| Message ID | alpine.DEB.2.00.1105131614440.913@router.home |
|---|---|
| State | Not Applicable, archived |
| Delegated to: | David Miller |
| Headers | show |
Le vendredi 13 mai 2011 à 16:15 -0500, Christoph Lameter a écrit : > I ran this with hackbench under KVM with CONFIG_DEBUG_PAGEALLOC and I saw > no failures. > > > Subject: slub: Make CONFIG_PAGE_ALLOC work with new fastpath > > Fastpath can do a speculative access to a page that CONFIG_PAGE_ALLOC may have > marked as invalid to retrieve the pointer to the next free object. > > Use probe_kernel_read in that case in order not to cause a page fault. > > Signed-off-by: Christoph Lameter <cl@linux.com> Reported-by: Eric Dumazet <eric.dumazet@gmail.com> Acked-by: Eric Dumazet <eric.dumazet@gmail.com> Thanks ! -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Index: linux-2.6/mm/slub.c =================================================================== --- linux-2.6.orig/mm/slub.c 2011-05-10 14:31:28.000000000 -0500 +++ linux-2.6/mm/slub.c 2011-05-10 14:31:35.000000000 -0500 @@ -261,6 +261,18 @@ static inline void *get_freepointer(stru return *(void **)(object + s->offset); } +static inline void *get_freepointer_safe(struct kmem_cache *s, void *object) +{ + void *p; + +#ifdef CONFIG_DEBUG_PAGEALLOC + probe_kernel_read(&p, (void **)(object + s->offset), sizeof(p)); +#else + p = get_freepointer(s, object); +#endif + return p; +} + static inline void set_freepointer(struct kmem_cache *s, void *object, void *fp) { *(void **)(object + s->offset) = fp; @@ -1933,7 +1945,7 @@ redo: if (unlikely(!irqsafe_cpu_cmpxchg_double( s->cpu_slab->freelist, s->cpu_slab->tid, object, tid, - get_freepointer(s, object), next_tid(tid)))) { + get_freepointer_safe(s, object), next_tid(tid)))) { note_cmpxchg_failure("slab_alloc", s, tid); goto redo;
I ran this with hackbench under KVM with CONFIG_DEBUG_PAGEALLOC and I saw no failures. Subject: slub: Make CONFIG_PAGE_ALLOC work with new fastpath Fastpath can do a speculative access to a page that CONFIG_PAGE_ALLOC may have marked as invalid to retrieve the pointer to the next free object. Use probe_kernel_read in that case in order not to cause a page fault. Signed-off-by: Christoph Lameter <cl@linux.com> --- mm/slub.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html