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-rw-r--r--mm/rmap.c121
1 files changed, 25 insertions, 96 deletions
diff --git a/mm/rmap.c b/mm/rmap.c
index e813785da613..459dc1c44d8a 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1085,38 +1085,6 @@ int pfn_mkclean_range(unsigned long pfn, unsigned long nr_pages, pgoff_t pgoff,
return page_vma_mkclean_one(&pvmw);
}
-struct compound_mapcounts {
- unsigned int compound_mapcount;
- unsigned int subpages_mapcount;
-};
-
-/*
- * lock_compound_mapcounts() first locks, then copies subpages_mapcount and
- * compound_mapcount from head[1].compound_mapcount and subpages_mapcount,
- * converting from struct page's internal representation to logical count
- * (that is, adding 1 to compound_mapcount to hide its offset by -1).
- */
-static void lock_compound_mapcounts(struct page *head,
- struct compound_mapcounts *local)
-{
- bit_spin_lock(PG_locked, &head[1].flags);
- local->compound_mapcount = atomic_read(compound_mapcount_ptr(head)) + 1;
- local->subpages_mapcount = atomic_read(subpages_mapcount_ptr(head));
-}
-
-/*
- * After caller has updated subpage._mapcount, local subpages_mapcount and
- * local compound_mapcount, as necessary, unlock_compound_mapcounts() converts
- * and copies them back to the compound head[1] fields, and then unlocks.
- */
-static void unlock_compound_mapcounts(struct page *head,
- struct compound_mapcounts *local)
-{
- atomic_set(compound_mapcount_ptr(head), local->compound_mapcount - 1);
- atomic_set(subpages_mapcount_ptr(head), local->subpages_mapcount);
- bit_spin_unlock(PG_locked, &head[1].flags);
-}
-
int total_compound_mapcount(struct page *head)
{
int mapcount = head_compound_mapcount(head);
@@ -1140,34 +1108,6 @@ int total_compound_mapcount(struct page *head)
return mapcount;
}
-/*
- * page_dup_compound_rmap(), used when copying mm,
- * provides a simple example of using lock_ and unlock_compound_mapcounts().
- */
-void page_dup_compound_rmap(struct page *head)
-{
- struct compound_mapcounts mapcounts;
-
- /*
- * Hugetlb pages could use lock_compound_mapcounts(), like THPs do;
- * but at present they are still being managed by atomic operations:
- * which are likely to be somewhat faster, so don't rush to convert
- * them over without evaluating the effect.
- *
- * Note that hugetlb does not call page_add_file_rmap():
- * here is where hugetlb shared page mapcount is raised.
- */
- if (PageHuge(head)) {
- atomic_inc(compound_mapcount_ptr(head));
- } else if (PageTransHuge(head)) {
- /* That test is redundant: it's for safety or to optimize out */
-
- lock_compound_mapcounts(head, &mapcounts);
- mapcounts.compound_mapcount++;
- unlock_compound_mapcounts(head, &mapcounts);
- }
-}
-
/**
* page_move_anon_rmap - move a page to our anon_vma
* @page: the page to move to our anon_vma
@@ -1277,7 +1217,7 @@ static void __page_check_anon_rmap(struct page *page,
void page_add_anon_rmap(struct page *page,
struct vm_area_struct *vma, unsigned long address, rmap_t flags)
{
- struct compound_mapcounts mapcounts;
+ atomic_t *mapped;
int nr = 0, nr_pmdmapped = 0;
bool compound = flags & RMAP_COMPOUND;
bool first = true;
@@ -1290,24 +1230,20 @@ void page_add_anon_rmap(struct page *page,
first = atomic_inc_and_test(&page->_mapcount);
nr = first;
if (first && PageCompound(page)) {
- struct page *head = compound_head(page);
-
- lock_compound_mapcounts(head, &mapcounts);
- mapcounts.subpages_mapcount++;
- nr = !mapcounts.compound_mapcount;
- unlock_compound_mapcounts(head, &mapcounts);
+ mapped = subpages_mapcount_ptr(compound_head(page));
+ nr = atomic_inc_return_relaxed(mapped);
+ nr = !(nr & COMPOUND_MAPPED);
}
} else if (PageTransHuge(page)) {
