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Message-ID: <20221021163703.3218176-25-jthoughton@google.com>
Date: Fri, 21 Oct 2022 16:36:40 +0000
From: James Houghton <jthoughton@...gle.com>
To: Mike Kravetz <mike.kravetz@...cle.com>,
Muchun Song <songmuchun@...edance.com>,
Peter Xu <peterx@...hat.com>
Cc: David Hildenbrand <david@...hat.com>,
David Rientjes <rientjes@...gle.com>,
Axel Rasmussen <axelrasmussen@...gle.com>,
Mina Almasry <almasrymina@...gle.com>,
"Zach O'Keefe" <zokeefe@...gle.com>,
Manish Mishra <manish.mishra@...anix.com>,
Naoya Horiguchi <naoya.horiguchi@....com>,
"Dr . David Alan Gilbert" <dgilbert@...hat.com>,
"Matthew Wilcox (Oracle)" <willy@...radead.org>,
Vlastimil Babka <vbabka@...e.cz>,
Baolin Wang <baolin.wang@...ux.alibaba.com>,
Miaohe Lin <linmiaohe@...wei.com>,
Yang Shi <shy828301@...il.com>,
Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
James Houghton <jthoughton@...gle.com>
Subject: [RFC PATCH v2 24/47] hugetlb: update page_vma_mapped to do
high-granularity walks
This updates the HugeTLB logic to look a lot more like the PTE-mapped
THP logic. When a user calls us in a loop, we will update pvmw->address
to walk to each page table entry that could possibly map the hugepage
containing pvmw->pfn.
This makes use of the new pte_order so callers know what size PTE
they're getting.
Signed-off-by: James Houghton <jthoughton@...gle.com>
---
include/linux/rmap.h | 4 +++
mm/page_vma_mapped.c | 59 ++++++++++++++++++++++++++++++++++++--------
mm/rmap.c | 48 +++++++++++++++++++++--------------
3 files changed, 83 insertions(+), 28 deletions(-)
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index e0557ede2951..d7d2d9f65a01 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -13,6 +13,7 @@
#include <linux/highmem.h>
#include <linux/pagemap.h>
#include <linux/memremap.h>
+#include <linux/hugetlb.h>
/*
* The anon_vma heads a list of private "related" vmas, to scan if
@@ -409,6 +410,9 @@ static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw)
pte_unmap(pvmw->pte);
if (pvmw->ptl)
spin_unlock(pvmw->ptl);
+ if (pvmw->pte && is_vm_hugetlb_page(pvmw->vma) &&
+ hugetlb_hgm_enabled(pvmw->vma))
+ hugetlb_vma_unlock_read(pvmw->vma);
}
bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw);
diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index 395ca4e21c56..1994b3f9a4c2 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -133,7 +133,8 @@ static void step_forward(struct page_vma_mapped_walk *pvmw, unsigned long size)
*
* Returns true if the page is mapped in the vma. @pvmw->pmd and @pvmw->pte point
* to relevant page table entries. @pvmw->ptl is locked. @pvmw->address is
- * adjusted if needed (for PTE-mapped THPs).
+ * adjusted if needed (for PTE-mapped THPs and high-granularity--mapped HugeTLB
+ * pages).
*
* If @pvmw->pmd is set but @pvmw->pte is not, you have found PMD-mapped page
* (usually THP). For PTE-mapped THP, you should run page_vma_mapped_walk() in
@@ -166,19 +167,57 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
if (unlikely(is_vm_hugetlb_page(vma))) {
struct hstate *hstate = hstate_vma(vma);
unsigned long size = huge_page_size(hstate);
- /* The only possible mapping was handled on last iteration */
- if (pvmw->pte)
- return not_found(pvmw);
+ struct hugetlb_pte hpte;
+ pte_t *pte;
+ pte_t pteval;
+
+ end = (pvmw->address & huge_page_mask(hstate)) +
+ huge_page_size(hstate);
/* when pud is not present, pte will be NULL */
- pvmw->pte = huge_pte_offset(mm, pvmw->address, size);
- if (!pvmw->pte)
+ pte = huge_pte_offset(mm, pvmw->address, size);
+ if (!pte)
return false;
- pvmw->pte_order = huge_page_order(hstate);
- pvmw->ptl = huge_pte_lock(hstate, mm, pvmw->pte);
- if (!check_pte(pvmw))
- return not_found(pvmw);
+ do {
+ hugetlb_pte_populate(&hpte, pte, huge_page_shift(hstate),
+ hpage_size_to_level(size));
+
+ /*
+ * Do a high granularity page table walk. The vma lock
+ * is grabbed to prevent the page table from being
+ * collapsed mid-walk. It is dropped in
+ * page_vma_mapped_walk_done().
