linux/mm/page_alloc.c, branch v6.4

Merge tag 'mm-stable-2023-05-03-16-22' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2023-05-04T20:09:43Z

Pull more MM updates from Andrew Morton: - Some DAMON cleanups from Kefeng Wang - Some KSM work from David Hildenbrand, to make the PR_SET_MEMORY_MERGE ioctl's behavior more similar to KSM's behavior. [ Andrew called these "final", but I suspect we'll have a series fixing up the fact that the last commit in the dmapools series in the previous pull seems to have unintentionally just reverted all the other commits in the same series.. - Linus ] * tag 'mm-stable-2023-05-03-16-22' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: mm: hwpoison: coredump: support recovery from dump_user_range() mm/page_alloc: add some comments to explain the possible hole in __pageblock_pfn_to_page() mm/ksm: move disabling KSM from s390/gmap code to KSM code selftests/ksm: ksm_functional_tests: add prctl unmerge test mm/ksm: unmerge and clear VM_MERGEABLE when setting PR_SET_MEMORY_MERGE=0 mm/damon/paddr: fix missing folio_sz update in damon_pa_young() mm/damon/paddr: minor refactor of damon_pa_mark_accessed_or_deactivate() mm/damon/paddr: minor refactor of damon_pa_pageout()

mm/page_alloc: add some comments to explain the possible hole in __pageblock_pfn_to_page()

2023-05-03T00:21:50Z

Now the __pageblock_pfn_to_page() is used by set_zone_contiguous(), which checks whether the given zone contains holes, and uses pfn_to_online_page() to validate if the start pfn is online and valid, as well as using pfn_valid() to validate the end pfn. However, the __pageblock_pfn_to_page() function may return non-NULL even if the end pfn of a pageblock is in a memory hole in some situations. For example, if the pageblock order is MAX_ORDER, which will fall into 2 sub-sections, and the end pfn of the pageblock may be hole even though the start pfn is online and valid. See below memory layout as an example and suppose the pageblock order is MAX_ORDER. [ 0.000000] Zone ranges: [ 0.000000] DMA [mem 0x0000000040000000-0x00000000ffffffff] [ 0.000000] DMA32 empty [ 0.000000] Normal [mem 0x0000000100000000-0x0000001fa7ffffff] [ 0.000000] Movable zone start for each node [ 0.000000] Early memory node ranges [ 0.000000] node 0: [mem 0x0000000040000000-0x0000001fa3c7ffff] [ 0.000000] node 0: [mem 0x0000001fa3c80000-0x0000001fa3ffffff] [ 0.000000] node 0: [mem 0x0000001fa4000000-0x0000001fa402ffff] [ 0.000000] node 0: [mem 0x0000001fa4030000-0x0000001fa40effff] [ 0.000000] node 0: [mem 0x0000001fa40f0000-0x0000001fa73cffff] [ 0.000000] node 0: [mem 0x0000001fa73d0000-0x0000001fa745ffff] [ 0.000000] node 0: [mem 0x0000001fa7460000-0x0000001fa746ffff] [ 0.000000] node 0: [mem 0x0000001fa7470000-0x0000001fa758ffff] [ 0.000000] node 0: [mem 0x0000001fa7590000-0x0000001fa7dfffff] Focus on the last memory range, and there is a hole for the range [mem 0x0000001fa7590000-0x0000001fa7dfffff]. That means the last pageblock will contain the range from 0x1fa7c00000 to 0x1fa7ffffff, since the pageblock must be 4M aligned. And in this pageblock, these pfns will fall into 2 sub-section (the sub-section size is 2M aligned). So, the 1st sub-section (indicates pfn range: 0x1fa7c00000 - 0x1fa7dfffff ) in this pageblock is valid by calling subsection_map_init() in free_area_init(), but the 2nd sub-section (indicates pfn range: 0x1fa7e00000 - 0x1fa7ffffff ) in this pageblock is not valid. This did not break anything until now, but the zone continuous is fragile in this possible scenario. So as previous discussion[1], it is better to add some comments to explain this possible issue in case there are some future pfn walkers that rely on this. [1] https://lore.kernel.org/all/87r0sdsmr6.fsf@yhuang6-desk2.ccr.corp.intel.com/ Link: https://lkml.kernel.org/r/5c26368865e79c743a453dea48d30670b19d2e4f.1682425534.git.baolin.wang@linux.alibaba.com Link: https://lkml.kernel.org/r/5c26368865e79c743a453dea48d30670b19d2e4f.1682425534.git.baolin.wang@linux.alibaba.com Signed-off-by: Baolin Wang Acked-by: Michal Hocko Reviewed-by: "Huang, Ying" Cc: Baolin Wang Cc: David Hildenbrand Cc: Mel Gorman Cc: Mike Rapoport (IBM) Cc: Vlastimil Babka Signed-off-by: Andrew Morton

