Re: [RFC PATCH 06/11] mm/mempolicy: modify do_mbind to operate on task argument instead of current
From: Michal Hocko <mhocko@suse.com>
Date: 2023-11-28 14:11:12
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linux-arch, linux-doc, linux-fsdevel, linux-mm, lkml
On Wed 22-11-23 16:11:55, Gregory Price wrote: [...]
+ * Like get_vma_policy and get_task_policy, must hold alloc/task_lock + * while calling this. + */ +static struct mempolicy *get_task_vma_policy(struct task_struct *task, + struct vm_area_struct *vma, + unsigned long addr, int order, + pgoff_t *ilx)
[...] You should add lockdep annotation for alloc_lock/task_lock here for clarity and also...
quoted hunk ↗ jump to hunk
@@ -1844,16 +1899,7 @@ struct mempolicy *__get_vma_policy(struct vm_area_struct *vma, struct mempolicy *get_vma_policy(struct vm_area_struct *vma, unsigned long addr, int order, pgoff_t *ilx) { - struct mempolicy *pol; - - pol = __get_vma_policy(vma, addr, ilx); - if (!pol) - pol = get_task_policy(current); - if (pol->mode == MPOL_INTERLEAVE) { - *ilx += vma->vm_pgoff >> order; - *ilx += (addr - vma->vm_start) >> (PAGE_SHIFT + order); - } - return pol; + return get_task_vma_policy(current, vma, addr, order, ilx);
I do not think that all get_vma_policy take task_lock (just random check dequeue_hugetlb_folio_vma->huge_node->get_vma_policy AFAICS) Also I do not see policy_nodemask to be handled anywhere. That one is used along with get_vma_policy (sometimes hidden like in alloc_pages_mpol). It has a dependency on cpuset_nodemask_valid_mems_allowed. That means that e.g. mbind on a remote task would be constrained by current task cpuset when allocating migration targets for the target task. I am wondering how many other dependencies like that are lurking there. -- Michal Hocko SUSE Labs