From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794702902; b=s/W4GELPaAF81zc9lVNtSfb6yWPGI4YKHrWJsAkAVhSmYZBMSTTfvFLHZXYU4FFuB2wR ZwLMq26ljAwl7r1WJmzHoTmdPr+iGJXingPVLlpC0/ipztox7J0tAaeJRAdHIwVf6AU0+ yLbYHzJmYOy0y9XM+gyQ/e1zBt6jsjQBRCcHwtuOuDsgK/VD7l9yf/jal4HKhu+uA6XmA vD1sD5H09YDUyh8DLXAlv47F8d/GIcXxupJeNBGGi6wy23QJKtNjKOGLyfNMT4kTjYRe2 26m/zdhKxpBzn3EVG31PI1qYALxGt3H5XxWHCgicF5ImHnal3s9QWQ5atYwbMv7VyEg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794702902; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=T9RCugWu9k0Yi0yuOLOvwdPbmC6z5rJsmF4k940UFxw=; b=OV38rTQFb4HYM3ddEpzajW2emRtyJFErAQXORAOedwB0maZTMM3+lZOCccQkmzHU6dEQ v68eDiflUuad5Qyh9XLL1UOQK8y3DM6CQofnpH37xbQSTnYB9GuRMUqy6C71H9R+oFLDc W+l1S3ED1OJbO3VTTmG5hAfsd0KD0HT0O3gitCdFOxfE30mGNIyojOCoqriHgHTR/FSa5 hVkFIEc2Yb1+yJZU+EujvCAUU9BjQ16Y54BYzvXrhzUG3dCoMmpetc7kafIZT5Vf4icsf rJRyAnIx7Rr+2ETlEZYVydlwhgRtmdLmNCpGIrp+qWeFx0DfZz3PUlPiXK2FBvtP/hA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=fxce28XB; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2A759606A329 for ; Sun, 15 Nov 2026 00:35:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=fxce28XB Received: by smtp.kernel.org (Postfix) with ESMTPSA id DDC311F000C4; Sun, 15 Nov 2026 00:35:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794702901; bh=T9RCugWu9k0Yi0yuOLOvwdPbmC6z5rJsmF4k940UFxw=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=fxce28XBA7bzPUJqCjMEFN0AhTYKig1svrvGvW/yFVLd83Qcx/DDUakROlEnN4be7 Y+5WXMUwhQj4qSKe9tr3BZz0dQ+YpTqvpE08+oHCei0IhdndCK9cJB33AQWCODy1iF mGjhPg1DRj6OEfUnUUXdH7w65GR1yA5WowiUFj8SVH6CYCnq8cY+FlGJ0ELrfWwx/9 DIGCP5Ls7gaJOjgtbTNcpNZaIR7w6WiWmstNvTDFG8RE/QAHCZXxHIFGSUWBVWWpjX UW+Go0OXv5mJpH7t7XWqLdxufz57wWO5j5F038Sc5s/F6tQqJdjBDIK3PHi4qn3jLC wg54DE08NJWuQ== From: Sasha Levin To: stable@vger.kernel.org Cc: "David Hildenbrand (Arm)" , Chris Mason , Thadeu Lima de Souza Cascardo , Muhammad Usama Anjum , Sasha Levin Subject: [PATCH 6.1.y] mm/filemap: finish fault cleanup before dropping the fault lock Date: Sat, 14 Nov 2026 19:34:59 -0500 Message-ID: <20261115003438.562027-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261109201600-failed-6.1-97156a6c355c@kernel.org> References: <20261109201600-failed-6.1-97156a6c355c@kernel.org> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: "David Hildenbrand (Arm)" [ Upstream commit 97156a6c355c21f7122421915f05461bd11699a4 ] On a retried fault, a fatal signal interrupting the folio lock wait makes lock_folio_maybe_drop_mmap() drop the fault lock without pinning the file. However, filemap_fault() may still need to release mapping->invalidate_lock. A concurrent munmap() can release the last file reference and free the mapping before that unlock. Defer dropping the fault lock to filemap_fault()'s retry cleanup, after releasing invalidate_lock. If the fault lock was already dropped for I/O, release the existing file reference instead. Keep the fault lock held for FAULT_FLAG_RETRY_NOWAIT as before. Fixes: 730633f0b7f9 ("mm: Protect operations adding pages to page cache with invalidate_lock") Cc: stable@vger.kernel.org Reported-by: Chris Mason Reviewed-by: Thadeu Lima de Souza Cascardo Tested-by: Muhammad Usama Anjum Link: