rc9/mm/fremap.c linux/mm/fremap.c
--- linux-2.6.23-rc9/mm/fremap.c 2007-10-07 15:03:33.000000000 +0800
+++ linux/mm/fremap.c 2007-10-08 19:33:44.000000000 +0800
@@ -160,7 +160,7 @@
if (vma->vm_private_data && !(vma->vm_flags & VM_NONLINEAR))
goto out;
- if (!vma->vm_flags & VM_CAN_NONLINEAR)
+ if (!(vma->vm_flags & VM_CAN_NONLINEAR))
goto out;
if (end <= start || start < vma->vm_start || end > vma->vm_end)
On Mon, Oct 08, 2007 at 07:45:08PM +0800, Yan Zheng wrote:
>Hi all
>
>The test for VM_CAN_NONLINEAR always fails
>
>Signed-off-by: Yan Zheng<[email protected]>
>----
>diff -ur linux-2.6.23-rc9/mm/fremap.c linux/mm/fremap.c
>--- linux-2.6.23-rc9/mm/fremap.c 2007-10-07 15:03:33.000000000 +0800
>+++ linux/mm/fremap.c 2007-10-08 19:33:44.000000000 +0800
>@@ -160,7 +160,7 @@
> if (vma->vm_private_data && !(vma->vm_flags & VM_NONLINEAR))
> goto out;
>
>- if (!vma->vm_flags & VM_CAN_NONLINEAR)
>+ if (!(vma->vm_flags & VM_CAN_NONLINEAR))
Good catch!
! operator has higher priority than & operator.
Acked by me. ;-)
> goto out;
>
> if (end <= start || start < vma->vm_start || end > vma->vm_end)
On Mon, 8 Oct 2007 19:45:08 +0800 "Yan Zheng" <[email protected]> wrote:
> Hi all
>
> The test for VM_CAN_NONLINEAR always fails
>
> Signed-off-by: Yan Zheng<[email protected]>
> ----
> diff -ur linux-2.6.23-rc9/mm/fremap.c linux/mm/fremap.c
> --- linux-2.6.23-rc9/mm/fremap.c 2007-10-07 15:03:33.000000000 +0800
> +++ linux/mm/fremap.c 2007-10-08 19:33:44.000000000 +0800
> @@ -160,7 +160,7 @@
> if (vma->vm_private_data && !(vma->vm_flags & VM_NONLINEAR))
> goto out;
>
> - if (!vma->vm_flags & VM_CAN_NONLINEAR)
> + if (!(vma->vm_flags & VM_CAN_NONLINEAR))
> goto out;
>
> if (end <= start || start < vma->vm_start || end > vma->vm_end)
Lovely. From this we can deduce that nobody has run remap_file_pages() since
2.6.23-rc1 and that nobody (including the developer who made that change) ran it
while that change was in -mm.
I'm surprise that LTP doesn't have any remap_file_pages() tests.
Have you runtime tested this change?
Thanks.
On Mon, 8 Oct 2007 10:04:56 -0700 Andrew Morton wrote:
> On Mon, 8 Oct 2007 19:45:08 +0800 "Yan Zheng" <[email protected]> wrote:
>
> > Hi all
> >
> > The test for VM_CAN_NONLINEAR always fails
> >
> > Signed-off-by: Yan Zheng<[email protected]>
> > ----
> > diff -ur linux-2.6.23-rc9/mm/fremap.c linux/mm/fremap.c
> > --- linux-2.6.23-rc9/mm/fremap.c 2007-10-07 15:03:33.000000000 +0800
> > +++ linux/mm/fremap.c 2007-10-08 19:33:44.000000000 +0800
> > @@ -160,7 +160,7 @@
> > if (vma->vm_private_data && !(vma->vm_flags & VM_NONLINEAR))
> > goto out;
> >
> > - if (!vma->vm_flags & VM_CAN_NONLINEAR)
> > + if (!(vma->vm_flags & VM_CAN_NONLINEAR))
> > goto out;
> >
> > if (end <= start || start < vma->vm_start || end > vma->vm_end)
>
> Lovely. From this we can deduce that nobody has run remap_file_pages() since
> 2.6.23-rc1 and that nobody (including the developer who made that change) ran it
> while that change was in -mm.
