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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6D643CCA48D for ; Fri, 22 Jul 2022 07:14:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234377AbiGVHOH (ORCPT ); Fri, 22 Jul 2022 03:14:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37250 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234230AbiGVHOE (ORCPT ); Fri, 22 Jul 2022 03:14:04 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B0A7893C25; Fri, 22 Jul 2022 00:14:03 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 379086218F; Fri, 22 Jul 2022 07:14:03 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 54F7DC341CA; Fri, 22 Jul 2022 07:14:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1658474042; bh=hDPLaCgqAD8dm7MXlD1Frq819oFYqTXZlI03nvS/+yc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=CPs/ExZkA4M08BS5otGXisiQMuIlX3galN1C6QnfwwVe625akli4n5LfrbrAY5mM2 gvmOv++UaOhrkJlC0OWZv7Hpb3sLD5R72hYrlghJ/wlwR1RzQRMfT6IyFXZayOL8I3 XWfUBG5eX6aBtDFWLMffxIxw0bdoz7zQfD3uYNgMtEjmMk87GCylmrpiJKoQnrU8r9 SoaYkjkNIlnjLPP9jOxqgm5HtRlsgXEAUjW69aK4+Uub3cT9Mx5ubIJFgCBAamU3Ub UV8xRndANioHaLHmlnYMsELapg0KhYKX2icgHOs2aXVcJ/r0ejCtmK0kBYgAWbqQb9 V8Hgqo6gX+cIA== From: Eric Biggers To: linux-fsdevel@vger.kernel.org Cc: linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-xfs@vger.kernel.org, linux-api@vger.kernel.org, linux-fscrypt@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Keith Busch , Christoph Hellwig Subject: [PATCH v4 1/9] statx: add direct I/O alignment information Date: Fri, 22 Jul 2022 00:12:20 -0700 Message-Id: <20220722071228.146690-2-ebiggers@kernel.org> X-Mailer: git-send-email 2.37.0 In-Reply-To: <20220722071228.146690-1-ebiggers@kernel.org> References: <20220722071228.146690-1-ebiggers@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org From: Eric Biggers Traditionally, the conditions for when DIO (direct I/O) is supported were fairly simple. For both block devices and regular files, DIO had to be aligned to the logical block size of the block device. However, due to filesystem features that have been added over time (e.g. multi-device support, data journalling, inline data, encryption, verity, compression, checkpoint disabling, log-structured mode), the conditions for when DIO is allowed on a regular file have gotten increasingly complex. Whether a particular regular file supports DIO, and with what alignment, can depend on various file attributes and filesystem mount options, as well as which block device(s) the file's data is located on. Moreover, the general rule of DIO needing to be aligned to the block device's logical block size is being relaxed to allow user buffers (but not file offsets) aligned to the DMA alignment instead (https://lore.kernel.org/linux-block/20220610195830.3574005-1-kbusch@fb.com/T/#u). XFS has an ioctl XFS_IOC_DIOINFO that exposes DIO alignment information. Uplifting this to the VFS is one possibility. However, as discussed (https://lore.kernel.org/linux-fsdevel/20220120071215.123274-1-ebiggers@kernel.org/T/#u), this ioctl is rarely used and not known to be used outside of XFS-specific code. It was also never intended to indicate when a file doesn't support DIO at all, nor was it intended for block devices. Therefore, let's expose this information via statx(). Add the STATX_DIOALIGN flag and two new statx fields associated with it: * stx_dio_mem_align: the alignment (in bytes) required for user memory buffers for DIO, or 0 if DIO is not supported on the file. * stx_dio_offset_align: the alignment (in bytes) required for file offsets and I/O segment lengths for DIO, or 0 if DIO is not supported on the file. This will only be nonzero if stx_dio_mem_align is nonzero, and vice versa. Note that as with other statx() extensions, if STATX_DIOALIGN isn't set in the returned statx struct, then these new fields won't be filled in. This will happen if the file is neither a regular file nor a block device, or if the file is a regular file and the filesystem doesn't support STATX_DIOALIGN. It might also happen if the caller didn't include STATX_DIOALIGN in the request mask, since statx() isn't required to return unrequested information. This commit only adds the VFS-level plumbing for STATX_DIOALIGN. For regular files, individual filesystems will still need to add code to support it. For block devices, a separate commit will wire it up too. Reviewed-by: Christoph Hellwig Signed-off-by: Eric Biggers --- fs/stat.c | 2 ++ include/linux/stat.h | 2 ++ include/uapi/linux/stat.h | 4 +++- 3 files changed, 7 insertions(+), 1 deletion(-) diff --git a/fs/stat.c b/fs/stat.c index 9ced8860e0f35d..a7930d74448304 100644 --- a/fs/stat.c +++ b/fs/stat.c @@ -611,6 +611,8 @@ cp_statx(const struct kstat *stat, struct statx __user *buffer) tmp.stx_dev_major = MAJOR(stat->dev); tmp.stx_dev_minor = MINOR(stat->dev); tmp.stx_mnt_id = stat->mnt_id; + tmp.stx_dio_mem_align = stat->dio_mem_align; + tmp.stx_dio_offset_align = stat->dio_offset_align; return copy_to_user(buffer, &tmp, sizeof(tmp)) ? -EFAULT : 0; } diff --git a/include/linux/stat.h b/include/linux/stat.h index 7df06931f25d85..ff277ced50e9fd 100644 --- a/include/linux/stat.h +++ b/include/linux/stat.h @@ -50,6 +50,8 @@ struct kstat { struct timespec64 btime; /* File creation time */ u64 blocks; u64 mnt_id; + u32 dio_mem_align; + u32 dio_offset_align; }; #endif diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h index 1500a0f58041ae..7cab2c65d3d7fc 100644 --- a/include/uapi/linux/stat.h +++ b/include/uapi/linux/stat.h @@ -124,7 +124,8 @@ struct statx { __u32 stx_dev_minor; /* 0x90 */ __u64 stx_mnt_id; - __u64 __spare2; + __u32 stx_dio_mem_align; /* Memory buffer alignment for direct I/O */ + __u32 stx_dio_offset_align; /* File offset alignment for direct I/O */ /* 0xa0 */ __u64 __spare3[12]; /* Spare space for future expansion */ /* 0x100 */ @@ -152,6 +153,7 @@ struct statx { #define STATX_BASIC_STATS 0x000007ffU /* The stuff in the normal stat struct */ #define STATX_BTIME 0x00000800U /* Want/got stx_btime */ #define STATX_MNT_ID 0x00001000U /* Got stx_mnt_id */ +#define STATX_DIOALIGN 0x00002000U /* Want/got direct I/O alignment info */ #define STATX__RESERVED 0x80000000U /* Reserved for future struct statx expansion */ -- 2.37.0