1

mm: swap: add nr argument in swapcache_prepare and swapcache_clear to support large folios

Right now, swapcache_prepare() and swapcache_clear() supports one entry
only, to support large folios, we need to handle multiple swap entries.

To optimize stack usage, we iterate twice in __swap_duplicate(): the first
time to verify that all entries are valid, and the second time to apply
the modifications to the entries.

Currently, we're using nr=1 for the existing users.

[v-songbaohua@oppo.com: clarify swap_count_continued and improve readability for  __swap_duplicate]
  Link: https://lkml.kernel.org/r/20240802071817.47081-1-21cnbao@gmail.com
Link: https://lkml.kernel.org/r/20240730071339.107447-2-21cnbao@gmail.com
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: David Hildenbrand <david@redhat.com>
Tested-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: Gao Xiang <xiang@kernel.org>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kairui Song <kasong@tencent.com>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Barry Song 2024-07-30 19:13:39 +12:00 committed by Andrew Morton
parent 7e60dcb222
commit 9f101bef40
5 changed files with 64 additions and 50 deletions

View File

@ -480,7 +480,7 @@ extern int get_swap_pages(int n, swp_entry_t swp_entries[], int order);
extern int add_swap_count_continuation(swp_entry_t, gfp_t); extern int add_swap_count_continuation(swp_entry_t, gfp_t);
extern void swap_shmem_alloc(swp_entry_t); extern void swap_shmem_alloc(swp_entry_t);
extern int swap_duplicate(swp_entry_t); extern int swap_duplicate(swp_entry_t);
extern int swapcache_prepare(swp_entry_t); extern int swapcache_prepare(swp_entry_t entry, int nr);
extern void swap_free_nr(swp_entry_t entry, int nr_pages); extern void swap_free_nr(swp_entry_t entry, int nr_pages);
extern void swapcache_free_entries(swp_entry_t *entries, int n); extern void swapcache_free_entries(swp_entry_t *entries, int n);
extern void free_swap_and_cache_nr(swp_entry_t entry, int nr); extern void free_swap_and_cache_nr(swp_entry_t entry, int nr);
@ -554,7 +554,7 @@ static inline int swap_duplicate(swp_entry_t swp)
return 0; return 0;
} }
static inline int swapcache_prepare(swp_entry_t swp) static inline int swapcache_prepare(swp_entry_t swp, int nr)
{ {
return 0; return 0;
} }

View File

@ -4081,7 +4081,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
* reusing the same entry. It's undetectable as * reusing the same entry. It's undetectable as
* pte_same() returns true due to entry reuse. * pte_same() returns true due to entry reuse.
*/ */
if (swapcache_prepare(entry)) { if (swapcache_prepare(entry, 1)) {
/* Relax a bit to prevent rapid repeated page faults */ /* Relax a bit to prevent rapid repeated page faults */
schedule_timeout_uninterruptible(1); schedule_timeout_uninterruptible(1);
goto out; goto out;
@ -4387,7 +4387,7 @@ unlock:
out: out:
/* Clear the swap cache pin for direct swapin after PTL unlock */ /* Clear the swap cache pin for direct swapin after PTL unlock */
if (need_clear_cache) if (need_clear_cache)
swapcache_clear(si, entry); swapcache_clear(si, entry, 1);
if (si) if (si)
put_swap_device(si); put_swap_device(si);
return ret; return ret;
@ -4403,7 +4403,7 @@ out_release:
folio_put(swapcache); folio_put(swapcache);
} }
if (need_clear_cache) if (need_clear_cache)
swapcache_clear(si, entry); swapcache_clear(si, entry, 1);
if (si) if (si)
put_swap_device(si); put_swap_device(si);
return ret; return ret;

