From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f70.google.com (mail-oi0-f70.google.com [209.85.218.70]) by kanga.kvack.org (Postfix) with ESMTP id 4424B6B0038 for ; Fri, 3 Nov 2017 06:56:37 -0400 (EDT) Received: by mail-oi0-f70.google.com with SMTP id h200so2347453oib.18 for ; Fri, 03 Nov 2017 03:56:37 -0700 (PDT) Received: from www262.sakura.ne.jp (www262.sakura.ne.jp. [2001:e42:101:1:202:181:97:72]) by mx.google.com with ESMTPS id u73si2847421oie.335.2017.11.03.03.56.35 for (version=TLS1 cipher=AES128-SHA bits=128/128); Fri, 03 Nov 2017 03:56:35 -0700 (PDT) Subject: Re: [PATCH v17 1/6] lib/xbitmap: Introduce xbitmap From: Tetsuo Handa References: <1509696786-1597-1-git-send-email-wei.w.wang@intel.com> <1509696786-1597-2-git-send-email-wei.w.wang@intel.com> In-Reply-To: <1509696786-1597-2-git-send-email-wei.w.wang@intel.com> Message-Id: <201711031955.FFE57823.VFLMFtFJSOOQHO@I-love.SAKURA.ne.jp> Date: Fri, 3 Nov 2017 19:55:43 +0900 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org List-ID: To: wei.w.wang@intel.com, virtio-dev@lists.oasis-open.org, linux-kernel@vger.kernel.org, qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, linux-mm@kvack.org, mst@redhat.com, mhocko@kernel.org, akpm@linux-foundation.org, mawilcox@microsoft.com Cc: david@redhat.com, cornelia.huck@de.ibm.com, mgorman@techsingularity.net, aarcange@redhat.com, amit.shah@redhat.com, pbonzini@redhat.com, willy@infradead.org, liliang.opensource@gmail.com, yang.zhang.wz@gmail.com, quan.xu@aliyun.com I'm commenting without understanding the logic. Wei Wang wrote: > + > +bool xb_preload(gfp_t gfp); > + Want __must_check annotation, for __radix_tree_preload() is marked with __must_check annotation. By error failing to check result of xb_preload() will lead to preemption kept disabled unexpectedly. > +int xb_set_bit(struct xb *xb, unsigned long bit) > +{ > + int err; > + unsigned long index = bit / IDA_BITMAP_BITS; > + struct radix_tree_root *root = &xb->xbrt; > + struct radix_tree_node *node; > + void **slot; > + struct ida_bitmap *bitmap; > + unsigned long ebit; > + > + bit %= IDA_BITMAP_BITS; > + ebit = bit + 2; > + > + err = __radix_tree_create(root, index, 0, &node, &slot); > + if (err) > + return err; > + bitmap = rcu_dereference_raw(*slot); > + if (radix_tree_exception(bitmap)) { > + unsigned long tmp = (unsigned long)bitmap; > + > + if (ebit < BITS_PER_LONG) { > + tmp |= 1UL << ebit; > + rcu_assign_pointer(*slot, (void *)tmp); > + return 0; > + } > + bitmap = this_cpu_xchg(ida_bitmap, NULL); > + if (!bitmap) Please write locking rules, in order to explain how memory allocated by __radix_tree_create() will not leak. > + return -EAGAIN; > + memset(bitmap, 0, sizeof(*bitmap)); > + bitmap->bitmap[0] = tmp >> RADIX_TREE_EXCEPTIONAL_SHIFT; > + rcu_assign_pointer(*slot, bitmap); > + } > + > + if (!bitmap) { > + if (ebit < BITS_PER_LONG) { > + bitmap = (void *)((1UL << ebit) | > + RADIX_TREE_EXCEPTIONAL_ENTRY); > + __radix_tree_replace(root, node, slot, bitmap, NULL, > + NULL); > + return 0; > + } > + bitmap = this_cpu_xchg(ida_bitmap, NULL); > + if (!bitmap) Same