/* That test is redundant: it's for safety or to optimize out */
- lock_compound_mapcounts(page, &mapcounts);
- first = !mapcounts.compound_mapcount;
- mapcounts.compound_mapcount++;
+ first = atomic_inc_and_test(compound_mapcount_ptr(page));
if (first) {
+ mapped = subpages_mapcount_ptr(page);
+ nr = atomic_add_return_relaxed(COMPOUND_MAPPED, mapped);
nr_pmdmapped = thp_nr_pages(page);
- nr = nr_pmdmapped - mapcounts.subpages_mapcount;
+ nr = nr_pmdmapped - (nr & SUBPAGES_MAPPED);
}
- unlock_compound_mapcounts(page, &mapcounts);
}
VM_BUG_ON_PAGE(!first && (flags & RMAP_EXCLUSIVE), page);
@@ -1360,6 +1296,7 @@ void page_add_new_anon_rmap(struct page *page,
VM_BUG_ON_PAGE(!PageTransHuge(page), page);
/* increment count (starts at -1) */
atomic_set(compound_mapcount_ptr(page), 0);
+ atomic_set(subpages_mapcount_ptr(page), COMPOUND_MAPPED);
nr = thp_nr_pages(page);
__mod_lruvec_page_state(page, NR_ANON_THPS, nr);
}
@@ -1379,7 +1316,7 @@ void page_add_new_anon_rmap(struct page *page,
void page_add_file_rmap(struct page *page,
struct vm_area_struct *vma, bool compound)
{
- struct compound_mapcounts mapcounts;
+ atomic_t *mapped;
int nr = 0, nr_pmdmapped = 0;
bool first;
@@ -1391,24 +1328,20 @@ void page_add_file_rmap(struct page *page,
first = atomic_inc_and_test(&page->_mapcount);
nr = first;
if (first && PageCompound(page)) {
- struct page *head = compound_head(page);
-
- lock_compound_mapcounts(head, &mapcounts);
- mapcounts.subpages_mapcount++;
- nr = !mapcounts.compound_mapcount;
- unlock_compound_mapcounts(head, &mapcounts);
+ mapped = subpages_mapcount_ptr(compound_head(page));
+ nr = atomic_inc_return_relaxed(mapped);
+ nr = !(nr & COMPOUND_MAPPED);
}
} else if (PageTransHuge(page)) {
/* That test is redundant: it's for safety or to optimize out */
- lock_compound_mapcounts(page, &mapcounts);
- first = !mapcounts.compound_mapcount;
- mapcounts.compound_mapcount++;
+ first = atomic_inc_and_test(compound_mapcount_ptr(page));
if (first) {
+ mapped = subpages_mapcount_ptr(page);
+ nr = atomic_add_return_relaxed(COMPOUND_MAPPED, mapped);
nr_pmdmapped = thp_nr_pages(page);
- nr = nr_pmdmapped - mapcounts.subpages_mapcount;
+ nr = nr_pmdmapped - (nr & SUBPAGES_MAPPED);
}
- unlock_compound_mapcounts(page, &mapcounts);
}
if (nr_pmdmapped)
@@ -1432,7 +1365,7 @@ void page_add_file_rmap(struct page *page,
void page_remove_rmap(struct page *page,
struct vm_area_struct *vma, bool compound)
{
- struct compound_mapcounts mapcounts;
+ atomic_t *mapped;
int nr = 0, nr_pmdmapped = 0;
bool last;
@@ -1452,24 +1385,20 @@ void page_remove_rmap(struct page *page,
last = atomic_add_negative(-1, &page->_mapcount);
nr = last;
if (last && PageCompound(page)) {
- struct page *head = compound_head(page);
-
- lock_compound_mapcounts(head, &mapcounts);
- mapcounts.subpages_mapcount--;
- nr = !mapcounts.compound_mapcount;
- unlock_compound_mapcounts(head, &mapcounts);
+ mapped = subpages_mapcount_ptr(compound_head(page));
+ nr = atomic_dec_return_relaxed(mapped);
+ nr = !(nr & COMPOUND_MAPPED);
}
} else if (PageTransHuge(page)) {
/* That test is redundant: it's for safety or to optimize out */
- lock_compound_mapcounts(page, &mapcounts);
- mapcounts.compound_mapcount--;
- last = !mapcounts.compound_mapcount;
+ last = atomic_add_negative(-1, compound_mapcount_ptr(page));
if (last) {
+ mapped = subpages_mapcount_ptr(page);
+ nr = atomic_sub_return_relaxed(COMPOUND_MAPPED, mapped);
nr_pmdmapped = thp_nr_pages(page);
- nr = nr_pmdmapped - mapcounts.subpages_mapcount;
+ nr = nr_pmdmapped - (nr & SUBPAGES_MAPPED);
}
- unlock_compound_mapcounts(page, &mapcounts);
}
if (nr_pmdmapped) {
generated by cgit v1.2.3 (git 2.39.0) at 2024-11-22 12:43:48 +0300