kernel/git/stable/linux.git/mm/shmem.c, branch linux-7.2.y

fs: push nr_cached_objects memcg gating into individual filesystems

2026-07-23T09:35:02+00:00

Commit 0baad6f9b997 ("fs/super: skip non-memcg-aware nr_cached_objects in memcg slab shrink") added a check in fs/super.c that skipped every ->nr_cached_objects() hook whenever the shrinker was invoked for a non-root memcg, on the assumption that none of them honour sc->memcg. That assumption is wrong for XFS, whose inode-reclaim hook is intentionally driven from per-memcg contexts to free memcg-charged slab. Encoding a blanket "never memcg-aware" policy in fs/super.c short-circuits that path. Push the check down into the callbacks whose counters really are irrelevant to per-memcg reclaim - btrfs_nr_cached_objects() and shmem_unused_huge_count() - and drop the fs/super.c gate. Each filesystem can now lift the restriction independently if its counter later grows memcg awareness, without touching fs/super.c. Introduce mem_cgroup_shrink_is_root() in so the callbacks don't open-code "sc->memcg is NULL or root". Fixes: 0baad6f9b997 ("fs/super: skip non-memcg-aware nr_cached_objects in memcg slab shrink") Acked-by: Qi Zheng Reviewed-by: Jan Kara Reviewed-by: Shakeel Butt Signed-off-by: Usama Arif Link: https://patch.msgid.link/20260715103516.2410175-1-usama.arif@linux.dev Acked-by: David Sterba Reviewed-by: Baolin Wang Signed-off-by: Christian Brauner (Amutable)

Merge tag 'mm-stable-2026-06-18-09-26' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2026-06-19T17:14:34+00:00

