The patch titled
Subject: mm: introduce mmap_lock_speculation_{begin|end}
has been added to the -mm mm-unstable branch. Its filename is
mm-introduce-mmap_lock_speculation_beginend.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-introduce-mmap_lock_speculation_beginend.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Subject: mm: introduce mmap_lock_speculation_{begin|end}
Date: Thu, 24 Oct 2024 13:52:31 -0700
Add helper functions to speculatively perform operations without
read-locking mmap_lock, expecting that mmap_lock will not be write-locked
and mm is not modified from under us.
Link: https://lkml.kernel.org/r/20241024205231.1944747-2-surenb@xxxxxxxxxx
Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Andrii Nakryiko <andrii@xxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Christian Brauner <brauner@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: <hca@xxxxxxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Cc: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Shakeel Butt <shakeel.butt@xxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Wei Yang <richard.weiyang@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/mmap_lock.h | 29 +++++++++++++++++++++++++++--
1 file changed, 27 insertions(+), 2 deletions(-)
--- a/include/linux/mmap_lock.h~mm-introduce-mmap_lock_speculation_beginend
+++ a/include/linux/mmap_lock.h
@@ -71,6 +71,7 @@ static inline void mmap_assert_write_loc
}
#ifdef CONFIG_PER_VMA_LOCK
+
static inline void mm_lock_seqcount_init(struct mm_struct *mm)
{
seqcount_init(&mm->mm_lock_seq);
@@ -86,11 +87,35 @@ static inline void mm_lock_seqcount_end(
do_raw_write_seqcount_end(&mm->mm_lock_seq);
}
-#else
+static inline bool mmap_lock_speculation_begin(struct mm_struct *mm, unsigned int *seq)
+{
+ *seq = raw_read_seqcount(&mm->mm_lock_seq);
+ /* Allow speculation if mmap_lock is not write-locked */
+ return (*seq & 1) == 0;
+}
+
+static inline bool mmap_lock_speculation_end(struct mm_struct *mm, unsigned int seq)
+{
+ return !do_read_seqcount_retry(&mm->mm_lock_seq, seq);
+}
+
+#else /* CONFIG_PER_VMA_LOCK */
+
static inline void mm_lock_seqcount_init(struct mm_struct *mm) {}
static inline void mm_lock_seqcount_begin(struct mm_struct *mm) {}
static inline void mm_lock_seqcount_end(struct mm_struct *mm) {}
-#endif
+
+static inline bool mmap_lock_speculation_begin(struct mm_struct *mm, unsigned int *seq)
+{
+ return false;
+}
+
+static inline bool mmap_lock_speculation_end(struct mm_struct *mm, unsigned int seq)
+{
+ return false;
+}
+
+#endif /* CONFIG_PER_VMA_LOCK */
static inline void mmap_init_lock(struct mm_struct *mm)
{
_
Patches currently in -mm which might be from surenb@xxxxxxxxxx are
maple_tree-add-mas_for_each_rev-helper.patch
alloc_tag-introduce-shutdown_mem_profiling-helper-function.patch
alloc_tag-load-module-tags-into-separate-contiguous-memory.patch
alloc_tag-populate-memory-for-module-tags-as-needed.patch
alloc_tag-introduce-pgtag_ref_handle-to-abstract-page-tag-references.patch
alloc_tag-support-for-page-allocation-tag-compression.patch
mm-convert-mm_lock_seq-to-a-proper-seqcount.patch
mm-introduce-mmap_lock_speculation_beginend.patch
