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khugepaged: use a folio throughout collapse_file()

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Pull folios from the page cache instead of pages.  Half of this work had
been done already, but we were still operating on pages for a large chunk
of this function.  There is no attempt in this patch to handle large
folios that are smaller than a THP; that will have to wait for a future
patch.

[willy@infradead.org: the unlikely() is embedded in IS_ERR()]
  Link: https://lkml.kernel.org/r/ZhIWX8K0E2tSyMSr@casper.infradead.org
Link: https://lkml.kernel.org/r/20240403171838.1445826-7-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Matthew Wilcox (Oracle) 2024-04-03 18:18:35 +01:00 committed by Andrew Morton
parent 610ff817b9
commit 8d1e24c0b8
1 changed files with 54 additions and 59 deletions
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113
mm/khugepaged.c
View file

@ -1780,9 +1780,8 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
struct collapse_control *cc)
{
struct address_space *mapping = file->f_mapping;
struct page *page;
struct page *tmp, *dst;
struct folio *folio, *new_folio;
struct page *dst;
struct folio *folio, *tmp, *new_folio;
pgoff_t index = 0, end = start + HPAGE_PMD_NR;
LIST_HEAD(pagelist);
XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER);
@ -1820,11 +1819,11 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
for (index = start; index < end; index++) {
xas_set(&xas, index);
page = xas_load(&xas);
folio = xas_load(&xas);
VM_BUG_ON(index != xas.xa_index);
if (is_shmem) {
if (!page) {
if (!folio) {
/*
* Stop if extent has been truncated or
* hole-punched, and is now completely
@ -1840,7 +1839,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
continue;
}
if (xa_is_value(page) || !PageUptodate(page)) {
if (xa_is_value(folio) || !folio_test_uptodate(folio)) {
xas_unlock_irq(&xas);
/* swap in or instantiate fallocated page */
if (shmem_get_folio(mapping->host, index,
@ -1850,28 +1849,27 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
}
/* drain lru cache to help isolate_lru_page() */
lru_add_drain();
page = folio_file_page(folio, index);
} else if (trylock_page(page)) {
get_page(page);
} else if (folio_trylock(folio)) {
folio_get(folio);
xas_unlock_irq(&xas);
} else {
result = SCAN_PAGE_LOCK;
goto xa_locked;
}
} else { /* !is_shmem */
if (!page || xa_is_value(page)) {
if (!folio || xa_is_value(folio)) {
xas_unlock_irq(&xas);
page_cache_sync_readahead(mapping, &file->f_ra,
file, index,
end - index);
/* drain lru cache to help isolate_lru_page() */
lru_add_drain();
page = find_lock_page(mapping, index);
if (unlikely(page == NULL)) {
folio = filemap_lock_folio(mapping, index);
if (IS_ERR(folio)) {
result = SCAN_FAIL;
goto xa_unlocked;
}
} else if (PageDirty(page)) {
} else if (folio_test_dirty(folio)) {
/*
* khugepaged only works on read-only fd,
* so this page is dirty because it hasn't
@ -1889,12 +1887,12 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
filemap_flush(mapping);
result = SCAN_FAIL;
goto xa_unlocked;
} else if (PageWriteback(page)) {
} else if (folio_test_writeback(folio)) {
xas_unlock_irq(&xas);
result = SCAN_FAIL;
goto xa_unlocked;
} else if (trylock_page(page)) {
get_page(page);
} else if (folio_trylock(folio)) {
folio_get(folio);
xas_unlock_irq(&xas);
} else {
result = SCAN_PAGE_LOCK;
@ -1903,35 +1901,31 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
}
/*
* The page must be locked, so we can drop the i_pages lock
* The folio must be locked, so we can drop the i_pages lock
* without racing with truncate.
*/
VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
/* make sure the page is up to date */
if (unlikely(!PageUptodate(page))) {
/* make sure the folio is up to date */
if (unlikely(!folio_test_uptodate(folio))) {
result = SCAN_FAIL;
goto out_unlock;
}
/*
* If file was truncated then extended, or hole-punched, before
* we locked the first page, then a THP might be there already.
