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mm: convert ksm_might_need_to_copy() to work on folios 

Patch series "Finish two folio conversions".

Most callers of page_add_new_anon_rmap() and
lru_cache_add_inactive_or_unevictable() have been converted to their folio
equivalents, but there are still a few stragglers.  There's a bit of
preparatory work in ksm and unuse_pte(), but after that it's pretty
mechanical.


This patch (of 9):

Accept a folio as an argument and return a folio result.  Removes a call
to compound_head() in do_swap_page(), and prevents folio & page from
getting out of sync in unuse_pte().

Reviewed-by: David Hildenbrand <david@redhat.com>
[willy@infradead.org: fix smatch warning]
  Link: https://lkml.kernel.org/r/ZXnPtblC6A1IkyAB@casper.infradead.org
[david@redhat.com: only adjust the page if the folio changed]
  Link: https://lkml.kernel.org/r/6a8f2110-fa91-4c10-9eae-88315309a6e3@redhat.com
Link: https://lkml.kernel.org/r/20231211162214.2146080-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20231211162214.2146080-2-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Matthew Wilcox (Oracle) 2023-12-11 16:22:06 +00:00 committed by Andrew Morton
parent a2bf6a9ca8
commit 96db66d9c8
4 changed files with 26 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
include/linux/ksm.h
View File

@ -76,7 +76,7 @@ static inline void ksm_exit(struct mm_struct *mm)
* We'd like to make this conditional on vma->vm_flags & VM_MERGEABLE,
* but what if the vma was unmerged while the page was swapped out?
*/
struct page *ksm_might_need_to_copy(struct page *page,
struct folio *ksm_might_need_to_copy(struct folio *folio,
struct vm_area_struct *vma, unsigned long addr);
void rmap_walk_ksm(struct folio *folio, struct rmap_walk_control *rwc);
@ -129,10 +129,10 @@ static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
return 0;
}
static inline struct page *ksm_might_need_to_copy(struct page *page,
static inline struct folio *ksm_might_need_to_copy(struct folio *folio,
struct vm_area_struct *vma, unsigned long addr)
{
return page;
return folio;
}
static inline void rmap_walk_ksm(struct folio *folio,

21
mm/ksm.c
View File

@ -2873,30 +2873,30 @@ void __ksm_exit(struct mm_struct *mm)
trace_ksm_exit(mm);
}
struct page *ksm_might_need_to_copy(struct page *page,
struct folio *ksm_might_need_to_copy(struct folio *folio,
struct vm_area_struct *vma, unsigned long addr)
{
struct folio *folio = page_folio(page);
struct page *page = folio_page(folio, 0);
struct anon_vma *anon_vma = folio_anon_vma(folio);
struct folio *new_folio;
if (folio_test_large(folio))
return page;
return folio;
if (folio_test_ksm(folio)) {
if (folio_stable_node(folio) &&
!(ksm_run & KSM_RUN_UNMERGE))
return page; /* no need to copy it */
return folio; /* no need to copy it */
} else if (!anon_vma) {
return page; /* no need to copy it */
return folio; /* no need to copy it */
} else if (folio->index == linear_page_index(vma, addr) &&
anon_vma->root == vma->anon_vma->root) {
return page; /* still no need to copy it */
return folio; /* still no need to copy it */
}
if (PageHWPoison(page))
return ERR_PTR(-EHWPOISON);
if (!folio_test_uptodate(folio))
return page; /* let do_swap_page report the error */
return folio; /* let do_swap_page report the error */
new_folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, vma, addr, false);
if (new_folio &&
@ -2905,9 +2905,10 @@ struct page *ksm_might_need_to_copy(struct page *page,
new_folio = NULL;
}
if (new_folio) {
if (copy_mc_user_highpage(&new_folio->page, page, addr, vma)) {
if (copy_mc_user_highpage(folio_page(new_folio, 0), page,
addr, vma)) {
folio_put(new_folio);
memory_failure_queue(page_to_pfn(page), 0);
memory_failure_queue(folio_pfn(folio), 0);
return ERR_PTR(-EHWPOISON);
}
folio_set_dirty(new_folio);
@ -2918,7 +2919,7 @@ struct page *ksm_might_need_to_copy(struct page *page,
#endif
}
return new_folio ? &new_folio->page : NULL;
return new_folio;
}
void rmap_walk_ksm(struct folio *folio, struct rmap_walk_control *rwc)

11
mm/memory.c
View File

@ -3942,15 +3942,18 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
* page->index of !PageKSM() pages would be nonlinear inside the
* anon VMA -- PageKSM() is lost on actual swapout.
*/
page = ksm_might_need_to_copy(page, vma, vmf->address);
if (unlikely(!page)) {
folio = ksm_might_need_to_copy(folio, vma, vmf->address);
if (unlikely(!folio)) {
ret = VM_FAULT_OOM;
folio = swapcache;
goto out_page;
} else if (unlikely(PTR_ERR(page) == -EHWPOISON)) {
} else if (unlikely(folio == ERR_PTR(-EHWPOISON))) {
ret = VM_FAULT_HWPOISON;
folio = swapcache;
goto out_page;
}
folio = page_folio(page);
if (folio != swapcache)
page = folio_page(folio, 0);
/*
* If we want to map a page that's in the swapcache writable, we

8
mm/swapfile.c
View File

@ -1749,11 +1749,13 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
int ret = 1;
swapcache = page;
page = ksm_might_need_to_copy(page, vma, addr);
if (unlikely(!page))
folio = ksm_might_need_to_copy(folio, vma, addr);
if (unlikely(!folio))
return -ENOMEM;
else if (unlikely(PTR_ERR(page) == -EHWPOISON))
else if (unlikely(folio == ERR_PTR(-EHWPOISON)))
hwpoisoned = true;
else
page = folio_file_page(folio, swp_offset(entry));
pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
if (unlikely(!pte || !pte_same_as_swp(ptep_get(pte),