From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 3B3F9C44509 for ; Tue, 14 Jul 2026 06:37:03 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [127.0.0.1]) by lists.ozlabs.org (Postfix) with ESMTP id 4gzqNF5F1Rz2xqn; Tue, 14 Jul 2026 16:37:01 +1000 (AEST) Authentication-Results: lists.ozlabs.org; arc=none smtp.remote-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1784011021; cv=none; b=U+2pa91FwjIKSAhekupSLWRqQy02gYs0cVeBozQHl059Hqu04PIduGnnWL9pBA7NsVuGeVu0vownC/RLQvPDcRNQfJq87Udp2uJz0y7F5qiKhJLE5Wbtlvm5rpoJ4oxDi6vQgtXr3LJKMmrd0oq26C5loKvleYWFyKBrn3B1H/0cJKlgKfkJ11aLS0/zGQpiF5MYsYuiJaWiCokZLID2C5CjtCWjbePKD8IWQIUl0IKKTo95tBeEu1pdv2/zAdIiQnoWz+olbxXq0AJRp5ik8KaRkYs8FchYkWFxgO9qXFncFhkto+ZjChoIqO5/I7YFcy2Z3fds1AT2N7ctZNno7Q== ARC-Message-Signature: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1784011021; c=relaxed/relaxed; bh=7Rl9EBcDj5Rw07yZgsZcSBReQweTqcqI79roXrGYq+k=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=b1u3YlMSEvZfgmi7Sf+dQASWoRVMAKNax4N0dC+lQGDICSrbpZsQKEXQuaMQ9oVZG2UOr2O5Or3/nhZUmn5Cf5s/rm/xGnQibg3T0wcx0s2ecZAogj+BNwMgeZgwCqwUxCfjjS8v0qXzppp3bv5wAcMvtb0dtLjj8OZYPzTYHKhIftCD7SkMASKeSwgEKt+WmcNxypEEBMM6p4HKr6Nox7GgVuVSxrQmBdDKVgXX7Pvksnm2vn2XRYyDMLWZgU3beepRrP325KFJHuU1TZR8hMC4oKyMgg4yDz2hVgnXk+7MOR9RspgWFvgo4c7g6pvi4UjE8ePlUG0/I9WhH36nEA== ARC-Authentication-Results: i=1; lists.ozlabs.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=XVl8CYEL; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=XVl8CYEL; dkim-atps=neutral; spf=permerror (client-ip=170.10.129.124; helo=us-smtp-delivery-124.mimecast.com; envelope-from=gscrivan@redhat.com; receiver=lists.ozlabs.org) smtp.mailfrom=redhat.com Authentication-Results: lists.ozlabs.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=XVl8CYEL; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=XVl8CYEL; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=permerror (SPF Permanent Error: Void lookup limit of 2 exceeded) smtp.mailfrom=redhat.com (client-ip=170.10.129.124; helo=us-smtp-delivery-124.mimecast.com; envelope-from=gscrivan@redhat.com; receiver=lists.ozlabs.org) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange x25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4gzqND4JlGz2xPb for ; Tue, 14 Jul 2026 16:36:57 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1784011014; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=7Rl9EBcDj5Rw07yZgsZcSBReQweTqcqI79roXrGYq+k=; b=XVl8CYELL993KKoHqHUqmWRayh9rdrQeDKSCpiK7NsZjKyhYHwi1x+oVjytXvAyzcamcn4 OWbwwOm3Isj8kZngjmjSNcncHY5yAiglFn3v3ym9bgUK9iYHLr0dRCBepbjiqNGqM3gtnB 3JsLFChHYylMd3CLpaBcQQZWQFcnum0= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1784011014; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=7Rl9EBcDj5Rw07yZgsZcSBReQweTqcqI79roXrGYq+k=; b=XVl8CYELL993KKoHqHUqmWRayh9rdrQeDKSCpiK7NsZjKyhYHwi1x+oVjytXvAyzcamcn4 OWbwwOm3Isj8kZngjmjSNcncHY5yAiglFn3v3ym9bgUK9iYHLr0dRCBepbjiqNGqM3gtnB 3JsLFChHYylMd3CLpaBcQQZWQFcnum0= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-657-OmJJdam5Nn6tvayeIcVZ3w-1; Tue, 14 Jul 2026 02:36:48 -0400 X-MC-Unique: OmJJdam5Nn6tvayeIcVZ3w-1 X-Mimecast-MFC-AGG-ID: OmJJdam5Nn6tvayeIcVZ3w_1784011007 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 035C31800366; Tue, 14 Jul 2026 06:36:47 +0000 (UTC) Received: from localhost (unknown [10.44.32.95]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 227AC1800676; Tue, 14 Jul 2026 06:36:45 +0000 (UTC) From: Giuseppe Scrivano To: Gao Xiang Cc: Aleksa Sarai , Christian Brauner , linux-erofs@lists.ozlabs.