From patchwork Sun May 26 12:20:16 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jeff Layton X-Patchwork-Id: 13674254 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BF356C2D6; Sun, 26 May 2024 12:20:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716726023; cv=none; b=h9iJ+r00cUOrrB0T5/yJWDd1PYYjF0n0l7zj6qy5PjNKbailO3wScb18TP9o3R+JDBT95nnKaLUx3HN0bDeNILM8lKbwdCmXGciswC6PC9mgNU8wr2qo31QSnw6hrWFwrPAPPSxxoOWvTFpYJtJLhzDbaZUwohlzu0UxHV3wRmc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716726023; c=relaxed/simple; bh=vaox6C/5vKHxXFGk4CEyr/LzDKIY/J0CIiuiJyykHek=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:To:Cc; b=IZtGDx6T/vvJolazyCisJnJkINiPcFcv9YaSubjl8jU6KIZhZVWu7XLAPT9A8XxC2vY8OtUEoeLZ/zv6xhRNq2LjkvwR073qLqkrQa1iUyqyIi8QZ+uIfnyrNbL8HcBC+1mj7CDVgsWY0wF+jS0QtBJSzjuqSuaGgsnOQYeuneA= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=GVfmAuCT; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="GVfmAuCT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8EFF2C2BD10; Sun, 26 May 2024 12:20:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1716726023; bh=vaox6C/5vKHxXFGk4CEyr/LzDKIY/J0CIiuiJyykHek=; h=From:Date:Subject:To:Cc:From; b=GVfmAuCTDm2k7wjoJMrE/Y5Jx3RFofSI/A+9FRFhlJFDYROLSINICrlsTJ/rMvE+2 lvPQXx7zZCVnPBdPZDcXEZPPGCrp9L6OzLNI5R1M2ScsUHYtd/4PMc1C9snikOf8Jp 6/cxSJ2gj42idZlhbPDuF/w+LkhNkpp4ScGsACqtgEdROOT10FDv6OystyBirh2kPM CN6bCdTgU1cuUMSg2zJjHX23hNFRC9pgSprAVNNy/6KwpzFk8Z2XmRu51NH4RJQOYd 4JxK7muJMc5tiuqu0Q78IAVCm5gf6jwMJw9Er5kj2OApfIJo8sZnQtUkJGgtVPGmDd ansdfY1fT1AeA== From: Jeff Layton Date: Sun, 26 May 2024 08:20:16 -0400 Subject: [PATCH RFC] fs: turn inode->i_ctime into a ktime_t Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20240526-ctime-ktime-v1-1-016ca6c1e19a@kernel.org> X-B4-Tracking: v=1; b=H4sIAP8oU2YC/6tWKk4tykwtVrJSqFYqSi3LLM7MzwNyDHUUlJIzE vPSU3UzU4B8JSMDIxMDUyMz3eSSzNxU3WwwmWJiaGqUkmphaGhqrATUUVCUmpZZATYtWinIzVk ptrYWADLB4TZiAAAA To: Alexander Viro , Christian Brauner , Jan Kara Cc: Linus Torvalds , Matthew Wilcox , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Jeff Layton X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3692; i=jlayton@kernel.org; h=from:subject:message-id; bh=vaox6C/5vKHxXFGk4CEyr/LzDKIY/J0CIiuiJyykHek=; b=owEBbQKS/ZANAwAIAQAOaEEZVoIVAcsmYgBmUykFGfWXjogqlx0kTGbCIxPDMLJ/+LnSVWox/ /9P0qRBgruJAjMEAAEIAB0WIQRLwNeyRHGyoYTq9dMADmhBGVaCFQUCZlMpBQAKCRAADmhBGVaC FZg/D/9Ouih6Qb8A825LnXh8eyDl7mGgk/t1bSuTnuW7mlJ52hqLVDyFfOS6PsxuBsj/4qJUsmT I15VLG2/i0mfOLWEQfxyPScT9L8HKuVHbd0iZsqV2SLboBjuDvc7kTHYv9IIChhRW0YZMrIPRLN 6g5wXq58I+SHciw5eo/hAmGlNwL787u8dQTVQg+vhsP0M25+4vt40NwptD/cLbMBlbFoUsg8Xpx exSNPoFU46sE1draokpTL7nlujNc9O/Gi75s+k34U7v03SVSJekzPMsLXIikF424FnBuoCRwc/I y7KF8kjMWSqhUoL8y5lD4XU84iYhNiT2PzKXsgWRmYQQcS95Z+iA69S2E1nycoYGqZK3b3A2mbp hXs9qGgz671EGpDkfTtr26ZBgN90QWjkwMfxqmcFtDSSQClwwjX3QNbrQ2goPYGREmk52S05eVL j4KGiF2SSFEMuiROqgphZG/9YnPlr0sxtwMVxM8tf+Ns2hlu3Lo1uwXaoA2BF/7q1+XQjO9qcJU WV2tqBDtHfZ/v1v/DF65sVQubkRnRx7WXMISBtUiLNH8us0LNXf8OKOdMslAuEWagYJuvLxAqbh gOx9x96EoVQXd3XAx1H5haoYKGzBMOJCagjWjAKrbnwUgqkAU8oeqOZgzyb6IdP8uEQV8+SpmW5 oqxkcvGLCLcPasw== X-Developer-Key: i=jlayton@kernel.org; a=openpgp; fpr=4BC0D7B24471B2A184EAF5D3000E684119568215 The ctime is not settable to arbitrary values. It always comes from the system clock, so we'll never