linux/Documentation/admin-guide/sysctl, branch v6.15

Merge tag 'fuse-update-6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse

2025-04-02T23:36:59Z

Pull fuse updates from Miklos Szeredi: - Allow connection to server to time out (Joanne Koong) - If server doesn't support creating a hard link, return EPERM rather than ENOSYS (Matt Johnston) - Allow file names longer than 1024 chars (Bernd Schubert) - Fix a possible race if request on io_uring queue is interrupted (Bernd Schubert) - Misc fixes and cleanups * tag 'fuse-update-6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse: fuse: remove unneeded atomic set in uring creation fuse: fix uring race condition for null dereference of fc fuse: Increase FUSE_NAME_MAX to PATH_MAX fuse: Allocate only namelen buf memory in fuse_notify_ fuse: add default_request_timeout and max_request_timeout sysctls fuse: add kernel-enforced timeout option for requests fuse: optmize missing FUSE_LINK support fuse: Return EPERM rather than ENOSYS from link() fuse: removed unused function fuse_uring_create() from header fuse: {io-uring} Fix a possible req cancellation race

fuse: add default_request_timeout and max_request_timeout sysctls

2025-03-31T12:59:27Z

Introduce two new sysctls, "default_request_timeout" and "max_request_timeout". These control how long (in seconds) a server can take to reply to a request. If the server does not reply by the timeout, then the connection will be aborted. The upper bound on these sysctl values is 65535. "default_request_timeout" sets the default timeout if no timeout is specified by the fuse server on mount. 0 (default) indicates no default timeout should be enforced. If the server did specify a timeout, then default_request_timeout will be ignored. "max_request_timeout" sets the max amount of time the server may take to reply to a request. 0 (default) indicates no maximum timeout. If max_request_timeout is set and the fuse server attempts to set a timeout greater than max_request_timeout, the system will use max_request_timeout as the timeout. Similarly, if default_request_timeout is greater than max_request_timeout, the system will use max_request_timeout as the timeout. If the server does not request a timeout and default_request_timeout is set to 0 but max_request_timeout is set, then the timeout will be max_request_timeout. Please note that these timeouts are not 100% precise. The request may take roughly an extra FUSE_TIMEOUT_TIMER_FREQ seconds beyond the set max timeout due to how it's internally implemented. $ sysctl -a | grep fuse.default_request_timeout fs.fuse.default_request_timeout = 0 $ echo 65536 | sudo tee /proc/sys/fs/fuse/default_request_timeout tee: /proc/sys/fs/fuse/default_request_timeout: Invalid argument $ echo 65535 | sudo tee /proc/sys/fs/fuse/default_request_timeout 65535 $ sysctl -a | grep fuse.default_request_timeout fs.fuse.default_request_timeout = 65535 $ echo 0 | sudo tee /proc/sys/fs/fuse/default_request_timeout 0 $ sysctl -a | grep fuse.default_request_timeout fs.fuse.default_request_timeout = 0 [Luis Henriques: Limit the timeout to the range [FUSE_TIMEOUT_TIMER_FREQ, fuse_max_req_timeout]] Signed-off-by: Joanne Koong Reviewed-by: Bernd Schubert Reviewed-by: Josef Bacik Reviewed-by: Sergey Senozhatsky Reviewed-by: Luis Henriques Reviewed-by: Jeff Layton Signed-off-by: Miklos Szeredi