* we locked the first folio, then a THP might be there already.
* This will be discovered on the first iteration.
*/
if (PageTransCompound(page)) {
struct page *head = compound_head(page);
result = compound_order(head) == HPAGE_PMD_ORDER &&
head->index == start
if (folio_test_large(folio)) {
result = folio_order(folio) == HPAGE_PMD_ORDER &&
folio->index == start
/* Maybe PMD-mapped */
? SCAN_PTE_MAPPED_HUGEPAGE
: SCAN_PAGE_COMPOUND;
goto out_unlock;
}
folio = page_folio(page);
if (folio_mapping(folio) != mapping) {
result = SCAN_TRUNCATED;
goto out_unlock;
@ -1941,7 +1935,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
folio_test_writeback(folio))) {
/*
* khugepaged only works on read-only fd, so this
* page is dirty because it hasn't been flushed
* folio is dirty because it hasn't been flushed
* since first write.
*/
result = SCAN_FAIL;
@ -1965,33 +1959,34 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
xas_lock_irq(&xas);
VM_BUG_ON_PAGE(page != xa_load(xas.xa, index), page);
VM_BUG_ON_FOLIO(folio != xa_load(xas.xa, index), folio);
/*
* We control three references to the page:
* We control three references to the folio:
* - we hold a pin on it;
* - one reference from page cache;
* - one from isolate_lru_page;
* If those are the only references, then any new usage of the
* page will have to fetch it from the page cache. That requires
* locking the page to handle truncate, so any new usage will be
* blocked until we unlock page after collapse/during rollback.
* - one from lru_isolate_folio;
* If those are the only references, then any new usage
* of the folio will have to fetch it from the page
* cache. That requires locking the folio to handle
* truncate, so any new usage will be blocked until we
* unlock folio after collapse/during rollback.
*/
if (page_count(page) != 3) {
if (folio_ref_count(folio) != 3) {
result = SCAN_PAGE_COUNT;
xas_unlock_irq(&xas);
putback_lru_page(page);
folio_putback_lru(folio);
goto out_unlock;
}
/*
* Accumulate the pages that are being collapsed.
* Accumulate the folios that are being collapsed.
*/
list_add_tail(&page->lru, &pagelist);
list_add_tail(&folio->lru, &pagelist);
continue;
out_unlock:
unlock_page(page);
put_page(page);
folio_unlock(folio);
folio_put(folio);
goto xa_unlocked;
}
@ -2030,17 +2025,17 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
}
/*
* The old pages are locked, so they won't change anymore.
* The old folios are locked, so they won't change anymore.
*/
index = start;
dst = folio_page(new_folio, 0);
list_for_each_entry(page, &pagelist, lru) {
while (index < page->index) {
list_for_each_entry(folio, &pagelist, lru) {
while (index < folio->index) {
clear_highpage(dst);
index++;
dst++;
}
if (copy_mc_highpage(dst, page) > 0) {
if (copy_mc_highpage(dst, folio_page(folio, 0)) > 0) {
result = SCAN_COPY_MC;
goto rollback;
}
@ -2152,15 +2147,15 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
folio_unlock(new_folio);
/*
* The collapse has succeeded, so free the old pages.
* The collapse has succeeded, so free the old folios.
*/
list_for_each_entry_safe(page, tmp, &pagelist, lru) {
list_del(&page->lru);
page->mapping = NULL;
ClearPageActive(page);
ClearPageUnevictable(page);
unlock_page(page);
folio_put_refs(page_folio(page), 3);
list_for_each_entry_safe(folio, tmp, &pagelist, lru) {
list_del(&folio->lru);
folio->mapping = NULL;
folio_clear_active(folio);
folio_clear_unevictable(folio);
folio_unlock(folio);
folio_put_refs(folio, 3);
}
goto out;
@ -2174,11 +2169,11 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
shmem_uncharge(mapping->host, nr_none);
}
list_for_each_entry_safe(page, tmp, &pagelist, lru) {
list_del(&page->lru);
unlock_page(page);
putback_lru_page(page);
put_page(page);
list_for_each_entry_safe(folio, tmp, &pagelist, lru) {
list_del(&folio->lru);
folio_unlock(folio);
folio_putback_lru(folio);
folio_put(folio);
}
/*
* Undo the updates of filemap_nr_thps_inc for non-SHMEM