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Thanks for the > > idea. > > That works fine for RDS but not for skbuff. I would definately put the RDS stuff like that.. > We still need a vm_account in the struct sock or somewhere else for > that. For example in msg_zerocopy_realloc() we only have a struct > ubuf_info_msgzc available. We can't add a struct vm_account field to > that because ultimately it is stored in struct sk_buff->ck[] which > is not large enough to contain ubuf_info_msgzc + vm_account. Well, AFAICT this is using iov_iter to get the pages and in general iov_iter - eg as used for O_DIRECT - doesn't charge anything. If this does somehow allow a userspace to hold pin a page for a long time then it is already technically wrong because it doesn't use FOLL_LONGTERM. Arguably FOLL_LONGTERM should be the key precondition to require accounting. So I wonder if it should just be deleted? Jason