mm: page_alloc: defrag_mode

2025-03-18T05:07:07Z

The page allocator groups requests by migratetype to stave off fragmentation. However, in practice this is routinely defeated by the fact that it gives up *before* invoking reclaim and compaction - which may well produce suitable pages. As a result, fragmentation of physical memory is a common ongoing process in many load scenarios. Fragmentation deteriorates compaction's ability to produce huge pages. Depending on the lifetime of the fragmenting allocations, those effects can be long-lasting or even permanent, requiring drastic measures like forcible idle states or even reboots as the only reliable ways to recover the address space for THP production. In a kernel build test with supplemental THP pressure, the THP allocation rate steadily declines over 15 runs: thp_fault_alloc 61988 56474 57258 50187 52388 55409 52925 47648 43669 40621 36077 41721 36685 34641 33215 This is a hurdle in adopting THP in any environment where hosts are shared between multiple overlapping workloads (cloud environments), and rarely experience true idle periods. To make THP a reliable and predictable optimization, there needs to be a stronger guarantee to avoid such fragmentation. Introduce defrag_mode. When enabled, reclaim/compaction is invoked to its full extent *before* falling back. Specifically, ALLOC_NOFRAGMENT is enforced on the allocator fastpath and the reclaiming slowpath. For now, fallbacks are permitted to avert OOMs. There is a plan to add defrag_mode=2 to prefer OOMs over fragmentation, but this requires additional prep work in compaction and the reserve management to make it ready for all possible allocation contexts. The following test results are from a kernel build with periodic bursts of THP allocations, over 15 runs: vanilla defrag_mode=1 @claimer[unmovable]: 189 103 @claimer[movable]: 92 103 @claimer[reclaimable]: 207 61 @pollute[unmovable from movable]: 25 0 @pollute[unmovable from reclaimable]: 28 0 @pollute[movable from unmovable]: 38835 0 @pollute[movable from reclaimable]: 147136 0 @pollute[reclaimable from unmovable]: 178 0 @pollute[reclaimable from movable]: 33 0 @steal[unmovable from movable]: 11 0 @steal[unmovable from reclaimable]: 5 0 @steal[reclaimable from unmovable]: 107 0 @steal[reclaimable from movable]: 90 0 @steal[movable from reclaimable]: 354 0 @steal[movable from unmovable]: 130 0 Both types of polluting fallbacks are eliminated in this workload. Interestingly, whole block conversions are reduced as well. This is because once a block is claimed for a type, its empty space remains available for future allocations, instead of being padded with fallbacks; this allows the native type to group up instead of spreading out to new blocks. The assumption in the allocator has been that pollution from movable allocations is less harmful than from other types, since they can be reclaimed or migrated out should the space be needed. However, since fallbacks occur *before* reclaim/compaction is invoked, movable pollution will still cause non-movable allocations to spread out and claim more blocks. Without fragmentation, THP rates hold steady with defrag_mode=1: thp_fault_alloc 32478 20725 45045 32130 14018 21711 40791 29134 34458 45381 28305 17265 22584 28454 30850 While the downward trend is eliminated, the keen reader will of course notice that the baseline rate is much smaller than the vanilla kernel's to begin with. This is due to deficiencies in how reclaim and compaction are currently driven: ALLOC_NOFRAGMENT increases the extent to which smaller allocations are competing with THPs for pageblocks, while making no effort themselves to reclaim or compact beyond their own request size. This effect already exists with the current usage of ALLOC_NOFRAGMENT, but is amplified by defrag_mode insisting on whole block stealing much more strongly. Subsequent patches will address defrag_mode reclaim strategy to raise the THP success baseline above the vanilla kernel. Link: https://lkml.kernel.org/r/20250313210647.1314586-4-hannes@cmpxchg.org Signed-off-by: Johannes Weiner Cc: Mel Gorman Cc: Vlastimil Babka Cc: Zi Yan Signed-off-by: Andrew Morton

coredump: Only sort VMAs when core_sort_vma sysctl is set

2025-02-24T18:51:57Z

The sorting of VMAs by size in commit 7d442a33bfe8 ("binfmt_elf: Dump smaller VMAs first in ELF cores") breaks elfutils[1]. Instead, sort based on the setting of the new sysctl, core_sort_vma, which defaults to 0, no sorting. Reported-by: Michael Stapelberg Closes: https://lore.kernel.org/all/20250218085407.61126-1-michael@stapelberg.de/ [1] Fixes: 7d442a33bfe8 ("binfmt_elf: Dump smaller VMAs first in ELF cores") Signed-off-by: Kees Cook

Documentation/sysctl: Add timer_migration to kernel.rst

2025-01-16T18:18:04Z

There is no mention of timer_migration in the docs. Add a short description. Signed-off-by: Phil Auld Cc: Jonathan Corbet Cc: linux-doc@vger.kernel.org Signed-off-by: Jonathan Corbet Link: https://lore.kernel.org/r/20250114190525.169022-1-pauld@redhat.com

docs: remove duplicate word

2024-12-11T16:07:40Z

- Remove duplicate word, 'to'. Signed-off-by: Jonathan Corbet Link: https://lore.kernel.org/r/20241120043414.78811-1-RuffaloLavoisier@gmail.com

Merge tag 'fuse-update-6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse

2024-11-26T20:41:27Z

Pull fuse updates from Miklos Szeredi: - Add page -> folio conversions (Joanne Koong, Josef Bacik) - Allow max size of fuse requests to be configurable with a sysctl (Joanne Koong) - Allow FOPEN_DIRECT_IO to take advantage of async code path (yangyun) - Fix large kernel reads (like a module load) in virtio_fs (Hou Tao) - Fix attribute inconsistency in case readdirplus (and plain lookup in corner cases) is racing with inode eviction (Zhang Tianci) - Fix a WARN_ON triggered by virtio_fs (Asahi Lina) * tag 'fuse-update-6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse: (30 commits) virtiofs: dax: remove ->writepages() callback fuse: check attributes staleness on fuse_iget() fuse: remove pages for requests and exclusively use folios fuse: convert direct io to use folios mm/writeback: add folio_mark_dirty_lock() fuse: convert writebacks to use folios fuse: convert retrieves to use folios fuse: convert ioctls to use folios fuse: convert writes (non-writeback) to use folios fuse: convert reads to use folios fuse: convert readdir to use folios fuse: convert readlink to use folios fuse: convert cuse to use folios fuse: add support in virtio for requests using folios fuse: support folios in struct fuse_args_pages and fuse_copy_pages() fuse: convert fuse_notify_store to use folios fuse: convert fuse_retrieve to use folios fuse: use the folio based vmstat helpers fuse: convert fuse_writepage_need_send to take a folio fuse: convert fuse_do_readpage to use folios ...

