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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> MIME-Version: 1.0 In-Reply-To: <20250219112519.92853-1-21cnbao@gmail.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: D3MFRh5Qle69XWIjHl26zR3rJP1pvMLIfe3bV5TAYxM_1740004309 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: BDC5F14000C X-Stat-Signature: czoap5oi41p5z5fyz7q1soi8npawugff X-Rspam-User: X-HE-Tag: 1740004311-792478 X-HE-Meta: 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 7jd3R5yG xcKZKZ/hxZmSI+hbA2pLy5VUWvEm933PhKsJofCWiiYhrK++Rbs6y9Qc9Hoxcm+VXb80H2CO89Tf6M+CEsuGpnkuIsJvWlO8hHGgeugGdQgCF29RdRuiXobZALVJuurzWg0JVQfpWwYvcdmb3v78yaXKGsJpJvwrDrW7gYMn1KfxzmgbxbmorjOFjEv998DTFk2rd4bDtlrbjGuF8+xmZy3slw9WzOTUCwGT99Cda/1WoPNxQHptJLf49X/Gu5l7/v0cN1Vsa2sTxVEesp3TQlFZW9Q7Y+Ti1OzdOyhzI/6qJPPZTX5LCmS6snH73Jo69UK5g8/JBv5zv3QZDqotFyfsVkK97+JlYmpU0UjswVyTE/9tl01jWyzV2SZVxM+67Fd0b6aQtPBYG4lQ1gYaKO0rIMVBtWxedK8BNAjneUfj9oQ+wvjO2qjVAw3roOQTPdarMzDqUJ1Z9s+hZQMiFrlfzS2u/69IUifA1 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 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