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mm: introduce mmap_lock_speculate_{try_begin|retry}

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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.

[akpm@linux-foundation.org: use read_seqcount_retry() in mmap_lock_speculate_retry(), per Wei Yang]
Link: https://lkml.kernel.org/r/20241122174416.1367052-3-surenb@google.com
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Sourav Panda <souravpanda@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Suren Baghdasaryan
2025-01-13 22:40:50 -08:00
committed by Andrew Morton
parent e5e7fb278e
commit 6f030e32e4
1 changed files with 31 additions and 2 deletions
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include/linux/mmap_lock.h
+31 -2
View File
@@ -71,6 +71,7 @@ static inline void mmap_assert_write_locked(const struct mm_struct *mm)
}
#ifdef CONFIG_PER_VMA_LOCK
static inline void mm_lock_seqcount_init(struct mm_struct *mm)
{
seqcount_init(&mm->mm_lock_seq);
@@ -87,11 +88,39 @@ static inline void mm_lock_seqcount_end(struct mm_struct *mm)
do_raw_write_seqcount_end(&mm->mm_lock_seq);
}
#else
static inline bool mmap_lock_speculate_try_begin(struct mm_struct *mm, unsigned int *seq)
{
/*
* Since mmap_lock is a sleeping lock, and waiting for it to become
* unlocked is more or less equivalent with taking it ourselves, don't
* bother with the speculative path if mmap_lock is already write-locked
* and take the slow path, which takes the lock.
*/
return raw_seqcount_try_begin(&mm->mm_lock_seq, *seq);
}
static inline bool mmap_lock_speculate_retry(struct mm_struct *mm, unsigned int seq)
{
return 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_speculate_try_begin(struct mm_struct *mm, unsigned int *seq)
{
return false;
}
static inline bool mmap_lock_speculate_retry(struct mm_struct *mm, unsigned int seq)
{
return true;
}
#endif /* CONFIG_PER_VMA_LOCK */
static inline void mmap_init_lock(struct mm_struct *mm)
{