Merge tag 'cgroup-for-6.4' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

2023-04-29T17:05:22Z

Pull cgroup updates from Tejun Heo: - cpuset changes including the fix for an incorrect interaction with CPU hotplug and an optimization - Other doc and cosmetic changes * tag 'cgroup-for-6.4' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: docs: cgroup-v1/cpusets: update libcgroup project link cgroup/cpuset: Minor updates to test_cpuset_prs.sh cgroup/cpuset: Include offline CPUs when tasks' cpumasks in top_cpuset are updated cgroup/cpuset: Skip task update if hotplug doesn't affect current cpuset cpuset: Clean up cpuset_node_allowed cgroup: bpf: use cgroup_lock()/cgroup_unlock() wrappers

mm, page_alloc: use check_pages_enabled static key to check tail pages

2023-04-18T23:29:54Z

Commit 700d2e9a36b9 ("mm, page_alloc: reduce page alloc/free sanity checks") has introduced a new static key check_pages_enabled to control when struct pages are sanity checked during allocation and freeing. Mel Gorman suggested that free_tail_pages_check() could use this static key as well, instead of relying on CONFIG_DEBUG_VM. That makes sense, so do that. Also rename the function to free_tail_page_prepare() because it works on a single tail page and has a struct page preparation component as well as the optional checking component. Also remove some unnecessary unlikely() within static_branch_unlikely() statements that Mel pointed out for commit 700d2e9a36b9. Link: https://lkml.kernel.org/r/20230405142840.11068-1-vbabka@suse.cz Signed-off-by: Vlastimil Babka Suggested-by: Mel Gorman Acked-by: Mel Gorman Cc: Alexander Halbuer Cc: Kees Cook Signed-off-by: Andrew Morton

