From patchwork Fri Aug 26 02:10:43 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: NeilBrown X-Patchwork-Id: 12955454 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 726F5ECAAD1 for ; Fri, 26 Aug 2022 02:17:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244767AbiHZCRb (ORCPT ); Thu, 25 Aug 2022 22:17:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36240 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244746AbiHZCRX (ORCPT ); Thu, 25 Aug 2022 22:17:23 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [IPv6:2001:67c:2178:6::1c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1D8F6CB5DB; Thu, 25 Aug 2022 19:17:21 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id A1F1E2298A; Fri, 26 Aug 2022 02:17:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1661480239; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=5oQjdZ4RU13qv7ERg7wUf7fqXZRo2xGMUxfTKvystxA=; b=K8TMCl0dzuN7diDZUyyOSvTgk3rs7dP3YNTF/SkXDwRx2jhMqqd1XITc+aMCww1u3YCgO2 1hX4VSOkpnyo/Q0+Zam4eRai05jEnIZ7ujrI/AQ8CbnMyGgGtpe1/C4qs2hIOgtCQwJn67 yUz0RKZwyVHtS4oscsZ4CCz8lFGwCtk= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1661480239; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=5oQjdZ4RU13qv7ERg7wUf7fqXZRo2xGMUxfTKvystxA=; b=WulEif6gsEbqX0y/kzjG+IfUQfXjh9oKaMAMkjof9HLt6hnuZiAZf05zE06CrWk+oOtwAC EPNS7aEswe1OMWAQ== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 48AD913A65; Fri, 26 Aug 2022 02:17:17 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id Pc1dAi0tCGNwMQAAMHmgww (envelope-from ); Fri, 26 Aug 2022 02:17:17 +0000 Subject: [PATCH 03/10] VFS: move want_write checks into lookup_hash_update() From: NeilBrown To: Al Viro , Linus Torvalds , Daire Byrne , Trond Myklebust , Chuck Lever Cc: Linux NFS Mailing List , linux-fsdevel@vger.kernel.org, LKML Date: Fri, 26 Aug 2022 12:10:43 +1000 Message-ID: <166147984374.25420.3477094952897986387.stgit@noble.brown> In-Reply-To: <166147828344.25420.13834885828450967910.stgit@noble.brown> References: <166147828344.25420.13834885828450967910.stgit@noble.brown> User-Agent: StGit/1.5 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org mnt_want_write() is always called before lookup_hash_update(), so we can simplify the code by moving the call into that function. If lookup_hash_update() succeeds, it now will have claimed the want_write lock. If it fails, the want_write lock isn't held. To allow this, lookup_hash_update() now receives a 'struct path *' instead of 'struct dentry *' Note that when creating a name, any error from mnt_want_write() does not get reported unless there is no other error. For unlink/rmdir though, an error from mnt_want_write() is immediately fatal - overriding ENOENT for example. This behaviour seems strange, but this patch is careful to preserve it. Signed-off-by: NeilBrown --- fs/namei.c | 72 ++++++++++++++++++++++++++---------------------------------- 1 file changed, 31 insertions(+), 41 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index 09c2d007814a..73c3319a1703 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1632,12 +1632,22 @@ static struct dentry *__lookup_hash(const struct qstr *name, */ static struct dentry *lookup_hash_update( const struct qstr *name, - struct dentry *base, unsigned int flags, + struct path *path, unsigned int flags, wait_queue_head_t *wq) { struct dentry *dentry; + struct dentry *base = path->dentry; struct inode *dir = base->d_inode; - int err; + int err, err2; + + /* For create, don't fail immediately if it's r/o, + * at least try to report other errors. + * For unlink/rmdir where LOOKUP_REVAl is the only + * flag, fail immediately