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

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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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
include/linux/swap.h
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 void swap_shmem_alloc(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 swapcache_free_entries(swp_entry_t *entries, int n);
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;
}
static inline int swapcache_prepare(swp_entry_t swp)
static inline int swapcache_prepare(swp_entry_t swp, int nr)
{
return 0;
}

6
mm/memory.c
View File

@ -4081,7 +4081,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
* reusing the same entry. It's undetectable as
* 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 */
schedule_timeout_uninterruptible(1);
goto out;
@ -4387,7 +4387,7 @@ unlock:
out:
/* Clear the swap cache pin for direct swapin after PTL unlock */
if (need_clear_cache)
swapcache_clear(si, entry);
swapcache_clear(si, entry, 1);
if (si)
put_swap_device(si);
return ret;
@ -4403,7 +4403,7 @@ out_release:
folio_put(swapcache);
}
if (need_clear_cache)
swapcache_clear(si, entry);
swapcache_clear(si, entry, 1);
if (si)
put_swap_device(si);
return ret;

5
mm/swap.h
View File

@ -59,7 +59,7 @@ 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,
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 vm_area_struct *vma, unsigned long addr);
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;
}
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;
}
#endif /* CONFIG_SWAP */
#endif /* _MM_SWAP_H */

2
mm/swap_state.c
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.
*/
err = swapcache_prepare(entry);
err = swapcache_prepare(entry, 1);
if (!err)
break;

83
mm/swapfile.c
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.
* - success -> 0
@ -3373,21 +3373,25 @@ void si_swapinfo(struct sysinfo *val)
* - swap-cache reference is requested but the entry is not used. -> ENOENT
* - 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_cluster_info *ci;
unsigned long offset;
unsigned char count;
unsigned char has_cache;
int err;
int err, i;
p = swp_swap_info(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);
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
@ -3400,33 +3404,42 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
has_cache = count & SWAP_HAS_CACHE;
count &= ~SWAP_HAS_CACHE;
err = 0;
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;
else if (has_cache) /* someone else added cache */
err = -EEXIST;
else /* no users remaining */
if (!count && !has_cache) {
err = -ENOENT;
} else if (count || has_cache) {
if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
count += usage;
else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX)
} else if (usage == SWAP_HAS_CACHE) {
if (has_cache)
err = -EEXIST;
} else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX) {
err = -EINVAL;
else if (swap_count_continued(p, offset, count))
count = COUNT_CONTINUED;
else
err = -ENOMEM;
} else
err = -ENOENT; /* unused swap entry */
}
if (!err)
WRITE_ONCE(p->swap_map[offset], count | has_cache);
if (err)
goto unlock_out;
}
for (i = 0; i < nr; i++) {
count = p->swap_map[offset + i];
has_cache = count & SWAP_HAS_CACHE;
count &= ~SWAP_HAS_CACHE;
if (usage == SWAP_HAS_CACHE)
has_cache = SWAP_HAS_CACHE;
else if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
count += usage;
else if (swap_count_continued(p, offset + i, count))
count = COUNT_CONTINUED;
else {
/*
* Don't need to rollback changes, because if
* usage == 1, there must be nr == 1.
*/
err = -ENOMEM;
goto unlock_out;
}
WRITE_ONCE(p->swap_map[offset + i], count | has_cache);
}
unlock_out:
unlock_cluster_or_swap_info(p, ci);
@ -3439,7 +3452,7 @@ unlock_out:
*/
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;
while (!err && __swap_duplicate(entry, 1) == -ENOMEM)
while (!err && __swap_duplicate(entry, 1, 1) == -ENOMEM)
err = add_swap_count_continuation(entry, GFP_ATOMIC);
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.
* -EEXIST means there is a swap cache.
* 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);
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)