starfive-tech/linux.git/mm, branch rt-ethercat-release

mm/zsmalloc: Replace bit spinlock and get_cpu_var() usage.

2023-11-06T11:24:49+00:00

For efficiency reasons, zsmalloc is using a slim `handle'. The value is the address of a memory allocation of 4 or 8 bytes depending on the size of the long data type. The lowest bit in that allocated memory is used as a bit spin lock. The usage of the bit spin lock is problematic because with the bit spin lock held zsmalloc acquires a rwlock_t and spinlock_t which are both sleeping locks on PREEMPT_RT and therefore must not be acquired with disabled preemption. Extend the handle to struct zsmalloc_handle which holds the old handle as addr and a spinlock_t which replaces the bit spinlock. Replace all the wrapper functions accordingly. The usage of get_cpu_var() in zs_map_object() is problematic because it disables preemption and makes it impossible to acquire any sleeping lock on PREEMPT_RT such as a spinlock_t. Replace the get_cpu_var() usage with a local_lock_t which is embedded struct mapping_area. It ensures that the access the struct is synchronized against all users on the same CPU. This survived LTP testing. Signed-off-by: Mike Galbraith Signed-off-by: Thomas Gleixner [bigeasy: replace the bitspin_lock() with a mutex, get_locked_var() and patch description. Mike then fixed the size magic and made handle lock spinlock_t.] Signed-off-by: Sebastian Andrzej Siewior

mm/vmalloc: Another preempt disable region which sucks

2023-11-06T11:24:45+00:00

Avoid the preempt disable version of get_cpu_var(). The inner-lock should provide enough serialisation. Signed-off-by: Thomas Gleixner

mm: workingset: replace IRQ-off check with a lockdep assert.

2023-11-06T11:24:43+00:00

Commit 68d48e6a2df57 ("mm: workingset: add vmstat counter for shadow nodes") introduced an IRQ-off check to ensure that a lock is held which also disabled interrupts. This does not work the same way on -RT because none of the locks, that are held, disable interrupts. Replace this check with a lockdep assert which ensures that the lock is held. Cc: Peter Zijlstra Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Thomas Gleixner Link: https://lkml.kernel.org/r/20190211113829.sqf6bdi4c4cdd3rp@linutronix.de

sched: Remove preempt_offset argument from __might_sleep()

2023-11-06T11:24:42+00:00

All callers hand in 0 and never will hand in anything else. Signed-off-by: Thomas Gleixner Signed-off-by: Sebastian Andrzej Siewior Link: https://lore.kernel.org/r/20210923165358.054321586@linutronix.de

mm: Disable NUMA_BALANCING_DEFAULT_ENABLED and TRANSPARENT_HUGEPAGE on PREEMPT_RT

2023-11-06T11:24:39+00:00

TRANSPARENT_HUGEPAGE: There are potential non-deterministic delays to an RT thread if a critical memory region is not THP-aligned and a non-RT buffer is located in the same hugepage-aligned region. It's also possible for an unrelated thread to migrate pages belonging to an RT task incurring unexpected page faults due to memory defragmentation even if khugepaged is disabled. Regular HUGEPAGEs are not affected by this can be used. NUMA_BALANCING: There is a non-deterministic delay to mark PTEs PROT_NONE to gather NUMA fault samples, increased page faults of regions even if mlocked and non-deterministic delays when migrating pages. [Mel Gorman worded 99% of the commit description]. Link: https://lore.kernel.org/all/20200304091159.GN3818@techsingularity.net/ Link: https://lore.kernel.org/all/20211026165100.ahz5bkx44lrrw5pt@linutronix.de/ Cc: Mel Gorman Signed-off-by: Sebastian Andrzej Siewior Acked-by: Mel Gorman Link: https://lore.kernel.org/r/20211028143327.hfbxjze7palrpfgp@linutronix.de

mm: page_alloc: Use migrate_disable() in drain_local_pages_wq()

