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    SubjectRe: [RFC PATCH 06/19] RDMA/usnic: convert to use vm_account
    On Tue, Jan 24, 2023 at 04:42:35PM +1100, Alistair Popple wrote:
    > diff --git a/drivers/infiniband/hw/usnic/usnic_uiom.c b/drivers/infiniband/hw/usnic/usnic_uiom.c
    > index c301b3b..250276e 100644
    > --- a/drivers/infiniband/hw/usnic/usnic_uiom.c
    > +++ b/drivers/infiniband/hw/usnic/usnic_uiom.c
    > @@ -89,8 +89,6 @@ static int usnic_uiom_get_pages(unsigned long addr, size_t size, int writable,
    > struct page **page_list;
    > struct scatterlist *sg;
    > struct usnic_uiom_chunk *chunk;
    > - unsigned long locked;
    > - unsigned long lock_limit;
    > unsigned long cur_base;
    > unsigned long npages;
    > int ret;
    > @@ -123,10 +121,8 @@ static int usnic_uiom_get_pages(unsigned long addr, size_t size, int writable,
    > uiomr->owning_mm = mm = current->mm;
    > mmap_read_lock(mm);
    >
    > - locked = atomic64_add_return(npages, &current->mm->pinned_vm);
    > - lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
    > -
    > - if ((locked > lock_limit) && !capable(CAP_IPC_LOCK)) {
    > + vm_account_init_current(&uiomr->vm_account);
    > + if (vm_account_pinned(&uiomr->vm_account, npages)) {
    > ret = -ENOMEM;
    > goto out;
    > }

    Is this error handling right? This driver tried to avoid the race by
    using atomic64_add_return() but it means that the out label undoes the add:


    > @@ -178,7 +174,8 @@ static int usnic_uiom_get_pages(unsigned long addr, size_t size, int writable,
    > out:
    > if (ret < 0) {
    > usnic_uiom_put_pages(chunk_list, 0);
    > - atomic64_sub(npages, &current->mm->pinned_vm);

    Here

    > + vm_unaccount_pinned(&uiomr->vm_account, npages);
    > + vm_account_release(&uiomr->vm_account);

    But with the new API we shouldn't call vm_unaccount_pinned() if
    vm_account_pinned() doesn't succeed?

    Jason

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