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Date: Mon, 4 Dec 2017 08:49:08 +0800 From: Yisheng Xie <xieyisheng1@...wei.com> To: Vlastimil Babka <vbabka@...e.cz>, <akpm@...ux-foundation.org> CC: <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>, <linux-api@...r.kernel.org>, Andi Kleen <ak@...ux.intel.com>, Chris Salls <salls@...ucsb.edu>, Christopher Lameter <cl@...ux.com>, David Rientjes <rientjes@...gle.com>, Ingo Molnar <mingo@...nel.org>, Naoya Horiguchi <n-horiguchi@...jp.nec.com>, Tan Xiaojun <tanxiaojun@...wei.com> Subject: Re: [PATCH v4 3/3] mm/mempolicy: add nodes_empty check in SYSC_migrate_pages Hi Vlastimil, On 2017/12/1 23:18, Vlastimil Babka wrote: > On 12/01/2017 10:55 AM, Yisheng Xie wrote: >> As in manpage of migrate_pages, the errno should be set to EINVAL when >> none of the node IDs specified by new_nodes are on-line and allowed by the >> process's current cpuset context, or none of the specified nodes contain >> memory. However, when test by following case: >> >> new_nodes = 0; >> old_nodes = 0xf; >> ret = migrate_pages(pid, old_nodes, new_nodes, MAX); >> >> The ret will be 0 and no errno is set. As the new_nodes is empty, we >> should expect EINVAL as documented. >> >> To fix the case like above, this patch check whether target nodes AND >> current task_nodes is empty, and then check whether AND >> node_states[N_MEMORY] is empty. >> >> Meanwhile,this patch also remove the check of EPERM on CAP_SYS_NICE. >> The caller of migrate_pages should be able to migrate the target process >> pages anywhere the caller can allocate memory, if the caller can access >> the mm_struct. >> >> Signed-off-by: Yisheng Xie <xieyisheng1@...wei.com> >> Cc: Andi Kleen <ak@...ux.intel.com> >> Cc: Chris Salls <salls@...ucsb.edu> >> Cc: Christopher Lameter <cl@...ux.com> >> Cc: David Rientjes <rientjes@...gle.com> >> Cc: Ingo Molnar <mingo@...nel.org> >> Cc: Naoya Horiguchi <n-horiguchi@...jp.nec.com> >> Cc: Tan Xiaojun <tanxiaojun@...wei.com> >> Cc: Vlastimil Babka <vbabka@...e.cz> >> --- >> v3: >> * check whether node is empty after AND current task node, and then nodes >> which have memory >> v4: >> * remove the check of EPERM on CAP_SYS_NICE. >> >> Hi Vlastimil and Christopher, >> >> Could you please help to review this version? > > Hi, I think we should stay with v3 after all. What I missed when > reviewing it, is that the EPERM check is for cpuset_mems_allowed(task) > and in v3 you add EINVAL check for cpuset_mems_allowed(current), which > may not be the same, and the intention of CAP_SYS_NICE is not whether we > can bypass our own cpuset, but whether we can bypass the target task's > cpuset. Sorry for the confusion. Ok, so please ignore this version. Thanks Yisheng Xie > > > . >
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