2023-11-06T11:24:39+00:00

drain_local_pages_wq() disables preemption to avoid CPU migration during CPU hotplug and can't use cpus_read_lock(). Using migrate_disable() works here, too. The scheduler won't take the CPU offline until the task left the migrate-disable section. The problem with disabled preemption here is that drain_local_pages() acquires locks which are turned into sleeping locks on PREEMPT_RT and can't be acquired with disabled preemption. Use migrate_disable() in drain_local_pages_wq(). Signed-off-by: Sebastian Andrzej Siewior Link: https://lore.kernel.org/r/20211015210933.viw6rjvo64qtqxn4@linutronix.de

mm: Disable zsmalloc on PREEMPT_RT

2023-11-06T11:24:38+00:00

For efficiency reasons, zsmalloc is using a slim `handle'. The value is the address of a memory allocation of 4 or 8 bytes depending on the size of the long data type. The lowest bit in that allocated memory is used as a bit spin lock. The usage of the bit spin lock is problematic because with the bit spin lock held zsmalloc acquires a rwlock_t and spinlock_t which are both sleeping locks on PREEMPT_RT and therefore must not be acquired with disabled preemption. There is a patch which extends the handle on PREEMPT_RT so that a full spinlock_t fits (even with lockdep enabled) and then eliminates the bit spin lock. I'm not sure how sensible zsmalloc on PREEMPT_RT is given that it is used to store compressed user memory. Disable ZSMALLOC on PREEMPT_RT. If there is need for it, we can try to get it to work. Signed-off-by: Sebastian Andrzej Siewior Link: https://lkml.kernel.org/r/20210923170121.1860133-1-bigeasy@linutronix.de

mm: page_alloc: fix building error on -Werror=array-compare

2023-07-10T07:16:48+00:00

Arthur Marsh reported we would hit the error below when building kernel with gcc-12: CC mm/page_alloc.o mm/page_alloc.c: In function `mem_init_print_info': mm/page_alloc.c:8173:27: error: comparison between two arrays [-Werror=array-compare] 8173 | if (start <= pos && pos < end && size > adj) \ | In C++20, the comparision between arrays should be warned. Link: https://lkml.kernel.org/r/20211125130928.32465-1-sxwjean@me.com Signed-off-by: Xiongwei Song Reported-by: Arthur Marsh Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/damon/core-test: fix wrong expectations for 'damon_split_regions_of()'

2021-10-29T00:18:55+00:00

Kunit test cases for 'damon_split_regions_of()' expects the number of regions after calling the function will be same to their request ('nr_sub'). However, the requested number is just an upper-limit, because the function randomly decides the size of each sub-region. This fixes the wrong expectation. Link: https://lkml.kernel.org/r/20211028090628.14948-1-sj@kernel.org Fixes: 17ccae8bb5c9 ("mm/damon: add kunit tests") Signed-off-by: SeongJae Park Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: khugepaged: skip huge page collapse for special files

2021-10-29T00:18:55+00:00

The read-only THP for filesystems will collapse THP for files opened readonly and mapped with VM_EXEC. The intended usecase is to avoid TLB misses for large text segments. But it doesn't restrict the file types so a THP could be collapsed for a non-regular file, for example, block device, if it is opened readonly and mapped with EXEC permission. This may cause bugs, like [1] and [2]. This is definitely not the intended usecase, so just collapse THP for regular files in order to close the attack surface. [shy828301@gmail.com: fix vm_file check [3]] Link: https://lore.kernel.org/lkml/CACkBjsYwLYLRmX8GpsDpMthagWOjWWrNxqY6ZLNQVr6yx+f5vA@mail.gmail.com/ [1] Link: https://lore.kernel.org/linux-mm/000000000000c6a82505ce284e4c@google.com/ [2] Link: https://lkml.kernel.org/r/CAHbLzkqTW9U3VvTu1Ki5v_cLRC9gHW+znBukg_ycergE0JWj-A@mail.gmail.com [3] Link: https://lkml.kernel.org/r/20211027195221.3825-1-shy828301@gmail.com Fixes: 99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shmem) FS") Signed-off-by: Hugh Dickins Signed-off-by: Yang Shi Reported-by: Hao Sun Reported-by: syzbot+aae069be1de40fb11825@syzkaller.appspotmail.com Cc: Matthew Wilcox Cc: Kirill A. Shutemov Cc: Song Liu Cc: Andrea Righi Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds