kernel.git/Documentation/filesystems/porting.rst, branch linux-rolling-stable

Merge tag 'pull-persistency' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2025-12-05T22:36:21Z

Pull persistent dentry infrastructure and conversion from Al Viro: "Some filesystems use a kinda-sorta controlled dentry refcount leak to pin dentries of created objects in dcache (and undo it when removing those). A reference is grabbed and not released, but it's not actually _stored_ anywhere. That works, but it's hard to follow and verify; among other things, we have no way to tell _which_ of the increments is intended to be an unpaired one. Worse, on removal we need to decide whether the reference had already been dropped, which can be non-trivial if that removal is on umount and we need to figure out if this dentry is pinned due to e.g. unlink() not done. Usually that is handled by using kill_litter_super() as ->kill_sb(), but there are open-coded special cases of the same (consider e.g. /proc/self). Things get simpler if we introduce a new dentry flag (DCACHE_PERSISTENT) marking those "leaked" dentries. Having it set claims responsibility for +1 in refcount. The end result this series is aiming for: - get these unbalanced dget() and dput() replaced with new primitives that would, in addition to adjusting refcount, set and clear persistency flag. - instead of having kill_litter_super() mess with removing the remaining "leaked" references (e.g. for all tmpfs files that hadn't been removed prior to umount), have the regular shrink_dcache_for_umount() strip DCACHE_PERSISTENT of all dentries, dropping the corresponding reference if it had been set. After that kill_litter_super() becomes an equivalent of kill_anon_super(). Doing that in a single step is not feasible - it would affect too many places in too many filesystems. It has to be split into a series. This work has really started early in 2024; quite a few preliminary pieces have already gone into mainline. This chunk is finally getting to the meat of that stuff - infrastructure and most of the conversions to it. Some pieces are still sitting in the local branches, but the bulk of that stuff is here" * tag 'pull-persistency' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (54 commits) d_make_discardable(): warn if given a non-persistent dentry kill securityfs_recursive_remove() convert securityfs get rid of kill_litter_super() convert rust_binderfs convert nfsctl convert rpc_pipefs convert hypfs hypfs: swich hypfs_create_u64() to returning int hypfs: switch hypfs_create_str() to returning int hypfs: don't pin dentries twice convert gadgetfs gadgetfs: switch to simple_remove_by_name() convert functionfs functionfs: switch to simple_remove_by_name() functionfs: fix the open/removal races functionfs: need to cancel ->reset_work in ->kill_sb() functionfs: don't bother with ffs->ref in ffs_data_{opened,closed}() functionfs: don't abuse ffs_data_closed() on fs shutdown convert selinuxfs ...

Merge tag 'mm-stable-2025-12-03-21-26' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2025-12-05T21:52:43Z

