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mm: convert mm_lock_seq to a proper seqcount

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Convert mm_lock_seq to be seqcount_t and change all mmap_write_lock
variants to increment it, in-line with the usual seqcount usage pattern.
This lets us check whether the mmap_lock is write-locked by checking
mm_lock_seq.sequence counter (odd=locked, even=unlocked). This will be
used when implementing mmap_lock speculation functions.
As a result vm_lock_seq is also change to be unsigned to match the type
of mm_lock_seq.sequence.

Link: https://lkml.kernel.org/r/20241122174416.1367052-2-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
2024-11-22 09:44:15 -08:00
committed by Andrew Morton
parent dba4761a3e
commit e5e7fb278e
7 changed files with 74 additions and 57 deletions
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5
kernel/fork.c
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@@ -448,7 +448,7 @@ static bool vma_lock_alloc(struct vm_area_struct *vma)
return false;
init_rwsem(&vma->vm_lock->lock);
vma->vm_lock_seq = -1;
vma->vm_lock_seq = UINT_MAX;
return true;
}
@@ -1262,9 +1262,6 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
seqcount_init(&mm->write_protect_seq);
mmap_init_lock(mm);
INIT_LIST_HEAD(&mm->mmlist);
#ifdef CONFIG_PER_VMA_LOCK
mm->mm_lock_seq = 0;
#endif
mm_pgtables_bytes_init(mm);
mm->map_count = 0;
mm->locked_vm = 0;