From mboxrd@z Thu Jan 1 00:00:00 1970 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 CE12A38DD1; Fri, 13 Jun 2025 19:32:29 +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=1749843149; cv=none; b=fB6VbH+RajXX042Ub4N67Uu3GHxmPaJ/+XsvhJYw9UQ6/gyx7YoFSu7NhSwcxOnVN9++U3H4p2A+Lvsn9RnyAV0n8ujZmacbOMrfq6G9pErMbqqcsc6lcXWVDrydjqcWpyX2osCv3ri+CZYp6paDvq9rPWGtvPU/vncmU5XV9TY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749843149; c=relaxed/simple; bh=wCIFiasx5TiBVQfMuc1lC5s7UlatRp3ZA6rjHwuBunY=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=c2w1J2I/FC1gxSydFOWC2M7bF8YZu8berGk2Ln/0m8XBPsXxvP0du1Mk+KQ/ZMMNQvf83/weaJ9H3T0DxWgo37d3ZTkS/z9jhUdjTYkVo9bewSDdl0uRHDA2rhJAcjE490YDSePCmtogdOpUFYixc8TGkeSTDpI8IsNjBDuPOLs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=uZerIyK+; 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="uZerIyK+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 07831C4CEE3; Fri, 13 Jun 2025 19:32:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1749843149; bh=wCIFiasx5TiBVQfMuc1lC5s7UlatRp3ZA6rjHwuBunY=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=uZerIyK+aJPgsnOwm9qMys8QpUC9h3RS/nRLY3do0uIgEydGWcSCvXcNcegDyDNpo D0o0mZaujPLyjrDoRLXT0naZq8P8rKU/s8JOFK7W+2IwaScF1k81QkqY0cDhbAXhDt XbjZ9gNC+L3sAdzv3FTBOVakbgVMWJr/pC1WSWiDl+JUukOWtOHFBTEzSlBOCFUOvU EJ5qGS/pOpISHRpiyfC1xq4syXbrEwW4daRSjaPNK4YWj7NSx6mbieXyXCxh2CtKmF PTY4X2j/A0+81ZUXCykCf3MEZ03BV8PuzrEvR6LQQCq5rSQaUcWuTIK+NWDrrcXra0 a2KOyyg/6MFgA== Message-ID: <5de18b23238aa2056f56ad541737788af615be62.camel@kernel.org> Subject: Re: [PATCHES][RFC][CFT] rpc_pipefs cleanups From: Jeff Layton To: Al Viro , linux-fsdevel@vger.kernel.org Cc: linux-nfs@vger.kernel.org, Chuck Lever , NeilBrown , Trond Myklebust , Linus Torvalds Date: Fri, 13 Jun 2025 15:32:27 -0400 In-Reply-To: <20250613073149.GI1647736@ZenIV> References: <20250613073149.GI1647736@ZenIV> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 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tree-in-dcache pile; it massages > rpc_pipefs to use saner primitives. Lives in > git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git #work.rpc_pipe > 6.16-rc1-based, 17 commits, -314 lines of code... >=20 > Individual patches in followups. >=20 > Folks, please test and review. In various forms this has sat in my tree > for more than a year and I'd rather get that logjam dealt with. >=20 > Overview: >=20 > Prep/infrastructure (#1 is shared with #work.simple_recursive_removal) >=20 > 1) simple_recursive_removal(): saner interaction with fsnotify > fsnotify events are triggered before the callback, unlike in real > unlink(2)/rmdir(2) syscalls. Obviously matters only in case when callbac= k > is non-empty, which excludes most of the current users in the kernel. >=20 > 2) new helper: simple_start_creating() > Set the things up for kernel-initiated creation of object in a > tree-in-dcache filesystem. With respect to locking it's an equivalent of > filename_create() - we either get a negative dentry with locked parent, > or ERR_PTR() and no locks taken. > tracefs and debugfs had that open-coded as part of their object > creation machinery; switched to calling new helper. >=20 > rpc_pipefs proper: >=20 > 3) rpc_pipe: clean failure exits in fill_super > ->kill_sb() will be called immediately after a failure > return anyway, so we don't need to bother with notifier chain and > rpc_gssd_dummy_depopulate(). What's more, rpc_gssd_dummy_populate() > failure exits do not need to bother with __rpc_depopulate() - anything > added to the tree will be taken out by ->kill_sb(). >=20 > 4) rpc_{rmdir_,}depopulate(): use simple_recursive_removal() instead > no need to give an exact