Pull MM updates from Andrew Morton: "__vmalloc()/kvmalloc() and no-block support" (Uladzislau Rezki) Rework the vmalloc() code to support non-blocking allocations (GFP_ATOIC, GFP_NOWAIT) "ksm: fix exec/fork inheritance" (xu xin) Fix a rare case where the KSM MMF_VM_MERGE_ANY prctl state is not inherited across fork/exec "mm/zswap: misc cleanup of code and documentations" (SeongJae Park) Some light maintenance work on the zswap code "mm/page_owner: add debugfs files 'show_handles' and 'show_stacks_handles'" (Mauricio Faria de Oliveira) Enhance the /sys/kernel/debug/page_owner debug feature by adding unique identifiers to differentiate the various stack traces so that userspace monitoring tools can better match stack traces over time "mm/page_alloc: pcp->batch cleanups" (Joshua Hahn) Minor alterations to the page allocator's per-cpu-pages feature "Improve UFFDIO_MOVE scalability by removing anon_vma lock" (Lokesh Gidra) Address a scalability issue in userfaultfd's UFFDIO_MOVE operation "kasan: cleanups for kasan_enabled() checks" (Sabyrzhan Tasbolatov) "drivers/base/node: fold node register and unregister functions" (Donet Tom) Clean up the NUMA node handling code a little "mm: some optimizations for prot numa" (Kefeng Wang) Cleanups and small optimizations to the NUMA allocation hinting code "mm/page_alloc: Batch callers of free_pcppages_bulk" (Joshua Hahn) Address long lock hold times at boot on large machines. These were causing (harmless) softlockup warnings "optimize the logic for handling dirty file folios during reclaim" (Baolin Wang) Remove some now-unnecessary work from page reclaim "mm/damon: allow DAMOS auto-tuned for per-memcg per-node memory usage" (SeongJae Park) Enhance the DAMOS auto-tuning feature "mm/damon: fixes for address alignment issues in DAMON_LRU_SORT and DAMON_RECLAIM" (Quanmin Yan) Fix DAMON_LRU_SORT and DAMON_RECLAIM with certain userspace configuration "expand mmap_prepare functionality, port more users" (Lorenzo Stoakes) Enhance the new(ish) file_operations.mmap_prepare() method and port additional callsites from the old ->mmap() over to ->mmap_prepare() "Fix stale IOTLB entries for kernel address space" (Lu Baolu) Fix a bug (and possible security issue on non-x86) in the IOMMU code. In some situations the IOMMU could be left hanging onto a stale kernel pagetable entry "mm/huge_memory: cleanup __split_unmapped_folio()" (Wei Yang) Clean up and optimize the folio splitting code "mm, swap: misc cleanup and bugfix" (Kairui Song) Some cleanups and a minor fix in the swap discard code "mm/damon: misc documentation fixups" (SeongJae Park) "mm/damon: support pin-point targets removal" (SeongJae Park) Permit userspace to remove a specific monitoring target in the middle of the current targets list "mm: MISC follow-up patches for linux/pgalloc.h" (Harry Yoo) A couple of cleanups related to mm header file inclusion "mm/swapfile.c: select swap devices of default priority round robin" (Baoquan He) improve the selection of swap devices for NUMA machines "mm: Convert memory block states (MEM_*) macros to enums" (Israel Batista) Change the memory block labels from macros to enums so they will appear in kernel debug info "ksm: perform a range-walk to jump over holes in break_ksm" (Pedro Demarchi Gomes) Address an inefficiency when KSM unmerges an address range "mm/damon/tests: fix memory bugs in kunit tests" (SeongJae Park) Fix leaks and unhandled malloc() failures in DAMON userspace unit tests "some cleanups for pageout()" (Baolin Wang) Clean up a couple of minor things in the page scanner's writeback-for-eviction code "mm/hugetlb: refactor sysfs/sysctl interfaces" (Hui Zhu) Move hugetlb's sysfs/sysctl handling code into a new file "introduce VM_MAYBE_GUARD and make it sticky" (Lorenzo Stoakes) Make the VMA guard regions available in /proc/pid/smaps and improves the mergeability of guarded VMAs "mm: perform guard region install/remove under VMA lock" (Lorenzo Stoakes) Reduce mmap lock contention for callers performing VMA guard region operations "vma_start_write_killable" (Matthew Wilcox) Start work on permitting applications to be killed when they are waiting on a read_lock on the VMA lock "mm/damon/tests: add more tests for online parameters commit" (SeongJae Park) Add additional userspace testing of DAMON's "commit" feature "mm/damon: misc cleanups" (SeongJae Park) "make VM_SOFTDIRTY a sticky VMA flag" (Lorenzo Stoakes) Address the possible loss of a VMA's VM_SOFTDIRTY flag when that VMA is merged with another "mm: support device-private THP" (Balbir Singh) Introduce support for Transparent Huge Page (THP) migration in zone device-private memory "Optimize folio split in memory failure" (Zi Yan) "mm/huge_memory: Define split_type and consolidate split support checks" (Wei Yang) Some more cleanups in the folio splitting code "mm: remove is_swap_[pte, pmd]() + non-swap entries, introduce leaf entries" (Lorenzo Stoakes) Clean up our handling of pagetable leaf entries by introducing the concept of 'software leaf entries', of type softleaf_t "reparent the THP split queue" (Muchun Song) Reparent the THP split queue to its parent memcg. This is in preparation for addressing the long-standing "dying memcg" problem, wherein dead memcg's linger for too long, consuming memory resources "unify PMD scan results and remove redundant cleanup" (Wei Yang) A little cleanup in the hugepage collapse code "zram: introduce writeback bio batching" (Sergey Senozhatsky) Improve zram writeback efficiency by introducing batched bio writeback support "memcg: cleanup the memcg stats interfaces" (Shakeel Butt) Clean up our handling of the interrupt safety of some memcg stats "make vmalloc gfp flags usage more apparent" (Vishal Moola) Clean up vmalloc's handling of incoming GFP flags "mm: Add soft-dirty and uffd-wp support for RISC-V" (Chunyan Zhang) Teach soft dirty and userfaultfd write protect tracking to use RISC-V's Svrsw60t59b extension "mm: swap: small fixes and comment cleanups" (Youngjun Park) Fix a small bug and clean up some of the swap code "initial work on making VMA flags a bitmap" (Lorenzo Stoakes) Start work on converting the vma struct's flags to a bitmap, so we stop running out of them, especially on 32-bit "mm/swapfile: fix and cleanup swap list iterations" (Youngjun Park) Address a possible bug in the swap discard code and clean things up a little [ This merge also reverts commit ebb9aeb980e5 ("vfio/nvgrace-gpu: register device memory for poison handling") because it looks broken to me, I've asked for clarification - Linus ] * tag 'mm-stable-2025-12-03-21-26' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (321 commits) mm: fix vma_start_write_killable() signal handling mm/swapfile: use plist_for_each_entry in __folio_throttle_swaprate mm/swapfile: fix list iteration when next node is removed during discard fs/proc/task_mmu.c: fix make_uffd_wp_huge_pte() huge pte handling mm/kfence: add reboot notifier to disable KFENCE on shutdown memcg: remove inc/dec_lruvec_kmem_state helpers selftests/mm/uffd: initialize char variable to Null mm: fix DEBUG_RODATA_TEST indentation in Kconfig mm: introduce VMA flags bitmap type tools/testing/vma: eliminate dependency on vma->__vm_flags mm: simplify and rename mm flags function for clarity mm: declare VMA flags by bit zram: fix a spelling mistake mm/page_alloc: optimize lowmem_reserve max lookup using its semantic monotonicity mm/vmscan: skip increasing kswapd_failures when reclaim was boosted pagemap: update BUDDY flag documentation mm: swap: remove scan_swap_map_slots() references from comments mm: swap: change swap_alloc_slow() to void mm, swap: remove redundant comment for read_swap_cache_async mm, swap: use SWP_SOLIDSTATE to determine if swap is rotational ...