here. > + return -EAGAIN; > + memset(bitmap, 0, sizeof(*bitmap)); > + __radix_tree_replace(root, node, slot, bitmap, NULL, NULL); > + } > + > + __set_bit(bit, bitmap->bitmap); > + return 0; > +} > +void xb_clear_bit(struct xb *xb, unsigned long bit) > +{ > + unsigned long index = bit / IDA_BITMAP_BITS; > + struct radix_tree_root *root = &xb->xbrt; > + struct radix_tree_node *node; > + void **slot; > + struct ida_bitmap *bitmap; > + unsigned long ebit; > + > + bit %= IDA_BITMAP_BITS; > + ebit = bit + 2; > + > + bitmap = __radix_tree_lookup(root, index, &node, &slot); > + if (radix_tree_exception(bitmap)) { > + unsigned long tmp = (unsigned long)bitmap; > + > + if (ebit >= BITS_PER_LONG) > + return; > + tmp &= ~(1UL << ebit); > + if (tmp == RADIX_TREE_EXCEPTIONAL_ENTRY) > + __radix_tree_delete(root, node, slot); > + else > + rcu_assign_pointer(*slot, (void *)tmp); > + return; > + } > + > + if (!bitmap) > + return; > + > + __clear_bit(bit, bitmap->bitmap); > + if (bitmap_empty(bitmap->bitmap, IDA_BITMAP_BITS)) { Please write locking rules, in order to explain how double kfree() and/or use-after-free can be avoided. > + kfree(bitmap); > + __radix_tree_delete(root, node, slot); > + } > +} > +void xb_clear_bit_range(struct xb *xb, unsigned long start, unsigned long end) > +{ > + struct radix_tree_root *root = &xb->xbrt; > + struct radix_tree_node *node; > + void **slot; > + struct ida_bitmap *bitmap; > + unsigned int nbits; > + > + for (; start < end; start = (start | (IDA_BITMAP_BITS - 1)) + 1) { > + unsigned long index = start / IDA_BITMAP_BITS; > + unsigned long bit = start % IDA_BITMAP_BITS; > + > + bitmap = __radix_tree_lookup(root, index, &node, &slot); > + if (radix_tree_exception(bitmap)) { > + unsigned long ebit = bit + 2; > + unsigned long tmp = (unsigned long)bitmap; > + > + nbits = min(end - start + 1, BITS_PER_LONG - ebit); > + > + if (ebit >= BITS_PER_LONG) > + continue; > + bitmap_clear(&tmp, ebit, nbits); > + if (tmp == RADIX_TREE_EXCEPTIONAL_ENTRY) > + __radix_tree_delete(root, node, slot); > + else > + rcu_assign_pointer(*slot, (void *)tmp); > + } else if (bitmap) { > + nbits = min(end - start + 1, IDA_BITMAP_BITS - bit); > + > + if (nbits != IDA_BITMAP_BITS) > + bitmap_clear(bitmap->bitmap, bit, nbits); > + > + if (nbits == IDA_BITMAP_BITS || > + bitmap_empty(bitmap->bitmap, IDA_BITMAP_BITS)) { Same here. > + kfree(bitmap); > + __radix_tree_delete(root, node, slot); > + } > + } > + } > +} > +bool xb_test_bit(struct xb *xb, unsigned long bit) > +{ > + unsigned long index = bit / IDA_BITMAP_BITS; > + const struct radix_tree_root *root = &xb->xbrt; > + struct ida_bitmap *bitmap = radix_tree_lookup(root, index); > + > + bit %= IDA_BITMAP_BITS; > + > + if (!bitmap) > + return false; > + if (radix_tree_exception(bitmap)) { > + bit += RADIX_TREE_EXCEPTIONAL_SHIFT; > + if (bit > BITS_PER_LONG) Why not bit >= BITS_PER_LONG here? > + return false; > + return (unsigned long)bitmap & (1UL << bit); > + } > + > + return test_bit(bit, bitmap->bitmap); > +} -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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