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405e44f2e3
"page" may have changed to point to the next hugepage after the loop completed, The references have been taken on the head page, so the put_page must happen there too. This is a longstanding issue pre-thp inclusion. It's totally unclear how these page_cache_add_speculative and pte_val(pte) != pte_val(*ptep) checks are necessary across all the powerpc gup_fast code, when x86 doesn't need any of that: there's no way the page can be freed with irq disabled so we're guaranteed the atomic_inc will happen on a page with page_count > 0 (so not needing the speculative check). The pte check is also meaningless on x86: no need to rollback on x86 if the pte changed, because the pte can still change a CPU tick after the check succeeded and it won't be rolled back in that case. The important thing is we got a reference on a valid page that was mapped there a CPU tick ago. So not knowing the soft tlb refill code of ppc64 in great detail I'm not removing the "speculative" page_count increase and the pte checks across all the code, but unless there's a strong reason for it they should be later cleaned up too. If a pte can change from huge to non-huge (like it could happen with THP) passing a pte_t *ptep to gup_hugepte() would also require to repeat the is_hugepd in gup_hugepte(), but that shouldn't happen with hugetlbfs only so I'm not altering that. Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <jweiner@redhat.com> Cc: Rik van Riel <riel@redhat.com> Cc: Mel Gorman <mgorman@suse.de> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Acked-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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| .. | ||
| 40x_mmu.c | ||
| 44x_mmu.c | ||
| dma-noncoherent.c | ||
| fault.c | ||
| fsl_booke_mmu.c | ||
| gup.c | ||
| hash_low_32.S | ||
| hash_low_64.S | ||
| hash_native_64.c | ||
| hash_utils_64.c | ||
| highmem.c | ||
| hugetlbpage-hash64.c | ||
| hugetlbpage.c | ||
| init_32.c | ||
| init_64.c | ||
| Makefile | ||
| mem.c | ||
| mmap_64.c | ||
| mmu_context_hash32.c | ||
| mmu_context_hash64.c | ||
| mmu_context_nohash.c | ||
| mmu_decl.h | ||
| numa.c | ||
| pgtable_32.c | ||
| pgtable_64.c | ||
| pgtable.c | ||
| ppc_mmu_32.c | ||
| slb_low.S | ||
| slb.c | ||
| slice.c | ||
| stab.c | ||
| subpage-prot.c | ||
| tlb_hash32.c | ||
| tlb_hash64.c | ||
| tlb_low_64e.S | ||
| tlb_nohash_low.S | ||
| tlb_nohash.c | ||