Merge tag 'vfs-6.19-rc1.directory.locking' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2025-12-02T00:13:46Z

Pull directory locking updates from Christian Brauner: "This contains the work to add centralized APIs for directory locking operations. This series is part of a larger effort to change directory operation locking to allow multiple concurrent operations in a directory. The ultimate goal is to lock the target dentry(s) rather than the whole parent directory. To help with changing the locking protocol, this series centralizes locking and lookup in new helper functions. The helpers establish a pattern where it is the dentry that is being locked and unlocked (currently the lock is held on dentry->d_parent->d_inode, but that can change in the future). This also changes vfs_mkdir() to unlock the parent on failure, as well as dput()ing the dentry. This allows end_creating() to only require the target dentry (which may be IS_ERR() after vfs_mkdir()), not the parent" * tag 'vfs-6.19-rc1.directory.locking' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: nfsd: fix end_creating() conversion VFS: introduce end_creating_keep() VFS: change vfs_mkdir() to unlock on failure. ecryptfs: use new start_creating/start_removing APIs Add start_renaming_two_dentries() VFS/ovl/smb: introduce start_renaming_dentry() VFS/nfsd/ovl: introduce start_renaming() and end_renaming() VFS: add start_creating_killable() and start_removing_killable() VFS: introduce start_removing_dentry() smb/server: use end_removing_noperm for for target of smb2_create_link() VFS: introduce start_creating_noperm() and start_removing_noperm() VFS/nfsd/cachefiles/ovl: introduce start_removing() and end_removing() VFS/nfsd/cachefiles/ovl: add start_creating() and end_creating() VFS: tidy up do_unlinkat() VFS: introduce start_dirop() and end_dirop() debugfs: rename end_creating() to debugfs_end_creating()

get rid of kill_litter_super()

2025-11-18T04:59:27Z

Not used anymore. Signed-off-by: Al Viro

doc: update porting, vfs documentation for mmap_prepare actions

2025-11-17T01:28:13Z

Now we have introduced the ability to specify that actions should be taken after a VMA is established via the vm_area_desc->action field as specified in mmap_prepare, update both the VFS documentation and the porting guide to describe this. Link: https://lkml.kernel.org/r/472ce3da7662ed1065cc299d14bffb70b1a845e7.1760959442.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes Reviewed-by: Jan Kara Cc: Alexander Gordeev Cc: Al Viro Cc: Andreas Larsson Cc: Andrey Konovalov Cc: Arnd Bergmann Cc: Baolin Wang Cc: Baoquan He Cc: Chatre, Reinette Cc: Christian Borntraeger Cc: Christian Brauner Cc: Dan Williams Cc: Dave Jiang Cc: Dave Martin Cc: Dave Young Cc: David Hildenbrand Cc: David S. Miller Cc: Dmitriy Vyukov Cc: Greg Kroah-Hartman Cc: Guo Ren Cc: Heiko Carstens Cc: Hugh Dickins Cc: James Morse Cc: Jann Horn Cc: Jason Gunthorpe Cc: Jonathan Corbet Cc: Kevin Tian Cc: Konstantin Komarov Cc: Liam Howlett Cc: "Luck, Tony" Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Mike Rapoport Cc: Muchun Song Cc: Nicolas Pitre Cc: Oscar Salvador Cc: Pedro Falcato Cc: Robin Murohy Cc: Sumanth Korikkar Cc: Suren Baghdasaryan Cc: Sven Schnelle Cc: Thomas Bogendoerfer Cc: "Uladzislau Rezki (Sony)" Cc: Vasily Gorbik Cc: Vishal Verma Cc: Vivek Goyal Cc: Vlastimil Babka Cc: Will Deacon Signed-off-by: Andrew Morton

