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 X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 42B9CC433DF for ; Thu, 2 Jul 2020 16:51:35 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 047C320780 for ; Thu, 2 Jul 2020 16:51:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="fadzxGD/" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 047C320780 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 8F1866B0030; Thu, 2 Jul 2020 12:51:34 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8A1A16B00A8; Thu, 2 Jul 2020 12:51:34 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7B8316B00AB; Thu, 2 Jul 2020 12:51:34 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0203.hostedemail.com [216.40.44.203]) by kanga.kvack.org (Postfix) with ESMTP id 6601E6B0030 for ; Thu, 2 Jul 2020 12:51:34 -0400 (EDT) Received: from smtpin09.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 07354824556B for ; Thu, 2 Jul 2020 16:51:33 +0000 (UTC) X-FDA: 76993726866.09.brush13_0615e2a26e8a Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin09.hostedemail.com (Postfix) with ESMTP id DB8AE180AD80F for ; Thu, 2 Jul 2020 16:51:32 +0000 (UTC) X-HE-Tag: brush13_0615e2a26e8a X-Filterd-Recvd-Size: 4678 Received: from us-smtp-delivery-1.mimecast.com (us-smtp-1.mimecast.com [207.211.31.81]) by imf17.hostedemail.com (Postfix) with ESMTP for ; Thu, 2 Jul 2020 16:51:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1593708691; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=lasbI7WSZBNJiaWUYinp95/I+mBtTJm3Z60zJ8X/hrU=; b=fadzxGD/XkDTPnAnphYgEF7C53oeR3Fgq3s/e+SVtRk+NtHxJuUGiAbZWBESYNtoFBVy+2 zr0cZIUlGabLrkyWgnYeRqCBV1FHo6U34HHxD54rpuZpX/SUy+XXgMjqCVgLVBKEUBK/Zo 4/Vr49tnK5P2OqTe36gcw+jAoZjJUTM= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-79-sU6N5AAGOCmW1YN2G2tkNA-1; Thu, 02 Jul 2020 12:51:30 -0400 X-MC-Unique: sU6N5AAGOCmW1YN2G2tkNA-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id DA29513E9C1; Thu, 2 Jul 2020 16:51:28 +0000 (UTC) Received: from max.home.com (unknown [10.40.192.26]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1F5E979231; Thu, 2 Jul 2020 16:51:26 +0000 (UTC) From: Andreas Gruenbacher To: Matthew Wilcox Cc: Dave Chinner , Linus Torvalds , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andreas Gruenbacher Subject: [RFC 2/4] fs: Add IOCB_NOIO flag for generic_file_read_iter Date: Thu, 2 Jul 2020 18:51:18 +0200 Message-Id: <20200702165120.1469875-3-agruenba@redhat.com> In-Reply-To: <20200702165120.1469875-1-agruenba@redhat.com> References: <20200702165120.1469875-1-agruenba@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Rspamd-Queue-Id: DB8AE180AD80F X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam01 Content-Transfer-Encoding: quoted-printable 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: Add an IOCB_NOIO flag that indicates to generic_file_read_iter that it shouldn't trigger any filesystem I/O for the actual request or for readahead. This allows to do tentative reads out of the page cache as some filesystems allow, and to take the appropriate locks and retry the reads only if the requested pages are not cached. Signed-off-by: Andreas Gruenbacher --- include/linux/fs.h | 1 + mm/filemap.c | 16 ++++++++++++++-- 2 files changed, 15 insertions(+), 2 deletions(-) diff --git a/include/linux/fs.h b/include/linux/fs.h index 3f881a892ea7..1ab2ea19e883 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -315,6 +315,7 @@ enum rw_hint { #define IOCB_SYNC (1 << 5) #define IOCB_WRITE (1 << 6) #define IOCB_NOWAIT (1 << 7) +#define IOCB_NOIO (1 << 8) =20 struct kiocb { struct file *ki_filp; diff --git a/mm/filemap.c b/mm/filemap.c index f0ae9a6308cb..e8318f99f468 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2028,7 +2028,7 @@ ssize_t generic_file_buffered_read(struct kiocb *io= cb, =20 page =3D find_get_page(mapping, index); if (!page) { - if (iocb->ki_flags & IOCB_NOWAIT) + if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_NOIO)) goto would_block; page_cache_sync_readahead(mapping, ra, filp, @@ -2038,12 +2038,16 @@ ssize_t generic_file_buffered_read(struct kiocb *= iocb, goto no_cached_page; } if (PageReadahead(page)) { + if (iocb->ki_flags & IOCB_NOIO) { + put_page(page); + goto out; + } page_cache_async_readahead(mapping, ra, filp, page, index, last_index - index); } if (!PageUptodate(page)) { - if (iocb->ki_flags & IOCB_NOWAIT) { + if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_NOIO)) { put_page(page); goto would_block; } @@ -2249,6 +2253,14 @@ EXPORT_SYMBOL_GPL(generic_file_buffered_read); * * This is the "read_iter()" routine for all filesystems * that can use the page cache directly. + * + * The IOCB_NOWAIT flag in iocb->ki_flags indicates that -EAGAIN shall + * be returned when no data can be read without issuing I/O requests; + * this doesn't prevent readahead. The IOCB_NOIO flag indicates that + * -EAGAIN shall be returned when no data can be read without issuing + * I/O requests, and 0 shall be returned when readhead would be + * triggered. + * * Return: * * number of bytes copied, even for partial reads * * negative error code if nothing was read --=20 2.26.2