if r/o. + */ + err2 = mnt_want_write(path->mnt); + if (err2 && (flags & ~LOOKUP_REVAL) == 0) + return ERR_PTR(err2); if (wq && IS_PAR_UPDATE(dir)) inode_lock_shared_nested(dir, I_MUTEX_PARENT); @@ -1677,6 +1687,13 @@ static struct dentry *lookup_hash_update( goto out_err; } } + if (err2) { + err = err2; + d_lookup_done(dentry); + d_unlock_update(dentry); + dput(dentry); + goto out_err; + } return dentry; out_err: @@ -1684,6 +1701,8 @@ static struct dentry *lookup_hash_update( inode_unlock_shared(dir); else inode_unlock(dir); + if (!err2) + mnt_drop_write(path->mnt); return ERR_PTR(err); } @@ -1700,7 +1719,7 @@ struct dentry *lookup_hash_update_len(const char *name, int nlen, path->dentry, nlen, &this); if (err) return ERR_PTR(err); - return lookup_hash_update(&this, path->dentry, flags, wq); + return lookup_hash_update(&this, path, flags, wq); } EXPORT_SYMBOL(lookup_hash_update_len); @@ -3891,15 +3910,10 @@ static struct dentry *filename_create_one(struct qstr *last, struct path *path, unsigned int lookup_flags, wait_queue_head_t *wq) { - struct dentry *dentry; bool want_dir = lookup_flags & LOOKUP_DIRECTORY; unsigned int reval_flag = lookup_flags & LOOKUP_REVAL; unsigned int create_flag = LOOKUP_CREATE; - int err2; - int error; - /* don't fail immediately if it's r/o, at least try to report other errors */ - err2 = mnt_want_write(path->mnt); /* * Do the final lookup. Suppress 'create' if there is a trailing * '/', and a directory wasn't requested. @@ -3910,24 +3924,9 @@ static struct dentry *filename_create_one(struct qstr *last, struct path *path, * or -EEXIST. */ create_flag = 0; - dentry = lookup_hash_update(last, path->dentry, - reval_flag | create_flag | LOOKUP_EXCL, wq); - if (IS_ERR(dentry)) - goto drop_write; - - if (unlikely(err2)) { - error = err2; - goto fail; - } - return dentry; -fail: - done_path_update(path, dentry, !!wq); - dput(dentry); - dentry = ERR_PTR(error); -drop_write: - if (!err2) - mnt_drop_write(path->mnt); - return dentry; + return lookup_hash_update(last, path, + reval_flag | create_flag | LOOKUP_EXCL, + wq); } struct dentry *filename_create_one_len(const char *name, int nlen, @@ -4300,23 +4299,18 @@ int do_rmdir(int dfd, struct filename *name) goto exit2; } - error = mnt_want_write(path.mnt); - if (error) - goto exit2; - - dentry = lookup_hash_update(&last, path.dentry, lookup_flags, &wq); + dentry = lookup_hash_update(&last, &path, lookup_flags, &wq); error = PTR_ERR(dentry); if (IS_ERR(dentry)) - goto exit3; + goto exit2; error = security_path_rmdir(&path, dentry); if (error) - goto exit4; + goto exit3; mnt_userns = mnt_user_ns(path.mnt); error = vfs_rmdir(mnt_userns, path.dentry->d_inode, dentry); -exit4: +exit3: done_path_update(&path, dentry, true); dput(dentry); -exit3: mnt_drop_write(path.mnt); exit2: path_put(&path); @@ -4433,12 +4427,8 @@ int do_unlinkat(int dfd, struct filename *name) if (type != LAST_NORM) goto exit2; - error = mnt_want_write(path.mnt); - if (error) - goto exit2; - retry_deleg: - dentry = lookup_hash_update(&last, path.dentry, lookup_flags, &wq); + dentry = lookup_hash_update(&last, &path, lookup_flags, &wq); error = PTR_ERR(dentry); if (!IS_ERR(dentry)) { struct user_namespace *mnt_userns; @@ -4457,6 +4447,7 @@ int do_unlinkat(int dfd, struct filename *name) exit3: done_path_update(&path, dentry, true); dput(dentry); + mnt_drop_write(path.mnt); } if (inode) iput(inode); /* truncate the inode here */ @@ -4466,7 +4457,6 @@ int do_unlinkat(int dfd, struct filename *name) if (!error) goto retry_deleg; } - mnt_drop_write(path.mnt); exit2: path_put(&path); if (retry_estale(error, lookup_flags)) {