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Howlett" , Lokesh Gidra , Matthew Wilcox , Michal Hocko , Mike Rapoport , Nicolas Geoffray , Ryan Roberts , Shuah Khan , ZhangPeng Subject: Re: [PATCH RFC] mm: Fix kernel BUG when userfaultfd_move encounters swapcache Message-ID: References: <20250219112519.92853-1-21cnbao@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20250219112519.92853-1-21cnbao@gmail.com> On Thu, Feb 20, 2025 at 12:25:19AM +1300, Barry Song wrote: > @@ -1079,9 +1080,19 @@ static int move_swap_pte(struct mm_struct *mm, > pmd_t *dst_pmd, pmd_t dst_pmdval, > spinlock_t *dst_ptl, spinlock_t *src_ptl) > { > + struct folio *folio; > + swp_entry_t entry; > + > if (!pte_swp_exclusive(orig_src_pte)) > return -EBUSY; > > + entry = pte_to_swp_entry(orig_src_pte); > + folio = filemap_get_folio(swap_address_space(entry), swap_cache_index(entry)); [Besides what's being discussed elsewhere..] swap_cache_get_folio() says: * Caller must lock the swap device or hold a reference to keep it valid. Do we need get_swap_device() too here to avoid swapoff race? > + if (!IS_ERR(folio)) { > + folio_put(folio); > + return -EBUSY; > + } > + > double_pt_lock(dst_ptl, src_ptl); > > if (!is_pte_pages_stable(dst_pte, src_pte, orig_dst_pte, orig_src_pte, > -- > 2.39.3 (Apple Git-146) > -- Peter Xu