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From: Al Viro <viro@ZenIV.linux.org.uk>
To: linux-fsdevel@vger.kernel.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	linux-kernel@vger.kernel.org, Aleksa Sarai <cyphar@cyphar.com>,
	David Howells <dhowells@redhat.com>,
	Eric Biederman <ebiederm@xmission.com>,
	Christian Brauner <christian.brauner@ubuntu.com>,
	Al Viro <viro@zeniv.linux.org.uk>
Subject: [PATCH 12/17] teach handle_mounts() to handle RCU mode
Date: Sun, 19 Jan 2020 03:17:24 +0000	[thread overview]
Message-ID: <20200119031738.2681033-12-viro@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20200119031738.2681033-1-viro@ZenIV.linux.org.uk>

From: Al Viro <viro@zeniv.linux.org.uk>

... and make the callers of __follow_mount_rcu() use handle_mounts().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/namei.c | 46 +++++++++++++++++-----------------------------
 1 file changed, 17 insertions(+), 29 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 2e416bd8ee26..a3bed1307a4b 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1312,6 +1312,18 @@ static inline int handle_mounts(struct nameidata *nd, struct dentry *dentry,
 
 	path->mnt = nd->path.mnt;
 	path->dentry = dentry;
+	if (nd->flags & LOOKUP_RCU) {
+		unsigned int seq = *seqp;
+		if (unlikely(!*inode))
+			return -ENOENT;
+		if (likely(__follow_mount_rcu(nd, path, inode, seqp)))
+			return 1;
+		if (unlazy_child(nd, dentry, seq))
+			return -ECHILD;
+		// *path might've been clobbered by __follow_mount_rcu()
+		path->mnt = nd->path.mnt;
+		path->dentry = dentry;
+	}
 	ret = follow_managed(path, nd);
 	if (likely(ret >= 0)) {
 		*inode = d_backing_inode(path->dentry);
@@ -1527,7 +1539,6 @@ static int lookup_fast(struct nameidata *nd,
 		       struct path *path, struct inode **inode,
 		       unsigned *seqp)
 {
-	struct vfsmount *mnt = nd->path.mnt;
 	struct dentry *dentry, *parent = nd->path.dentry;
 	int status = 1;
 
@@ -1565,21 +1576,8 @@ static int lookup_fast(struct nameidata *nd,
 
 		*seqp = seq;
 		status = d_revalidate(dentry, nd->flags);
-		if (likely(status > 0)) {
-			/*
-			 * Note: do negative dentry check after revalidation in
-			 * case that drops it.
-			 */
-			if (unlikely(!inode))
-				return -ENOENT;
-			path->mnt = mnt;
-			path->dentry = dentry;
-			if (likely(__follow_mount_rcu(nd, path, inode, seqp)))
-				return 1;
-			if (unlazy_child(nd, dentry, seq))
-				return -ECHILD;
+		if (likely(status > 0))
 			return handle_mounts(nd, dentry, path, inode, seqp);
-		}
 		if (unlazy_child(nd, dentry, seq))
 			return -ECHILD;
 		if (unlikely(status == -ECHILD))
@@ -2229,21 +2227,11 @@ static int handle_lookup_down(struct nameidata *nd)
 	unsigned seq = nd->seq;
 	int err;
 
-	if (nd->flags & LOOKUP_RCU) {
-		/*
-		 * don't bother with unlazy_walk on failure - we are
-		 * at the very beginning of walk, so we lose nothing
-		 * if we simply redo everything in non-RCU mode
-		 */
-		path = nd->path;
-		if (unlikely(!__follow_mount_rcu(nd, &path, &inode, &seq)))
-			return -ECHILD;
-	} else {
+	if (!(nd->flags & LOOKUP_RCU))
 		dget(nd->path.dentry);
-		err = handle_mounts(nd, nd->path.dentry, &path, &inode, &seq);
-		if (unlikely(err < 0))
-			return err;
-	}
+	err = handle_mounts(nd, nd->path.dentry, &path, &inode, &seq);
+	if (unlikely(err < 0))
+		return err;
 	path_to_nameidata(&path, nd);
 	nd->inode = inode;
 	nd->seq = seq;
-- 
2.20.1


  parent reply	other threads:[~2020-01-19  3:21 UTC|newest]

