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mm: tweak __vma_enter_locked()

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Move the commentary on how __vma_enter_locked() behaves from the body of
__vma_start_write() to the head of __vma_enter_locked() and merge it with
the existing documentation.  Also add a call to
mmap_assert_write_locked().

Link: https://lkml.kernel.org/r/20251119042639.3937024-1-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Matthew Wilcox (Oracle)
2025-11-19 04:26:35 +00:00
committed by Andrew Morton
parent 31807483d3
commit ecf371b2ca
1 changed files with 5 additions and 8 deletions
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13
mm/mmap_lock.c
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@@ -46,9 +46,9 @@ EXPORT_SYMBOL(__mmap_lock_do_trace_released);
#ifdef CONFIG_MMU
#ifdef CONFIG_PER_VMA_LOCK
/*
* Return value: 0 if vma detached,
* 1 if vma attached with no readers,
* -EINTR if signal received,
* __vma_enter_locked() returns 0 immediately if the vma is not
* attached, otherwise it waits for any current readers to finish and
* returns 1. Returns -EINTR if a signal is received while waiting.
*/
static inline int __vma_enter_locked(struct vm_area_struct *vma,
bool detaching, int state)
@@ -56,6 +56,8 @@ static inline int __vma_enter_locked(struct vm_area_struct *vma,
int err;
unsigned int tgt_refcnt = VMA_LOCK_OFFSET;
mmap_assert_write_locked(vma->vm_mm);
/* Additional refcnt if the vma is attached. */
if (!detaching)
tgt_refcnt++;
@@ -91,11 +93,6 @@ int __vma_start_write(struct vm_area_struct *vma, unsigned int mm_lock_seq,
{
int locked;
/*
* __vma_enter_locked() returns false immediately if the vma is not
* attached, otherwise it waits until refcnt is indicating that vma
* is attached with no readers.
*/
locked = __vma_enter_locked(vma, false, state);
if (locked < 0)
return locked;