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Message-Id: <20240629111010.230484-2-21cnbao@gmail.com>
Date: Sat, 29 Jun 2024 23:10:09 +1200
From: Barry Song <21cnbao@...il.com>
To: akpm@...ux-foundation.org,
linux-mm@...ck.org
Cc: chrisl@...nel.org,
david@...hat.com,
hannes@...xchg.org,
kasong@...cent.com,
linux-kernel@...r.kernel.org,
mhocko@...e.com,
nphamcs@...il.com,
ryan.roberts@....com,
shy828301@...il.com,
surenb@...gle.com,
kaleshsingh@...gle.com,
hughd@...gle.com,
v-songbaohua@...o.com,
willy@...radead.org,
xiang@...nel.org,
ying.huang@...el.com,
yosryahmed@...gle.com,
baolin.wang@...ux.alibaba.com,
shakeel.butt@...ux.dev,
senozhatsky@...omium.org,
minchan@...nel.org
Subject: [PATCH RFC v4 1/2] mm: swap: introduce swapcache_prepare_nr and swapcache_clear_nr for large folios swap-in
From: Barry Song <v-songbaohua@...o.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.
Signed-off-by: Barry Song <v-songbaohua@...o.com>
---
include/linux/swap.h | 4 +-
mm/swap.h | 4 +-
mm/swapfile.c | 114 +++++++++++++++++++++++++------------------
3 files changed, 70 insertions(+), 52 deletions(-)
diff --git a/include/linux/swap.h b/include/linux/swap.h
index e473fe6cfb7a..c0f4f2073ca6 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -481,7 +481,7 @@ 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_nr(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);
@@ -555,7 +555,7 @@ 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_nr(swp_entry_t swp, int nr)
{
return 0;
}
diff --git a/mm/swap.h b/mm/swap.h
index baa1fa946b34..b96b1157441f 100644
--- a/mm/swap.h
+++ b/mm/swap.h
@@ -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_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,
@@ -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_nr(struct swap_info_struct *si, swp_entry_t entry, int nr)
{
}
diff --git a/mm/swapfile.c b/mm/swapfile.c
index f7224bc1320c..8f60dd10fdef 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1352,7 +1352,8 @@ static void swap_entry_free(struct swap_info_struct *p, swp_entry_t entry)
}
static void cluster_swap_free_nr(struct swap_info_struct *sis,
- unsigned long offset, int nr_pages)
+ unsigned long offset, int nr_pages,
+ unsigned char usage)
{
struct swap_cluster_info *ci;
DECLARE_BITMAP(to_free, BITS_PER_LONG) = { 0 };
@@ -1362,7 +1363,7 @@ static void cluster_swap_free_nr(struct swap_info_struct *sis,
while (nr_pages) {
nr = min(BITS_PER_LONG, nr_pages);
for (i = 0; i < nr; i++) {
- if (!__swap_entry_free_locked(sis, offset + i, 1))
+ if (!__swap_entry_free_locked(sis, offset + i, usage))
bitmap_set(to_free, i, 1);
}
if (!bitmap_empty(to_free, BITS_PER_LONG)) {
@@ -1396,7 +1397,7 @@ void swap_free_nr(swp_entry_t entry, int nr_pages)
while (nr_pages) {
nr = min_t(int, nr_pages, SWAPFILE_CLUSTER - offset % SWAPFILE_CLUSTER);
- cluster_swap_free_nr(sis, offset, nr);
+ cluster_swap_free_nr(sis, offset, nr, 1);
offset += nr;
nr_pages -= nr;
}
@@ -3382,7 +3383,7 @@ 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
@@ -3392,66 +3393,88 @@ 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, 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);
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
- * 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;
- }
+ /*
+ * 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;
+ }
- has_cache = count & SWAP_HAS_CACHE;
- count &= ~SWAP_HAS_CACHE;
- 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)
+ continue;
+ else if (has_cache) /* someone else added cache */
+ err = -EEXIST;
+ else /* no users remaining */
+ err = -ENOENT;
- /* 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 */
- err = -ENOENT;
+ } else if (count || has_cache) {
- } else if (count || has_cache) {
+ if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
+ continue;
+ else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX)
+ err = -EINVAL;
+ else if (swap_count_continued(p, offset + i, count))
+ continue;
+ else
+ err = -ENOMEM;
+ } else
+ err = -ENOENT; /* unused swap entry */
- if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX)
+ 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 ((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 */
+ count = COUNT_CONTINUED;
- if (!err)
- WRITE_ONCE(p->swap_map[offset], count | has_cache);
+ WRITE_ONCE(p->swap_map[offset + i], count | has_cache);
+ }
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, usage, 1);
+}
+
/*
* Help swapoff by noting that swap entry belongs to shmem/tmpfs
* (in which case its reference count is never incremented).
@@ -3485,22 +3508,17 @@ int swap_duplicate(swp_entry_t entry)
* -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_nr(swp_entry_t entry, int nr)
{
- return __swap_duplicate(entry, SWAP_HAS_CACHE);
+ return __swap_duplicate_nr(entry, SWAP_HAS_CACHE, nr);
}
-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 swap_cluster_info *ci;
- unsigned long offset = swp_offset(entry);
- unsigned char usage;
+ pgoff_t offset = swp_offset(entry);
- ci = lock_cluster_or_swap_info(si, offset);
- usage = __swap_entry_free_locked(si, offset, SWAP_HAS_CACHE);
- unlock_cluster_or_swap_info(si, ci);
- if (!usage)
- free_swap_slot(entry);
+ VM_WARN_ON(nr > SWAPFILE_CLUSTER - offset % SWAPFILE_CLUSTER);
+ cluster_swap_free_nr(si, offset, nr, SWAP_HAS_CACHE);
}
struct swap_info_struct *swp_swap_info(swp_entry_t entry)
--
2.34.1
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