On 2022-12-15 09:49, Michal Hocko wrote:
On Thu 15-12-22 09:33:54, Mathieu Desnoyers wrote:
On 2022-12-15 02:51, Michal Hocko wrote:
[...]
Btw. looking at the code again it seems rather pointless to duplicate the policy just to throw it away anyway. A slightly bigger diff but this looks more reasonable to me. What do you think? I can also send it as a clean up on top of your fix.
I think it would be best if this comes as a cleanup on top of my fix. The diff is larger than the minimal change needed to fix the leak in stable branches.
Your approach looks fine, except for the vma_policy(vma) -> old change already spotted by Aneesh.
This shouldn't have any real effect on the functionality. Anyway, here is a follow up cleanup:
From f3fdb6f65fa3977aab13378b8e299b168719577c Mon Sep 17 00:00:00 2001 From: Michal Hocko mhocko@suse.com Date: Thu, 15 Dec 2022 15:41:27 +0100 Subject: [PATCH] mm/mempolicy: do not duplicate policy if it is not applicable for set_mempolicy_home_node
set_mempolicy_home_node tries to duplicate a memory policy before checking it whether it is applicable for the operation. There is no real reason for doing that and it might actually be a pointless memory allocation and deallocation exercise for MPOL_INTERLEAVE.
Not a big problem but we can do better. Simply check the policy before acting on it.
Signed-off-by: Michal Hocko mhocko@suse.com
Reviewed-by: Mathieu Desnoyers mathieu.desnoyers@efficios.com
mm/mempolicy.c | 28 ++++++++++++---------------- 1 file changed, 12 insertions(+), 16 deletions(-)
diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 02c8a712282f..becf41e10076 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -1489,7 +1489,7 @@ SYSCALL_DEFINE4(set_mempolicy_home_node, unsigned long, start, unsigned long, le { struct mm_struct *mm = current->mm; struct vm_area_struct *vma;
- struct mempolicy *new;
- struct mempolicy *new, *old; unsigned long vmstart; unsigned long vmend; unsigned long end;
@@ -1521,31 +1521,27 @@ SYSCALL_DEFINE4(set_mempolicy_home_node, unsigned long, start, unsigned long, le return 0; mmap_write_lock(mm); for_each_vma_range(vmi, vma, end) {
vmstart = max(start, vma->vm_start);vmend = min(end, vma->vm_end);new = mpol_dup(vma_policy(vma));if (IS_ERR(new)) {err = PTR_ERR(new);break;}/** Only update home node if there is an existing vma policy*/if (!new)continue;- /*
*/
- If any vma in the range got policy other than MPOL_BIND
- or MPOL_PREFERRED_MANY we return error. We don't reset
- the home node for vmas we already updated before.
if (new->mode != MPOL_BIND && new->mode != MPOL_PREFERRED_MANY) {mpol_put(new);
old = vma_policy(vma);if (!old)continue;if (old->mode != MPOL_BIND && old->mode != MPOL_PREFERRED_MANY) { err = -EOPNOTSUPP; break;new = mpol_dup(old);if (IS_ERR(new)) {err = PTR_ERR(new);break;}new->home_node = home_node;
vmstart = max(start, vma->vm_start);vmend = min(end, vma->vm_end);