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Mon, 13 Oct 2025 08:09:48 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id +lpJDMyz7GiMHAAAD6G6ig (envelope-from ); Mon, 13 Oct 2025 08:09:48 +0000 Date: Mon, 13 Oct 2025 10:09:46 +0200 From: Oscar Salvador To: Deepanshu Kartikey Cc: muchun.song@linux.dev, david@redhat.com, akpm@linux-foundation.org, broonie@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, syzbot+f26d7c75c26ec19790e7@syzkaller.appspotmail.com Subject: Re: [PATCH v4] hugetlbfs: check for shareable lock before calling huge_pmd_unshare() Message-ID: References: <20251003174553.3078839-1-kartikey406@gmail.com> <20251008052759.469714-1-kartikey406@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251008052759.469714-1-kartikey406@gmail.com> X-Rspamd-Action: no action X-Rspamd-Queue-Id: 6A95A16000A X-Rspamd-Server: rspam11 X-Rspam-User: X-Stat-Signature: ufhnr6yaqpum4dhq8kmsz9hhoamsk65w X-HE-Tag: 1760342990-420628 X-HE-Meta: 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 sWW8ERLh 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 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, Oct 08, 2025 at 10:57:59AM +0530, Deepanshu Kartikey wrote: > When hugetlb_vmdelete_list() processes VMAs during truncate operations, > it may encounter VMAs where huge_pmd_unshare() is called without the > required shareable lock. This triggers an assertion failure in > hugetlb_vma_assert_locked(). > > The previous fix in commit dd83609b8898 ("hugetlbfs: skip VMAs without > shareable locks in hugetlb_vmdelete_list") skipped entire VMAs without > shareable locks to avoid the assertion. However, this prevented pages > from being unmapped and freed, causing a regression in fallocate(PUNCH_HOLE) > operations where pages were not freed immediately, as reported by Mark Brown. > > Instead of skipping VMAs or adding new flags, check __vma_shareable_lock() > directly in __unmap_hugepage_range() right before calling huge_pmd_unshare(). > This ensures PMD unsharing only happens when the VMA has a shareable lock > structure, while still allowing page unmapping and freeing to proceed for > all VMAs. > > Reported-by: syzbot+f26d7c75c26ec19790e7@syzkaller.appspotmail.com > Tested-by: syzbot+f26d7c75c26ec19790e7@syzkaller.appspotmail.com > Reported-by: Mark Brown > Fixes: dd83609b8898 ("hugetlbfs: skip VMAs without shareable locks in hugetlb_vmdelete_list") > Suggested-by: Oscar Salvador > Suggested-by: David Hildenbrand > Link: https://lore.kernel.org/mm-commits/20250925203504.7BE02C4CEF7@smtp.kernel.org/ [v1] > Link: https://lore.kernel.org/mm-commits/20250928185232.BEDB6C4CEF0@smtp.kernel.org/ [v2] > Link: https://lore.kernel.org/linux-mm/20251003174553.3078839-1-kartikey406@gmail.com/ [v3] > Signed-off-by: Deepanshu Kartikey Acked-by: Oscar Salvador -- Oscar Salvador SUSE Labs