From: Stefan Roesch shr@devkernel.io
mainline inclusion from mainline-v6.7-rc1 commit 3c6f33b7273a7e2f2b2497b62c8400bd957b2fbe category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I9GT87
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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Patch series "mm/ksm: add fork-exec support for prctl", v4.
A process can enable KSM with the prctl system call. When the process is forked the KSM flag is inherited by the child process. However if the process is executing an exec system call directly after the fork, the KSM setting is cleared. This patch series addresses this problem.
1) Change the mask in coredump.h for execing a new process 2) Add a new test case in ksm_functional_tests
This patch (of 2):
Today we have two ways to enable KSM:
1) madvise system call This allows to enable KSM for a memory region for a long time.
2) prctl system call This is a recent addition to enable KSM for the complete process. In addition when a process is forked, the KSM setting is inherited.
This change only affects the second case.
One of the use cases for (2) was to support the ability to enable KSM for cgroups. This allows systemd to enable KSM for the seed process. By enabling it in the seed process all child processes inherit the setting.
This works correctly when the process is forked. However it doesn't support fork/exec workflow.
From the previous cover letter:
.... Use case 3: With the madvise call sharing opportunities are only enabled for the current process: it is a workload-local decision. A considerable number of sharing opportunities may exist across multiple workloads or jobs (if they are part of the same security domain). Only a higler level entity like a job scheduler or container can know for certain if its running one or more instances of a job. That job scheduler however doesn't have the necessary internal workload knowledge to make targeted madvise calls. ....
In addition it can also be a bit surprising that fork keeps the KSM setting and fork/exec does not.
Link: https://lkml.kernel.org/r/20230922211141.320789-1-shr@devkernel.io Link: https://lkml.kernel.org/r/20230922211141.320789-2-shr@devkernel.io Signed-off-by: Stefan Roesch shr@devkernel.io Fixes: d7597f59d1d3 ("mm: add new api to enable ksm per process") Reviewed-by: David Hildenbrand david@redhat.com Reported-by: Carl Klemm carl@uvos.xyz Tested-by: Carl Klemm carl@uvos.xyz Cc: Johannes Weiner hannes@cmpxchg.org Cc: Rik van Riel riel@surriel.com Signed-off-by: Andrew Morton akpm@linux-foundation.org
Conflicts: include/linux/sched/coredump.h [Context conflicts.] Signed-off-by: Jinjiang Tu tujinjiang@huawei.com --- include/linux/sched/coredump.h | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/include/linux/sched/coredump.h b/include/linux/sched/coredump.h index 6a4d85c7a5f3..103ca84e379c 100644 --- a/include/linux/sched/coredump.h +++ b/include/linux/sched/coredump.h @@ -70,13 +70,15 @@ static inline int get_dumpable(struct mm_struct *mm) #define MMF_UNSTABLE 22 /* mm is unstable for copy_from_user */ #define MMF_HUGE_ZERO_PAGE 23 /* mm has ever used the global huge zero page */ #define MMF_DISABLE_THP 24 /* disable THP for all VMAs */ +#define MMF_DISABLE_THP_MASK (1 << MMF_DISABLE_THP) #define MMF_OOM_VICTIM 25 /* mm is the oom victim */ #define MMF_OOM_REAP_QUEUED 26 /* mm was queued for oom_reaper */ #define MMF_MULTIPROCESS 27 /* mm is shared between processes */ -#define MMF_DISABLE_THP_MASK (1 << MMF_DISABLE_THP) +#define MMF_VM_MERGE_ANY 29 +#define MMF_VM_MERGE_ANY_MASK (1 << MMF_VM_MERGE_ANY)
#define MMF_INIT_MASK (MMF_DUMPABLE_MASK | MMF_DUMP_FILTER_MASK |\ - MMF_DISABLE_THP_MASK) + MMF_DISABLE_THP_MASK | MMF_VM_MERGE_ANY_MASK)
#define MMF_VM_MERGE_ANY 29 #endif /* _LINUX_SCHED_COREDUMP_H */