Thread overview: 92+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-30  5:20 [PATCH RFC 0/1] mount: universally disallow mounting over symlinks Aleksa Sarai
2019-12-30  5:20 ` [PATCH RFC 1/1] " Aleksa Sarai
2019-12-30  7:34   ` Linus Torvalds
2019-12-30  8:28     ` Aleksa Sarai
2020-01-08  4:39       ` Andy Lutomirski
2019-12-30  5:44 ` [PATCH RFC 0/1] " Al Viro
2019-12-30  5:49   ` Aleksa Sarai
2019-12-30  7:29     ` Aleksa Sarai
2019-12-30  7:53       ` Linus Torvalds
2019-12-30  8:32         ` Aleksa Sarai
2020-01-02  8:58           ` David Laight
2020-01-02  9:09             ` Aleksa Sarai
2020-01-01  0:43       ` Al Viro
2020-01-01  0:54         ` Al Viro
2020-01-01  3:08           ` Al Viro
2020-01-01 14:44             ` Aleksa Sarai
2020-01-01 23:40               ` Al Viro
2020-01-02  3:59                 ` Aleksa Sarai
2020-01-03  1:49                   ` Al Viro
2020-01-04  4:46                     ` Ian Kent
2020-01-08  3:13                     ` Al Viro
2020-01-08  3:54                       ` Linus Torvalds
2020-01-08 21:34                         ` Al Viro
2020-01-10  0:08                           ` Linus Torvalds
2020-01-10  4:15                             ` Al Viro
2020-01-10  5:03                               ` Linus Torvalds
2020-01-10  6:20                               ` Ian Kent
2020-01-12 21:33                                 ` Al Viro
2020-01-13  2:59                                   ` Ian Kent
2020-01-14  0:25                                     ` Ian Kent
2020-01-14  4:39                                       ` Al Viro
2020-01-14  5:01                                         ` Ian Kent
2020-01-14  5:59                                           ` Ian Kent
2020-01-10 21:07                         ` Aleksa Sarai
2020-01-14  4:57                           ` Al Viro
2020-01-14  5:12                             ` Al Viro
2020-01-14 20:01                             ` Aleksa Sarai
2020-01-15 14:25                               ` Al Viro
2020-01-15 14:29                                 ` Aleksa Sarai
2020-01-15 14:34                                   ` Aleksa Sarai
2020-01-15 14:48                                     ` Al Viro
2020-01-18 12:07                                       ` [PATCH v3 0/2] openat2: minor uapi cleanups Aleksa Sarai
2020-01-18 12:07                                         ` [PATCH v3 1/2] open: introduce openat2(2) syscall Aleksa Sarai
2020-01-18 12:08                                         ` [PATCH v3 2/2] selftests: add openat2(2) selftests Aleksa Sarai
2020-01-18 15:28                                         ` [PATCH v3 0/2] openat2: minor uapi cleanups Al Viro
2020-01-18 18:09                                           ` Al Viro
2020-01-18 23:03                                             ` Aleksa Sarai
2020-01-19  1:12                                               ` Al Viro
2020-01-15 13:57                             ` [PATCH RFC 0/1] mount: universally disallow mounting over symlinks Aleksa Sarai
2020-01-19  3:14                               ` [RFC][PATCHSET][CFT] pathwalk cleanups and fixes Al Viro
2020-01-19  3:17                                 ` [PATCH 01/17] do_add_mount(): lift lock_mount/unlock_mount into callers Al Viro
2020-01-19  3:17                                   ` [PATCH 02/17] fix automount/automount race properly Al Viro
2020-01-30 14:34                                     ` Christian Brauner
2020-01-19  3:17                                   ` [PATCH 03/17] follow_automount(): get rid of dead^Wstillborn code Al Viro
2020-01-30 14:38                                     ` Christian Brauner
2020-01-19  3:17                                   ` [PATCH 04/17] follow_automount() doesn't need the entire nameidata Al Viro
