kernel/git/stable/linux.git/mm/swapfile.c, branch linux-rolling-stable

mm, swap: ratelimit bad swap entry reports

2026-09-07T15:36:32+00:00

commit f9dc428249ed962a70acf301f01eae8578449161 upstream. A corrupt page table hands the same bogus entry to get_swap_device() on every access to the mapping, and every rejection is logged. One machine logged 6185620 copies of the same line in a few hours. swap_dup_entry_direct() prints the same message from the fork path, once per call: the WARN_ON_ONCE() guarding it warns once, the pr_err() inside does not. Rate limit all three prints. Link: https://lore.kernel.org/20260818-swap_part_one-v1-1-a4fc58119fc0@debian.org Fixes: 23b230ba8ac3 ("mm/swap: print bad swap offset entry in get_swap_device") Signed-off-by: Breno Leitao Reviewed-by: Barry Song Reviewed-by: Nhat Pham Acked-by: Kairui Song Acked-by: David Hildenbrand (Arm) Cc: Baoquan He Cc: Chris Li Cc: Kemeng Shi Cc: Miaohe Lin Cc: Oscar Salvador Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

mm, swap: don't free a hibernation slot that is in the swap cache

2026-09-07T15:36:32+00:00

commit 10d9012e83efedde8718ceaa5053f836e0c8596c upstream. A slot with a folio in the swap cache is freed when the folio leaves the cache, not when its count drops. swap_put_entries_cluster() follows that rule. swap_free_hibernation_slot() does not, it calls __swap_cluster_free_entries() whether or not a folio sits on the slot. Cluster readahead can put one there. It walks a raw page_cluster sized window of offsets around the faulting entry, and a hibernation slot passes __swap_cache_add_check() because it is not a folio and its count is not zero. Freeing the slot then clears the entry under that folio. The folio is now unreachable from the swap table, and the offset goes back to the allocator. The folio is still on the LRU though, so reclaim can pick it up later. It then takes the old offset out of folio->swap and overwrites the table entry there, which by then may belong to someone else. This bug can trigger silent memory corruption, process crashes, or data instability across completely unrelated userspace applications - typically occurring when uswsusp is preparing the hibernation image. I found this while working on giving hibernation slots their own marker in the swap table, which I had discussed with Kairui. (https://lore.kernel.org/linux-mm/abp7aDgYLrxF3Me8@KASONG-MC4/) As far as I know there are no reports, so there is no Reported-by/Closes to add. Check for a cached folio before freeing. The slot is then left in the ordinary state where only the swap cache holds it, and it is freed when the folio leaves the cache, either through the reclaim below or through normal reclaim later. Link: https://lore.kernel.org/20260811132209.2862708-2-youngjun.park@lge.com Fixes: 0d6af9bcf383 ("mm, swap: use the swap table to track the swap count") Signed-off-by: Youngjun Park Acked-by: Kairui Song Cc: Baoquan He Cc: Barry Song Cc: Chris Li Cc: Kemeng Shi Cc: Nhat Pham Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

mm/swap: reject swapon() on filesystem-level encrypted files

2026-09-02T12:33:20+00:00

commit c310a8932a3107c9bc8f01d473e9d085f8aa9c98 upstream. ext4 and f2fs don't prevent filesystem-level encrypted files from being set up directly as swap files. In this case, encryption is bypassed. No one should be doing this, vs. the methods of encrypted swap that actually do work (such as swapping to a dm-crypt device, or swapping to a loopback device on top of a filesystem-level encrypted file). Nevertheless, to prevent user error, make swapon() explicitly reject this case. Document this behavior in fscrypt.rst as well. Link: https://lore.kernel.org/20260803180426.3123-1-ebiggers@kernel.org Fixes: 9bd8212f981e ("ext4 crypto: add encryption policy and password salt support") Fixes: f424f664f0e8 ("f2fs crypto: add encryption policy and password salt support") Signed-off-by: Eric Biggers Reviewed-by: Baoquan He Reviewed-by: Muhammad Usama Anjum Reviewed-by: "Darrick J. Wong" Cc: Barry Song Cc: Chris Li Cc: Kairui Song Cc: Kemeng Shi Cc: Nhat Pham Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

