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mm/huge_memory: convert split_huge_pages_pid() from follow_page() to folio_walk

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Let's remove yet another follow_page() user.  Note that we have to do the
split without holding the PTL, after folio_walk_end().  We don't care
about losing the secretmem check in follow_page().

[david@redhat.com: teach can_split_folio() that we are not holding an additional reference]
  Link: https://lkml.kernel.org/r/c75d1c6c-8ea6-424f-853c-1ccda6c77ba2@redhat.com
Link: https://lkml.kernel.org/r/20240802155524.517137-8-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Janosch Frank <frankja@linux.ibm.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
David Hildenbrand
2024-08-02 17:55:20 +02:00
committed by Andrew Morton
parent b1d3e9bbcc
commit 8710f6ed34
3 changed files with 19 additions and 14 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
include/linux/huge_mm.h
View File

@@ -314,7 +314,7 @@ unsigned long thp_get_unmapped_area_vmflags(struct file *filp, unsigned long add
unsigned long len, unsigned long pgoff, unsigned long flags,
vm_flags_t vm_flags);
bool can_split_folio(struct folio *folio, int *pextra_pins);
bool can_split_folio(struct folio *folio, int caller_pins, int *pextra_pins);
int split_huge_page_to_list_to_order(struct page *page, struct list_head *list,
unsigned int new_order);
static inline int split_huge_page(struct page *page)
@@ -470,7 +470,7 @@ thp_get_unmapped_area_vmflags(struct file *filp, unsigned long addr,
}
static inline bool
can_split_folio(struct folio *folio, int *pextra_pins)
can_split_folio(struct folio *folio, int caller_pins, int *pextra_pins)
{
return false;
}

27
mm/huge_memory.c
View File

@@ -40,6 +40,7 @@
#include <linux/memory-tiers.h>
#include <linux/compat.h>
#include <linux/pgalloc_tag.h>
#include <linux/pagewalk.h>
#include <asm/tlb.h>
#include <asm/pgalloc.h>
@@ -3017,7 +3018,7 @@ static void __split_huge_page(struct page *page, struct list_head *list,
}
/* Racy check whether the huge page can be split */
bool can_split_folio(struct folio *folio, int *pextra_pins)
bool can_split_folio(struct folio *folio, int caller_pins, int *pextra_pins)
{
int extra_pins;
@@ -3029,7 +3030,8 @@ bool can_split_folio(struct folio *folio, int *pextra_pins)
extra_pins = folio_nr_pages(folio);
if (pextra_pins)
*pextra_pins = extra_pins;
return folio_mapcount(folio) == folio_ref_count(folio) - extra_pins - 1;
return folio_mapcount(folio) == folio_ref_count(folio) - extra_pins -
caller_pins;
}
/*
@@ -3197,7 +3199,7 @@ int split_huge_page_to_list_to_order(struct page *page, struct list_head *list,
* Racy check if we can split the page, before unmap_folio() will
* split PMDs
*/
if (!can_split_folio(folio, &extra_pins)) {
if (!can_split_folio(folio, 1, &extra_pins)) {
ret = -EAGAIN;
goto out_unlock;
}
@@ -3504,7 +3506,7 @@ static int split_huge_pages_pid(int pid, unsigned long vaddr_start,
*/
for (addr = vaddr_start; addr < vaddr_end; addr += PAGE_SIZE) {
struct vm_area_struct *vma = vma_lookup(mm, addr);
struct page *page;
struct folio_walk fw;
struct folio *folio;
if (!vma)
@@ -3516,13 +3518,10 @@ static int split_huge_pages_pid(int pid, unsigned long vaddr_start,
continue;
}
/* FOLL_DUMP to ignore special (like zero) pages */
page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
if (IS_ERR_OR_NULL(page))
folio = folio_walk_start(&fw, vma, addr, 0);
if (!folio)
continue;
folio = page_folio(page);
if (!is_transparent_hugepage(folio))
goto next;
@@ -3536,18 +3535,24 @@ static int split_huge_pages_pid(int pid, unsigned long vaddr_start,
* can be split or not. So skip the check here.
*/
if (!folio_test_private(folio) &&
!can_split_folio(folio, NULL))
!can_split_folio(folio, 0, NULL))
goto next;
if (!folio_trylock(folio))
goto next;
folio_get(folio);
folio_walk_end(&fw, vma);
if (!split_folio_to_order(folio, new_order))
split++;
folio_unlock(folio);
next:
folio_put(folio);
cond_resched();
continue;
next:
folio_walk_end(&fw, vma);
cond_resched();
}
mmap_read_unlock(mm);

2
mm/vmscan.c
View File

@@ -1227,7 +1227,7 @@ static unsigned int shrink_folio_list(struct list_head *folio_list,
goto keep_locked;
if (folio_test_large(folio)) {
/* cannot split folio, skip it */
if (!can_split_folio(folio, NULL))
if (!can_split_folio(folio, 1, NULL))
goto activate_locked;
/*
* Split partially mapped folios right away.