Commit e976936c authored by Michal Hocko's avatar Michal Hocko Committed by Andrew Morton
Browse files

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.

Link: https://lkml.kernel.org/r/20221216194537.238047-2-mathieu.desnoyers@efficios.com


Signed-off-by: default avatarMichal Hocko <mhocko@suse.com>
Reviewed-by: default avatarMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: default avatarMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Huang Ying <ying.huang@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent a5fd8390

mm/mempolicy.c

+12 −16
Original line number Diff line number Diff line
@@ -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);

		err = mbind_range(mm, vmstart, vmend, new);

		mpol_put(new);

		if (err)