mm/swap: remove redundant swap device reference in alloc/free

2026-06-09T01:21:32+00:00

In the previous commit, uswsusp was modified to pin the swap device when the swap type is determined, ensuring the device remains valid throughout the hibernation I/O path. Therefore, it is no longer necessary to repeatedly get and put the swap device reference for each swap slot allocation and free operation. For hibernation via the sysfs interface, user-space tasks are frozen before swap allocation begins, so swapoff cannot race with allocation. After resume, tasks remain frozen while swap slots are freed, so additional reference management is not required there either. Remove the redundant swap device get/put operations from the hibernation swap allocation and free paths. Also remove the SWP_WRITEOK check before allocation, as the cluster allocation logic already validates the swap device state. Update function comments to document the caller's responsibility for ensuring swap device stability. Link: https://lore.kernel.org/20260323160822.1409904-3-youngjun.park@lge.com Signed-off-by: Youngjun Park Reviewed-by: Kairui Song Cc: Baoquan He Cc: Barry Song Cc: Chris Li Cc: Kemeng Shi Cc: Nhat Pham Cc: "Rafael J . Wysocki" Signed-off-by: Andrew Morton

mm/swap, PM: hibernate: fix swapoff race in uswsusp by pinning swap device

2026-06-09T01:21:31+00:00

Patch series "mm/swap, PM: hibernate: fix swapoff race in uswsusp by pinning swap device", v8. Currently, in the uswsusp path, only the swap type value is retrieved at lookup time without holding a reference. If swapoff races after the type is acquired, subsequent slot allocations operate on a stale swap device. Additionally, grabbing and releasing the swap device reference on every slot allocation is inefficient across the entire hibernation swap path. This patch series addresses these issues: - Patch 1: Fixes the swapoff race in uswsusp by pinning the swap device from the point it is looked up until the session completes. - Patch 2: Removes the overhead of per-slot reference counting in alloc/free paths and cleans up the redundant SWP_WRITEOK check. This patch (of 2): Hibernation via uswsusp (/dev/snapshot ioctls) has a race window: after selecting the resume swap area but before user space is frozen, swapoff may run and invalidate the selected swap device. Fix this by pinning the swap device with SWP_HIBERNATION while it is in use. The pin is exclusive, which is sufficient since hibernate_acquire() already prevents concurrent hibernation sessions. The kernel swsusp path (sysfs-based hibernate/resume) uses find_hibernation_swap_type() which is not affected by the pin. It freezes user space before touching swap, so swapoff cannot race. Introduce dedicated helpers: - pin_hibernation_swap_type(): Look up and pin the swap device. Used by the uswsusp path. - find_hibernation_swap_type(): Lookup without pinning. Used by the kernel swsusp path. - unpin_hibernation_swap_type(): Clear the hibernation pin. While a swap device is pinned, swapoff is prevented from proceeding. Link: https://lore.kernel.org/20260323160822.1409904-1-youngjun.park@lge.com Link: https://lore.kernel.org/20260323160822.1409904-2-youngjun.park@lge.com Signed-off-by: Youngjun Park Reviewed-by: Kairui Song Cc: Baoquan He Cc: Barry Song Cc: Chris Li Cc: Kemeng Shi Cc: Nhat Pham Cc: "Rafael J . Wysocki" Signed-off-by: Andrew Morton

mm, swap: merge zeromap into swap table

2026-06-02T22:22:23+00:00

By allocating one additional bit in the swap table entry's flags field alongside the count, we can store the zeromap inline For 64 bit systems, zeromap will store in the swap table, avoiding zeromap allocation. It reduces the allocated memory. That is the happy path. For certain 32-bit archs, there might not be enough bits in the swap table to contain both PFN and flags. Therefore, conditionally let each cluster have a zeromap field at build time, and use that instead. If the swapfile cluster is not fully used, it will still save memory for zeromap. The empty cluster does not allocate a zeromap. In the worst case, all cluster are fully populated. We will use memory similar to the previous zeromap implementation. A few macros were moved to different headers for build time struct definition. [akpm@linux-foundation.org: swap_cluster_alloc_table(): remove unused local `ret] [akpm@linux-foundation.org: fix unused label `err_free'] Link: https://lore.kernel.org/20260517-swap-table-p4-v5-12-88ae43e064c7@tencent.com Signed-off-by: Kairui Song Acked-by: Chris Li Reviewed-by: Youngjun Park Cc: Baolin Wang Cc: Baoquan He Cc: Barry Song Cc: Chengming Zhou Cc: David Hildenbrand Cc: Hugh Dickins Cc: Johannes Weiner Cc: Kemeng Shi Cc: Lorenzo Stoakes Cc: Muchun Song Cc: Nhat Pham Cc: Roman Gushchin Cc: Shakeel Butt Cc: Zi Yan Signed-off-by: Andrew Morton