I've run rmap-test with -M (use remap_file_pages) and
remap-test from ext3-tools, but not remap_file_pages for some reason.
I'll now add remap_file_pages soon.
Maybe those other 2 tests aren't strong enough (?).
Or maybe they don't return a non-0 exit status even when they fail...
(I'll check.)
> I'm surprise that LTP doesn't have any remap_file_pages() tests.
quick grep didn't find any for me.
> Have you runtime tested this change?
>
> Thanks.
---
~Randy
On Mon, 8 Oct 2007 10:28:43 -0700
Randy Dunlap <[email protected]> wrote:
> On Mon, 8 Oct 2007 10:04:56 -0700 Andrew Morton wrote:
>
> > On Mon, 8 Oct 2007 19:45:08 +0800 "Yan Zheng" <[email protected]> wrote:
> >
> > > Hi all
> > >
> > > The test for VM_CAN_NONLINEAR always fails
> > >
> > > Signed-off-by: Yan Zheng<[email protected]>
> > > ----
> > > diff -ur linux-2.6.23-rc9/mm/fremap.c linux/mm/fremap.c
> > > --- linux-2.6.23-rc9/mm/fremap.c 2007-10-07 15:03:33.000000000 +0800
> > > +++ linux/mm/fremap.c 2007-10-08 19:33:44.000000000 +0800
> > > @@ -160,7 +160,7 @@
> > > if (vma->vm_private_data && !(vma->vm_flags & VM_NONLINEAR))
> > > goto out;
> > >
> > > - if (!vma->vm_flags & VM_CAN_NONLINEAR)
> > > + if (!(vma->vm_flags & VM_CAN_NONLINEAR))
> > > goto out;
> > >
> > > if (end <= start || start < vma->vm_start || end > vma->vm_end)
> >
> > Lovely. From this we can deduce that nobody has run remap_file_pages() since
> > 2.6.23-rc1 and that nobody (including the developer who made that change) ran it
> > while that change was in -mm.
>
> I've run rmap-test with -M (use remap_file_pages) and
> remap-test from ext3-tools, but not remap_file_pages for some reason.
>
> I'll now add remap_file_pages soon.
> Maybe those other 2 tests aren't strong enough (?).
> Or maybe they don't return a non-0 exit status even when they fail...
> (I'll check.)
Perhaps Yan Zheng can tell us what test was used to demonstrate this?
>
> > I'm surprise that LTP doesn't have any remap_file_pages() tests.
>
> quick grep didn't find any for me.
Me either. There are a few lying around the place which could be
integrated.
It would be good if LTP were to have some remap_file_pages() tests
(please). As we see here, it is something which we can easily break, and
leave broken for some time.
On Mon, 8 Oct 2007, Yan Zheng wrote:
>
> The test for VM_CAN_NONLINEAR always fails
Good catch indeed. Though I was puzzled how we do nonlinear at all,
until I realized it's "The test for not VM_CAN_NONLINEAR always fails".
It's not as serious as it appears, since code further down has been
added more recently to simulate nonlinear on non-RAM-backed filesystems,
instead of going the real nonlinear way; so most filesystems are now not
required to do what VM_CAN_NONLINEAR was put in to ensure they could do.
I'm confused as to where that leaves us: is this actually a fix that
needs to go into 2.6.23? or will it suddenly disable a system call
which has been silently working fine on various filesystems which did
not add VM_CAN_NONLINEAR? could we just rip out VM_CAN_NONLINEAR?
I hope Nick or Miklos is clearer on what the risks are.
(Apologies for all the "not"s and "non"s here, I'm embarrassed
after just criticizing Ingo's SCHED_NO_NO_OMIT_FRAME_POINTER!)
