[PATCH 2/2] mm/mempolicy: do not duplicate policy if it is not applicable for set_mempolicy_home_node
From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: 2022-12-16 19:45:48
Also in:
linux-mm
Subsystem:
memory management, memory management - memory policy and migration, the rest · Maintainers:
Andrew Morton, David Hildenbrand, Linus Torvalds
From: Michal Hocko <mhocko@suse.com> 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. [ Mathieu: compile-tested only. Tested-by would be welcome. ] Signed-off-by: Michal Hocko <mhocko@suse.com> Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Aneesh Kumar K.V <redacted> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Feng Tang <redacted> Cc: Michal Hocko <mhocko@kernel.org> Cc: Andrea Arcangeli <redacted> Cc: Mel Gorman <redacted> Cc: Mike Kravetz <redacted> Cc: Randy Dunlap <redacted> Cc: Vlastimil Babka <redacted> Cc: Andi Kleen <redacted> Cc: Dan Williams <redacted> Cc: Huang Ying <redacted> Cc: linux-api@vger.kernel.org Cc: Andrew Morton <akpm@linux-foundation.org> Cc: linux-mm@kvack.org --- 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); err = mbind_range(mm, vmstart, vmend, new); mpol_put(new); if (err)
--
2.25.1