This is a note to let you know that I've just added the patch titled
mm: mempolicy: keep VMA walk if both MPOL_MF_STRICT and MPOL_MF_MOVE are specified
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-mempolicy-keep-vma-walk-if-both-mpol_mf_strict-an.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 03117032d2162841bbbe9c4bafd56777cab40033
Author: Yang Shi <yang@xxxxxxxxxxxxxxxxxxxxxx>
Date: Wed Sep 20 15:32:42 2023 -0700
mm: mempolicy: keep VMA walk if both MPOL_MF_STRICT and MPOL_MF_MOVE are specified
[ Upstream commit 24526268f4e38c9ec0c4a30de4f37ad2a2a84e47 ]
When calling mbind() with MPOL_MF_{MOVE|MOVEALL} | MPOL_MF_STRICT, kernel
should attempt to migrate all existing pages, and return -EIO if there is
misplaced or unmovable page. Then commit 6f4576e3687b ("mempolicy: apply
page table walker on queue_pages_range()") messed up the return value and
didn't break VMA scan early ianymore when MPOL_MF_STRICT alone. The
return value problem was fixed by commit a7f40cfe3b7a ("mm: mempolicy:
make mbind() return -EIO when MPOL_MF_STRICT is specified"), but it broke
the VMA walk early if unmovable page is met, it may cause some pages are
not migrated as expected.
The code should conceptually do:
if (MPOL_MF_MOVE|MOVEALL)
scan all vmas
try to migrate the existing pages
return success
else if (MPOL_MF_MOVE* | MPOL_MF_STRICT)
scan all vmas
try to migrate the existing pages
return -EIO if unmovable or migration failed
else /* MPOL_MF_STRICT alone */
break early if meets unmovable and don't call mbind_range() at all
else /* none of those flags */
check the ranges in test_walk, EFAULT without mbind_range() if discontig.
Fixed the behavior.
Link: https://lkml.kernel.org/r/20230920223242.3425775-1-yang@xxxxxxxxxxxxxxxxxxxxxx
Fixes: a7f40cfe3b7a ("mm: mempolicy: make mbind() return -EIO when MPOL_MF_STRICT is specified")
Signed-off-by: Yang Shi <yang@xxxxxxxxxxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Rafael Aquini <aquini@xxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill@xxxxxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [4.9+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 158b0bcd12fd7..bfe2d1d50fbee 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -424,6 +424,7 @@ struct queue_pages {
unsigned long start;
unsigned long end;
struct vm_area_struct *first;
+ bool has_unmovable;
};
/*
@@ -444,9 +445,8 @@ static inline bool queue_pages_required(struct page *page,
/*
* queue_folios_pmd() has three possible return values:
* 0 - folios are placed on the right node or queued successfully, or
- * special page is met, i.e. huge zero page.
- * 1 - there is unmovable folio, and MPOL_MF_MOVE* & MPOL_MF_STRICT were
- * specified.
+ * special page is met, i.e. zero page, or unmovable page is found
+ * but continue walking (indicated by queue_pages.has_unmovable).
* -EIO - is migration entry or only MPOL_MF_STRICT was specified and an
* existing folio was already on a node that does not follow the
* policy.
@@ -477,7 +477,7 @@ static int queue_folios_pmd(pmd_t *pmd, spinlock_t *ptl, unsigned long addr,
if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) {
if (!vma_migratable(walk->vma) ||
migrate_folio_add(folio, qp->pagelist, flags)) {
- ret = 1;
+ qp->has_unmovable = true;
goto unlock;
}
} else
@@ -493,9 +493,8 @@ static int queue_folios_pmd(pmd_t *pmd, spinlock_t *ptl, unsigned long addr,
*
* queue_folios_pte_range() has three possible return values:
* 0 - folios are placed on the right node or queued successfully, or
- * special page is met, i.e. zero page.
- * 1 - there is unmovable folio, and MPOL_MF_MOVE* & MPOL_MF_STRICT were
- * specified.
+ * special page is met, i.e. zero page, or unmovable page is found
+ * but continue walking (indicated by queue_pages.has_unmovable).
* -EIO - only MPOL_MF_STRICT was specified and an existing folio was already
* on a node that does not follow the policy.
*/
@@ -506,7 +505,6 @@ static int queue_folios_pte_range(pmd_t *pmd, unsigned long addr,
struct folio *folio;
struct queue_pages *qp = walk->private;
unsigned long flags = qp->flags;
- bool has_unmovable = false;
pte_t *pte, *mapped_pte;
spinlock_t *ptl;
@@ -533,11 +531,12 @@ static int queue_folios_pte_range(pmd_t *pmd, unsigned long addr,
if (!queue_pages_required(&folio->page, qp))
continue;
if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) {
- /* MPOL_MF_STRICT must be specified if we get here */
- if (!vma_migratable(vma)) {
- has_unmovable = true;
- break;
- }
+ /*
+ * MPOL_MF_STRICT must be specified if we get here.
+ * Continue walking vmas due to MPOL_MF_MOVE* flags.
+ */
+ if (!vma_migratable(vma))
+ qp->has_unmovable = true;
/*
* Do not abort immediately since there may be
@@ -545,16 +544,13 @@ static int queue_folios_pte_range(pmd_t *pmd, unsigned long addr,
* need migrate other LRU pages.
*/
if (migrate_folio_add(folio, qp->pagelist, flags))
- has_unmovable = true;
+ qp->has_unmovable = true;
} else
break;
}
pte_unmap_unlock(mapped_pte, ptl);
cond_resched();
- if (has_unmovable)
- return 1;
-
return addr != end ? -EIO : 0;
}
@@ -594,7 +590,7 @@ static int queue_pages_hugetlb(pte_t *pte, unsigned long hmask,
* Detecting misplaced page but allow migrating pages which
* have been queued.
*/
- ret = 1;
+ qp->has_unmovable = true;
goto unlock;
}
@@ -608,7 +604,7 @@ static int queue_pages_hugetlb(pte_t *pte, unsigned long hmask,
* Failed to isolate page but allow migrating pages
* which have been queued.
*/
- ret = 1;
+ qp->has_unmovable = true;
}
unlock:
spin_unlock(ptl);
@@ -737,10 +733,13 @@ queue_pages_range(struct mm_struct *mm, unsigned long start, unsigned long end,
.start = start,
.end = end,
.first = NULL,
+ .has_unmovable = false,
};
err = walk_page_range(mm, start, end, &queue_pages_walk_ops, &qp);
+ if (qp.has_unmovable)
+ err = 1;
if (!qp.first)
/* whole range in hole */
err = -EFAULT;
@@ -1338,7 +1337,7 @@ static long do_mbind(unsigned long start, unsigned long len,
putback_movable_pages(&pagelist);
}
- if ((ret > 0) || (nr_failed && (flags & MPOL_MF_STRICT)))
+ if (((ret > 0) || nr_failed) && (flags & MPOL_MF_STRICT))
err = -EIO;
} else {
up_out:
