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mm,thp,rmap: handle the normal !PageCompound case first

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Commit ("mm,thp,rmap: lock_compound_mapcounts() on THP mapcounts")
propagated the "if (compound) {lock} else if (PageCompound) {lock} else
{atomic}" pattern throughout; but Linus hated the way that gives primacy
to the uncommon case: switch to "if (!PageCompound) {atomic} else if
(compound) {lock} else {lock}" throughout.  Linus has a bigger idea for
how to improve it all, but here just make that rearrangement.

Link: https://lkml.kernel.org/r/fca2f694-2098-b0ef-d4e-f1d8b94d318c@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: James Houghton <jthoughton@google.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Hugh Dickins 2022-11-09 18:18:49 -08:00 committed by Andrew Morton
parent 9bd3155ed8
commit d8dd5e979d
1 changed files with 27 additions and 27 deletions
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54
mm/rmap.c
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@ -1311,7 +1311,11 @@ void page_add_anon_rmap(struct page *page,
else
VM_BUG_ON_PAGE(!PageLocked(page), page);
if (compound && PageTransHuge(page)) {
if (likely(!PageCompound(page))) {
first = atomic_inc_and_test(&page->_mapcount);
nr = first;
} else if (compound && PageTransHuge(page)) {
lock_compound_mapcounts(page, &mapcounts);
first = !mapcounts.compound_mapcount;
mapcounts.compound_mapcount++;
@ -1321,8 +1325,7 @@ void page_add_anon_rmap(struct page *page,
nr = nr_subpages_unmapped(page, nr_pmdmapped);
}
unlock_compound_mapcounts(page, &mapcounts);
} else if (PageCompound(page)) {
} else {
struct page *head = compound_head(page);
lock_compound_mapcounts(head, &mapcounts);
@ -1330,10 +1333,6 @@ void page_add_anon_rmap(struct page *page,
first = subpage_mapcount_inc(page);
nr = first && !mapcounts.compound_mapcount;
unlock_compound_mapcounts(head, &mapcounts);
} else {
first = atomic_inc_and_test(&page->_mapcount);
nr = first;
}
VM_BUG_ON_PAGE(!first && (flags & RMAP_EXCLUSIVE), page);
@ -1373,20 +1372,23 @@ void page_add_anon_rmap(struct page *page,
void page_add_new_anon_rmap(struct page *page,
struct vm_area_struct *vma, unsigned long address)
{
const bool compound = PageCompound(page);
int nr = compound ? thp_nr_pages(page) : 1;
int nr;
VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
__SetPageSwapBacked(page);
if (compound) {
if (likely(!PageCompound(page))) {
/* increment count (starts at -1) */
atomic_set(&page->_mapcount, 0);
nr = 1;
} else {
VM_BUG_ON_PAGE(!PageTransHuge(page), page);
/* increment count (starts at -1) */
atomic_set(compound_mapcount_ptr(page), 0);
nr = thp_nr_pages(page);
__mod_lruvec_page_state(page, NR_ANON_THPS, nr);
} else {
/* increment count (starts at -1) */
atomic_set(&page->_mapcount, 0);
}
__mod_lruvec_page_state(page, NR_ANON_MAPPED, nr);
__page_set_anon_rmap(page, vma, address, 1);
}
@ -1409,7 +1411,11 @@ void page_add_file_rmap(struct page *page,
VM_BUG_ON_PAGE(compound && !PageTransHuge(page), page);
lock_page_memcg(page);
if (compound && PageTransHuge(page)) {
if (likely(!PageCompound(page))) {
first = atomic_inc_and_test(&page->_mapcount);
nr = first;
} else if (compound && PageTransHuge(page)) {
lock_compound_mapcounts(page, &mapcounts);
first = !mapcounts.compound_mapcount;
mapcounts.compound_mapcount++;
@ -1419,8 +1425,7 @@ void page_add_file_rmap(struct page *page,
nr = nr_subpages_unmapped(page, nr_pmdmapped);
}
unlock_compound_mapcounts(page, &mapcounts);
} else if (PageCompound(page)) {
} else {
struct page *head = compound_head(page);
lock_compound_mapcounts(head, &mapcounts);
@ -1428,10 +1433,6 @@ void page_add_file_rmap(struct page *page,
first = subpage_mapcount_inc(page);
nr = first && !mapcounts.compound_mapcount;
unlock_compound_mapcounts(head, &mapcounts);
} else {
first = atomic_inc_and_test(&page->_mapcount);
nr = first;
}
if (nr_pmdmapped)
@ -1471,7 +1472,11 @@ void page_remove_rmap(struct page *page,
lock_page_memcg(page);
/* page still mapped by someone else? */
if (compound && PageTransHuge(page)) {
if (likely(!PageCompound(page))) {
last = atomic_add_negative(-1, &page->_mapcount);
nr = last;
} else if (compound && PageTransHuge(page)) {
lock_compound_mapcounts(page, &mapcounts);
mapcounts.compound_mapcount--;
last = !mapcounts.compound_mapcount;
@ -1481,8 +1486,7 @@ void page_remove_rmap(struct page *page,
nr = nr_subpages_unmapped(page, nr_pmdmapped);
}
unlock_compound_mapcounts(page, &mapcounts);
} else if (PageCompound(page)) {
} else {
struct page *head = compound_head(page);
lock_compound_mapcounts(head, &mapcounts);
@ -1490,10 +1494,6 @@ void page_remove_rmap(struct page *page,
last = subpage_mapcount_dec(page);
nr = last && !mapcounts.compound_mapcount;
unlock_compound_mapcounts(head, &mapcounts);
} else {
last = atomic_add_negative(-1, &page->_mapcount);
nr = last;
}
if (nr_pmdmapped) {