+ */
+ if (pvmw->pte) {
+ if (pvmw->ptl)
+ spin_unlock(pvmw->ptl);
+ pvmw->ptl = NULL;
+ pvmw->address += PAGE_SIZE << pvmw->pte_order;
+ if (pvmw->address >= end)
+ return not_found(pvmw);
+ } else if (hugetlb_hgm_enabled(vma))
+ /* Only grab the lock once. */
+ hugetlb_vma_lock_read(vma);
+
+retry_walk:
+ hugetlb_hgm_walk(mm, vma, &hpte, pvmw->address,
+ PAGE_SIZE, /*stop_at_none=*/true);
+
+ pvmw->pte = hpte.ptep;
+ pvmw->pte_order = hpte.shift - PAGE_SHIFT;
+ pvmw->ptl = hugetlb_pte_lock(mm, &hpte);
+ pteval = huge_ptep_get(hpte.ptep);
+ if (pte_present(pteval) && !hugetlb_pte_present_leaf(
+ &hpte, pteval)) {
+ /*
+ * Someone split from under us, so keep
+ * walking.
+ */
+ spin_unlock(pvmw->ptl);
+ goto retry_walk;
+ }
+ } while (!check_pte(pvmw));
return true;
}
diff --git a/mm/rmap.c b/mm/rmap.c
index 527463c1e936..a8359584467e 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1552,17 +1552,23 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
flush_cache_range(vma, range.start, range.end);
/*
- * To call huge_pmd_unshare, i_mmap_rwsem must be
- * held in write mode. Caller needs to explicitly
- * do this outside rmap routines.
- *
- * We also must hold hugetlb vma_lock in write mode.
- * Lock order dictates acquiring vma_lock BEFORE
- * i_mmap_rwsem. We can only try lock here and fail
- * if unsuccessful.
+ * If HGM is enabled, we have already grabbed the VMA
+ * lock for reading, and we cannot safely release it.
+ * Because HGM-enabled VMAs have already unshared all
+ * PMDs, we can safely ignore PMD unsharing here.
*/
- if (!anon) {
+ if (!anon && !hugetlb_hgm_enabled(vma)) {
VM_BUG_ON(!(flags & TTU_RMAP_LOCKED));
+ /*
+ * To call huge_pmd_unshare, i_mmap_rwsem must
+ * be held in write mode. Caller needs to
+ * explicitly do this outside rmap routines.
+ *
+ * We also must hold hugetlb vma_lock in write
+ * mode. Lock order dictates acquiring vma_lock
+ * BEFORE i_mmap_rwsem. We can only try lock
+ * here and fail if unsuccessful.
+ */
if (!hugetlb_vma_trylock_write(vma)) {
page_vma_mapped_walk_done(&pvmw);
ret = false;
@@ -1946,17 +1952,23 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma,
flush_cache_range(vma, range.start, range.end);
/*
- * To call huge_pmd_unshare, i_mmap_rwsem must be
- * held in write mode. Caller needs to explicitly
- * do this outside rmap routines.
- *
- * We also must hold hugetlb vma_lock in write mode.
- * Lock order dictates acquiring vma_lock BEFORE
- * i_mmap_rwsem. We can only try lock here and
- * fail if unsuccessful.
+ * If HGM is enabled, we have already grabbed the VMA
+ * lock for reading, and we cannot safely release it.
+ * Because HGM-enabled VMAs have already unshared all
+ * PMDs, we can safely ignore PMD unsharing here.
*/
- if (!anon) {
+ if (!anon && !hugetlb_hgm_enabled(vma)) {
VM_BUG_ON(!(flags & TTU_RMAP_LOCKED));
+ /*
+ * To call huge_pmd_unshare, i_mmap_rwsem must
+ * be held in write mode. Caller needs to
+ * explicitly do this outside rmap routines.
+ *
+ * We also must hold hugetlb vma_lock in write
+ * mode. Lock order dictates acquiring vma_lock
+ * BEFORE i_mmap_rwsem. We can only try lock
+ * here and fail if unsuccessful.
+ */
if (!hugetlb_vma_trylock_write(vma)) {
page_vma_mapped_walk_done(&pvmw);
ret = false;
--
2.38.0.135.g90850a2211-goog
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