patches/old/hugetlbfs-drop-shared-numa-mempolicy-pretence.patch

From: Hugh Dickins <hughd@google.com>
Subject: hugetlbfs: drop shared NUMA mempolicy pretence
Date: Tue, 3 Oct 2023 02:15:09 -0700 (PDT)

Patch series "mempolicy: cleanups leading to NUMA mpol without vma", v2.

Mostly cleanups in mm/mempolicy.c, but finally removing the pseudo-vma
from shmem folio allocation, and removing the mmap_lock around folio
migration for mbind and migrate_pages syscalls.


This patch (of 12):

hugetlbfs_fallocate() goes through the motions of pasting a shared NUMA
mempolicy onto its pseudo-vma, but how could there ever be a shared NUMA
mempolicy for this file?  hugetlb_vm_ops has never offered a set_policy
method, and hugetlbfs_parse_param() has never supported any mpol options
for a mount-wide default policy.

It's just an illusion: clean it away so as not to confuse others, giving
us more freedom to adjust shmem's set_policy/get_policy implementation. 
But hugetlbfs_inode_info is still required, just to accommodate seals.

Yes, shared NUMA mempolicy support could be added to hugetlbfs, with a
set_policy method and/or mpol mount option (Andi's first posting did
include an admitted-unsatisfactory hugetlb_set_policy()); but it seems
that nobody has bothered to add that in the nineteen years since v2.6.7
made it possible, and there is at least one company that has invested
enough into hugetlbfs, that I guess they have learnt well enough how to
manage its NUMA, without needing shared mempolicy.

Remove linux/mempolicy.h from linux/hugetlb.h: include linux/pagemap.h in
its place, because hugetlb.h's recently added use of filemap_lock_folio()
requires that (although most .configs and .c's get it in some other way).

Link: https://lkml.kernel.org/r/ebc0987e-beff-8bfb-9283-234c2cbd17c5@google.com
Link: https://lkml.kernel.org/r/cae82d4b-904a-faaf-282a-34fcc188c81f@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Tejun heo <tj@kernel.org>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/hugetlbfs/inode.c    |   41 --------------------------------------
 include/linux/hugetlb.h |    3 --
 2 files changed, 2 insertions(+), 42 deletions(-)

--- a/fs/hugetlbfs/inode.c~hugetlbfs-drop-shared-numa-mempolicy-pretence
+++ a/fs/hugetlbfs/inode.c
@@ -83,29 +83,6 @@ static const struct fs_parameter_spec hu
 	{}
 };
 
-#ifdef CONFIG_NUMA
-static inline void hugetlb_set_vma_policy(struct vm_area_struct *vma,
-					struct inode *inode, pgoff_t index)
-{
-	vma->vm_policy = mpol_shared_policy_lookup(&HUGETLBFS_I(inode)->policy,
-							index);
-}
-
-static inline void hugetlb_drop_vma_policy(struct vm_area_struct *vma)
-{
-	mpol_cond_put(vma->vm_policy);
-}
-#else
-static inline void hugetlb_set_vma_policy(struct vm_area_struct *vma,
-					struct inode *inode, pgoff_t index)
-{
-}
-
-static inline void hugetlb_drop_vma_policy(struct vm_area_struct *vma)
-{
-}
-#endif
-
 /*
  * Mask used when checking the page offset value passed in via system
  * calls.  This value will be converted to a loff_t which is signed.
@@ -853,8 +830,7 @@ static long hugetlbfs_fallocate(struct f
 
 	/*
 	 * Initialize a pseudo vma as this is required by the huge page
-	 * allocation routines.  If NUMA is configured, use page index
-	 * as input to create an allocation policy.
+	 * allocation routines.
 	 */
 	vma_init(&pseudo_vma, mm);
 	vm_flags_init(&pseudo_vma, VM_HUGETLB | VM_MAYSHARE | VM_SHARED);
@@ -902,9 +878,7 @@ static long hugetlbfs_fallocate(struct f
 		 * folios in these areas, we need to consume the reserves
 		 * to keep reservation accounting consistent.
 		 */
-		hugetlb_set_vma_policy(&pseudo_vma, inode, index);
 		folio = alloc_hugetlb_folio(&pseudo_vma, addr, 0);
-		hugetlb_drop_vma_policy(&pseudo_vma);
 		if (IS_ERR(folio)) {
 			mutex_unlock(&hugetlb_fault_mutex_table[hash]);
 			error = PTR_ERR(folio);
@@ -1283,18 +1257,6 @@ static struct inode *hugetlbfs_alloc_ino
 		hugetlbfs_inc_free_inodes(sbinfo);
 		return NULL;
 	}
-
-	/*
-	 * Any time after allocation, hugetlbfs_destroy_inode can be called
-	 * for the inode.  mpol_free_shared_policy is unconditionally called
-	 * as part of hugetlbfs_destroy_inode.  So, initialize policy here
-	 * in case of a quick call to destroy.
-	 *
-	 * Note that the policy is initialized even if we are creating a
-	 * private inode.  This simplifies hugetlbfs_destroy_inode.
-	 */
-	mpol_shared_policy_init(&p->policy, NULL);
-
 	return &p->vfs_inode;
 }
 
@@ -1306,7 +1268,6 @@ static void hugetlbfs_free_inode(struct
 static void hugetlbfs_destroy_inode(struct inode *inode)
 {
 	hugetlbfs_inc_free_inodes(HUGETLBFS_SB(inode->i_sb));
-	mpol_free_shared_policy(&HUGETLBFS_I(inode)->policy);
 }
 
 static const struct address_space_operations hugetlbfs_aops = {
--- a/include/linux/hugetlb.h~hugetlbfs-drop-shared-numa-mempolicy-pretence
+++ a/include/linux/hugetlb.h
@@ -30,7 +30,7 @@ void free_huge_folio(struct folio *folio
 
 #ifdef CONFIG_HUGETLB_PAGE
 
-#include <linux/mempolicy.h>
+#include <linux/pagemap.h>
 #include <linux/shm.h>
 #include <asm/tlbflush.h>
 
@@ -545,7 +545,6 @@ static inline struct hugetlbfs_sb_info *
 }
 
 struct hugetlbfs_inode_info {
-	struct shared_policy policy;
 	struct inode vfs_inode;
 	unsigned int seals;
 };
_