Hugh
>
> Signed-off-by: Yan Zheng<[email protected]>
> ----
> diff -ur linux-2.6.23-rc9/mm/fremap.c linux/mm/fremap.c
> --- linux-2.6.23-rc9/mm/fremap.c 2007-10-07 15:03:33.000000000 +0800
> +++ linux/mm/fremap.c 2007-10-08 19:33:44.000000000 +0800
> @@ -160,7 +160,7 @@
> if (vma->vm_private_data && !(vma->vm_flags & VM_NONLINEAR))
> goto out;
>
> - if (!vma->vm_flags & VM_CAN_NONLINEAR)
> + if (!(vma->vm_flags & VM_CAN_NONLINEAR))
> goto out;
>
> if (end <= start || start < vma->vm_start || end > vma->vm_end)
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
>
2007/10/8, Hugh Dickins <[email protected]>:
> On Mon, 8 Oct 2007, Yan Zheng wrote:
> >
> > The test for VM_CAN_NONLINEAR always fails
> Good catch indeed. Though I was puzzled how we do nonlinear at all,
> until I realized it's "The test for not VM_CAN_NONLINEAR always fails".
> It's not as serious as it appears, since code further down has been
> added more recently to simulate nonlinear on non-RAM-backed filesystems,
> instead of going the real nonlinear way; so most filesystems are now not
> required to do what VM_CAN_NONLINEAR was put in to ensure they could do.
> I'm confused as to where that leaves us: is this actually a fix that
> needs to go into 2.6.23? or will it suddenly disable a system call
> which has been silently working fine on various filesystems which did
> not add VM_CAN_NONLINEAR? could we just rip out VM_CAN_NONLINEAR?
> I hope Nick or Miklos is clearer on what the risks are.
> (Apologies for all the "not"s and "non"s here, I'm embarrassed
> after just criticizing Ingo's SCHED_NO_NO_OMIT_FRAME_POINTER!)
> Hugh
Yes, I mean "The test for not VM_CAN_NONLINEAR always fails". please
forgive my poor English.
On Monday 08 October 2007 23:37, Hugh Dickins wrote:
> On Mon, 8 Oct 2007, Yan Zheng wrote:
> > The test for VM_CAN_NONLINEAR always fails
>
> Good catch indeed. Though I was puzzled how we do nonlinear at all,
> until I realized it's "The test for not VM_CAN_NONLINEAR always fails".
>
> It's not as serious as it appears, since code further down has been
> added more recently to simulate nonlinear on non-RAM-backed filesystems,
> instead of going the real nonlinear way; so most filesystems are now not
> required to do what VM_CAN_NONLINEAR was put in to ensure they could do.
Well, I think all filesystems can do VM_CAN_NONLINEAR anyway. Device
drivers and "weird" things tend to have trouble...
> I'm confused as to where that leaves us: is this actually a fix that
> needs to go into 2.6.23? or will it suddenly disable a system call
> which has been silently working fine on various filesystems which did
> not add VM_CAN_NONLINEAR? could we just rip out VM_CAN_NONLINEAR?
We probably should keep VM_CAN_NONLINEAR for the moment, I think.
But now that we have the fallback path, we _could_ use that instead of
failing. I doubt anybody will be using nonlinear mappings on anything but
regular files for the time being, but as a trivial fix, I think this probably
should go into 2.6.23.
Thanks for spotting this problem
Acked-by: Nick Piggin <[email protected]>
> I hope Nick or Miklos is clearer on what the risks are.
>
> (Apologies for all the "not"s and "non"s here, I'm embarrassed
> after just criticizing Ingo's SCHED_NO_NO_OMIT_FRAME_POINTER!)