sync mm-stable with mm-hotfixes-stable to pick up depended-upon upstream changes

2023-04-18T21:53:49Z

mm: page_alloc: skip regions with hugetlbfs pages when allocating 1G pages

2023-04-18T21:22:14Z

A bug was reported by Yuanxi Liu where allocating 1G pages at runtime is taking an excessive amount of time for large amounts of memory. Further testing allocating huge pages that the cost is linear i.e. if allocating 1G pages in batches of 10 then the time to allocate nr_hugepages from 10->20->30->etc increases linearly even though 10 pages are allocated at each step. Profiles indicated that much of the time is spent checking the validity within already existing huge pages and then attempting a migration that fails after isolating the range, draining pages and a whole lot of other useless work. Commit eb14d4eefdc4 ("mm,page_alloc: drop unnecessary checks from pfn_range_valid_contig") removed two checks, one which ignored huge pages for contiguous allocations as huge pages can sometimes migrate. While there may be value on migrating a 2M page to satisfy a 1G allocation, it's potentially expensive if the 1G allocation fails and it's pointless to try moving a 1G page for a new 1G allocation or scan the tail pages for valid PFNs. Reintroduce the PageHuge check and assume any contiguous region with hugetlbfs pages is unsuitable for a new 1G allocation. The hpagealloc test allocates huge pages in batches and reports the average latency per page over time. This test happens just after boot when fragmentation is not an issue. Units are in milliseconds. hpagealloc 6.3.0-rc6 6.3.0-rc6 6.3.0-rc6 vanilla hugeallocrevert-v1r1 hugeallocsimple-v1r2 Min Latency 26.42 ( 0.00%) 5.07 ( 80.82%) 18.94 ( 28.30%) 1st-qrtle Latency 356.61 ( 0.00%) 5.34 ( 98.50%) 19.85 ( 94.43%) 2nd-qrtle Latency 697.26 ( 0.00%) 5.47 ( 99.22%) 20.44 ( 97.07%) 3rd-qrtle Latency 972.94 ( 0.00%) 5.50 ( 99.43%) 20.81 ( 97.86%) Max-1 Latency 26.42 ( 0.00%) 5.07 ( 80.82%) 18.94 ( 28.30%) Max-5 Latency 82.14 ( 0.00%) 5.11 ( 93.78%) 19.31 ( 76.49%) Max-10 Latency 150.54 ( 0.00%) 5.20 ( 96.55%) 19.43 ( 87.09%) Max-90 Latency 1164.45 ( 0.00%) 5.53 ( 99.52%) 20.97 ( 98.20%) Max-95 Latency 1223.06 ( 0.00%) 5.55 ( 99.55%) 21.06 ( 98.28%) Max-99 Latency 1278.67 ( 0.00%) 5.57 ( 99.56%) 22.56 ( 98.24%) Max Latency 1310.90 ( 0.00%) 8.06 ( 99.39%) 26.62 ( 97.97%) Amean Latency 678.36 ( 0.00%) 5.44 * 99.20%* 20.44 * 96.99%* 6.3.0-rc6 6.3.0-rc6 6.3.0-rc6 vanilla revert-v1 hugeallocfix-v2 Duration User 0.28 0.27 0.30 Duration System 808.66 17.77 35.99 Duration Elapsed 830.87 18.08 36.33 The vanilla kernel is poor, taking up to 1.3 second to allocate a huge page and almost 10 minutes in total to run the test. Reverting the problematic commit reduces it to 8ms at worst and the patch takes 26ms. This patch fixes the main issue with skipping huge pages but leaves the page_count() out because a page with an elevated count potentially can migrate. BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=217022 Link: https://lkml.kernel.org/r/20230414141429.pwgieuwluxwez3rj@techsingularity.net Fixes: eb14d4eefdc4 ("mm,page_alloc: drop unnecessary checks from pfn_range_valid_contig") Signed-off-by: Mel Gorman Reported-by: Yuanxi Liu Acked-by: Vlastimil Babka Reviewed-by: David Hildenbrand Acked-by: Michal Hocko Reviewed-by: Oscar Salvador Cc: Matthew Wilcox Cc: Signed-off-by: Andrew Morton