mm/memcg: remove no longer used swap cgroup array

2026-06-02T22:22:23+00:00

Now all swap cgroup records are stored in the swap cluster directly, the static array is no longer needed. Link: https://lore.kernel.org/20260517-swap-table-p4-v5-11-88ae43e064c7@tencent.com Signed-off-by: Kairui Song Acked-by: Chris Li Cc: Baolin Wang Cc: Baoquan He Cc: Barry Song Cc: Chengming Zhou Cc: David Hildenbrand Cc: Hugh Dickins Cc: Johannes Weiner Cc: Kemeng Shi Cc: Lorenzo Stoakes Cc: Muchun Song Cc: Nhat Pham Cc: Roman Gushchin Cc: Shakeel Butt Cc: Youngjun Park Cc: Zi Yan Signed-off-by: Andrew Morton

mm/memcg, swap: store cgroup id in cluster table directly

2026-06-02T22:22:23+00:00

Drop the usage of the swap_cgroup_ctrl, and use the dynamic cluster table instead. The per-cluster memcg table is 1024 / 512 bytes on most archs, and does not need RCU protection: the cgroup data is only read and written under the cluster lock. That keeps things simple, lets the allocation use plain kmalloc with immediate kfree (no deferred free), and keeps fragmentation acceptable. [akpm@linux-foundation.org: memcgv1: don't compile swap functions when CONFIG_SWAP=n] Link: https://lore.kernel.org/202605281711.bSeZlErK-lkp@intel.com [akpm@linux-foundation.org: fix CONFIG_SWAP=n build] Link: https://lore.kernel.org/20260517-swap-table-p4-v5-10-88ae43e064c7@tencent.com Signed-off-by: Kairui Song Acked-by: Chris Li Cc: Baolin Wang Cc: Baoquan He Cc: Barry Song Cc: Chengming Zhou Cc: David Hildenbrand Cc: Hugh Dickins Cc: Johannes Weiner Cc: Kemeng Shi Cc: Lorenzo Stoakes Cc: Muchun Song Cc: Nhat Pham Cc: Roman Gushchin Cc: Shakeel Butt Cc: Youngjun Park Cc: Zi Yan Signed-off-by: Andrew Morton

mm, swap: consolidate cluster allocation helpers

2026-06-02T22:22:22+00:00

Swap cluster table management is spread across several narrow helpers. As a result, the allocation and fallback sequences are open-coded in multiple places. A few more per-cluster tables will be added soon, so avoid duplicating these sequences per table type. Fold the existing pairs into cluster-oriented helpers, and rename for consistency. No functional change, only a few sanity checks are slightly adjusted. Link: https://lore.kernel.org/20260517-swap-table-p4-v5-9-88ae43e064c7@tencent.com Signed-off-by: Kairui Song Acked-by: Chris Li Cc: Baolin Wang Cc: Baoquan He Cc: Barry Song Cc: Chengming Zhou Cc: David Hildenbrand Cc: Hugh Dickins Cc: Johannes Weiner Cc: Kemeng Shi Cc: Lorenzo Stoakes Cc: Muchun Song Cc: Nhat Pham Cc: Roman Gushchin Cc: Shakeel Butt Cc: Youngjun Park Cc: Zi Yan Signed-off-by: Andrew Morton

mm, swap: support flexible batch freeing of slots in different memcgs

2026-06-02T22:22:22+00:00

Instead of requiring the caller to ensure all slots are in the same memcg, make the function handle different memcgs at once. This is both a micro optimization and required for removing the memcg lookup in the page table layer, so it can be unified at the swap layer. We are not removing the memcg lookup in the page table in this commit. It has to be done after the memcg lookup is deferred to the swap layer. Link: https://lore.kernel.org/20260517-swap-table-p4-v5-7-88ae43e064c7@tencent.com Signed-off-by: Kairui Song Acked-by: Chris Li Cc: Baolin Wang Cc: Baoquan He Cc: Barry Song Cc: Chengming Zhou Cc: David Hildenbrand Cc: Hugh Dickins Cc: Johannes Weiner Cc: Kemeng Shi Cc: Lorenzo Stoakes Cc: Muchun Song Cc: Nhat Pham Cc: Roman Gushchin Cc: Shakeel Butt Cc: Youngjun Park Cc: Zi Yan Signed-off-by: Andrew Morton