kernel/linux.git/mm/zsmalloc.c, branch v7.0.10

mm/zsmalloc: copy KMSAN metadata in zs_page_migrate()

2026-05-07T04:13:48+00:00

commit 4fb61d95ad21c3b6f1c09f357ff49d70abb0535e upstream. zs_page_migrate() uses copy_page() to copy the contents of a zspage page during migration. However, copy_page() is not instrumented by KMSAN, so the shadow and origin metadata of the destination page are not updated. As a result, subsequent accesses to the migrated page are reported as use-after-free by KMSAN, despite the data being correctly copied. Add a kmsan_copy_page_meta() call after copy_page() to propagate the KMSAN metadata to the new page, matching what copy_highpage() does internally. Link: https://lkml.kernel.org/r/20260321132912.93434-1-syoshida@redhat.com Fixes: afb2d666d025 ("zsmalloc: use copy_page for full page copy") Signed-off-by: Shigeru Yoshida Reviewed-by: Sergey Senozhatsky Cc: Mark-PK Tsai Cc: Minchan Kim Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

Convert 'alloc_obj' family to use the new default GFP_KERNEL argument

2026-02-22T01:09:51+00:00

This was done entirely with mindless brute force, using git grep -l '\

treewide: Replace kmalloc with kmalloc_obj for non-scalar types

2026-02-21T09:02:28+00:00

This is the result of running the Coccinelle script from scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to avoid scalar types (which need careful case-by-case checking), and instead replace kmalloc-family calls that allocate struct or union object instances: Single allocations: kmalloc(sizeof(TYPE), ...) are replaced with: kmalloc_obj(TYPE, ...) Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...) are replaced with: kmalloc_objs(TYPE, COUNT, ...) Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...) are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...) (where TYPE may also be *VAR) The resulting allocations no longer return "void *", instead returning "TYPE *". Signed-off-by: Kees Cook

zsmalloc: make common caches global

2026-02-06T23:47:17+00:00

Currently, zsmalloc creates kmem_cache of handles and zspages for each pool, which may be suboptimal from the memory usage point of view (extra internal fragmentation per pool). Systems that create multiple zsmalloc pools may benefit from shared common zsmalloc caches. Make handles and zspages kmem caches global. The memory savings depend on particular setup and data patterns and can be found via slabinfo. Link: https://lkml.kernel.org/r/20260117025406.799428-1-senozhatsky@chromium.org Signed-off-by: Sergey Senozhatsky Reviewed-by: Nhat Pham Reviewed-by: Yosry Ahmed Cc: Brian Geffon Cc: Johannes Weiner Cc: Minchan Kim Signed-off-by: Andrew Morton

zsmalloc: introduce SG-list based object read API

2026-01-27T04:02:32+00:00

Currently, zsmalloc performs address linearization on read (which sometimes requires memcpy() to a local buffer). Not all zsmalloc users need a linear address. For example, Crypto API supports SG-list, performing linearization under the hood, if needed. In addition, some compressors can have native SG-list support, completely avoiding the linearization step. Provide an SG-list based zsmalloc read API: - zs_obj_read_sg_begin() - zs_obj_read_sg_end() This API allows callers to obtain an SG representation of the object (one entry for objects that are contained in a single page and two entries for spanning objects), avoiding the need for a bounce buffer and memcpy. [senozhatsky@chromium.org: make zs_obj_read_sg_begin() return void, per Yosry] Link: https://lkml.kernel.org/r/20260117024900.792237-1-senozhatsky@chromium.org Link: https://lkml.kernel.org/r/20260113034645.2729998-1-senozhatsky@chromium.org Signed-off-by: Sergey Senozhatsky Acked-by: Herbert Xu Tested-by: Yosry Ahmed Cc: Herbert Xu Cc: Brian Geffon Cc: Johannes Weiner Cc: Minchan Kim Cc: Nhat Pham Signed-off-by: Andrew Morton