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH v2] erofs: accept source file descriptor via fsconfig In-Reply-To: (Gao Xiang's message of "Tue, 14 Jul 2026 09:56:57 +0800") References: <20260711071137.4130824-1-gscrivan@redhat.com> <2026-07-13-dandy-better-exposure-wager-9hBmfv@cyphar.com> <871pd748kh.fsf@redhat.com> <2026-07-13-chief-single-carnival-graders-7dI4ue@cyphar.com> <87wluz2nnc.fsf@redhat.com> <2026-07-14-drafty-folded-woes-volumes-Z93P4V@cyphar.com> Date: Tue, 14 Jul 2026 08:36:44 +0200 Message-ID: <87pl0q2i2r.fsf@redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) X-Mailing-List: linux-erofs@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 X-Mimecast-MFC-PROC-ID: Gy61w-sSHVnLnyTMw1t-BaxlW_iyi0ms2AuPUX4tbsI_1784011007 X-Mimecast-Originator: redhat.com Content-Type: text/plain Gao Xiang writes: > On 2026/7/14 08:49, Aleksa Sarai wrote: >> On 2026-07-13, Giuseppe Scrivano wrote: >>> thanks for the hints. >>> >>> I'll prepare a v3 if you are fine with the version below: >> No worries, and this seems more reasonable at a first glance. >> >>> diff --git a/fs/erofs/super.c b/fs/erofs/super.c >>> index 86fa5c6a0c70..72c85cc53085 100644 >>> --- a/fs/erofs/super.c >>> +++ b/fs/erofs/super.c >> ... >>> @@ -437,6 +439,38 @@ static bool erofs_fc_set_dax_mode(struct fs_context *fc, unsigned int mode) >>> return false; >>> } >>> +static int erofs_fc_parse_source(struct fs_context *fc, >>> + struct fs_parameter *param) >>> +{ >>> + struct erofs_sb_info *sbi = fc->s_fs_info; >>> + >>> + if (fc->source || sbi->dif0.file) >>> + return invalf(fc, "Multiple sources"); >>> + >>> + switch (param->type) { >>> + case fs_value_is_string: >>> + fc->source = param->string; >>> + param->string = NULL; >>> + return 0; >>> + case fs_value_is_file: { >>> + char *buf, *p; >>> + >>> + sbi->dif0.file = get_file(param->file); >> A very minor nit, but you can actually steal the file reference here >> with >> sbi->dif0.file = no_free_ptr(param->file); >> A few other places do this. (You'll also need to change the >> param->file >> reference below.) >> >>> + buf = kmalloc(PATH_MAX, GFP_KERNEL); >>> + if (!buf) >>> + return -ENOMEM; >>> + p = file_path(param->file, buf, PATH_MAX); >>> + fc->source = kstrdup(IS_ERR(p) ? "(fd)" : p, GFP_KERNEL); >> I think that /proc/self/fd/%d would be a more useful name for >> debugging >> if file_path() fails (not that it is really possible here AFAICS). But >> I'm not really too fussed. > > Not quite sure if we should get in agreement with the format of this > one in advance (IOWs, users use source_fd and how fc->source looks like; > since other fses may follow the same practice if source_fd becomes common > later) since it's a user-visible field and I believe we shouldn't treat > this one as a dontcare field as some pseudo fses (since those fses don't > rely on `fc->source` by design but typically EROFS can rely on.) > > I hope Christian and others could share move thought on this part too > before I land this feature for the next cycle. would it be better to just return the error from file_path without any fallback? Thanks, Giuseppe