https://patch.msgid.link/20261031-fixes_core-v3-8-d6437171ecc3@kernel.org Signed-off-by: David Hildenbrand (Arm) [ sashal: Replaced release_fault_lock(vmf) with mmap_read_unlock(vmf->vma->vm_mm) for mmap-only fault locking. ] Signed-off-by: Sasha Levin --- mm/filemap.c | 36 +++++++++++++----------------------- 1 file changed, 13 insertions(+), 23 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index 7c996dc4dad28..08f0f17447cf4 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -3075,11 +3075,11 @@ loff_t mapping_seek_hole_data(struct address_space *mapping, loff_t start, * @folio - the folio to lock. * @fpin - the pointer to the file we may pin (or is already pinned). * - * This works similar to lock_folio_or_retry in that it can drop the - * mmap_lock. It differs in that it actually returns the folio locked - * if it returns 1 and 0 if it couldn't lock the folio. If we did have - * to drop the mmap_lock then fpin will point to the pinned file and - * needs to be fput()'ed at a later point. + * Returns 1 with the folio locked, or 0 if locking failed. + * + * On both entry and return, a non-NULL *fpin means the fault lock has + * already been dropped and the caller must eventually fput() the file. + * Otherwise the fault lock is still held, including on failure. */ static int lock_folio_maybe_drop_mmap(struct vm_fault *vmf, struct folio *folio, struct file **fpin) @@ -3096,20 +3096,9 @@ static int lock_folio_maybe_drop_mmap(struct vm_fault *vmf, struct folio *folio, return 0; *fpin = maybe_unlock_mmap_for_io(vmf, *fpin); - if (vmf->flags & FAULT_FLAG_KILLABLE) { - if (__folio_lock_killable(folio)) { - /* - * We didn't have the right flags to drop the mmap_lock, - * but all fault_handlers only check for fatal signals - * if we return VM_FAULT_RETRY, so we need to drop the - * mmap_lock here and return 0 if we don't have a fpin. - */ - if (*fpin == NULL) - mmap_read_unlock(vmf->vma->vm_mm); - return 0; - } - } else - __folio_lock(folio); + if (vmf->flags & FAULT_FLAG_KILLABLE) + return !__folio_lock_killable(folio); + __folio_lock(folio); return 1; } @@ -3228,7 +3217,7 @@ static struct file *do_async_mmap_readahead(struct vm_fault *vmf, * vma->vm_mm->mmap_lock must be held on entry. * * If our return value has VM_FAULT_RETRY set, it's because the mmap_lock - * may be dropped before doing I/O or by lock_folio_maybe_drop_mmap(). + * may be dropped before doing I/O or when aborting an interrupted wait. * * If our return value does not have VM_FAULT_RETRY set, the mmap_lock * has not been released. @@ -3371,9 +3360,8 @@ vm_fault_t filemap_fault(struct vm_fault *vmf) out_retry: /* - * We dropped the mmap_lock, we need to return to the fault handler to - * re-find the vma and come back and find our hopefully still populated - * page. + * With fpin set, the fault lock was already dropped. Otherwise it is + * still held. Release invalidate_lock before dropping either protection. */ if (folio) folio_put(folio); @@ -3381,6 +3369,8 @@ vm_fault_t filemap_fault(struct vm_fault *vmf) filemap_invalidate_unlock_shared(mapping); if (fpin) fput(fpin); + else if (!(vmf->flags & FAULT_FLAG_RETRY_NOWAIT)) + mmap_read_unlock(vmf->vma->vm_mm); return ret | VM_FAULT_RETRY; } EXPORT_SYMBOL(filemap_fault); -- 2.53.0