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swapfile: convert unuse_pte_range() to use a folio

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Delay fetching the precise page from the folio until we're in unuse_pte().
Saves many calls to compound_head().

Link: https://lkml.kernel.org/r/20220902194653.1739778-37-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) 2022-09-02 20:46:32 +01:00 committed by Andrew Morton
parent 2c3f6194b0
commit f102cd8b17
1 changed files with 19 additions and 14 deletions
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33
mm/swapfile.c
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@ -1758,8 +1758,9 @@ static inline int pte_same_as_swp(pte_t pte, pte_t swp_pte)
* force COW, vm_page_prot omits write permission from any private vma.
*/
static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
unsigned long addr, swp_entry_t entry, struct page *page)
unsigned long addr, swp_entry_t entry, struct folio *folio)
{
struct page *page = folio_file_page(folio, swp_offset(entry));
struct page *swapcache;
spinlock_t *ptl;
pte_t *pte, new_pte;
@ -1831,17 +1832,18 @@ static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
unsigned long addr, unsigned long end,
unsigned int type)
{
struct page *page;
swp_entry_t entry;
pte_t *pte;
struct swap_info_struct *si;
unsigned long offset;
int ret = 0;
volatile unsigned char *swap_map;
si = swap_info[type];
pte = pte_offset_map(pmd, addr);
do {
struct folio *folio;
unsigned long offset;
if (!is_swap_pte(*pte))
continue;
@ -1852,8 +1854,9 @@ static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
offset = swp_offset(entry);
pte_unmap(pte);
swap_map = &si->swap_map[offset];
page = lookup_swap_cache(entry, vma, addr);
if (!page) {
folio = swap_cache_get_folio(entry, vma, addr);
if (!folio) {
struct page *page;
struct vm_fault vmf = {
.vma = vma,
.address = addr,
@ -1863,25 +1866,27 @@ static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
page = swapin_readahead(entry, GFP_HIGHUSER_MOVABLE,
&vmf);
if (page)
folio = page_folio(page);
}
if (!page) {
if (!folio) {
if (*swap_map == 0 || *swap_map == SWAP_MAP_BAD)
goto try_next;
return -ENOMEM;
}
lock_page(page);
wait_on_page_writeback(page);
ret = unuse_pte(vma, pmd, addr, entry, page);
folio_lock(folio);
folio_wait_writeback(folio);
ret = unuse_pte(vma, pmd, addr, entry, folio);
if (ret < 0) {
unlock_page(page);
put_page(page);
folio_unlock(folio);
folio_put(folio);
goto out;
}
try_to_free_swap(page);
unlock_page(page);
put_page(page);
folio_free_swap(folio);
folio_unlock(folio);
folio_put(folio);
try_next:
pte = pte_offset_map(pmd, addr);
} while (pte++, addr += PAGE_SIZE, addr != end);