| Message ID | 20220330102534.1053240-3-chenwandun@huawei.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | fix several contiguous memmap assumptions | expand |
On 30.03.22 12:25, Chen Wandun wrote: > It isn't true for only SPARSEMEM configs to assume that a compound page > has virtually contiguous page structs, so use nth_page to iterate each > page. I really don't see how that is currently the case. The buddy deals with order < MAX_ORDER and we know that these always fall into a single memory section. IOW, this patch here would result in overhead where it's not required to have that overhead. What am I missing and which scenario are we fixing? > > Signed-off-by: Chen Wandun <chenwandun@huawei.com> > --- > mm/page_alloc.c | 16 +++++++++------- > 1 file changed, 9 insertions(+), 7 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 855211dea13e..758d8f069b32 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -721,7 +721,7 @@ static void prep_compound_head(struct page *page, unsigned int order) > > static void prep_compound_tail(struct page *head, int tail_idx) > { > - struct page *p = head + tail_idx; > + struct page *p = nth_page(head, tail_idx); > > p->mapping = TAIL_MAPPING; > set_compound_head(p, head); > @@ -1199,10 +1199,10 @@ static inline int check_free_page(struct page *page) > return 1; > } > > -static int free_tail_pages_check(struct page *head_page, struct page *page) > +static int free_tail_pages_check(struct page *head_page, int index) > { > + struct page *page = nth_page(head_page, index); > int ret = 1; > - > /* > * We rely page->lru.next never has bit 0 set, unless the page > * is PageTail(). Let's make sure that's true even for poisoned ->lru. > @@ -1213,7 +1213,7 @@ static int free_tail_pages_check(struct page *head_page, struct page *page) > ret = 0; > goto out; > } > - switch (page - head_page) { > + switch (index) { > case 1: > /* the first tail page: ->mapping may be compound_mapcount() */ > if (unlikely(compound_mapcount(page))) { > @@ -1322,6 +1322,7 @@ static __always_inline bool free_pages_prepare(struct page *page, > if (unlikely(order)) { > bool compound = PageCompound(page); > int i; > + struct page *tail_page; > > VM_BUG_ON_PAGE(compound && compound_order(page) != order, page); > > @@ -1330,13 +1331,14 @@ static __always_inline bool free_pages_prepare(struct page *page, > ClearPageHasHWPoisoned(page); > } > for (i = 1; i < (1 << order); i++) { > + tail_page = nth_page(page, i); > if (compound) > - bad += free_tail_pages_check(page, page + i); > - if (unlikely(check_free_page(page + i))) { > + bad += free_tail_pages_check(page, i); > + if (unlikely(check_free_page(tail_page))) { > bad++; > continue; > } > - (page + i)->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; > + tail_page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; > } > } > if (PageMappingFlags(page))
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 855211dea13e..758d8f069b32 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -721,7 +721,7 @@ static void prep_compound_head(struct page *page, unsigned int order) static void prep_compound_tail(struct page *head, int tail_idx) { - struct page *p = head + tail_idx; + struct page *p = nth_page(head, tail_idx); p->mapping = TAIL_MAPPING; set_compound_head(p, head); @@ -1199,10 +1199,10 @@ static inline int check_free_page(struct page *page) return 1; } -static int free_tail_pages_check(struct page *head_page, struct page *page) +static int free_tail_pages_check(struct page *head_page, int index) { + struct page *page = nth_page(head_page, index); int ret = 1; - /* * We rely page->lru.next never has bit 0 set, unless the page * is PageTail(). Let's make sure that's true even for poisoned ->lru. @@ -1213,7 +1213,7 @@ static int free_tail_pages_check(struct page *head_page, struct page *page) ret = 0; goto out; } - switch (page - head_page) { + switch (index) { case 1: /* the first tail page: ->mapping may be compound_mapcount() */ if (unlikely(compound_mapcount(page))) { @@ -1322,6 +1322,7 @@ static __always_inline bool free_pages_prepare(struct page *page, if (unlikely(order)) { bool compound = PageCompound(page); int i; + struct page *tail_page; VM_BUG_ON_PAGE(compound && compound_order(page) != order, page); @@ -1330,13 +1331,14 @@ static __always_inline bool free_pages_prepare(struct page *page, ClearPageHasHWPoisoned(page); } for (i = 1; i < (1 << order); i++) { + tail_page = nth_page(page, i); if (compound) - bad += free_tail_pages_check(page, page + i); - if (unlikely(check_free_page(page + i))) { + bad += free_tail_pages_check(page, i); + if (unlikely(check_free_page(tail_page))) { bad++; continue; } - (page + i)->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; + tail_page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; } } if (PageMappingFlags(page))
It isn't true for only SPARSEMEM configs to assume that a compound page has virtually contiguous page structs, so use nth_page to iterate each page. Signed-off-by: Chen Wandun <chenwandun@huawei.com> --- mm/page_alloc.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-)