stamp an inode with a value that can't be represented there. If we disregard people setting their system clock past the year 2262, there is no reason we can't replace the ctime fields with a ktime_t. Switch the __i_ctime fields to a single ktime_t. Move the i_generation down above i_fsnotify_mask and then move the i_version into the resulting 8 byte hole. This shrinks struct inode by 8 bytes total, and should improve the cache footprint as the i_version and __i_ctime are usually updated together. The one downside I can see to switching to a ktime_t is that if someone has a filesystem with files on it that has ctimes outside the ktime_t range (before ~1678 AD or after ~2262 AD), we won't be able to display them properly in stat() without some special treatment. I'm operating under the assumption that this is not a practical problem. Signed-off-by: Jeff Layton --- I've been looking at this as part of trying to resurrect the multigrain timestamp work, as Linus mentioned it in passing in an earlier discussion, but then Willy threw down the gauntlet. Thoughts? --- include/linux/fs.h | 26 +++++++++++--------------- 1 file changed, 11 insertions(+), 15 deletions(-) --- base-commit: a6f48ee9b741a6da6a939aa5c58d879327f452e1 change-id: 20240526-ctime-ktime-d4152de81153 Best regards, diff --git a/include/linux/fs.h b/include/linux/fs.h index 639885621608..6b9ed7dff6d5 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -662,11 +662,10 @@ struct inode { loff_t i_size; time64_t i_atime_sec; time64_t i_mtime_sec; - time64_t i_ctime_sec; u32 i_atime_nsec; u32 i_mtime_nsec; - u32 i_ctime_nsec; - u32 i_generation; + ktime_t __i_ctime; + atomic64_t i_version; spinlock_t i_lock; /* i_blocks, i_bytes, maybe i_size */ unsigned short i_bytes; u8 i_blkbits; @@ -701,7 +700,6 @@ struct inode { struct hlist_head i_dentry; struct rcu_head i_rcu; }; - atomic64_t i_version; atomic64_t i_sequence; /* see futex */ atomic_t i_count; atomic_t i_dio_count; @@ -724,6 +722,8 @@ struct inode { }; + u32 i_generation; + #ifdef CONFIG_FSNOTIFY __u32 i_fsnotify_mask; /* all events this inode cares about */ /* 32-bit hole reserved for expanding i_fsnotify_mask */ @@ -1608,29 +1608,25 @@ static inline struct timespec64 inode_set_mtime(struct inode *inode, return inode_set_mtime_to_ts(inode, ts); } -static inline time64_t inode_get_ctime_sec(const struct inode *inode) +static inline struct timespec64 inode_get_ctime(const struct inode *inode) { - return inode->i_ctime_sec; + return ktime_to_timespec64(inode->__i_ctime); } -static inline long inode_get_ctime_nsec(const struct inode *inode) +static inline time64_t inode_get_ctime_sec(const struct inode *inode) { - return inode->i_ctime_nsec; + return inode_get_ctime(inode).tv_sec; } -static inline struct timespec64 inode_get_ctime(const struct inode *inode) +static inline long inode_get_ctime_nsec(const struct inode *inode) { - struct timespec64 ts = { .tv_sec = inode_get_ctime_sec(inode), - .tv_nsec = inode_get_ctime_nsec(inode) }; - - return ts; + return inode_get_ctime(inode).tv_nsec; } static inline struct timespec64 inode_set_ctime_to_ts(struct inode *inode, struct timespec64 ts) { - inode->i_ctime_sec = ts.tv_sec; - inode->i_ctime_nsec = ts.tv_nsec; + inode->__i_ctime = ktime_set(ts.tv_sec, ts.tv_nsec); return ts; }