>
> Hugh
>
> > Signed-off-by: Yan Zheng<[email protected]>
> > ----
> > diff -ur linux-2.6.23-rc9/mm/fremap.c linux/mm/fremap.c
> > --- linux-2.6.23-rc9/mm/fremap.c 2007-10-07 15:03:33.000000000 +0800
> > +++ linux/mm/fremap.c 2007-10-08 19:33:44.000000000 +0800
> > @@ -160,7 +160,7 @@
> > if (vma->vm_private_data && !(vma->vm_flags & VM_NONLINEAR))
> > goto out;
> >
> > - if (!vma->vm_flags & VM_CAN_NONLINEAR)
> > + if (!(vma->vm_flags & VM_CAN_NONLINEAR))
> > goto out;
> >
> > if (end <= start || start < vma->vm_start || end > vma->vm_end)
> > -
> > To unsubscribe from this list: send the line "unsubscribe linux-kernel"
> > in the body of a message to [email protected]
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at http://www.tux.org/lkml/
On Tuesday 09 October 2007 03:04, Andrew Morton wrote:
> On Mon, 8 Oct 2007 19:45:08 +0800 "Yan Zheng" <[email protected]> wrote:
> > Hi all
> >
> > The test for VM_CAN_NONLINEAR always fails
> >
> > Signed-off-by: Yan Zheng<[email protected]>
> > ----
> > diff -ur linux-2.6.23-rc9/mm/fremap.c linux/mm/fremap.c
> > --- linux-2.6.23-rc9/mm/fremap.c 2007-10-07 15:03:33.000000000 +0800
> > +++ linux/mm/fremap.c 2007-10-08 19:33:44.000000000 +0800
> > @@ -160,7 +160,7 @@
> > if (vma->vm_private_data && !(vma->vm_flags & VM_NONLINEAR))
> > goto out;
> >
> > - if (!vma->vm_flags & VM_CAN_NONLINEAR)
> > + if (!(vma->vm_flags & VM_CAN_NONLINEAR))
> > goto out;
> >
> > if (end <= start || start < vma->vm_start || end > vma->vm_end)
>
> Lovely. From this we can deduce that nobody has run remap_file_pages()
> since 2.6.23-rc1 and that nobody (including the developer who made that
> change) ran it while that change was in -mm.
But you'd be wrong. remap_file_pages was tested both with my own tester
and Ingo's test program.
vm_flags != 0, !vm_flags = 0, 0 & x = 0, so the test always falls
through. Of course, what I _should_ have done is also test a driver which
does not have VM_CAN_NONLINEAR... but even I wouldn't rewrite half
the nonlinear mapping code without once testing it ;)
FWIW, Oracle (maybe the sole real user of this) has been testing it, which
I'm very happy about (rather than testing after 2.6.23 is released).
On Tuesday 09 October 2007 03:51, Andrew Morton wrote:
> On Mon, 8 Oct 2007 10:28:43 -0700
> > I'll now add remap_file_pages soon.
> > Maybe those other 2 tests aren't strong enough (?).
> > Or maybe they don't return a non-0 exit status even when they fail...
> > (I'll check.)
>
> Perhaps Yan Zheng can tell us what test was used to demonstrate this?
Was probably found by review. Otherwise, you could probably reproduce
it by mmaping, say, drm device node, running remap_file_pages() on it
to create a nonlinear mapping, and then finding that you get the wrong
data.
> > > I'm surprise that LTP doesn't have any remap_file_pages() tests.
> >
> > quick grep didn't find any for me.
>
> Me either. There are a few lying around the place which could be
> integrated.
>
> It would be good if LTP were to have some remap_file_pages() tests
> (please). As we see here, it is something which we can easily break, and
> leave broken for some time.
Here is Ingo's old test, since cleaned up and fixed a bit by me....
I'm sure he would distribute it GPL, but I've cc'ed him because I didn't
find an explicit statement about that.
2007/10/9, Andrew Morton <[email protected]>:
> Perhaps Yan Zheng can tell us what test was used to demonstrate this?
I found it by review, only do test to check remap_file_pages works
when VM_CAN_NONLINEAR flags is set.