Messages in this thread | | | Subject | Re: [PATCH 2/2] vhost-vdpa: fix page pinning leakage in error path (rework) | From | Jason Wang <> | Date | Thu, 5 Nov 2020 11:12:46 +0800 |
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On 2020/11/5 上午7:40, si-wei liu wrote: > > On 11/3/2020 6:42 PM, Jason Wang wrote: >> >> On 2020/10/30 下午3:45, Si-Wei Liu wrote: >>> Pinned pages are not properly accounted particularly when >>> mapping error occurs on IOTLB update. Clean up dangling >>> pinned pages for the error path. >>> >>> The memory usage for bookkeeping pinned pages is reverted >>> to what it was before: only one single free page is needed. >>> This helps reduce the host memory demand for VM with a large >>> amount of memory, or in the situation where host is running >>> short of free memory. >>> >>> Fixes: 4c8cf31885f6 ("vhost: introduce vDPA-based backend") >>> Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com> >>> --- >>> drivers/vhost/vdpa.c | 64 >>> +++++++++++++++++++++++++++++++++++++--------------- >>> 1 file changed, 46 insertions(+), 18 deletions(-) >>> >>> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c >>> index b6d9016..8da8558 100644 >>> --- a/drivers/vhost/vdpa.c >>> +++ b/drivers/vhost/vdpa.c >>> @@ -560,6 +560,8 @@ static int vhost_vdpa_map(struct vhost_vdpa *v, >>> if (r) >>> vhost_iotlb_del_range(dev->iotlb, iova, iova + size - 1); >>> + else >>> + atomic64_add(size >> PAGE_SHIFT, &dev->mm->pinned_vm); >>> return r; >>> } >>> @@ -591,14 +593,16 @@ static int >>> vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v, >>> unsigned long list_size = PAGE_SIZE / sizeof(struct page *); >>> unsigned int gup_flags = FOLL_LONGTERM; >>> unsigned long npages, cur_base, map_pfn, last_pfn = 0; >>> - unsigned long locked, lock_limit, pinned, i; >>> + unsigned long lock_limit, sz2pin, nchunks, i; >>> u64 iova = msg->iova; >>> + long pinned; >>> int ret = 0; >>> if (vhost_iotlb_itree_first(iotlb, msg->iova, >>> msg->iova + msg->size - 1)) >>> return -EEXIST; >>> + /* Limit the use of memory for bookkeeping */ >>> page_list = (struct page **) __get_free_page(GFP_KERNEL); >>> if (!page_list) >>> return -ENOMEM; >>> @@ -607,52 +611,64 @@ static int >>> vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v, >>> gup_flags |= FOLL_WRITE; >>> npages = PAGE_ALIGN(msg->size + (iova & ~PAGE_MASK)) >> >>> PAGE_SHIFT; >>> - if (!npages) >>> - return -EINVAL; >>> + if (!npages) { >>> + ret = -EINVAL; >>> + goto free; >>> + } >>> mmap_read_lock(dev->mm); >>> - locked = atomic64_add_return(npages, &dev->mm->pinned_vm); >>> lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT; >>> - >>> - if (locked > lock_limit) { >>> + if (npages + atomic64_read(&dev->mm->pinned_vm) > lock_limit) { >>> ret = -ENOMEM; >>> - goto out; >>> + goto unlock; >>> } >>> cur_base = msg->uaddr & PAGE_MASK; >>> iova &= PAGE_MASK; >>> + nchunks = 0; >>> while (npages) { >>> - pinned = min_t(unsigned long, npages, list_size); >>> - ret = pin_user_pages(cur_base, pinned, >>> - gup_flags, page_list, NULL); >>> - if (ret != pinned) >>> + sz2pin = min_t(unsigned long, npages, list_size); >>> + pinned = pin_user_pages(cur_base, sz2pin, >>> + gup_flags, page_list, NULL); >>> + if (sz2pin != pinned) { >>> + if (pinned < 0) { >>> + ret = pinned; >>> + } else { >>> + unpin_user_pages(page_list, pinned); >>> + ret = -ENOMEM; >>> + } >>> goto out; >>> + } >>> + nchunks++; >>> if (!last_pfn) >>> map_pfn = page_to_pfn(page_list[0]); >>> - for (i = 0; i < ret; i++) { >>> + for (i = 0; i < pinned; i++) { >>> unsigned long this_pfn = page_to_pfn(page_list[i]); >>> u64 csize; >>> if (last_pfn && (this_pfn != last_pfn + 1)) { >>> /* Pin a contiguous chunk of memory */ >>> csize = (last_pfn - map_pfn + 1) << PAGE_SHIFT; >>> - if (vhost_vdpa_map(v, iova, csize, >>> - map_pfn << PAGE_SHIFT, >>> - msg->perm)) >>> + ret = vhost_vdpa_map(v, iova, csize, >>> + map_pfn << PAGE_SHIFT, >>> + msg->perm); >>> + if (ret) >>> goto out; >>> + >>> map_pfn = this_pfn; >>> iova += csize; >>> + nchunks = 0; >>> } >>> last_pfn = this_pfn; >>> } >>> - cur_base += ret << PAGE_SHIFT; >>> - npages -= ret; >>> + cur_base += pinned << PAGE_SHIFT; >>> + npages -= pinned; >>> } >>> /* Pin the rest chunk */ >>> @@ -660,10 +676,22 @@ static int >>> vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v, >>> map_pfn << PAGE_SHIFT, msg->perm); >>> out: >>> if (ret) { >>> + if (nchunks && last_pfn) { >> >> >> Can we decrease npages where you did "nchunks++" then we can check >> npages here instead? > Hmmm, I am not sure I get what you want... @nchunks gets reset to 0 > whenever a certain range of pinned pages is successfully mapped. The > conditional (when nchunks is non-zero) here indicates if there's any > _outstanding_ pinned page that has to clean up in the error handling > path. While the decrement of @npages may not occur when resetting the > @nchunks counter, rendering incorrect cleanup in the error path.
Yes, I meant e can decrease npages where you did "nchunks++". Anyhow, it's just a optimization to avoid a local variable which is not a must.
> > BTW while reviewing it I got noticed of an error in my code. There > might be still page pinning leak from wherever the vhost_vdpa_map() > error occurs towards the end of page_list. I will post a v2 to fix this. >
Sure, will review.
Thanks
> Regards, > -Siwei > > --- a/drivers/vhost/vdpa.c > +++ b/drivers/vhost/vdpa.c > @@ -656,8 +656,19 @@ static int vhost_vdpa_process_iotlb_update(struct > vhost_vdpa *v, > ret = vhost_vdpa_map(v, iova, csize, > map_pfn << > PAGE_SHIFT, > msg->perm); > - if (ret) > + if (ret) { > + /* > + * Unpin the pages that are > left unmapped > + * from this point on in the > current > + * page_list. The remaining > outstanding > + * ones which may stride > across several > + * chunks will be covered in > the common > + * error path subsequently. > + */ > + unpin_user_pages(&page_list[i], > + pinned - i); > goto out; > + } > > map_pfn = this_pfn; > iova += csize; > > > >> >> Thanks >> >> >>> + unsigned long pfn; >>> + >>> + /* >>> + * Unpin the outstanding pages which are unmapped. >>> + * Mapped pages are accounted in vdpa_map(), thus >>> + * will be handled by vdpa_unmap(). >>> + */ >>> + for (pfn = map_pfn; pfn <= last_pfn; pfn++) >>> + unpin_user_page(pfn_to_page(pfn)); >>> + } >>> vhost_vdpa_unmap(v, msg->iova, msg->size); >>> - atomic64_sub(npages, &dev->mm->pinned_vm); >>> } >>> +unlock: >>> mmap_read_unlock(dev->mm); >>> +free: >>> free_page((unsigned long)page_list); >>> return ret; >>> } >> >
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