2020-01-30 14:45                                     ` Christian Brauner
2020-01-30 15:38                                       ` Al Viro
2020-01-30 15:55                                         ` Al Viro
2020-01-19  3:17                                   ` [PATCH 05/17] make build_open_flags() treat O_CREAT | O_EXCL as implying O_NOFOLLOW Al Viro
2020-01-19  3:17                                   ` [PATCH 06/17] handle_mounts(): start building a sane wrapper for follow_managed() Al Viro
2020-01-19  3:17                                   ` [PATCH 07/17] atomic_open(): saner calling conventions (return dentry on success) Al Viro
2020-01-19  3:17                                   ` [PATCH 08/17] lookup_open(): " Al Viro
2020-01-19  3:17                                   ` [PATCH 09/17] do_last(): collapse the call of path_to_nameidata() Al Viro
2020-01-19  3:17                                   ` [PATCH 10/17] handle_mounts(): pass dentry in, turn path into a pure out argument Al Viro
2020-01-19  3:17                                   ` [PATCH 11/17] lookup_fast(): consolidate the RCU success case Al Viro
2020-01-19  3:17                                   ` Al Viro [this message]
2020-01-19  3:17                                   ` [PATCH 13/17] lookup_fast(): take mount traversal into callers Al Viro
2020-01-19  3:17                                   ` [PATCH 14/17] new step_into() flag: WALK_NOFOLLOW Al Viro
2020-01-19  3:17                                   ` [PATCH 15/17] fold handle_mounts() into step_into() Al Viro
2020-01-19  3:17                                   ` [PATCH 16/17] LOOKUP_MOUNTPOINT: fold path_mountpointat() into path_lookupat() Al Viro
2020-01-19  3:17                                   ` [PATCH 17/17] expand the only remaining call of path_lookup_conditional() Al Viro
2020-01-19  3:17                                   ` [PATCH 1/9] merging pick_link() with get_link(), part 1 Al Viro
2020-01-19  3:17                                   ` [PATCH 2/9] merging pick_link() with get_link(), part 2 Al Viro
2020-01-19  3:17                                   ` [PATCH 3/9] merging pick_link() with get_link(), part 3 Al Viro
2020-01-19  3:17                                   ` [PATCH 4/9] merging pick_link() with get_link(), part 4 Al Viro
2020-01-19  3:17                                   ` [PATCH 5/9] merging pick_link() with get_link(), part 5 Al Viro
2020-01-19  3:17                                   ` [PATCH 6/9] merging pick_link() with get_link(), part 6 Al Viro
2020-01-19  3:17                                   ` [PATCH 7/9] finally fold get_link() into pick_link() Al Viro
2020-01-19  3:17                                   ` [PATCH 8/9] massage __follow_mount_rcu() a bit Al Viro
2020-01-19  3:17                                   ` [PATCH 9/9] new helper: traverse_mounts() Al Viro
2020-01-30 14:13                                   ` [PATCH 01/17] do_add_mount(): lift lock_mount/unlock_mount into callers Christian Brauner
2020-01-19 14:33                                 ` [RFC][PATCHSET][CFT] pathwalk cleanups and fixes Ian Kent
2020-01-10 23:19                     ` [PATCH RFC 0/1] mount: universally disallow mounting over symlinks Al Viro
2020-01-13  1:48                       ` Ian Kent
2020-01-13  3:54                         ` Al Viro
2020-01-13  6:00                           ` Ian Kent
2020-01-13  6:03                             ` Ian Kent
2020-01-13 13:30                               ` Al Viro
2020-01-14  7:25                                 ` Ian Kent
2020-01-14 12:17                                   ` Ian Kent
2020-01-04  5:52               ` Andy Lutomirski

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