list of objects to be remove when it's > simply every child of the victim directory. >=20 > 5) rpc_unlink(): use simple_recursive_removal() > Previous commit was dealing with directories; this one is for > named pipes (i.e. the thing rpc_pipefs is used for). Note that the > callback of simple_recursive_removal() is called with the parent locked; > the victim isn't locked by the caller. >=20 > 6) rpc_populate(): lift cleanup into callers > rpc_populate() is called either from fill_super (where we > don't need to remove any files on failure - rpc_kill_sb() will take > them all out anyway) or from rpc_mkdir_populate(), where we need to > remove the directory we'd been trying to populate along with whatever > we'd put into it before we failed. Simpler to combine that into > simple_recursive_removal() there. >=20 > 7) rpc_unlink(): saner calling conventions > * pass it pipe instead of pipe->dentry > * zero pipe->dentry afterwards > * it always returns 0; why bother? > =09 > 8) rpc_mkpipe_dentry(): saner calling conventions > Instead of returning a dentry or ERR_PTR(-E...), return 0 and > store dentry into pipe->dentry on success and return -E... on failure. > Callers are happier that way... >=20 > 9) rpc_pipe: don't overdo directory locking > Don't try to hold directories locked more than VFS requires; > lock just before getting a child to be made positive (using > simple_start_creating()) and unlock as soon as the child is created. > There's no benefit in keeping the parent locked while populating the > child - it won't stop dcache lookups anyway. >=20 > 10) rpc_pipe: saner primitive for creating subdirectories > All users of __rpc_mkdir() have the same form - start_creating(), > followed, in case of success, by __rpc_mkdir() and unlocking parent. > Combine that into a single helper, expanding __rpc_mkdir() into it, along > with the call of __rpc_create_common() in it. > Don't mess with d_drop() + d_add() - just d_instantiate() > and be done with that. The reason __rpc_create_common() goes for that > dance is that dentry it gets might or might not be hashed; here we know > it's hashed. >=20 > 11) rpc_pipe: saner primitive for creating regular files > rpc_new_file(); similar to rpc_new_dir(), except that here we > pass file_operations as well. Callers don't care about dentry, just > return 0 or -E... >=20 > 12) rpc_mkpipe_dentry(): switch to start_creating() > ... and make sure we set the rpc_pipe-private part of inode up > before attaching it to dentry. >=20 > 13) rpc_gssd_dummy_populate(): don't bother with rpc_populate() > Just have it create gssd (in root), clntXX in gssd, then info > and gssd in clntXX - all with explicit > rpc_new_dir()/rpc_new_file()/rpc_mkpipe_dentry(). >=20 > 14) rpc_pipe: expand the calls of rpc_mkdir_populate() > ... and get rid of convoluted callbacks. >=20 > 15) rpc_new_dir(): the last argument is always NULL > All callers except the one in rpc_populate() pass explicit NULL > there; rpc_populate() passes its last argument ('private') instead, > but in the only call of rpc_populate() that creates any subdirectories > (when creating fixed subdirectories of root) private itself is NULL. >=20 > 16) rpc_create_client_dir(): don't bother with rpc_populate() > not for a single file... >=20 > 17) rpc_create_client_dir(): return 0 or -E... > Callers couldn't care less which dentry did we get - anything > valid is treated as success. Aside from a couple of minor nits, this all looks great, Al. Pity you don't use git format-patch --cover-letter or we'd have the aggregate diffstat! I imagine this shrinks the rpc_pipefs code significantly. You can add this to the pile. Reviewed-by: Jeff Layton