zsmalloc: simplify read begin/end logic

2026-01-27T04:02:26+00:00

zs_obj_read_begin() currently maps or copies the compressed object with the prefix handle for !ZsHugePage case. Make the logic clearer and more efficient by moving the offset of the object in the page after the prefix handle instead, only copying the actual object and avoiding the need to adjust the returned address to account for the prefix. Adjust the logic to detect spanning objects in zs_obj_read_end() accordingly, slightly simplifying it by avoiding the need to account for the handle in both the offset and the object size. Link: https://lkml.kernel.org/r/20260107052145.3586917-2-senozhatsky@chromium.org Signed-off-by: Sergey Senozhatsky Co-developed-by: Yosry Ahmed Signed-off-by: Yosry Ahmed Cc: Brian Geffon Cc: Chengming Zhou Cc: Jens Axboe Cc: Johannes Weiner Cc: Minchan Kim Cc: Nhat Pham Signed-off-by: Andrew Morton

zsmalloc: use actual object size to detect spans

2026-01-27T04:02:25+00:00

Using class->size to detect spanning objects is not entirely correct, because some size classes can hold a range of object sizes of up to class->size bytes in length, due to size-classes merge. Such classes use padding for cases when actually written objects are smaller than class->size. zs_obj_read_begin() can incorrectly hit the slow path and perform memcpy of such objects, basically copying padding bytes. Instead of class->size zs_obj_read_begin() should use the actual compressed object length (both zram and zswap know it) so that it can correctly handle situations when a written object is small enough to fit into the first physical page. Link: https://lkml.kernel.org/r/20260107052145.3586917-1-senozhatsky@chromium.org Signed-off-by: Sergey Senozhatsky Reviewed-by: Yosry Ahmed [zsmalloc & zswap] Reviewed-by: Nhat Pham Cc: Brian Geffon Cc: Chengming Zhou Cc: Jens Axboe Cc: Johannes Weiner Cc: Minchan Kim Signed-off-by: Andrew Morton

mm: fix minor spelling mistakes in comments

2026-01-21T03:24:48+00:00

Correct several typos in comments across files in mm/ [akpm@linux-foundation.org: also fix comment grammar, per SeongJae] Link: https://lkml.kernel.org/r/20251218150906.25042-1-klourencodev@gmail.com Signed-off-by: Kevin Lourenco Reviewed-by: SeongJae Park Acked-by: David Hildenbrand (Red Hat) Reviewed-by: Lorenzo Stoakes Signed-off-by: Andrew Morton

mm: remove unused zpool layer

2025-09-21T21:21:59+00:00

With zswap using zsmalloc directly, there are no more in-tree users of this code. Remove it. With zpool gone, zsmalloc is now always a simple dependency and no longer something the user needs to configure. Hide CONFIG_ZSMALLOC from the user and have zswap and zram pull it in as needed. Link: https://lkml.kernel.org/r/20250829162212.208258-3-hannes@cmpxchg.org Signed-off-by: Johannes Weiner Acked-by: SeongJae Park Acked-by: Yosry Ahmed Cc: Chengming Zhou Cc: Nhat Pham Cc: Vitaly Wool Signed-off-by: Andrew Morton

treewide: remove MIGRATEPAGE_SUCCESS

2025-09-13T23:54:50+00:00

At this point MIGRATEPAGE_SUCCESS is misnamed for all folio users, and now that we remove MIGRATEPAGE_UNMAP, it's really the only "success" return value that the code uses and expects. Let's just get rid of MIGRATEPAGE_SUCCESS completely and just use "0" for success. Link: https://lkml.kernel.org/r/20250811143949.1117439-3-david@redhat.com Signed-off-by: David Hildenbrand Reviewed-by: Zi Yan [mm] Acked-by: Dave Kleikamp [jfs] Acked-by: David Sterba [btrfs] Acked-by: Greg Kroah-Hartman Reviewed-by: Byungchul Park Cc: Alistair Popple Cc: Al Viro Cc: Arnd Bergmann Cc: Benjamin LaHaise Cc: Chris Mason Cc: Christian Brauner Cc: Christophe Leroy Cc: Dave Kleikamp Cc: Eugenio Pé rez Cc: Gregory Price Cc: "Huang, Ying" Cc: Jan Kara Cc: Jason Wang Cc: Jerrin Shaji George Cc: Josef Bacik Cc: Joshua Hahn Cc: Madhavan Srinivasan Cc: Mathew Brost Cc: Michael Ellerman Cc: "Michael S. Tsirkin" Cc: Minchan Kim Cc: Muchun Song Cc: Nicholas Piggin Cc: Oscar Salvador Cc: Rakie Kim Cc: Sergey Senozhatsky Cc: Xuan Zhuo Cc: Lance Yang Signed-off-by: Andrew Morton