Messages in this thread | | | Subject | Re: [PATCH v2] vhost-vdpa: fix page pinning leakage in error path (rework) | From | Jason Wang <> | Date | Mon, 9 Nov 2020 11:21:56 +0800 |
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On 2020/11/6 上午6:57, si-wei liu wrote: > > On 11/4/2020 7:26 PM, Jason Wang wrote: >> >> On 2020/11/5 上午7:33, 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> >>> --- >>> Changes in v2: >>> - Drop the reversion patch >>> - Fix unhandled page leak towards the end of page_list >>> >>> drivers/vhost/vdpa.c | 79 >>> ++++++++++++++++++++++++++++++++++++++++------------ >>> 1 file changed, 61 insertions(+), 18 deletions(-) >>> >>> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c >>> index b6d9016..e112854 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 +611,75 @@ 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) { >>> + /* >>> + * 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); >> >> >> Can we simply do last_pfn = this_pfn here? > Nope. They are not contiguous segments of memory. Noted the > conditional (this_pfn != last_pfn + 1) being held here.
Right.
> >> >> >>> 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 +687,26 @@ static int >>> vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v, >>> map_pfn << PAGE_SHIFT, msg->perm); >>> out: >>> if (ret) { >>> + if (nchunks && last_pfn) { >> >> >> Any reason for checking last_pfn here? >> >> Note that we did: >> >> + nchunks++; >> >> if (!last_pfn) >> map_pfn = page_to_pfn(page_list[0]); > It's for explicit coding to make sure this common error path can be > reused no matter if last_pfn has a sane value assigned or not. I can > change it to an implicit WARN_ON() if need be.
Just to make sure I understand. A question, when will we get nchunks != 0 but last_pfn == 0?
Thanks
> Thanks, > -Siwei > >> >> >> Thanks >> >> >>> + unsigned long pfn; >>> + >>> + /* >>> + * Unpin the outstanding pages which are yet to be >>> + * mapped but haven't due to vdpa_map() or >>> + * pin_user_pages() failure. >>> + * >>> + * Mapped pages are accounted in vdpa_map(), hence >>> + * the corresponding unpinning 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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