From patchwork Wed May 10 10:52:48 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dominique Martinet X-Patchwork-Id: 13236769 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 5F41AC77B7C for ; Wed, 10 May 2023 10:53:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236250AbjEJKxR (ORCPT ); Wed, 10 May 2023 06:53:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55734 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230100AbjEJKxQ (ORCPT ); Wed, 10 May 2023 06:53:16 -0400 Received: from nautica.notk.org (ipv6.notk.org [IPv6:2001:41d0:1:7a93::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2DBF944B0; Wed, 10 May 2023 03:53:14 -0700 (PDT) Received: by nautica.notk.org (Postfix, from userid 108) id BBC83C01E; Wed, 10 May 2023 12:53:10 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=codewreck.org; s=2; t=1683715990; bh=2ATyOmXz9gM5g9c9sCOy2OnjdcTD3k16TX+u9CVj00Q=; h=From:Subject:Date:To:Cc:From; b=UIt4n0PrUA8ORk/bUfcneviEwFrVQ5DbhccTthi3qJRqTp4WgFOkILi93ZRnYPp6P g1U1iSPqAkuC35TFI6T6uRVjo2IXUm6QMqTIhN3TSXmL5RVY1oNUJClqeJo8cUmbcy D0uh9JG+tAZ0o3lHjC60EOnDPe/tm/nOvwciogdZFTk+czzVYNuzAMgwtRaIxdfurr WVfIgDsDElCM0y4wWaNSxUg/AuTeHnb+whyJL2XPtSBCjM6xfYf0u9TqibsTJbHoYZ RQNkdHtCrVyqGLmbprG9EmaJdwOej6tvBWcrMbi9HxjlyzI+mFr59R0pjLoAl5TytR RhRgjp7zy3XIw== Received: from odin.codewreck.org (localhost [127.0.0.1]) by nautica.notk.org (Postfix) with ESMTPS id CC15DC009; Wed, 10 May 2023 12:53:05 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=codewreck.org; s=2; t=1683715989; bh=2ATyOmXz9gM5g9c9sCOy2OnjdcTD3k16TX+u9CVj00Q=; h=From:Subject:Date:To:Cc:From; b=IDe2E37v6O3hJXa7airBrCA3TCn9eK+THa/3eT4TSiGz8/XIAKUL4W/eJJO7u4SH4 /zR5asagyS4fKpiCUcUzjCaHeIkRRhM+xMTGVPA3pLG0vLYFHll2Q9rsHT4/NAN58W h8P6BJPlNgvIZQyilHXRRAUlNb8hUfd8aWCiuE7VXwN9OUHGCmQivY/gnBVWPd5jkq MTPFA3/tdQOhc77P60GnKJ80KURXaMOB6sXTiFWEiCNh0JvbY0TfoqqoVd1s+21Apw eNuu1bYUjMQPukBkbaPifZxZTufWVAXAln905MnhsLMfIplbpB7wyu3cPeICg77c32 MB/u0E8jiVFaQ== Received: from [127.0.0.2] (localhost [::1]) by odin.codewreck.org (OpenSMTPD) with ESMTP id d02ee382; Wed, 10 May 2023 10:53:02 +0000 (UTC) From: Dominique Martinet Subject: [PATCH v2 0/6] io_uring: add getdents support, take 2 Date: Wed, 10 May 2023 19:52:48 +0900 Message-Id: <20230422-uring-getdents-v2-0-2db1e37dc55e@codewreck.org> MIME-Version: 1.0 X-B4-Tracking: v=1; b=H4sIAIB3W2QC/3WOzQrCMBCEX6Xs2UiyDVI9+R5SJD9rGoRENrUqp e9uWvDo8Ru+YWaGQhypwKmZgWmKJeZUAXcNuMGkQCL6yoASW6kRxZNjCiLQ6CmNRaAxttMetTQ GasmaQsKySW5Ya5t9/dmr8GC6xfe2eOkrD7GMmT/bgUmt6d+tSQkplHbK2/ZAx86dXfb0YnL3f eYA/bIsX9JoPNLRAAAA To: Alexander Viro , Christian Brauner , Jens Axboe , Pavel Begunkov , Stefan Roesch Cc: Clay Harris , Dave Chinner , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, io-uring@vger.kernel.org, Dominique Martinet X-Mailer: b4 0.13-dev-f371f X-Developer-Signature: v=1; a=openpgp-sha256; l=4262; i=asmadeus@codewreck.org; h=from:subject:message-id; bh=0OsutV/yoQv9ekBoChihF+xOGj4mEsA/cvJvIUMwTqg=; b=owEBbQKS/ZANAwAIAatOm+xqmOZwAcsmYgBkW3eNCdFZKyUG0jvdRZT0krquoS78tNuQww1Wm QpWgfM9MvSJAjMEAAEIAB0WIQT8g9txgG5a3TOhiE6rTpvsapjmcAUCZFt3jQAKCRCrTpvsapjm cABzD/0QK2sc7luOm5deMUyR+EFVfmz0r+IBqlAYIxT//RvUseai0GRFi+XWCD2tmyDWVGQBg20 HE5F0PQVBhMnjt+TkBKMsf2Sgwdx1TuuuTJu940dRHeLterDBKlmntSSc256sVK1haf4n5+/Po+ kQXc21uLYapK6pIwij44JX5TuXbScjMGuh4XCg8jTK2MOCHve6Y/2NqVHxtNLWPTQMpQ1eghNHh GE+SOnBVkXt7+wVKlOwwmoObrAVRI3K+KWosTRxtQcj+GY91qrCcWk8Rqc9YTk/QA0+GmEDm1Zq oFHP47sjWSy+2Th1IpDE1785N2eZjdOWludddLLeWg/IdMHuO63y8Dj1cn8/aszmuXNg+ub41XH 5PmnL6jP9PplYQQpWTggv3HFFofD3aDevR+Ariq9pjRI+YkcdpjXnk3zWzwj/afhdkr/dVdNGKY bf8eZDT/4IZ54uPW6/uDnc2h6DmJd1D7TLnYhLfYnJZT4GdtfAiOuSlZmPjPyXdhbvV1E+lr3Vi 5XKerdViPmAycdey1mm/Mx/6Dmbm3lZ1DESBv9YxF/5gcuqDRc8O9l3CEnsI78itGwgpImWrIK9 p1Wt+RGQUjVZdlVnxAIiPMPbe+OoR60TNsIr3gJUw5sH1t8h05FR9G7dt4RLv++VabH8RyllPJo Oi35qAW5TUIZm/Q== X-Developer-Key: i=asmadeus@codewreck.org; a=openpgp; fpr=B894379F662089525B3FB1B9333F1F391BBBB00A Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org