[PATCH RFC v2 4/5] mm: swap: introduce swapcache_prepare_nr and swapcache_clear_nr for large folios swap-in
Barry Song
21cnbao at gmail.com
Wed Feb 28 16:37:52 PST 2024
From: Barry Song <v-songbaohua at oppo.com>
Commit 13ddaf26be32 ("mm/swap: fix race when skipping swapcache") supports
one entry only, to support large folio swap-in, we need to handle multiple
swap entries.
Cc: Kairui Song <kasong at tencent.com>
Cc: "Huang, Ying" <ying.huang at intel.com>
Cc: Yu Zhao <yuzhao at google.com>
Cc: David Hildenbrand <david at redhat.com>
Cc: Chris Li <chrisl at kernel.org>
Cc: Hugh Dickins <hughd at google.com>
Cc: Johannes Weiner <hannes at cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy at infradead.org>
Cc: Michal Hocko <mhocko at suse.com>
Cc: Minchan Kim <minchan at kernel.org>
Cc: Yosry Ahmed <yosryahmed at google.com>
Cc: Yu Zhao <yuzhao at google.com>
Cc: SeongJae Park <sj at kernel.org>
Signed-off-by: Barry Song <v-songbaohua at oppo.com>
---
include/linux/swap.h | 1 +
mm/swap.h | 1 +
mm/swapfile.c | 117 ++++++++++++++++++++++++++-----------------
3 files changed, 72 insertions(+), 47 deletions(-)
diff --git a/include/linux/swap.h b/include/linux/swap.h
index b3581c976e5f..2691c739d9a4 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -480,6 +480,7 @@ 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_nr(swp_entry_t, int nr);
extern void swap_free(swp_entry_t);
extern void swap_nr_free(swp_entry_t entry, int nr_pages);
extern void swapcache_free_entries(swp_entry_t *entries, int n);
diff --git a/mm/swap.h b/mm/swap.h
index fc2f6ade7f80..1cec991efcda 100644
--- a/mm/swap.h
+++ b/mm/swap.h
@@ -42,6 +42,7 @@ 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_nr(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,
diff --git a/mm/swapfile.c b/mm/swapfile.c
index c0c058ee7b69..c8c8b6dbaeda 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -3308,7 +3308,7 @@ 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 count.
*
* Returns error code in following case.
* - success -> 0
@@ -3318,66 +3318,73 @@ 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_nr(swp_entry_t entry, int nr, unsigned char usage)
{
struct swap_info_struct *p;
struct swap_cluster_info *ci;
unsigned long offset;
- unsigned char count;
- unsigned char has_cache;
- int err;
+ unsigned char count[SWAPFILE_CLUSTER];
+ unsigned char has_cache[SWAPFILE_CLUSTER];
+ int err, i;
p = swp_swap_info(entry);
offset = swp_offset(entry);
ci = lock_cluster_or_swap_info(p, offset);
- count = p->swap_map[offset];
-
- /*
- * 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.
- */
- if (unlikely(swap_count(count) == SWAP_MAP_BAD)) {
- err = -ENOENT;
- goto unlock_out;
- }
+ for (i = 0; i < nr; i++) {
+ count[i] = p->swap_map[offset + i];
- 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 */
+ /*
+ * 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.
+ */
+ if (unlikely(swap_count(count[i]) == SWAP_MAP_BAD)) {
err = -ENOENT;
+ goto unlock_out;
+ }
- } else if (count || has_cache) {
-
- if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
- count += usage;
- 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);
+ has_cache[i] = count[i] & SWAP_HAS_CACHE;
+ count[i] &= ~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[i] && count[i])
+ has_cache[i] = SWAP_HAS_CACHE;
+ else if (has_cache[i]) /* someone else added cache */
+ err = -EEXIST;
+ else /* no users remaining */
+ err = -ENOENT;
+ } else if (count[i] || has_cache[i]) {
+
+ if ((count[i] & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
+ count[i] += usage;
+ else if ((count[i] & ~COUNT_CONTINUED) > SWAP_MAP_MAX)
+ err = -EINVAL;
+ else if (swap_count_continued(p, offset + i, count[i]))
+ count[i] = COUNT_CONTINUED;
+ else
+ err = -ENOMEM;
+ } else
+ err = -ENOENT; /* unused swap entry */
+ }
+ if (!err) {
+ for (i = 0; i < nr; i++)
+ WRITE_ONCE(p->swap_map[offset + i], count[i] | has_cache[i]);
+ }
unlock_out:
unlock_cluster_or_swap_info(p, ci);
return err;
}
+static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
+{
+ return __swap_duplicate_nr(entry, 1, usage);
+}
+
/*
* Help swapoff by noting that swap entry belongs to shmem/tmpfs
* (in which case its reference count is never incremented).
@@ -3416,17 +3423,33 @@ int swapcache_prepare(swp_entry_t entry)
return __swap_duplicate(entry, SWAP_HAS_CACHE);
}
-void swapcache_clear(struct swap_info_struct *si, swp_entry_t entry)
+int swapcache_prepare_nr(swp_entry_t entry, int nr)
+{
+ return __swap_duplicate_nr(entry, nr, SWAP_HAS_CACHE);
+}
+
+void swapcache_clear_nr(struct swap_info_struct *si, swp_entry_t entry, int nr)
{
struct swap_cluster_info *ci;
unsigned long offset = swp_offset(entry);
- unsigned char usage;
+ unsigned char usage[SWAPFILE_CLUSTER];
+ int i;
ci = lock_cluster_or_swap_info(si, offset);
- usage = __swap_entry_free_locked(si, offset, SWAP_HAS_CACHE);
+ for (i = 0; i < nr; i++)
+ usage[i] = __swap_entry_free_locked(si, offset + i, SWAP_HAS_CACHE);
unlock_cluster_or_swap_info(si, ci);
- if (!usage)
- free_swap_slot(entry);
+ for (i = 0; i < nr; i++) {
+ if (!usage[i]) {
+ free_swap_slot(entry);
+ entry.val++;
+ }
+ }
+}
+
+void swapcache_clear(struct swap_info_struct *si, swp_entry_t entry)
+{
+ swapcache_clear_nr(si, entry, 1);
}
struct swap_info_struct *swp_swap_info(swp_entry_t entry)
--
2.34.1
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