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mm: swap: enable swap_entry_range_free() to drop any kind of last ref

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The original VM_BUG_ON only allows swap_entry_range_free() to drop last
SWAP_HAS_CACHE ref.  By allowing other kind of last ref in VM_BUG_ON,
swap_entry_range_free() could be a more general-purpose function able to
handle all kind of last ref.  Following thi change, also rename
swap_entry_range_free() to swap_entries_free() and update it's comment
accordingly.

This is a preparation to use swap_entries_free() to drop more kind of last
ref other than SWAP_HAS_CACHE.

[shikemeng@huaweicloud.com: add __maybe_unused attribute for swap_is_last_ref() and update comment]
  Link: https://lkml.kernel.org/r/20250410153908.612984-1-shikemeng@huaweicloud.com
Link: https://lkml.kernel.org/r/20250325162528.68385-3-shikemeng@huaweicloud.com
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com>
Reviewed-by: Baoquan He <bhe@redhat.com>
Tested-by: SeongJae Park <sj@kernel.org>
Cc: Kairui Song <kasong@tencent.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Kemeng Shi
2025-03-26 00:25:22 +08:00
committed by Andrew Morton
parent 9c1c38bcdc
commit 64944ef6a1
1 changed files with 24 additions and 14 deletions
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38
mm/swapfile.c
View File

@@ -52,9 +52,9 @@
static bool swap_count_continued(struct swap_info_struct *, pgoff_t,
unsigned char);
static void free_swap_count_continuations(struct swap_info_struct *);
static void swap_entry_range_free(struct swap_info_struct *si,
struct swap_cluster_info *ci,
swp_entry_t entry, unsigned int nr_pages);
static void swap_entries_free(struct swap_info_struct *si,
struct swap_cluster_info *ci,
swp_entry_t entry, unsigned int nr_pages);
static void swap_range_alloc(struct swap_info_struct *si,
unsigned int nr_entries);
static bool folio_swapcache_freeable(struct folio *folio);
@@ -1471,7 +1471,7 @@ static unsigned char swap_entry_put(struct swap_info_struct *si,
ci = lock_cluster(si, offset);
usage = swap_entry_put_locked(si, offset, 1);
if (!usage)
swap_entry_range_free(si, ci, swp_entry(si->type, offset), 1);
swap_entries_free(si, ci, swp_entry(si->type, offset), 1);
unlock_cluster(ci);
return usage;
@@ -1501,7 +1501,7 @@ static bool swap_entries_put_nr(struct swap_info_struct *si,
for (i = 0; i < nr; i++)
WRITE_ONCE(si->swap_map[offset + i], SWAP_HAS_CACHE);
if (!has_cache)
swap_entry_range_free(si, ci, entry, nr);
swap_entries_free(si, ci, entry, nr);
unlock_cluster(ci);
return has_cache;
@@ -1520,12 +1520,22 @@ static bool swap_entries_put_nr(struct swap_info_struct *si,
}
/*
* Drop the last HAS_CACHE flag of swap entries, caller have to
* ensure all entries belong to the same cgroup.
* Check if it's the last ref of swap entry in the freeing path.
* Qualified vlaue includes 1, SWAP_HAS_CACHE or SWAP_MAP_SHMEM.
*/
static void swap_entry_range_free(struct swap_info_struct *si,
struct swap_cluster_info *ci,
swp_entry_t entry, unsigned int nr_pages)
static inline bool __maybe_unused swap_is_last_ref(unsigned char count)
{
return (count == SWAP_HAS_CACHE) || (count == 1) ||
(count == SWAP_MAP_SHMEM);
}
/*
* Drop the last ref of swap entries, caller have to ensure all entries
* belong to the same cgroup and cluster.
*/
static void swap_entries_free(struct swap_info_struct *si,
struct swap_cluster_info *ci,
swp_entry_t entry, unsigned int nr_pages)
{
unsigned long offset = swp_offset(entry);
unsigned char *map = si->swap_map + offset;
@@ -1538,7 +1548,7 @@ static void swap_entry_range_free(struct swap_info_struct *si,
ci->count -= nr_pages;
do {
VM_BUG_ON(*map != SWAP_HAS_CACHE);
VM_BUG_ON(!swap_is_last_ref(*map));
*map = 0;
} while (++map < map_end);
@@ -1561,7 +1571,7 @@ static void cluster_swap_free_nr(struct swap_info_struct *si,
ci = lock_cluster(si, offset);
do {
if (!swap_entry_put_locked(si, offset, usage))
swap_entry_range_free(si, ci, swp_entry(si->type, offset), 1);
swap_entries_free(si, ci, swp_entry(si->type, offset), 1);
} while (++offset < end);
unlock_cluster(ci);
}
@@ -1604,11 +1614,11 @@ void put_swap_folio(struct folio *folio, swp_entry_t entry)
ci = lock_cluster(si, offset);
if (swap_only_has_cache(si, offset, size))
swap_entry_range_free(si, ci, entry, size);
swap_entries_free(si, ci, entry, size);
else {
for (int i = 0; i < size; i++, entry.val++) {
if (!swap_entry_put_locked(si, offset + i, SWAP_HAS_CACHE))
swap_entry_range_free(si, ci, entry, 1);
swap_entries_free(si, ci, entry, 1);
}
}
unlock_cluster(ci);