Messages in this thread |  | | Date | Tue, 05 Nov 2013 17:17:05 -0800 | From | David Cohen <> | Subject | Re: [PATCH] staging: zsmalloc: Ensure handle is never 0 on success |
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Hi Olav,
On 11/05/2013 04:54 PM, Olav Haugan wrote: > zsmalloc encodes a handle using the page pfn and an object > index. On some hardware platforms the pfn could be 0 and this > causes the encoded handle to be 0 which is interpreted as an > allocation failure. > > To prevent this false error we ensure that the encoded handle > will not be 0 when allocation succeeds. > > Change-Id: Ifff930dcf254915b497aec5cb36f152a5e5365d6 > Signed-off-by: Olav Haugan <ohaugan@codeaurora.org> > --- > drivers/staging/zsmalloc/zsmalloc-main.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/staging/zsmalloc/zsmalloc-main.c b/drivers/staging/zsmalloc/zsmalloc-main.c > index 523b937..0e32c0f 100644 > --- a/drivers/staging/zsmalloc/zsmalloc-main.c > +++ b/drivers/staging/zsmalloc/zsmalloc-main.c > @@ -441,7 +441,7 @@ static void *obj_location_to_handle(struct page *page, unsigned long obj_idx) > } > > handle = page_to_pfn(page) << OBJ_INDEX_BITS; > - handle |= (obj_idx & OBJ_INDEX_MASK); > + handle |= ((obj_idx + 1) & OBJ_INDEX_MASK);
As suggestion you could use a macro instead of hardcoded 1.
I am not familiar with this code, but if it's a valid test to verify if the resulting address is page aligned, you might want to set this offset macro to a page aligned value as well.
> > return (void *)handle; > } > @@ -451,7 +451,7 @@ static void obj_handle_to_location(unsigned long handle, struct page **page, > unsigned long *obj_idx) > { > *page = pfn_to_page(handle >> OBJ_INDEX_BITS); > - *obj_idx = handle & OBJ_INDEX_MASK; > + *obj_idx = (handle & OBJ_INDEX_MASK) - 1;
Ditto.
Br, David Cohen
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