On Fri, Apr 09, 2021 at 01:33:24AM -0700, Xie He wrote: > On Fri, Apr 9, 2021 at 12:30 AM Mel Gorman <mgor...@techsingularity.net> > wrote: > > > > Under what circumstances do you expect sk_memalloc_socks() to be false > > and skb_pfmemalloc() to be true that would cause a problem? > > For example, if at the time the skb is allocated, > "sk_memalloc_socks()" was true, then the skb might be allocated as a > pfmemalloc skb. However, if after this skb is allocated and before > this skb reaches "__netif_receive_skb", "sk_memalloc_socks()" has > changed from "true" to "false", then "__netif_receive_skb" will see > "sk_memalloc_socks()" being false and "skb_pfmemalloc(skb)" being > true. > > This is a problem because this would cause a pfmemalloc skb to be > delivered to "taps" and protocols that don't support pfmemalloc skbs.
That would imply that the tap was communicating with a swap device to allocate a pfmemalloc skb which shouldn't happen. Furthermore, it would require the swap device to be deactivated while pfmemalloc skbs still existed. Have you encountered this problem? -- Mel Gorman SUSE Labs
