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SubjectRe: [PATCH 1/3] vmalloc: ignore vmalloc area holes in vwrite()
On Tue, Sep 15, 2009 at 11:18:29AM +0800, KAMEZAWA Hiroyuki wrote:
> On Tue, 15 Sep 2009 11:15:07 +0800
> Wu Fengguang <fengguang.wu@intel.com> wrote:
>
> > Hi Kame,
> >
> > I'll go out for a while. If you are going to do your improvements to
> > vmalloc.c, please feel free to do so. I can rebase the hwpoison bits
> > after yours.
> >
> > I could do the kmem part(in a modified patch 2/3) and let it return
> > any error code vread/vwrite reports. Ideally the kmem read/write
> > could do
> >
> > if (zero bytes successfully read/written)
> > return error_code;
> > else
> > return bytes_so_far;
> >
> > Do you agree?
> >
> Okay. I'll write patches for vread/vwrite. And make them just return bool.

bool may not be sufficient? For obviously you need to return -EFAULT
for invalid address and I need to return -EIO for hwpoison pages.
(I assume you put is_vmalloc_or_module_addr() immediately before the
vmalloc_to_page() calls in vmalloc.c, which seems a more natural place
than in mem.c.)

Thanks,
Fengguang

> true .....requested area includes valid memory range and worth to be copied.
> false.....no valid range found.
>
> Thanks,
> -Kame
>
>
>
>
> > Thanks,
> > Fengguang
> >
> > On Tue, Sep 15, 2009 at 10:34:25AM +0800, KAMEZAWA Hiroyuki wrote:
> > > On Tue, 15 Sep 2009 10:18:52 +0800
> > > Wu Fengguang <fengguang.wu@intel.com> wrote:
> > >
> > > > Siliently ignore all vmalloc area holes in vwrite(),
> > > > and report success to the caller even if nothing is written.
> > > >
> > > > CC: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > > > Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
> > >
> > > Why don't you modify vread() at the same time ?
> > > Because /proc/kcore ignores return value of vread(), I think you can
> > > modify it without no side-effect.
> > >
> > > Regards,
> > > -Kame
> > >
> > > > ---
> > > > mm/vmalloc.c | 13 ++-----------
> > > > 1 file changed, 2 insertions(+), 11 deletions(-)
> > > >
> > > > --- linux-mm.orig/mm/vmalloc.c 2009-09-15 10:08:33.000000000 +0800
> > > > +++ linux-mm/mm/vmalloc.c 2009-09-15 10:14:18.000000000 +0800
> > > > @@ -1805,10 +1805,8 @@ finished:
> > > > * @addr: vm address.
> > > > * @count: number of bytes to be read.
> > > > *
> > > > - * Returns # of bytes which addr and buf should be incresed.
> > > > + * Returns # of bytes which addr and buf should be increased.
> > > > * (same number to @count).
> > > > - * If [addr...addr+count) doesn't includes any intersect with valid
> > > > - * vmalloc area, returns 0.
> > > > *
> > > > * This function checks that addr is a valid vmalloc'ed area, and
> > > > * copy data from a buffer to the given addr. If specified range of
> > > > @@ -1816,8 +1814,6 @@ finished:
> > > > * proper area of @buf. If there are memory holes, no copy to hole.
> > > > * IOREMAP area is treated as memory hole and no copy is done.
> > > > *
> > > > - * If [addr...addr+count) doesn't includes any intersects with alive
> > > > - * vm_struct area, returns 0.
> > > > * @buf should be kernel's buffer. Because this function uses KM_USER0,
> > > > * the caller should guarantee KM_USER0 is not used.
> > > > *
> > > > @@ -1834,7 +1830,6 @@ long vwrite(char *buf, char *addr, unsig
> > > > struct vm_struct *tmp;
> > > > char *vaddr;
> > > > unsigned long n, buflen;
> > > > - int copied = 0;
> > > >
> > > > /* Don't allow overflow */
> > > > if ((unsigned long) addr + count < count)
> > > > @@ -1856,18 +1851,14 @@ long vwrite(char *buf, char *addr, unsig
> > > > n = vaddr + tmp->size - PAGE_SIZE - addr;
> > > > if (n > count)
> > > > n = count;
> > > > - if (!(tmp->flags & VM_IOREMAP)) {
> > > > + if (!(tmp->flags & VM_IOREMAP))
> > > > aligned_vwrite(buf, addr, n);
> > > > - copied++;
> > > > - }
> > > > buf += n;
> > > > addr += n;
> > > > count -= n;
> > > > }
> > > > finished:
> > > > read_unlock(&vmlist_lock);
> > > > - if (!copied)
> > > > - return 0;
> > > > return buflen;
> > > > }
> > > >
> > > >
> > > > --
> > > >
> > > >
> >


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