On 09/11/2018 12:38 PM, Tushar Dave wrote:
Helper bpg_msg_pull_data() can allocate multiple pages while linearizing multiple scatterlist elements into one shared page. However, if the shared page has size > PAGE_SIZE, using copy_page_to_iter() causes below warning. e.g. [ 6367.019832] WARNING: CPU: 2 PID: 7410 at lib/iov_iter.c:825 page_copy_sane.part.8+0x0/0x8 To avoid above warning, use __GFP_COMP while allocating multiple contiguous pages. Signed-off-by: Tushar Dave <tushar.n.d...@oracle.com> --- net/core/filter.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/core/filter.c b/net/core/filter.c index d301134..0b40f95 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -2344,7 +2344,8 @@ struct sock *do_msg_redirect_map(struct sk_msg_buff *msg) if (unlikely(bytes_sg_total > copy)) return -EINVAL;- page = alloc_pages(__GFP_NOWARN | GFP_ATOMIC, get_order(copy));+ page = alloc_pages(__GFP_NOWARN | GFP_ATOMIC | __GFP_COMP, + get_order(copy)); if (unlikely(!page)) return -ENOMEM; p = page_address(page);
I should have mentioned that I could re-order this patch anywhere in patch series (as long as it doesn't break git bisect). I kept it first because I think it is more like a bug fix. I sent it along with these patch series considering we have a context of why and for what I need this patch! Daniel, John, Not sure if you guys hit this page_copy_sane warning. I hit it when RDS copy sg page to userspace using copy_page_to_iter(). example: RDS packet size 8KB represented in scatterlist: sg_data[0].length = 1400 sg_data[1].length = 1448 sg_data[2].length = 1448 sg_data[3].length = 1448 sg_data[4].length = 1448 sg_data[5].length = 1000 If start=0 and end=8192, bpf_msg_pull_data() will linearize all sg_data elements into one shared page. e.g. sg_data[0].length = 8192. Using this sg_data[0].page in function copy_page_to_iter() causes: WARNING: CPU: 2 PID: 7410 at lib/iov_iter.c:825 page_copy_sane.part.8+0x0/0x8 (FYI, patch 4 has code that does copy_page_to_iter) Comments? Thanks in advance, -Tushar
