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| author | SeongJae Park <sj@kernel.org> | 2025-09-29 17:44:09 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-10-19 16:30:55 +0200 |
| commit | 677ebfe5d00f94adec0c0204f6e6e2a82d3f77bf (patch) | |
| tree | 98bad412d870e160d551a2d4831bf259518e3a70 /mm | |
| parent | bb5ef60ee84f5685292c2ada07e1ffe93fed98aa (diff) | |
| download | linux-677ebfe5d00f94adec0c0204f6e6e2a82d3f77bf.tar.gz linux-677ebfe5d00f94adec0c0204f6e6e2a82d3f77bf.tar.bz2 linux-677ebfe5d00f94adec0c0204f6e6e2a82d3f77bf.zip | |
mm/damon/vaddr: do not repeat pte_offset_map_lock() until success
commit b93af2cc8e036754c0d9970d9ddc47f43cc94b9f upstream.
DAMON's virtual address space operation set implementation (vaddr) calls
pte_offset_map_lock() inside the page table walk callback function. This
is for reading and writing page table accessed bits. If
pte_offset_map_lock() fails, it retries by returning the page table walk
callback function with ACTION_AGAIN.
pte_offset_map_lock() can continuously fail if the target is a pmd
migration entry, though. Hence it could cause an infinite page table walk
if the migration cannot be done until the page table walk is finished.
This indeed caused a soft lockup when CPU hotplugging and DAMON were
running in parallel.
Avoid the infinite loop by simply not retrying the page table walk. DAMON
is promising only a best-effort accuracy, so missing access to such pages
is no problem.
Link: https://lkml.kernel.org/r/20250930004410.55228-1-sj@kernel.org
Fixes: 7780d04046a2 ("mm/pagewalkers: ACTION_AGAIN if pte_offset_map_lock() fails")
Signed-off-by: SeongJae Park <sj@kernel.org>
Reported-by: Xinyu Zheng <zhengxinyu6@huawei.com>
Closes: https://lore.kernel.org/20250918030029.2652607-1-zhengxinyu6@huawei.com
Acked-by: Hugh Dickins <hughd@google.com>
Cc: <stable@vger.kernel.org> [6.5+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/damon/vaddr.c | 8 |
1 files changed, 2 insertions, 6 deletions
diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c index 5764b9885e7d..4d7dc9f65f68 100644 --- a/mm/damon/vaddr.c +++ b/mm/damon/vaddr.c @@ -324,10 +324,8 @@ static int damon_mkold_pmd_entry(pmd_t *pmd, unsigned long addr, } pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); - if (!pte) { - walk->action = ACTION_AGAIN; + if (!pte) return 0; - } if (!pte_present(ptep_get(pte))) goto out; damon_ptep_mkold(pte, walk->vma, addr); @@ -479,10 +477,8 @@ regular_page: #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); - if (!pte) { - walk->action = ACTION_AGAIN; + if (!pte) return 0; - } ptent = ptep_get(pte); if (!pte_present(ptent)) goto out; |