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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: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: 9EB7D40002 X-Rspamd-Server: rspam07 X-Stat-Signature: dnbsk8htfg4fy59gps1g613onmeneieb X-HE-Tag: 1740537866-544683 X-HE-Meta: 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 00H1wfte 8txWYIto0u1pXVHmkcqBGz73R6QJQWiizEvd/M/EujsLaIeisouQrJSW3LBHAU7F77RawelvbjhE7/aIWUpZXK1XxxfewNJV4iSpwu2wio6InCrr+TeJJsD+1GAAd4Y5Ztk01O7BaY2wxzOL6dnrfw12NKEhgNCZw5JCWhK1udKywUmuuVn7JIYsjI3cmEdFRv1hTbprNDfq3iMGnI4YxhUpZBWDdYneROQGazDj9vOFSeZ5pb5a64BYExWUokAXP8/IZ3xZP8YY/o981GT1Vy2H4mJsADPhOOdGLFjVl16oy6PnxfmvrIjkUy91QgNZ034n+6la2Ao+5H5PzoV/+h6xulE+oosCIn0XUyEJzKLrWYRmw9x1ft8YY7OBRjgstrr0D2bkuFgRO61jeNNTGLM7ru72JYuyfBB0WayZhZU79m0pSq1vstxJfLC8QzRBEqExG9GUflJ5/muUPHYShL2g/KgOBnxHOsaBlSuvvRgQ/hns= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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