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.sourceforge.net (lists.sourceforge.net [216.105.38.7]) (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 D8FA4C43334 for ; Fri, 22 Jul 2022 07:43:07 +0000 (UTC) Received: from [127.0.0.1] (helo=sfs-ml-2.v29.lw.sourceforge.com) by sfs-ml-2.v29.lw.sourceforge.com with esmtp (Exim 4.94.2) (envelope-from ) id 1oEnJR-0004it-6l; Fri, 22 Jul 2022 07:43:06 +0000 Received: from [172.30.20.202] (helo=mx.sourceforge.net) by sfs-ml-2.v29.lw.sourceforge.com with esmtps (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1oEnJQ-0004in-1P for linux-f2fs-devel@lists.sourceforge.net; Fri, 22 Jul 2022 07:43:04 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sourceforge.net; s=x; h=Content-Transfer-Encoding:MIME-Version:Message-Id: Date:Subject:Cc:To:From:Sender:Reply-To:Content-Type:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:In-Reply-To:References:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=cTiZhoa/9Po9W1T6PSKElRZxTk7r2+ITZZ2+w1GH9zQ=; b=NQgCrNO7iJLa6pGM4NfvnnW/yN yMi8PVVo4GLibDvYDZas51GajZASAFpCpQCXIzIrmIC12oS98ZbUZ/7kOZt7GkF4WHdygN1gkVG2/ fOZTJL5HUiJFy9WzcdTiCltE23VdKETk28+CV4ncoO3EtH+j9vT3+xRG3eyzKTr3+hEM=; DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sf.net; s=x ; h=Content-Transfer-Encoding:MIME-Version:Message-Id:Date:Subject:Cc:To:From :Sender:Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To: References:List-Id:List-Help:List-Unsubscribe:List-Subscribe:List-Post: List-Owner:List-Archive; bh=cTiZhoa/9Po9W1T6PSKElRZxTk7r2+ITZZ2+w1GH9zQ=; b=e wiB4wsQGtNWbpCIVRi1YhiYQXlzDFV+Dy+pDulwMX3cEKrSu4tsBSl43yKJNsC6aKiARI4qlG8iPs WTdLQhk1oKATzxoy1mMLLQGkfPBl5s2JsJZ6aaVeIapmRb6KlBawOUusr3mLhdtJiFg+KeddjchHe azXvg4SeoBWxzIB0=; Received: from ams.source.kernel.org ([145.40.68.75]) by sfi-mx-2.v28.lw.sourceforge.com with esmtps (TLS1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.94.2) id 1oEnJP-00028g-O2 for linux-f2fs-devel@lists.sourceforge.net; Fri, 22 Jul 2022 07:43:04 +0000 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 ams.source.kernel.org (Postfix) with ESMTPS id 743B1B826E7 for ; Fri, 22 Jul 2022 07:42:57 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E1A33C341C6; Fri, 22 Jul 2022 07:42:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1658475776; bh=ogA0HhpspCjS+a1icpgHI4aSwotqmHJVFm71Wnc0cl4=; h=From:To:Cc:Subject:Date:From; b=OaVFj+XFyb+191Fiq3g3CejvUN/c9Pun4nlCjR8G1LUMKqhw8U7wlq43z+9xnj87f Oi+A/SF7qArpUCv2diYRaj6o++MCSzNe0v2dpPKcwdD1S1Ss/IJVGsC0dnLkamPcg5 keJsBDJCk20l3G2V9E/8+2vGhRV9q3xu/dKiDIaA3zRBCkA7nERfwivYWB2V2dtTRp oTyvW2z4AY0X+nehR57g3EQBfcPSEuPol0SIherrMMCfp6h4X6WHURyEz3RkiLiGDW u3Geg2MtVq/oNiuENZPPsSLfh1QZz6crIsO3sLk+RtWcwEiMSugY8JjaD0PsS6Ktn8 /DshXvSmjr9iw== From: Eric Biggers To: linux-fsdevel@vger.kernel.org Date: Fri, 22 Jul 2022 00:42:28 -0700 Message-Id: <20220722074229.148925-1-ebiggers@kernel.org> X-Mailer: git-send-email 2.37.0 MIME-Version: 1.0 X-Headers-End: 1oEnJP-00028g-O2 Subject: [f2fs-dev] [man-pages RFC PATCH v2] statx.2, open.2: document STATX_DIOALIGN X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-man@vger.kernel.org, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-xfs@vger.kernel.org, linux-fscrypt@vger.kernel.org, linux-block@vger.kernel.org, Keith Busch , linux-ext4@vger.kernel.