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shmem: convert shmem_replace_page() to use folios throughout 

Introduce folio_set_swap_entry() to abstract how both folio->private and
swp_entry_t work.  Use swap_address_space() directly instead of
indirecting through folio_mapping().  Include an assertion that the old
folio is not large as we only allocate a single-page folio to replace it. 
Use folio_put_refs() instead of calling folio_put() twice.

Link: https://lkml.kernel.org/r/20220902194653.1739778-9-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 20:46:04 +01:00 committed by Andrew Morton
parent 4cd400fd1f
commit 907ea17eb2
2 changed files with 37 additions and 35 deletions
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5
include/linux/swap.h
View File

@ -355,6 +355,11 @@ static inline swp_entry_t folio_swap_entry(struct folio *folio)
return entry;
}
static inline void folio_set_swap_entry(struct folio *folio, swp_entry_t entry)
{
folio->private = (void *)entry.val;
}
/* linux/mm/workingset.c */
void workingset_age_nonresident(struct lruvec *lruvec, unsigned long nr_pages);
void *workingset_eviction(struct folio *folio, struct mem_cgroup *target_memcg);

67
mm/shmem.c
View File

@ -1560,12 +1560,6 @@ static struct folio *shmem_alloc_folio(gfp_t gfp,
return folio;
}
static struct page *shmem_alloc_page(gfp_t gfp,
struct shmem_inode_info *info, pgoff_t index)
{
return &shmem_alloc_folio(gfp, info, index)->page;
}
static struct folio *shmem_alloc_and_acct_folio(gfp_t gfp, struct inode *inode,
pgoff_t index, bool huge)
{
@ -1617,51 +1611,49 @@ static bool shmem_should_replace_folio(struct folio *folio, gfp_t gfp)
static int shmem_replace_page(struct page **pagep, gfp_t gfp,
struct shmem_inode_info *info, pgoff_t index)
{
struct page *oldpage, *newpage;
struct folio *old, *new;
struct address_space *swap_mapping;
swp_entry_t entry;
pgoff_t swap_index;
int error;
oldpage = *pagep;
entry.val = page_private(oldpage);
old = page_folio(*pagep);
entry = folio_swap_entry(old);
swap_index = swp_offset(entry);
swap_mapping = page_mapping(oldpage);
swap_mapping = swap_address_space(entry);
/*
* We have arrived here because our zones are constrained, so don't
* limit chance of success by further cpuset and node constraints.
*/
gfp &= ~GFP_CONSTRAINT_MASK;
newpage = shmem_alloc_page(gfp, info, index);
if (!newpage)
VM_BUG_ON_FOLIO(folio_test_large(old), old);
new = shmem_alloc_folio(gfp, info, index);
if (!new)
return -ENOMEM;
get_page(newpage);
copy_highpage(newpage, oldpage);
flush_dcache_page(newpage);
folio_get(new);
folio_copy(new, old);
flush_dcache_folio(new);
__SetPageLocked(newpage);
__SetPageSwapBacked(newpage);
SetPageUptodate(newpage);
set_page_private(newpage, entry.val);
SetPageSwapCache(newpage);
__folio_set_locked(new);
__folio_set_swapbacked(new);
folio_mark_uptodate(new);
folio_set_swap_entry(new, entry);
folio_set_swapcache(new);
/*
* Our caller will very soon move newpage out of swapcache, but it's
* a nice clean interface for us to replace oldpage by newpage there.
*/
xa_lock_irq(&swap_mapping->i_pages);
error = shmem_replace_entry(swap_mapping, swap_index, oldpage, newpage);
error = shmem_replace_entry(swap_mapping, swap_index, old, new);
if (!error) {
old = page_folio(oldpage);
new = page_folio(newpage);
mem_cgroup_migrate(old, new);
__inc_lruvec_page_state(newpage, NR_FILE_PAGES);
__inc_lruvec_page_state(newpage, NR_SHMEM);
__dec_lruvec_page_state(oldpage, NR_FILE_PAGES);
__dec_lruvec_page_state(oldpage, NR_SHMEM);
__lruvec_stat_mod_folio(new, NR_FILE_PAGES, 1);
__lruvec_stat_mod_folio(new, NR_SHMEM, 1);
__lruvec_stat_mod_folio(old, NR_FILE_PAGES, -1);
__lruvec_stat_mod_folio(old, NR_SHMEM, -1);
}
xa_unlock_irq(&swap_mapping->i_pages);
@ -1671,18 +1663,17 @@ static int shmem_replace_page(struct page **pagep, gfp_t gfp,
* both PageSwapCache and page_private after getting page lock;
* but be defensive. Reverse old to newpage for clear and free.
*/
oldpage = newpage;
old = new;
} else {
lru_cache_add(newpage);
*pagep = newpage;
folio_add_lru(new);
*pagep = &new->page;
}
ClearPageSwapCache(oldpage);
set_page_private(oldpage, 0);
folio_clear_swapcache(old);
old->private = NULL;
unlock_page(oldpage);
put_page(oldpage);
put_page(oldpage);
folio_unlock(old);
folio_put_refs(old, 2);
return error;
}
@ -2383,6 +2374,12 @@ static struct inode *shmem_get_inode(struct super_block *sb, struct inode *dir,
}
#ifdef CONFIG_USERFAULTFD
static struct page *shmem_alloc_page(gfp_t gfp,
struct shmem_inode_info *info, pgoff_t index)
{
return &shmem_alloc_folio(gfp, info, index)->page;
}
int shmem_mfill_atomic_pte(struct mm_struct *dst_mm,
pmd_t *dst_pmd,
struct vm_area_struct *dst_vma,