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Tue, 25 Feb 2025 18:44:25 -0800 (PST) From: Barry Song <21cnbao@gmail.com> To: peterx@redhat.com, akpm@linux-foundation.org Cc: 21cnbao@gmail.com, Liam.Howlett@oracle.com, aarcange@redhat.com, axelrasmussen@google.com, bgeffon@google.com, brauner@kernel.org, david@redhat.com, hughd@google.com, jannh@google.com, kaleshsingh@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lokeshgidra@google.com, mhocko@suse.com, ngeoffray@google.com, rppt@kernel.org, ryan.roberts@arm.com, shuah@kernel.org, stable@vger.kernel.org, surenb@google.com, v-songbaohua@oppo.com, viro@zeniv.linux.org.uk, willy@infradead.org, zhangpeng362@huawei.com, zhengtangquan@oppo.com Subject: Re: [PATCH v2] mm: Fix kernel BUG when userfaultfd_move encounters swapcache Date: Wed, 26 Feb 2025 15:44:11 +1300 Message-Id: <20250226024411.47092-1-21cnbao@gmail.com> X-Mailer: git-send-email 2.39.3 (Apple Git-146) In-Reply-To: References: Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On Wed, Feb 26, 2025 at 2:00 PM Peter Xu wrote: > > Acked-by: Peter Xu > Thanks! > Some nitpicks below, maybe no worth for a repost.. Hi Andrew, Could you please help squash the below change? >From 42273506ba00723151e3a08b4ffd3f2c303e7ccc Mon Sep 17 00:00:00 2001 From: Barry Song Date: Wed, 26 Feb 2025 15:22:17 +1300 Subject: [PATCH] minor cleanup according to Peter Xu According to Peter Xu: 1. Unnecessary line move. 2. Can drop this folio check as it just did check "!IS_ERR_OR_NULL(folio)" 3. Not sure if it can do any harm, but maybe still nicer to put swap before locking folio. Signed-off-by: Barry Song --- mm/userfaultfd.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 2df5d100e76d..2955e20f86bf 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -1101,8 +1101,8 @@ static int move_swap_pte(struct mm_struct *mm, struct vm_area_struct *dst_vma, orig_src_pte = ptep_get_and_clear(mm, src_addr, src_pte); set_pte_at(mm, dst_addr, dst_pte, orig_src_pte); - double_pt_unlock(dst_ptl, src_ptl); + return 0; } @@ -1369,7 +1369,7 @@ static int move_pages_pte(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, folio = filemap_get_folio(swap_address_space(entry), swap_cache_index(entry)); if (!IS_ERR_OR_NULL(folio)) { - if (folio && folio_test_large(folio)) { + if (folio_test_large(folio)) { err = -EBUSY; folio_put(folio); goto out; @@ -1380,10 +1380,10 @@ static int move_pages_pte(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, pte_unmap(&orig_src_pte); pte_unmap(&orig_dst_pte); src_pte = dst_pte = NULL; - /* now we can block and wait */ - folio_lock(src_folio); put_swap_device(si); si = NULL; + /* now we can block and wait */ + folio_lock(src_folio); goto retry; } } -- 2.39.3 (Apple Git-146) > Peter Xu > Thanks Barry