From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id EDE3A2E6116; Thu, 30 Jul 2026 13:13:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785417183; cv=none; b=T0V3do1bUdV2qxoxBKkB96//l75JgGgqG1L6FI6hrdNJbA/OV8pCfKWyvzb4/tXdiwMy2ZcN5C8UXLizx+WKpOQOQOs52yjD5bnsu6fp+rqId6GIDzex072HinNeebA6Edo3IolVvqEb4X/u2GUVPUNwFhNiWpR+yfgUn8++f7Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785417183; c=relaxed/simple; bh=TjDExxgf4LB6ZA4BUUci5QUmx9ripnHPSRkKc9ariGo=; h=From:To:Subject:CC:Date:Message-ID:MIME-Version:Content-Type; b=fXApuNn5bYLgUiw9BE/CZn6+AZ/OkzWQs0FZ/JZPIzexE4Rp+j6gK+YhCjrGQ8fCtRahEHk2L4fPSoFDZSvUsYNQo7HAh3xrdMt9/u/S1BCij8nXGQg2oTpAh8ywQLO8nSiysOA56Nua52JfqolGqaDX7qvo5CHLwNCE4Io6VOk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=N6ZPj5Sq; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="N6ZPj5Sq" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id C7E471684; Thu, 30 Jul 2026 06:12:55 -0700 (PDT) Received: from GX9GF4H4XN (unknown [10.1.26.148]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 3020D3F763; Thu, 30 Jul 2026 06:12:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1785417179; bh=TjDExxgf4LB6ZA4BUUci5QUmx9ripnHPSRkKc9ariGo=; h=From:To:Subject:CC:Date:From; b=N6ZPj5SqlluRft8mGv98lqZB1ih5ZjRbBCSGY+WWYR9TbOmqUXHc93z284NG0mYFy iTlBmT8nX9QQuAa9Pc/1nJv7fSyVyr20yjy6IaVtZgp0nFK7rHN0wyBkeaISclLVe4 SLC4NHt/q3pZnWMZVYfOk913ovRCZEH2m9VugJXo= From: Seunguk Shin To: , Andrew Morton , Alexander Viro , Christian Brauner , Matthew Wilcox , Jan Kara Subject: [PATCH v4, RESEND] fs/dax: check zero or empty entry before converting xarray entry CC: , , , , Date: Thu, 30 Jul 2026 14:12:55 +0100 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain dax_associate_entry(), dax_disassociate_entry(), and dax_busy_page() call dax_to_folio(entry) before checking whether entry is a zero or empty xarray entry. That ordering is wrong because zero and empty entries are not folio entries. Commit 98c183a4fccf ("fs/dax: don't disassociate zero page entries") added guards in the associate and disassociate paths, but the guards still come after dax_to_folio(entry), and dax_busy_page() still has the same problem. Move the zero/empty checks before dax_to_folio(entry) in all three helpers. Fixes: 38607c62b34b ("fs/dax: properly refcount fs dax pages") Signed-off-by: Seunguk Shin Reviewed-by: Jan Kara Reviewed-by: Alistair Popple --- Changes in v4: - Rebase on current upstream - Link to v3: https://lore.kernel.org/all/m2jythetpj.fsf@arm.com/ Changes in v3: - Rebase on current upstream - Update the changelog for the current code state - Link to v2: https://lore.kernel.org/all/m2jyv11mqe.fsf@arm.com/ Changes in v2: - Add Fixes and Reviewed-by tags. - Rebase on the latest. - Link to v1: https://lore.kernel.org/all/18af3213-6c46-4611-ba75-da5be5a1c9b0@arm.com/ --- fs/dax.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index 6d175cd47a99..4bca6e2bc342 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -480,11 +480,12 @@ static void dax_associate_entry(void *entry, struct address_space *mapping, unsigned long address, bool shared) { unsigned long size = dax_entry_size(entry), index; - struct folio *folio = dax_to_folio(entry); + struct folio *folio; if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) return; + folio = dax_to_folio(entry); index = linear_page_index(vma, address & ~(size - 1)); if (shared && (folio->mapping || dax_folio_is_shared(folio))) { if (folio->mapping) @@ -505,21 +506,23 @@ static void dax_associate_entry(void *entry, struct address_space *mapping, static void dax_disassociate_entry(void *entry, struct address_space *mapping, bool trunc) { - struct folio *folio = dax_to_folio(entry); + struct folio *folio; if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) return; + folio = dax_to_folio(entry); dax_folio_put(folio); } static struct page *dax_busy_page(void *entry) { - struct folio *folio = dax_to_folio(entry); + struct folio *folio; if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) return NULL; + folio = dax_to_folio(entry); if (folio_ref_count(folio) - folio_mapcount(folio)) return &folio->page; else -- 2.43.0