VFS: change vfs_mkdir() to unlock on failure.

2025-11-14T12:15:58Z

vfs_mkdir() already drops the reference to the dentry on failure but it leaves the parent locked. This complicates end_creating() which needs to unlock the parent even though the dentry is no longer available. If we change vfs_mkdir() to unlock on failure as well as releasing the dentry, we can remove the "parent" arg from end_creating() and simplify the rules for calling it. Note that cachefiles_get_directory() can choose to substitute an error instead of actually calling vfs_mkdir(), for fault injection. In that case it needs to call end_creating(), just as vfs_mkdir() now does on error. ovl_create_real() will now unlock on error. So the conditional end_creating() after the call is removed, and end_creating() is called internally on error. Reviewed-by: Amir Goldstein Reviewed-by: Jeff Layton Tested-by: syzbot@syzkaller.appspotmail.com Signed-off-by: NeilBrown Link: https://patch.msgid.link/20251113002050.676694-15-neilb@ownmail.net Signed-off-by: Christian Brauner

Manual conversion to use ->i_state accessors of all places not covered by coccinelle

2025-10-20T18:22:26Z

Nothing to look at apart from iput_final(). Signed-off-by: Mateusz Guzik Signed-off-by: Christian Brauner

Merge tag 'pull-fs_context' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2025-10-03T17:51:44Z

Pull fs_context updates from Al Viro: "Change vfs_parse_fs_string() calling conventions Get rid of the length argument (almost all callers pass strlen() of the string argument there), add vfs_parse_fs_qstr() for the cases that do want separate length" * tag 'pull-fs_context' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: do_nfs4_mount(): switch to vfs_parse_fs_string() change the calling conventions for vfs_parse_fs_string()

Merge tag 'vfs-6.18-rc1.async' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2025-09-29T18:55:15Z

Pull vfs async directory updates from Christian Brauner: "This contains further preparatory changes for the asynchronous directory locking scheme: - Add lookup_one_positive_killable() which allows overlayfs to perform lookup that won't block on a fatal signal - Unify the mount idmap handling in struct renamedata as a rename can only happen within a single mount - Introduce kern_path_parent() for audit which sets the path to the parent and returns a dentry for the target without holding any locks on return - Rename kern_path_locked() as it is only used to prepare for the removal of an object from the filesystem: kern_path_locked() => start_removing_path() kern_path_create() => start_creating_path() user_path_create() => start_creating_user_path() user_path_locked_at() => start_removing_user_path_at() done_path_create() => end_creating_path() NA => end_removing_path()" * tag 'vfs-6.18-rc1.async' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: debugfs: rename start_creating() to debugfs_start_creating() VFS: rename kern_path_locked() and related functions. VFS/audit: introduce kern_path_parent() for audit VFS: unify old_mnt_idmap and new_mnt_idmap in renamedata VFS: discard err2 in filename_create() VFS/ovl: add lookup_one_positive_killable()

VFS: rename kern_path_locked() and related functions.

2025-09-23T10:37:36Z

kern_path_locked() is now only used to prepare for removing an object from the filesystem (and that is the only credible reason for wanting a positive locked dentry). Thus it corresponds to kern_path_create() and so should have a corresponding name. Unfortunately the name "kern_path_create" is somewhat misleading as it doesn't actually create anything. The recently added simple_start_creating() provides a better pattern I believe. The "start" can be matched with "end" to bracket the creating or removing. So this patch changes names: kern_path_locked -> start_removing_path kern_path_create -> start_creating_path user_path_create -> start_creating_user_path user_path_locked_at -> start_removing_user_path_at done_path_create -> end_creating_path and also introduces end_removing_path() which is identical to end_creating_path(). __start_removing_path (which was __kern_path_locked) is enhanced to call mnt_want_write() for consistency with the start_creating_path(). Reviewed-by: Amir Goldstein Signed-off-by: NeilBrown Signed-off-by: Christian Brauner