View File

@ -59,7 +59,7 @@ void __delete_from_swap_cache(struct folio *folio,
void delete_from_swap_cache(struct folio *folio); void delete_from_swap_cache(struct folio *folio);
void clear_shadow_from_swap_cache(int type, unsigned long begin, void clear_shadow_from_swap_cache(int type, unsigned long begin,
unsigned long end); unsigned long end);
void swapcache_clear(struct swap_info_struct *si, swp_entry_t entry); void swapcache_clear(struct swap_info_struct *si, swp_entry_t entry, int nr);
struct folio *swap_cache_get_folio(swp_entry_t entry, struct folio *swap_cache_get_folio(swp_entry_t entry,
struct vm_area_struct *vma, unsigned long addr); struct vm_area_struct *vma, unsigned long addr);
struct folio *filemap_get_incore_folio(struct address_space *mapping, struct folio *filemap_get_incore_folio(struct address_space *mapping,
@ -120,7 +120,7 @@ static inline int swap_writepage(struct page *p, struct writeback_control *wbc)
return 0; return 0;
} }
static inline void swapcache_clear(struct swap_info_struct *si, swp_entry_t entry) static inline void swapcache_clear(struct swap_info_struct *si, swp_entry_t entry, int nr)
{ {
} }
@ -172,4 +172,5 @@ static inline unsigned int folio_swap_flags(struct folio *folio)
return 0; return 0;
} }
#endif /* CONFIG_SWAP */ #endif /* CONFIG_SWAP */
#endif /* _MM_SWAP_H */ #endif /* _MM_SWAP_H */

View File

@ -477,7 +477,7 @@ struct folio *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
/* /*
* Swap entry may have been freed since our caller observed it. * Swap entry may have been freed since our caller observed it.
*/ */
err = swapcache_prepare(entry); err = swapcache_prepare(entry, 1);
if (!err) if (!err)
break; break;

