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mm: change vmf_anon_prepare() to __vmf_anon_prepare()

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Some callers of vmf_anon_prepare() may not want us to release the per-VMA
lock ourselves.  Rename vmf_anon_prepare() to __vmf_anon_prepare() and let
the callers drop the lock when desired.

Also, make vmf_anon_prepare() a wrapper that releases the per-VMA lock
itself for any callers that don't care.

This is in preparation to fix this bug reported by syzbot:
https://lore.kernel.org/linux-mm/00000000000067c20b06219fbc26@google.com/

Link: https://lkml.kernel.org/r/20240914194243.245-1-vishal.moola@gmail.com
Fixes: 9acad7ba3e ("hugetlb: use vmf_anon_prepare() instead of anon_vma_prepare()")
Reported-by: syzbot+2dab93857ee95f2eeb08@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/linux-mm/00000000000067c20b06219fbc26@google.com/
Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Vishal Moola (Oracle) 2024-09-14 12:41:18 -07:00 committed by Andrew Morton
parent b4afe4183e
commit 2a058ab328
2 changed files with 13 additions and 6 deletions
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11
mm/internal.h
View File

@ -310,7 +310,16 @@ static inline void wake_throttle_isolated(pg_data_t *pgdat)
wake_up(wqh);
}
vm_fault_t vmf_anon_prepare(struct vm_fault *vmf);
vm_fault_t __vmf_anon_prepare(struct vm_fault *vmf);
static inline vm_fault_t vmf_anon_prepare(struct vm_fault *vmf)
{
vm_fault_t ret = __vmf_anon_prepare(vmf);
if (unlikely(ret & VM_FAULT_RETRY))
vma_end_read(vmf->vma);
return ret;
}
vm_fault_t do_swap_page(struct vm_fault *vmf);
void folio_rotate_reclaimable(struct folio *folio);
bool __folio_end_writeback(struct folio *folio);

8
mm/memory.c
View File

@ -3259,7 +3259,7 @@ static inline vm_fault_t vmf_can_call_fault(const struct vm_fault *vmf)
}
/**
* vmf_anon_prepare - Prepare to handle an anonymous fault.
* __vmf_anon_prepare - Prepare to handle an anonymous fault.
* @vmf: The vm_fault descriptor passed from the fault handler.
*
* When preparing to insert an anonymous page into a VMA from a
@ -3273,7 +3273,7 @@ static inline vm_fault_t vmf_can_call_fault(const struct vm_fault *vmf)
* Return: 0 if fault handling can proceed. Any other value should be
* returned to the caller.
*/
vm_fault_t vmf_anon_prepare(struct vm_fault *vmf)
vm_fault_t __vmf_anon_prepare(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
vm_fault_t ret = 0;
@ -3281,10 +3281,8 @@ vm_fault_t vmf_anon_prepare(struct vm_fault *vmf)
if (likely(vma->anon_vma))
return 0;
if (vmf->flags & FAULT_FLAG_VMA_LOCK) {
if (!mmap_read_trylock(vma->vm_mm)) {
vma_end_read(vma);
if (!mmap_read_trylock(vma->vm_mm))
return VM_FAULT_RETRY;
}
}
if (__anon_vma_prepare(vma))
ret = VM_FAULT_OOM;