This is an attempt to revive discussion after bringing it up as a reply to the last attempt last week. Since the problem with the previous attempt at adding getdents to io_uring was that offset was problematic, we can just not add an offset parameter: using different offsets is rarely useful in practice (maybe for some cacheless userspace NFS server?) and more isn't worth the cost of allowing arbitrary offsets: just allow rewind as a flag instead. [happy to drop even that flag for what I care about, but that might be useful enough on its own as io_uring rightfully has no seek API] The new API does nothing that cannot be achieved with plain syscalls so it shouldn't be introducing any new problem, the only downside is that having the state in the file struct isn't very uring-ish and if a better solution is found later that will probably require duplicating some logic in a new flag... But that seems like it would likely be a distant future, and this version should be usable right away. To repeat the rationale for having getdents available from uring as it has been a while, while I believe there can be real performance improvements as suggested in [1], the real reason is to allow coherency in code: applications using io_uring usually center their event loop around the ring, and having the occasional synchronous getdents call in there is cumbersome and hard to do properly when you consider e.g. a slow or acting up network fs... [1] https://lore.kernel.org/linux-fsdevel/20210218122640.GA334506@wantstofly.org/ (unfortunately the source is no longer available...) liburing implementation: https://github.com/martinetd/liburing/commits/getdents (will submit properly after initial discussions here) Previous discussion: https://lore.kernel.org/all/20211221164004.119663-1-shr@fb.com/T/#m517583f23502f32b040c819d930359313b3db00c Signed-off-by: Dominique Martinet --- Changes in v2: - implement NOWAIT as suggested by dchinner; I'm unable to provide reliable benchmarks but it does indeed look positive (and makes sense) to avoid spinning out to another thread when not required. FWIW though, the serializing readdirs per inode argument given in v1 thread isn't valid: serialization is only done in io_prep_async_work for regular files (REQ_F_ISREG, set from file mode through FFS_ISREG), so dir operations aren't serialized in our case. If I was pedantic I'd say we might want that hashing for filesystems that don't implement interate_shared, but that info comes too late and these filesystems should become less frequent so leaving as is. - implement NOWAIT for kernfs and libfs to test with /sys (the tentative patch for xfs didn't seem to work, didn't take the time to debug) - try to implement some EOF flag in CQE as suggested by Clay Harris, this is less clearly cut and left as RFC. The liburing test/getdents.t implementation has grown options to test this flag and also try async explicitly in the latest commit: https://github.com/martinetd/liburing/commits/getdents - vfs_getdents split: add missing internal.h include - Link to v1: https://lore.kernel.org/r/20230422-uring-getdents-v1-0-14c1db36e98c@codewreck.org --- Dominique Martinet (6): fs: split off vfs_getdents function of getdents64 syscall vfs_getdents/struct dir_context: add flags field io_uring: add support for getdents kernfs: implement readdir FMODE_NOWAIT libfs: set FMODE_NOWAIT on dir open RFC: io_uring getdents: test returning an EOF flag in CQE fs/internal.h | 8 ++++++ fs/kernfs/dir.c | 21 ++++++++++++++- fs/libfs.c | 10 ++++--- fs/readdir.c | 38 +++++++++++++++++++++------ include/linux/fs.h | 10 +++++++ include/uapi/linux/io_uring.h | 9 +++++++ io_uring/fs.c | 61 +++++++++++++++++++++++++++++++++++++++++++ io_uring/fs.h | 3 +++ io_uring/opdef.c | 8 ++++++ 9 files changed, 156 insertions(+), 12 deletions(-) --- base-commit: 58390c8ce1bddb6c623f62e7ed36383e7fa5c02f change-id: 20230422-uring-getdents-2aab84d240aa Best regards,