Pull MM updates from Andrew Morton: - "selftests/mm: clean up build output and verbosity" (Li Wang) Remove some noise from the MM selftests build - "mm: Free contiguous order-0 pages efficiently" (Ryan Roberts) Speed up the freeing of a batch of 0-order pages by first scanning them for coalescing opportunities. This is applicable to vfree() and to the releasing of frozen pages - "mm/damon: introduce DAMOS failed region quota charge ratio" (SeongJae Park) Address a DAMOS usability issue: The DAMOS quota often exhausts prematurely because it charges for all memory attempted, causing slow and inconsistent performance when actions fail on unreclaimable memory. To fix this, a new feature lets users set a smaller, flexible quota charge ratio (via a numerator and denominator) for failed regions. Since failed actions cause less overhead, reducing their quota cost ensures more predictable and efficient DAMOS processing - "selftests/cgroup: improve zswap tests robustness and support large page sizes" (Li Wang) Fix various spurious failures and improves the overall robustness of the cgroup zswap selftests - "fix MAP_DROPPABLE not supported errno" (Anthony Yznaga) Fix an issue in the mlock selftests on arm32 - "mm: huge_memory: clean up defrag sysfs with shared" (Breno Leitao) Some maintenance work in the huge_memory code - "treewide: fixup gfp_t printks" (Brendan Jackman) Use the special vprintf() gfp_t conversion in various places - "mm: Fix vmemmap optimization accounting and initialization" (Muchun Song) Fix several bugs in the vmemmap optimization, mainly around incorrect page accounting and memmap initialization in the DAX and memory hotplug paths. It also fixes pageblock migratetype initialization and struct page initialization for ZONE_DEVICE compound pages - "mm/damon: repost non-hotfix reviewed patches in damon/next tree" A sprinkle of unrelated minor bugfixes for DAMON - "mm: remove page_mapped()" (David Hildenbrand) Remove this function from the tree, replacing it with folio_mapped() - "mm/damon: let DAMON be paused and resumed" (SeongJae Park) Allow DAMON to be paused and resumed without losing its current state - "kasan: hw_tags: Disable tagging for stack and page-tables" (Muhammad Usama Anjum) Simplify and speed up kasan by removing its ineffective tagging of stacks and page tables - "mm/damon/reclaim,lru_sort: monitor all system rams by default" (SeongJae Park) Simplify deployment on diverse hardware like NUMA systems by updating DAMON_RECLAIM and DAMON_LRU_SORT to automatically monitor the physical address range covering all System RAM areas by default, replacing the overly restrictive behavior that only targeted the single largest memory block to save on negligible overhead - "mm/damon/sysfs: document filters/ directory as deprecated" (SeongJae Park) Update some DAMON docs - "mm: use spinlock guards for zone lock" (Dmitry Ilvokhin) Switch zone->lock handling over to using the guard() mechanisms - "mm/filemap: tighten mmap_miss hit accounting" (fujunjie) Fix a flaw where the mmap_miss counter over-credited page cache hits during fault-arounds and page-fault retries. This results in significant reduction of redundant synchronous mmap readahead I/O, drastically cutting down execution time and gigabytes read for sparse random or strided memory access workloads - "selftests/cgroup: Fix false positive failures in test_percpu_basic" (Li Wang) Fix a couple of false-positives in the cgroup kmem selftests - "mm/damon/reclaim: support monitoring intervals auto-tuning" (SeongJae Park) Add a new parameter to DAMON permitting DAMON_RECLAIM to automatically tune DAMON's sampling and aggregation intervals - "mm/damon/stat: add kdamond_pid parameter" (SeongJae Park) Change DAMON_STAT to provide the pid of its kdamond - "mm/kmemleak: dedupe verbose scan output" (Breno Leitao) Remove large amounts of duplicated backtraces from the verbose-mode kmemleak output - "mm: remove CONFIG_HAVE_BOOTMEM_INFO_NODE (Part 1)" (David Hildenbrand) Reduce our use of CONFIG_HAVE_BOOTMEM_INFO_NODE, with a view to removing it entirely in a later series - "mm/damon: validate min_region_size to be power of 2" (Liew Rui Yan) Prevent users from passing a non-power-of-2 value of `addr_unit', as this later results in undesirable behavior - "mm: document read_pages and simplify usage" (Frederick Mayle) - "tools/mm/page-types: Fix misc bugs" (Ye Liu) Fix three issues in tools/mm/page-types.c - "mm: misc cleanups from __GFP_UNMAPPED series" (Brendan Jackman) Implement several cleanups in the page allocator and related code - "mm, swap: swap table phase IV: unify allocation" (Kairui Song) Unify the allocation and charging of anon and shmem swap in folios, provides better synchronization, consolidates the metadata management, hence dropping the static array and map, and improves performance - "mm/damon: introduce data attributes monitoring" (SeongJae Park( Extend DAMON to monitor general data attributes other than accesses - "mm/vmalloc: free unused pages on vrealloc() shrink" (Shivam Kalra) Implement the TODO in vrealloc() to unmap and free unused pages when shrinking across a page boundary - "mm/damon: documentation and comment fixes" (niecheng) - "remove mmap_action success, error hooks" (Lorenzo Stoakes) Eliminate custom hooks from mmap_action by removing the problematic success_hook which allowed drivers to improperly access uninitialized VMAs. It replaces the error_hook with a simple error-code field and updates the memory char driver accordingly - "mm/damon: minor improvements for code readability and tests" (SeongJae Park) - "mm/damon: fix macro arguments and clarify quota goals doc" (Maksym Shcherba) - "userfaultfd: merge fs/userfaultfd.c into mm/userfaultfd.c" (Mike Rapoport) - "mm/mglru: improve reclaim loop and dirty folio" (Kairui Song and others) Clean up and slightly improves MGLRU's reclaim loop and dirty writeback handling. Large performance improvements are measured - "use vma locks for proc/pid/{smaps|numa_maps} reads" (Suren Baghdasaryan) Use per-vma locks when reading /proc/pid/smaps and numa_maps similar to reduce contention on central mmap_lock - "refactors thpsize_shmem_enabled_store() and thpsize_shmem_enabled_show()" (Ran Xiaokai) Some cleanup work in the THP code - "selftests/memfd: fix compilation warnings" (Konstantin Khorenko) Fix a few build glitches in the memfd selftest code. - "memcg: shrink obj_stock_pcp and cache multiple objcgs" (Shakeel Butt) Resolve a 68% performance regression caused by NUMA-node cache thrashing around struct obj_stock_pcp by shrinking its existing fields and expanding it into a multi-slot array that caches up to five obj_cgroup pointers per CPU, allowing per-node variants of the same memcg to coexist within a single 64-byte cache line. - "zram: writeback fixes" (Sergey Senozhatsky) address a couple of unrelated zram writeback issues - "mm: switch THP shrinker to list_lru" (Johannes Weiner) Resolve NUMA-awareness issues and streamlines callsite interaction by refactoring and extending the list_lru API to completely replace the complex, open-coded deferred split queue for Transparent Huge Pages - "mm: improve large folio readahead for exec memory" (Usama Arif) Improve large-folio readahead on systems like 64K-page arm64 by preventing the mmap_miss check from permanently disabling target-oriented VM_EXEC readahead, and by generalizing the force_thp_readahead gate to support mappings with any usefully large maximum folio order under the cache cap. - "userfaultfd/pagemap: pre-existing fixes" (Kiryl Shutsemau) Fix a bunch of minor issues in the userfaultfd/pagemap, all of which were flagged by Sashiko review of proposed new material - "mm/sparse-vmemmap: Provide generic vmemmap_set_pmd() and vmemmap_check_pmd()" (Muchun Song) Provide generic versions of these two functions so the four arch-specific implementations can be removed. - "mm/swap, PM: hibernate: fix swapoff race in uswsusp by pinning swap device" (Youngjun Park) Address a uswsusp-vs-swapoff race and reduces the swap device reference taking/releasing frequency. - "mm/hmm: A fix and a selftest" (Dev Jain) * tag 'mm-stable-2026-06-18-09-26' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (321 commits) selftests/mm/hmm-tests: test pagemap reads of PMD device-private entries fs/proc/task_mmu: do not warn on seeing non-migration pmd entry lib/test_hmm: check alloc_page_vma() return value and handle OOM mm/compaction: cap compact_gap() at COMPACT_CLUSTER_MAX mm/swap: remove redundant swap device reference in alloc/free mm/swap, PM: hibernate: fix swapoff race in uswsusp by pinning swap device mm/filemap: use folio_next_index() for start vmalloc: fix NULL pointer dereference in is_vm_area_hugepages() sparc/mm: drop vmemmap_check_pmd helper and use generic code loongarch/mm: drop vmemmap_check_pmd helper and use generic code riscv/mm: drop vmemmap_pmd helpers and use generic code arm64/mm: drop vmemmap_pmd helpers and use generic code mm/sparse-vmemmap: provide generic vmemmap_set_pmd() and vmemmap_check_pmd() rust: page: mark Page::nid as inline userfaultfd: build __VMA_UFFD_FLAGS from config-gated masks userfaultfd: gate must_wait writability check on pte_present() mm/huge_memory: preserve pmd_swp_uffd_wp on device-private PMD downgrade fs/proc/task_mmu: fix hugetlb self-deadlock in pagemap_scan_pte_hole() fs/proc/task_mmu: use huge_page_size() in pagemap_scan_hugetlb_entry() fs/proc/task_mmu: fix make_uffd_wp_huge_pte() prot-update race ...

simpe_xattr: use per-sb cache

2026-06-06T13:21:41+00:00

Move the hash table to the super block to remove excessive overhead in case of small number of xattrs per inode. Add linked list to the inode, used for listxattr and eviction. Listxattr uses rcu protection to iterate the list of xattrs. Before being made per-sb, lazy allocation was protected by inode lock. Now inode lock no longer provides sufficient exclusion, so use cmpxchg() to ensure atomicity. Though I haven't found a description of this pattern, after some research it seems that cmpxchg_release() and READ_ONCE() should provide the necessary memory barriers. Use simple_xattr_free_rcu() in simple_xattrs_free(). This is needed because the hash table is now shared between inodes and lookup on a different inode might be running the compare function on the just freed element within the RCU grace period. Following stats are based on slabinfo diff, after creating 100k empty files, then adding a "user.test=foo" xattr to each: v7.0 (no rhashtable): File creation: 993.40 bytes/file Xattr addition: 79.99 bytes/file v7.1-rc2 (per-inode rhashtable): File creation: 939.73 bytes/file Xattr addition: 1296.08 bytes/file v7.1-rc2 + this patch (per-sb rhashtable) File creation: 946.84 bytes/file Xattr addition: 111.86 bytes/file The overhead of a single xattr is reduced to nearly v7.0 levels. The per xattr overhead is slightly larger due to the addition of three pointers to struct simple_xattr. Fixes: b32c4a213698 ("xattr: add rhashtable-based simple_xattr infrastructure") Signed-off-by: Miklos Szeredi Link: https://patch.msgid.link/20260605135322.2632068-5-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable)

simple_xattr: change interface to pass struct simple_xattrs **

2026-06-06T13:21:41+00:00

Change the simple_xattr API to accept pointer-to-pointer (struct simple_xattrs **) instead of pointer. This allows the functions to handle lazy allocation internally without requiring callers to use simple_xattrs_lazy_alloc(). The simple_xattr_set(), simple_xattr_set_limited() and simple_xattr_add() functions now handle allocation when xattrs is NULL. simple_xattrs_free() now also frees the xattrs structure itself and sets the pointer to NULL. This simplifies callers and removes the need for most callers to explicitly manage xattrs allocation and lifetime. In shmem_initxattrs(), the total required space for all initial xattrs (ispace) is pre-calculated and deducted from sbinfo->free_ispace. Since this patch modifies the function to add new xattrs directly to the inode's &info->xattrs list rather than using a local temporary variable, a failure means that the partially populated info->xattrs list remains attached to the inode. When the VFS caller handles the -ENOMEM error, it drops the newly created inode via iput(), shmem_free_inode() adds freed to sbinfo->free_ispace a second time, permanently inflating the tmpfs free space quota. Fix by substracting already added xattrs from ispace. Signed-off-by: Miklos Szeredi Link: https://patch.msgid.link/20260605135322.2632068-4-mszeredi@redhat.com Signed-off-by: Christian Brauner (Amutable)

tmpfs: simplify constructing "security.foo" xattr names

2026-06-06T13:21:40+00:00

Use kasprintf() instead of doing it with kmalloc() + 2 x memcpy(). Signed-off-by: Miklos Szeredi Link: https://patch.msgid.link/20260605135322.2632068-3-mszeredi@redhat.com Tested-by: Calum Mackay Signed-off-by: Christian Brauner (Amutable)

mm: shmem: refactor thpsize_shmem_enabled_show() with helper arrays

2026-06-04T21:45:06+00:00

Replace the hardcoded if/else chain of test_bit() calls and string literals in thpsize_shmem_enabled_show() with a loop over huge_shmem_orders_by_mode[] and huge_shmem_enabled_mode_strings[] arrays. This makes thpsize_shmem_enabled_show() consistent with thpsize_shmem_enabled_store() and eliminates duplicated mode name strings. Link: https://lore.kernel.org/20260525102700.68707-3-ranxiaokai627@163.com Signed-off-by: Ran Xiaokai Reviewed-by: Baolin Wang Reviewed-by: Barry Song Reviewed-by: Breno Leitao Reviewed-by: Lorenzo Stoakes Tested-by: Baolin Wang Tested-by: Lance Yang Acked-by: David Hildenbrand (arm) Cc: Dev Jain Cc: Hugh Dickins Cc: Liam R. Howlett Cc: Nico Pache Cc: Ryan Roberts Cc: Zi Yan Signed-off-by: Andrew Morton

mm: shmem: refactor thpsize_shmem_enabled_store() with sysfs_match_string()

2026-06-04T21:45:06+00:00

Patch series "refactors thpsize_shmem_enabled_store() and thpsize_shmem_enabled_show()", v4. This patch (of 2): Inspired by commit 82d9ff648c6c ("mm: huge_memory: refactor anon_enabled_store() with set_anon_enabled_mode()"), refactor thpsize_shmem_enabled_store() using sysfs_match_string(). This eliminates the duplicated spin_lock/unlock(), set/clear_bit(), calls across all branches, reducing code duplication. Behavioral change: Call start_stop_khugepaged() only when the mode actually changes. If unchanged, call set_recommended_min_free_kbytes() to preserve legacy watermark behavior. This avoids unnecessary khugepaged restarts. Tested with selftests ./run_kselftest.sh -t mm:ksft_thp.sh, all test cases passed. Link: https://lore.kernel.org/20260525102700.68707-1-ranxiaokai627@163.com Link: https://lore.kernel.org/20260525102700.68707-2-ranxiaokai627@163.com Signed-off-by: Ran Xiaokai Reviewed-by: Baolin Wang Reviewed-by: Barry Song Tested-by: Baolin Wang Tested-by: Lance Yang Acked-by: David Hildenbrand (arm) Reviewed-by: Lorenzo Stoakes Cc: Breno Leitao Cc: Dev Jain Cc: Hugh Dickins Cc: Liam R. Howlett Cc: Nico Pache Cc: Ran Xiaokai Cc: Ryan Roberts Cc: Zi Yan Signed-off-by: Andrew Morton

mm, swap: unify large folio allocation

2026-06-02T22:22:21+00:00

Now that direct large order allocation is supported in the swap cache, both anon and shmem can use it instead of implementing their own methods. This unifies the fallback and swap cache check, which also reduces the TOCTOU race window of swap cache state: previously, high order swapin required checking swap cache states first, then allocating and falling back separately. Now all these steps happen in the same compact loop. Order fallback and statistics are also unified, callers just need to check and pass the acceptable order bitmask. There is basically no behavior change. This only makes things more unified and prepares for later commits. Cgroup and zero map checks can also be moved into the compact loop, further reducing race windows and redundancy Link: https://lore.kernel.org/20260517-swap-table-p4-v5-5-88ae43e064c7@tencent.com Signed-off-by: Kairui Song Cc: Baolin Wang Cc: Baoquan He Cc: Barry Song Cc: Chengming Zhou Cc: Chris Li 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/huge_memory: move THP gfp limit helper into header