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net From: Eric Biggers Document the proposed STATX_DIOALIGN support for statx() (https://lore.kernel.org/linux-fsdevel/20220722071228.146690-1-ebiggers@kernel.org/T/#u). Signed-off-by: Eric Biggers --- v2: rebased onto man-pages master branch, mentioned xfs, and updated link to patchset man2/open.2 | 43 ++++++++++++++++++++++++++++++++----------- man2/statx.2 | 29 +++++++++++++++++++++++++++++ 2 files changed, 61 insertions(+), 11 deletions(-) diff --git a/man2/open.2 b/man2/open.2 index d1485999f..ef29847c3 100644 --- a/man2/open.2 +++ b/man2/open.2 @@ -1732,21 +1732,42 @@ of user-space buffers and the file offset of I/Os. In Linux alignment restrictions vary by filesystem and kernel version and might be absent entirely. -However there is currently no filesystem\-independent -interface for an application to discover these restrictions for a given -file or filesystem. -Some filesystems provide their own interfaces -for doing so, for example the +The handling of misaligned +.B O_DIRECT +I/Os also varies; they can either fail with +.B EINVAL +or fall back to buffered I/O. +.PP +Since Linux 5.20, +.B O_DIRECT +support and alignment restrictions for a file can be queried using +.BR statx (2), +using the +.B STATX_DIOALIGN +flag. +Support for +.B STATX_DIOALIGN +varies by filesystem; see +.BR statx (2). +.PP +Some filesystems provide their own interfaces for querying +.B O_DIRECT +alignment restrictions, for example the .B XFS_IOC_DIOINFO operation in .BR xfsctl (3). +.B STATX_DIOALIGN +should be used instead when it is available. .PP -Under Linux 2.4, transfer sizes, the alignment of the user buffer, -and the file offset must all be multiples of the logical block size -of the filesystem. -Since Linux 2.6.0, alignment to the logical block size of the -underlying storage (typically 512 bytes) suffices. -The logical block size can be determined using the +If none of the above is available, then direct I/O support and alignment +restrictions can only be assumed from known characteristics of the filesystem, +the individual file, the underlying storage device(s), and the kernel version. +In Linux 2.4, most block device based filesystems require that the file offset +and the length and memory address of all I/O segments be multiples of the +filesystem block size (typically 4096 bytes). +In Linux 2.6.0, this was relaxed to the logical block size of the block device +(typically 512 bytes). +A block device's logical block size can be determined using the .BR ioctl (2) .B BLKSSZGET operation or from the shell using the command: diff --git a/man2/statx.2 b/man2/statx.2 index 0326e9af0..ea38ec829 100644 --- a/man2/statx.2 +++ b/man2/statx.2 @@ -61,7 +61,12 @@ struct statx { containing the filesystem where the file resides */ __u32 stx_dev_major; /* Major ID */ __u32 stx_dev_minor; /* Minor ID */ + __u64 stx_mnt_id; /* Mount ID */ + + /* Direct I/O alignment restrictions */ + __u32 stx_dio_mem_align; + __u32 stx_dio_offset_align; }; .EE .in @@ -247,6 +252,8 @@ STATX_BTIME Want stx_btime STATX_ALL The same as STATX_BASIC_STATS | STATX_BTIME. It is deprecated and should not be used. STATX_MNT_ID Want stx_mnt_id (since Linux 5.8) +STATX_DIOALIGN Want stx_dio_mem_align and stx_dio_offset_align + (since Linux 5.20; support varies by filesystem) .TE .in .PP @@ -407,6 +414,28 @@ This is the same number reported by .BR name_to_handle_at (2) and corresponds to the number in the first field in one of the records in .IR /proc/self/mountinfo . +.TP +.I stx_dio_mem_align +The alignment (in bytes) required for user memory buffers for direct I/O +.BR "" ( O_DIRECT ) +on this file. or 0 if direct I/O is not supported on this file. +.IP +.B STATX_DIOALIGN +.IR "" ( stx_dio_mem_align +and +.IR stx_dio_offset_align ) +is supported on block devices since Linux 5.20. +The support on regular files varies by filesystem; it is supported by ext4, +f2fs, and xfs since Linux 5.20. +.TP +.I stx_dio_offset_align +The alignment (in bytes) required for file offsets and I/O segment lengths for +direct I/O +.BR "" ( O_DIRECT ) +on this file, or 0 if direct I/O is not supported on this file. +This will only be nonzero if +.I stx_dio_mem_align +is nonzero, and vice versa. .PP For further information on the above fields, see .BR inode (7). base-commit: f9f25914e4ed393ac284ab921876e8a78722c504 -- 2.37.0 _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel