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charset="utf-8" From: Barry Song 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 Cc: "Huang, Ying" Cc: Yu Zhao Cc: David Hildenbrand Cc: Chris Li Cc: Hugh Dickins Cc: Johannes Weiner Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Minchan Kim Cc: Yosry Ahmed Cc: Yu Zhao Cc: SeongJae Park Signed-off-by: Barry Song --- 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, in= t 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) } =20 /* - * 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 coun= t. * * 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. -> EN= OMEM */ -static int __swap_duplicate(swp_entry_t entry, unsigned char usage) +static int __swap_duplicate_nr(swp_entry_t entry, int nr, unsigned char us= age) { 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; =20 p =3D swp_swap_info(entry); =20 offset =3D swp_offset(entry); ci =3D lock_cluster_or_swap_info(p, offset); =20 - count =3D 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) =3D=3D SWAP_MAP_BAD)) { - err =3D -ENOENT; - goto unlock_out; - } + for (i =3D 0; i < nr; i++) { + count[i] =3D p->swap_map[offset + i]; =20 - has_cache =3D count & SWAP_HAS_CACHE; - count &=3D ~SWAP_HAS_CACHE; - err =3D 0; - - if (usage =3D=3D SWAP_HAS_CACHE) { - - /* set SWAP_HAS_CACHE if there is no cache and entry is used */ - if (!has_cache && count) - has_cache =3D SWAP_HAS_CACHE; - else if (has_cache) /* someone else added cache */ - err =3D -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]) =3D=3D SWAP_MAP_BAD)) { err =3D -ENOENT; + goto unlock_out; + } =20 - } else if (count || has_cache) { - - if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX) - count +=3D usage; - else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX) - err =3D -EINVAL; - else if (swap_count_continued(p, offset, count)) - count =3D COUNT_CONTINUED; - else - err =3D -ENOMEM; - } else - err =3D -ENOENT; /* unused swap entry */ - - if (!err) - WRITE_ONCE(p->swap_map[offset], count | has_cache); + has_cache[i] =3D count[i] & SWAP_HAS_CACHE; + count[i] &=3D ~SWAP_HAS_CACHE; + err =3D 0; + + if (usage =3D=3D 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] =3D SWAP_HAS_CACHE; + else if (has_cache[i]) /* someone else added cache */ + err =3D -EEXIST; + else /* no users remaining */ + err =3D -ENOENT; + } else if (count[i] || has_cache[i]) { + + if ((count[i] & ~COUNT_CONTINUED) < SWAP_MAP_MAX) + count[i] +=3D usage; + else if ((count[i] & ~COUNT_CONTINUED) > SWAP_MAP_MAX) + err =3D -EINVAL; + else if (swap_count_continued(p, offset + i, count[i])) + count[i] =3D COUNT_CONTINUED; + else + err =3D -ENOMEM; + } else + err =3D -ENOENT; /* unused swap entry */ + } =20 + if (!err) { + for (i =3D 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; } =20 +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); } =20 -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, in= t nr) { struct swap_cluster_info *ci; unsigned long offset =3D swp_offset(entry); - unsigned char usage; + unsigned char usage[SWAPFILE_CLUSTER]; + int i; =20 ci =3D lock_cluster_or_swap_info(si, offset); - usage =3D __swap_entry_free_locked(si, offset, SWAP_HAS_CACHE); + for (i =3D 0; i < nr; i++) + usage[i] =3D __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 =3D 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); } =20 struct swap_info_struct *swp_swap_info(swp_entry_t entry) --=20 2.34.1