View File

@ -3363,7 +3363,7 @@ void si_swapinfo(struct sysinfo *val)
} }
/* /*
* Verify that a swap entry is valid and increment its swap map count. * Verify that nr swap entries are valid and increment their swap map counts.
* *
* Returns error code in following case. * Returns error code in following case.
* - success -> 0 * - success -> 0
@ -3373,60 +3373,73 @@ void si_swapinfo(struct sysinfo *val)
* - swap-cache reference is requested but the entry is not used. -> ENOENT * - swap-cache reference is requested but the entry is not used. -> ENOENT
* - swap-mapped reference requested but needs continued swap count. -> ENOMEM * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
*/ */
static int __swap_duplicate(swp_entry_t entry, unsigned char usage) static int __swap_duplicate(swp_entry_t entry, unsigned char usage, int nr)
{ {
struct swap_info_struct *p; struct swap_info_struct *p;
struct swap_cluster_info *ci; struct swap_cluster_info *ci;
unsigned long offset; unsigned long offset;
unsigned char count; unsigned char count;
unsigned char has_cache; unsigned char has_cache;
int err; int err, i;
p = swp_swap_info(entry); p = swp_swap_info(entry);
offset = swp_offset(entry); offset = swp_offset(entry);
VM_WARN_ON(nr > SWAPFILE_CLUSTER - offset % SWAPFILE_CLUSTER);
VM_WARN_ON(usage == 1 && nr > 1);
ci = lock_cluster_or_swap_info(p, offset); ci = lock_cluster_or_swap_info(p, offset);
count = p->swap_map[offset]; err = 0;
for (i = 0; i < nr; i++) {
count = p->swap_map[offset + i];
/* /*
* swapin_readahead() doesn't check if a swap entry is valid, so the * swapin_readahead() doesn't check if a swap entry is valid, so the
* swap entry could be SWAP_MAP_BAD. Check here with lock held. * swap entry could be SWAP_MAP_BAD. Check here with lock held.
*/ */
if (unlikely(swap_count(count) == SWAP_MAP_BAD)) { if (unlikely(swap_count(count) == SWAP_MAP_BAD)) {
err = -ENOENT; err = -ENOENT;
goto unlock_out; goto unlock_out;
}
has_cache = count & SWAP_HAS_CACHE;
count &= ~SWAP_HAS_CACHE;
if (!count && !has_cache) {
err = -ENOENT;
} else if (usage == SWAP_HAS_CACHE) {
if (has_cache)
err = -EEXIST;
} else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX) {
err = -EINVAL;
}
if (err)
goto unlock_out;
} }
has_cache = count & SWAP_HAS_CACHE; for (i = 0; i < nr; i++) {
count &= ~SWAP_HAS_CACHE; count = p->swap_map[offset + i];
err = 0; has_cache = count & SWAP_HAS_CACHE;
count &= ~SWAP_HAS_CACHE;
if (usage == SWAP_HAS_CACHE) { if (usage == SWAP_HAS_CACHE)
/* set SWAP_HAS_CACHE if there is no cache and entry is used */
if (!has_cache && count)
has_cache = SWAP_HAS_CACHE; has_cache = SWAP_HAS_CACHE;
else if (has_cache) /* someone else added cache */ else if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
err = -EEXIST;
else /* no users remaining */
err = -ENOENT;
} else if (count || has_cache) {
if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
count += usage; count += usage;
else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX) else if (swap_count_continued(p, offset + i, count))
err = -EINVAL;
else if (swap_count_continued(p, offset, count))
count = COUNT_CONTINUED; count = COUNT_CONTINUED;
else else {
/*
* Don't need to rollback changes, because if
* usage == 1, there must be nr == 1.
*/
err = -ENOMEM; err = -ENOMEM;
} else goto unlock_out;
err = -ENOENT; /* unused swap entry */ }
if (!err) WRITE_ONCE(p->swap_map[offset + i], count | has_cache);
WRITE_ONCE(p->swap_map[offset], count | has_cache); }
unlock_out: unlock_out:
unlock_cluster_or_swap_info(p, ci); unlock_cluster_or_swap_info(p, ci);
@ -3439,7 +3452,7 @@ unlock_out:
*/ */
void swap_shmem_alloc(swp_entry_t entry) void swap_shmem_alloc(swp_entry_t entry)
{ {
__swap_duplicate(entry, SWAP_MAP_SHMEM); __swap_duplicate(entry, SWAP_MAP_SHMEM, 1);
} }
/* /*
@ -3453,29 +3466,29 @@ int swap_duplicate(swp_entry_t entry)
{ {
int err = 0; int err = 0;
while (!err && __swap_duplicate(entry, 1) == -ENOMEM) while (!err && __swap_duplicate(entry, 1, 1) == -ENOMEM)
err = add_swap_count_continuation(entry, GFP_ATOMIC); err = add_swap_count_continuation(entry, GFP_ATOMIC);
return err; return err;
} }
/* /*
* @entry: swap entry for which we allocate swap cache. * @entry: first swap entry from which we allocate nr swap cache.
* *
* Called when allocating swap cache for existing swap entry, * Called when allocating swap cache for existing swap entries,
* This can return error codes. Returns 0 at success. * This can return error codes. Returns 0 at success.
* -EEXIST means there is a swap cache. * -EEXIST means there is a swap cache.
* Note: return code is different from swap_duplicate(). * Note: return code is different from swap_duplicate().
*/ */
int swapcache_prepare(swp_entry_t entry) int swapcache_prepare(swp_entry_t entry, int nr)
{ {
return __swap_duplicate(entry, SWAP_HAS_CACHE); return __swap_duplicate(entry, SWAP_HAS_CACHE, nr);
} }
void swapcache_clear(struct swap_info_struct *si, swp_entry_t entry) void swapcache_clear(struct swap_info_struct *si, swp_entry_t entry, int nr)
{ {
unsigned long offset = swp_offset(entry); unsigned long offset = swp_offset(entry);
cluster_swap_free_nr(si, offset, 1, SWAP_HAS_CACHE); cluster_swap_free_nr(si, offset, nr, SWAP_HAS_CACHE);
} }
struct swap_info_struct *swp_swap_info(swp_entry_t entry) struct swap_info_struct *swp_swap_info(swp_entry_t entry)