2026-06-02T22:22:21+00:00

Shmem has some special requirements for THP GFP and has to limit it in certain zones or provide a more lenient fallback. We'll use this helper for generic swap THP allocation, which needs to support shmem. For a typical GFP_HIGHUSER_MOVABLE swap-in, this helper is basically a no-op. But it's necessary for certain shmem users, mostly drivers. No feature change. Link: https://lore.kernel.org/20260517-swap-table-p4-v5-3-88ae43e064c7@tencent.com Signed-off-by: Kairui Song Acked-by: Chris Li Reviewed-by: Zi Yan 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 Signed-off-by: Andrew Morton

Revert "tmpfs: don't enable large folios if not supported"

2026-05-29T04:04:39+00:00

This reverts commit 5a90c155defa684f3a21f68c3f8e40c056e6114c. Currently, when shmem mounts are initialized, they only use 'sbinfo->huge' to determine whether the shmem mount supports large folios. However, for anonymous shmem, whether it supports large folios can be dynamically configured via sysfs interfaces, so setting or not setting mapping_set_large_folios() during initialization cannot accurately reflect whether anonymous shmem actually supports large folios, which has already caused some confusion[1]. Moreover, for tmpfs mounts, relying on 'sbinfo->huge' cannot keep the mapping_set_large_folios() setting consistent across all mappings in the entire tmpfs mount. In other words, under the same tmpfs mount, after remount, we might end up with some mappings supporting large folios (calling mapping_set_large_folios()) while others don't. After some investigation, I found that the write performance regression addressed by commit 5a90c155defa has already been fixed by the following commit 665575cff098b ("filemap: move prefaulting out of hot write path"). See the following test data: Base: dd if=/dev/zero of=/mnt/tmpfs/test bs=400K count=10485 (3.2 GB/s) dd if=/dev/zero of=/mnt/tmpfs/test bs=800K count=5242 (3.2 GB/s) dd if=/dev/zero of=/mnt/tmpfs/test bs=1600K count=2621 (3.1 GB/s) dd if=/dev/zero of=/mnt/tmpfs/test bs=2200K count=1906 (3.0 GB/s ) dd if=/dev/zero of=/mnt/tmpfs/test bs=3000K count=1398 (3.0 GB/s) dd if=/dev/zero of=/mnt/tmpfs/test bs=4500K count=932 (3.1 GB/s) Base + revert 5a90c155defa: dd if=/dev/zero of=/mnt/tmpfs/test bs=400K count=10485 (3.3 GB/s) dd if=/dev/zero of=/mnt/tmpfs/test bs=800K count=5242 (3.3 GB/s) dd if=/dev/zero of=/mnt/tmpfs/test bs=1600K count=2621 (3.2 GB/s) dd if=/dev/zero of=/mnt/tmpfs/test bs=2200K count=1906 (3.1 GB/s) dd if=/dev/zero of=/mnt/tmpfs/testbs=3000K count=1398 (3.0 GB/s) dd if=/dev/zero of=/mnt/tmpfs/test bs=4500K count=932 (3.1 GB/s) The data is basically consistent with minor fluctuation noise. So we can now safely revert commit 5a90c155defa to set mapping_set_large_folios() for all shmem mounts unconditionally. Link: https://lore.kernel.org/b2c7deee259a94b0d00a7c320d8d24d2c421f761.1776908112.git.baolin.wang@linux.alibaba.com Link: https://lore.kernel.org/all/ec927492-4577-4192-8fad-85eb1bb43121@linux.alibaba.com/ [1] Link: https://lore.kernel.org/all/116df9f9-4db7-40d4-a4a4-30a87c0feffa@linux.alibaba.com/ Fixes: 5a90c155defa ("tmpfs: don't enable large folios if not supported") Signed-off-by: Baolin Wang Acked-by: Zi Yan Reviewed-by: Kefeng Wang Reviewed-by: Lance Yang Acked-by: David Hildenbrand (Arm) Acked-by: Lorenzo Stoakes Cc: Hugh Dickins Cc: Matthew Wilcox (Oracle) Signed-off-by: Andrew Morton