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mm/vma: improve and document __is_vma_write_locked()

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We don't actually need to return an output parameter providing mm sequence
number, rather we can separate that out into another function -
__vma_raw_mm_seqnum() - and have any callers which need to obtain that
invoke that instead.

The access to the raw sequence number requires that we hold the exclusive
mmap lock such that we know we can't race vma_end_write_all(), so move the
assert to __vma_raw_mm_seqnum() to make this requirement clear.

Also while we're here, convert all of the VM_BUG_ON_VMA()'s to
VM_WARN_ON_ONCE_VMA()'s in line with the convention that we do not invoke
oopses when we can avoid it.

[lorenzo.stoakes@oracle.com: minor tweaks, per Vlastimil]
  Link: https://lkml.kernel.org/r/3fa89c13-232d-4eee-86cc-96caa75c2c67@lucifer.local
Link: https://lkml.kernel.org/r/ef6c415c2d2c03f529dca124ccaed66bc2f60edc.1769198904.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Waiman Long <longman@redhat.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Lorenzo Stoakes
2026-01-23 20:12:18 +00:00
committed by Andrew Morton
parent e28e575af9
commit 22f7639f2f
2 changed files with 28 additions and 25 deletions
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6
mm/mmap_lock.c
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@@ -136,14 +136,14 @@ static int __vma_start_exclude_readers(struct vma_exclude_readers_state *ves)
return 0;
}
int __vma_start_write(struct vm_area_struct *vma, unsigned int mm_lock_seq,
int state)
int __vma_start_write(struct vm_area_struct *vma, int state)
{
int err;
const unsigned int mm_lock_seq = __vma_raw_mm_seqnum(vma);
struct vma_exclude_readers_state ves = {
.vma = vma,
.state = state,
};
int err;
err = __vma_start_exclude_readers(&ves);
if (err) {