On 18 April 2014 08:24, Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> wrote: > commit 8dcc774 (slab: introduce byte sized index for the freelist of > a slab) changes the size of freelist index and also changes prototype > of accessor function to freelist index. And there was a mistake. > > The mistake is that although it changes the size of freelist index > correctly, it changes the size of the index of freelist index incorrectly. > With patch, freelist index can be 1 byte or 2 bytes, that means that > num of object on on a slab can be more than 255. So we need more than 1 > byte for the index to find the index of free object on freelist. But, > above patch makes this index type 1 byte, so slab which have more than > 255 objects cannot work properly and in consequence of it, the system > cannot boot. > > This issue was reported by Steven King on m68knommu which would use > 2 bytes freelist index. Please refer following link. > > https://lkml.org/lkml/2014/4/16/433 > > To fix it is so easy. To change the type of the index of freelist index > on accessor functions is enough to fix this bug. Although 2 bytes is > enough, I use 4 bytes since it have no bad effect and make things > more easier. This fix was suggested and tested by Steven in his > original report. > > Reported-by: Steven King <sfking@xxxxxxxxx> > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> I also hit this problem on MIPS with v3.15-rc2 and 16K pages. With this patch it boots fine. Tested-by: James Hogan <james.hogan@xxxxxxxxxx> Thanks James > --- > Hello, Pekka. > > Could you send this for v3.15-rc2? > Without this patch, many architecture using 2 bytes freelist index cannot > work properly, I guess. > > This patch is based on v3.15-rc1. > > Thanks. > > diff --git a/mm/slab.c b/mm/slab.c > index 388cb1a..d7f9f44 100644 > --- a/mm/slab.c > +++ b/mm/slab.c > @@ -2572,13 +2572,13 @@ static void *alloc_slabmgmt(struct kmem_cache *cachep, > return freelist; > } > > -static inline freelist_idx_t get_free_obj(struct page *page, unsigned char idx) > +static inline freelist_idx_t get_free_obj(struct page *page, unsigned int idx) > { > return ((freelist_idx_t *)page->freelist)[idx]; > } > > static inline void set_free_obj(struct page *page, > - unsigned char idx, freelist_idx_t val) > + unsigned int idx, freelist_idx_t val) > { > ((freelist_idx_t *)(page->freelist))[idx] = val; > } > -- > 1.7.9.5 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>