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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-16 03:22:47 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-16 03:22:47 +0000
commit31d3cc774e9124f10d3ed2ea144a6e232e93e822 (patch)
treede1ac8afc7248eec4b2fb60496b8e9273452d9f7 /mm/swapfile.c
parentAdding upstream version 6.1.82. (diff)
downloadlinux-31d3cc774e9124f10d3ed2ea144a6e232e93e822.tar.xz
linux-31d3cc774e9124f10d3ed2ea144a6e232e93e822.zip
Adding upstream version 6.1.85.upstream/6.1.85
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'mm/swapfile.c')
-rw-r--r--mm/swapfile.c25
1 files changed, 21 insertions, 4 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c
index cca9fda9d..0d6182db4 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1222,6 +1222,18 @@ static unsigned char __swap_entry_free_locked(struct swap_info_struct *p,
}
/*
+ * When we get a swap entry, if there aren't some other ways to
+ * prevent swapoff, such as the folio in swap cache is locked, page
+ * table lock is held, etc., the swap entry may become invalid because
+ * of swapoff. Then, we need to enclose all swap related functions
+ * with get_swap_device() and put_swap_device(), unless the swap
+ * functions call get/put_swap_device() by themselves.
+ *
+ * Note that when only holding the PTL, swapoff might succeed immediately
+ * after freeing a swap entry. Therefore, immediately after
+ * __swap_entry_free(), the swap info might become stale and should not
+ * be touched without a prior get_swap_device().
+ *
* Check whether swap entry is valid in the swap device. If so,
* return pointer to swap_info_struct, and keep the swap entry valid
* via preventing the swap device from being swapoff, until
@@ -1230,9 +1242,8 @@ static unsigned char __swap_entry_free_locked(struct swap_info_struct *p,
* Notice that swapoff or swapoff+swapon can still happen before the
* percpu_ref_tryget_live() in get_swap_device() or after the
* percpu_ref_put() in put_swap_device() if there isn't any other way
- * to prevent swapoff, such as page lock, page table lock, etc. The
- * caller must be prepared for that. For example, the following
- * situation is possible.
+ * to prevent swapoff. The caller must be prepared for that. For
+ * example, the following situation is possible.
*
* CPU1 CPU2
* do_swap_page()
@@ -1624,13 +1635,19 @@ int free_swap_and_cache(swp_entry_t entry)
if (non_swap_entry(entry))
return 1;
- p = _swap_info_get(entry);
+ p = get_swap_device(entry);
if (p) {
+ if (WARN_ON(data_race(!p->swap_map[swp_offset(entry)]))) {
+ put_swap_device(p);
+ return 0;
+ }
+
count = __swap_entry_free(p, entry);
if (count == SWAP_HAS_CACHE &&
!swap_page_trans_huge_swapped(p, entry))
__try_to_reclaim_swap(p, swp_offset(entry),
TTRS_UNMAPPED | TTRS_FULL);
+ put_swap_device(p);
}
return p != NULL;
}