mm/page_alloc: fix potential deadlock on zonelist_update_seq seqlock

2023-04-18T21:22:12Z

syzbot is reporting circular locking dependency which involves zonelist_update_seq seqlock [1], for this lock is checked by memory allocation requests which do not need to be retried. One deadlock scenario is kmalloc(GFP_ATOMIC) from an interrupt handler. CPU0 ---- __build_all_zonelists() { write_seqlock(&zonelist_update_seq); // makes zonelist_update_seq.seqcount odd // e.g. timer interrupt handler runs at this moment some_timer_func() { kmalloc(GFP_ATOMIC) { __alloc_pages_slowpath() { read_seqbegin(&zonelist_update_seq) { // spins forever because zonelist_update_seq.seqcount is odd } } } } // e.g. timer interrupt handler finishes write_sequnlock(&zonelist_update_seq); // makes zonelist_update_seq.seqcount even } This deadlock scenario can be easily eliminated by not calling read_seqbegin(&zonelist_update_seq) from !__GFP_DIRECT_RECLAIM allocation requests, for retry is applicable to only __GFP_DIRECT_RECLAIM allocation requests. But Michal Hocko does not know whether we should go with this approach. Another deadlock scenario which syzbot is reporting is a race between kmalloc(GFP_ATOMIC) from tty_insert_flip_string_and_push_buffer() with port->lock held and printk() from __build_all_zonelists() with zonelist_update_seq held. CPU0 CPU1 ---- ---- pty_write() { tty_insert_flip_string_and_push_buffer() { __build_all_zonelists() { write_seqlock(&zonelist_update_seq); build_zonelists() { printk() { vprintk() { vprintk_default() { vprintk_emit() { console_unlock() { console_flush_all() { console_emit_next_record() { con->write() = serial8250_console_write() { spin_lock_irqsave(&port->lock, flags); tty_insert_flip_string() { tty_insert_flip_string_fixed_flag() { __tty_buffer_request_room() { tty_buffer_alloc() { kmalloc(GFP_ATOMIC | __GFP_NOWARN) { __alloc_pages_slowpath() { zonelist_iter_begin() { read_seqbegin(&zonelist_update_seq); // spins forever because zonelist_update_seq.seqcount is odd spin_lock_irqsave(&port->lock, flags); // spins forever because port->lock is held } } } } } } } } spin_unlock_irqrestore(&port->lock, flags); // message is printed to console spin_unlock_irqrestore(&port->lock, flags); } } } } } } } } } write_sequnlock(&zonelist_update_seq); } } } This deadlock scenario can be eliminated by preventing interrupt context from calling kmalloc(GFP_ATOMIC) and preventing printk() from calling console_flush_all() while zonelist_update_seq.seqcount is odd. Since Petr Mladek thinks that __build_all_zonelists() can become a candidate for deferring printk() [2], let's address this problem by disabling local interrupts in order to avoid kmalloc(GFP_ATOMIC) and disabling synchronous printk() in order to avoid console_flush_all() . As a side effect of minimizing duration of zonelist_update_seq.seqcount being odd by disabling synchronous printk(), latency at read_seqbegin(&zonelist_update_seq) for both !__GFP_DIRECT_RECLAIM and __GFP_DIRECT_RECLAIM allocation requests will be reduced. Although, from lockdep perspective, not calling read_seqbegin(&zonelist_update_seq) (i.e. do not record unnecessary locking dependency) from interrupt context is still preferable, even if we don't allow calling kmalloc(GFP_ATOMIC) inside write_seqlock(&zonelist_update_seq)/write_sequnlock(&zonelist_update_seq) section... Link: https://lkml.kernel.org/r/8796b95c-3da3-5885-fddd-6ef55f30e4d3@I-love.SAKURA.ne.jp Fixes: 3d36424b3b58 ("mm/page_alloc: fix race condition between build_all_zonelists and page allocation") Link: https://lkml.kernel.org/r/ZCrs+1cDqPWTDFNM@alley [2] Reported-by: syzbot Link: https://syzkaller.appspot.com/bug?extid=223c7461c58c58a4cb10 [1] Signed-off-by: Tetsuo Handa Acked-by: Michal Hocko Acked-by: Mel Gorman Cc: Petr Mladek Cc: David Hildenbrand Cc: Ilpo Järvinen Cc: John Ogness Cc: Patrick Daly Cc: Sergey Senozhatsky Cc: Steven Rostedt Cc: Signed-off-by: Andrew Morton

mm: move mem_init_print_info() to mm_init.c

2023-04-06T02:42:54Z

mem_init_print_info() is only called from mm_core_init(). Move it close to the caller and make it static. Link: https://lkml.kernel.org/r/20230321170513.2401534-12-rppt@kernel.org Signed-off-by: Mike Rapoport (IBM) Acked-by: David Hildenbrand Reviewed-by: Vlastimil Babka Cc: Doug Berger Cc: Matthew Wilcox (Oracle) Cc: Mel Gorman Cc: Michal Hocko Cc: Thomas Bogendoerfer Signed-off-by: Andrew Morton

mm: move init_mem_debugging_and_hardening() to mm/mm_init.c

2023-04-06T02:42:54Z

init_mem_debugging_and_hardening() is only called from mm_core_init(). Move it close to the caller, make it static and rename it to mem_debugging_and_hardening_init() for consistency with surrounding convention. Link: https://lkml.kernel.org/r/20230321170513.2401534-10-rppt@kernel.org Signed-off-by: Mike Rapoport (IBM) Acked-by: David Hildenbrand Reviewed-by: Vlastimil Babka Cc: Doug Berger Cc: Matthew Wilcox (Oracle) Cc: Mel Gorman Cc: Michal Hocko Cc: Thomas Bogendoerfer Signed-off-by: Andrew Morton

mm/page_alloc: rename page_alloc_init() to page_alloc_init_cpuhp()

2023-04-06T02:42:53Z

The page_alloc_init() name is really misleading because all this function does is sets up CPU hotplug callbacks for the page allocator. Rename it to page_alloc_init_cpuhp() so that name will reflect what the function does. Link: https://lkml.kernel.org/r/20230321170513.2401534-6-rppt@kernel.org Signed-off-by: Mike Rapoport (IBM) Reviewed-by: David Hildenbrand Reviewed-by: Vlastimil Babka Cc: Doug Berger Cc: Matthew Wilcox (Oracle) Cc: Mel Gorman Cc: Michal Hocko Cc: Thomas Bogendoerfer Signed-off-by: Andrew Morton