Merge tag 'mm-nonmm-stable-2024-11-24-02-05' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2024-11-26T00:09:48Z

Pull non-MM updates from Andrew Morton: - The series "resource: A couple of cleanups" from Andy Shevchenko performs some cleanups in the resource management code - The series "Improve the copy of task comm" from Yafang Shao addresses possible race-induced overflows in the management of task_struct.comm[] - The series "Remove unnecessary header includes from {tools/}lib/list_sort.c" from Kuan-Wei Chiu adds some cleanups and a small fix to the list_sort library code and to its selftest - The series "Enhance min heap API with non-inline functions and optimizations" also from Kuan-Wei Chiu optimizes and cleans up the min_heap library code - The series "nilfs2: Finish folio conversion" from Ryusuke Konishi finishes off nilfs2's folioification - The series "add detect count for hung tasks" from Lance Yang adds more userspace visibility into the hung-task detector's activity - Apart from that, singelton patches in many places - please see the individual changelogs for details * tag 'mm-nonmm-stable-2024-11-24-02-05' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (71 commits) gdb: lx-symbols: do not error out on monolithic build kernel/reboot: replace sprintf() with sysfs_emit() lib: util_macros_kunit: add kunit test for util_macros.h util_macros.h: fix/rework find_closest() macros Improve consistency of '#error' directive messages ocfs2: fix uninitialized value in ocfs2_file_read_iter() hung_task: add docs for hung_task_detect_count hung_task: add detect count for hung tasks dma-buf: use atomic64_inc_return() in dma_buf_getfile() fs/proc/kcore.c: fix coccinelle reported ERROR instances resource: avoid unnecessary resource tree walking in __region_intersects() ocfs2: remove unused errmsg function and table ocfs2: cluster: fix a typo lib/scatterlist: use sg_phys() helper checkpatch: always parse orig_commit in fixes tag nilfs2: convert metadata aops from writepage to writepages nilfs2: convert nilfs_recovery_copy_block() to take a folio nilfs2: convert nilfs_page_count_clean_buffers() to take a folio nilfs2: remove nilfs_writepage nilfs2: convert checkpoint file to be folio-based ...

hung_task: add docs for hung_task_detect_count

2024-11-12T01:17:03Z

This commit introduces documentation for hung_task_detect_count in kernel.rst. Link: https://lkml.kernel.org/r/20241027120747.42833-3-ioworker0@gmail.com Signed-off-by: Mingzhe Yang Signed-off-by: Lance Yang Cc: Bang Li Cc: Baolin Wang Cc: David Hildenbrand Cc: Huang Cun Cc: Joel Granados Cc: Joel Granados Cc: John Siddle Cc: Kent Overstreet Cc: Ryan Roberts Cc: Thomas Weißschuh Cc: Yongliang Gao Cc: Zi Yan Signed-off-by: Andrew Morton

fuse: enable dynamic configuration of fuse max pages limit (FUSE_MAX_MAX_PAGES)

2024-10-25T15:05:49Z

Introduce the capability to dynamically configure the max pages limit (FUSE_MAX_MAX_PAGES) through a sysctl. This allows system administrators to dynamically set the maximum number of pages that can be used for servicing requests in fuse. Previously, this is gated by FUSE_MAX_MAX_PAGES which is statically set to 256 pages. One result of this is that the buffer size for a write request is limited to 1 MiB on a 4k-page system. The default value for this sysctl is the original limit (256 pages). $ sysctl -a | grep max_pages_limit fs.fuse.max_pages_limit = 256 $ sysctl -n fs.fuse.max_pages_limit 256 $ echo 1024 | sudo tee /proc/sys/fs/fuse/max_pages_limit 1024 $ sysctl -n fs.fuse.max_pages_limit 1024 $ echo 65536 | sudo tee /proc/sys/fs/fuse/max_pages_limit tee: /proc/sys/fs/fuse/max_pages_limit: Invalid argument $ echo 0 | sudo tee /proc/sys/fs/fuse/max_pages_limit tee: /proc/sys/fs/fuse/max_pages_limit: Invalid argument $ echo 65535 | sudo tee /proc/sys/fs/fuse/max_pages_limit 65535 $ sysctl -n fs.fuse.max_pages_limit 65535 Signed-off-by: Joanne Koong Reviewed-by: Josef Bacik Reviewed-by: Sweet Tea Dorminy Signed-off-by: Miklos Szeredi