From 64f44b27ae9184e13ebbca230fa83da02a10f283 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Wed, 3 May 2023 13:18:41 +0200 Subject: fs: use a for loop when locking a mount Currently, lock_mount() uses a goto to retry the lookup until it succeeded in acquiring the namespace_lock() preventing the top mount from being overmounted. While that's perfectly fine we want to lookup the mountpoint on the parent of the top mount in later patches. So adapt the code to make this easier to implement. Also, the for loop is arguably a little cleaner and makes the code easier to follow. No functional changes intended. Reviewed-by: Seth Forshee (DigitalOcean) Message-Id: <20230202-fs-move-mount-replace-v4-3-98f3d80d7eaa@kernel.org> Signed-off-by: Christian Brauner --- fs/namespace.c | 49 ++++++++++++++++++++++++++++--------------------- 1 file changed, 28 insertions(+), 21 deletions(-) (limited to 'fs/namespace.c') diff --git a/fs/namespace.c b/fs/namespace.c index 443b0fa564c4..f91a60e6039d 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -2318,30 +2318,37 @@ static int attach_recursive_mnt(struct mount *source_mnt, static struct mountpoint *lock_mount(struct path *path) { struct vfsmount *mnt; - struct dentry *dentry = path->dentry; -retry: - inode_lock(dentry->d_inode); - if (unlikely(cant_mount(dentry))) { - inode_unlock(dentry->d_inode); - return ERR_PTR(-ENOENT); - } - namespace_lock(); - mnt = lookup_mnt(path); - if (likely(!mnt)) { - struct mountpoint *mp = get_mountpoint(dentry); - if (IS_ERR(mp)) { - namespace_unlock(); + struct dentry *dentry; + struct mountpoint *mp; + + for (;;) { + dentry = path->dentry; + inode_lock(dentry->d_inode); + if (unlikely(cant_mount(dentry))) { inode_unlock(dentry->d_inode); - return mp; + return ERR_PTR(-ENOENT); } - return mp; + + namespace_lock(); + + mnt = lookup_mnt(path); + if (likely(!mnt)) + break; + + namespace_unlock(); + inode_unlock(dentry->d_inode); + path_put(path); + path->mnt = mnt; + path->dentry = dget(mnt->mnt_root); } - namespace_unlock(); - inode_unlock(path->dentry->d_inode); - path_put(path); - path->mnt = mnt; - dentry = path->dentry = dget(mnt->mnt_root); - goto retry; + + mp = get_mountpoint(dentry); + if (IS_ERR(mp)) { + namespace_unlock(); + inode_unlock(dentry->d_inode); + } + + return mp; } static void unlock_mount(struct mountpoint *where) -- cgit