From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from outgoing.mit.edu (outgoing-auth-1.mit.edu [18.9.28.11]) (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 83C5C1F2360 for ; Sun, 13 Apr 2025 17:29:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=18.9.28.11 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744565372; cv=none; b=N4KSGcVsdyknkAK499ZIL7WUsZwtSz6dyFn8OIJMuFLeJkVHhGGEvff1S6ZQlRGkEMU3Jnlb8WJ09fKy7chtOH4+g2JJqRlxq0jVLrnmkpOpGOj//bquN80dby20DxWFViUMWkbGvgs6hqoM2eCDdKtN5AIW1F2I327wUVE5U+Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744565372; c=relaxed/simple; bh=6m4AO4SXWJoic9wXT6AedSzOH1FGcYKu9178+RFlFLU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ilTTDCb4yy4gy/ySUe/WVeGaObWMOBWVJ0WcdmUP3UAH+PBjtEj9X1O2tGhPfOYQ1yeaKMR1YBvWbWXqHOV16LTLN3hve2hr4FT7z8f0k8Bdgt1gtRe3QnDvfKyrADHxY0WUkDwGsu/j1BGcTzG62CwZdlqdx6wrVK2I9ckDXbo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=mit.edu; spf=pass smtp.mailfrom=mit.edu; arc=none smtp.client-ip=18.9.28.11 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=mit.edu Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=mit.edu Received: from trampoline.thunk.org (pool-173-48-82-137.bstnma.fios.verizon.net [173.48.82.137]) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 53DHTGP9007002 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Sun, 13 Apr 2025 13:29:16 -0400 Received: by trampoline.thunk.org (Postfix, from userid 15806) id BC4382E00E9; Sun, 13 Apr 2025 13:29:15 -0400 (EDT) Date: Sun, 13 Apr 2025 13:29:15 -0400 From: "Theodore Ts'o" To: Mateusz Guzik Cc: Linus Torvalds , Christian Brauner , Al Viro , linux-fsdevel , Jan Kara , Ext4 Developers List Subject: Re: generic_permission() optimization Message-ID: <20250413172915.GI13132@mit.edu> References: <20250412215257.GF13132@mit.edu> <20250412235535.GH13132@mit.edu> <20250413124054.GA1116327@mit.edu> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Sun, Apr 13, 2025 at 02:52:32PM +0200, Mateusz Guzik wrote: > On Sun, Apr 13, 2025 at 2:40 PM Theodore Ts'o wrote: > > > > On Sun, Apr 13, 2025 at 11:41:47AM +0200, Mateusz Guzik wrote: > > > This is the rootfs of the thing, so I tried it out with merely > > > printing it. I got 70 entries at boot time. I don't think figuring out > > > what this is specifically is warranted (it is on debian though). > > > > Well, can you run: > > > > debugfs -R "stat " /dev/ROOT_DEV > > > > attached full list after boot So it looks like the test is working corretly. Most of the inodes either (a) have a Posix ACL defined, so we were definitely doing the right thing, or (b) had a user.crtime_usec xattr. My personal opinion is that crtime is fairly pointless, and having microsecond accuracy on the creation time is *completely* pointless, but we can't stop programs from doing that. (Therre was also a single xattr field that contained the xattr user.random-seed-creditable.) So it will ultimately come down to how much user think performance compares to microsecond-level accuracy on crtime, which as far as I know, no Linux programs other than samba / CIFS servers who want Microsoft feature-for-feature compatibility care about. (Or SELinux when it sets security ID's, but if you are using SELinux a few extra branch instructions are the *least* of your performace headaches....) - Ted