From: Jan Blunck <jblunck@xxxxxxx> XXX - This is broken and included just to make union mounts work. See discussion at: http://kerneltrap.org/mailarchive/linux-fsdevel/2010/1/15/6708053/thread Original commit message: This is a bugfix/replacement for commit 051d381259eb57d6074d02a6ba6e90e744f1a29f: During a path walk if an autofs trigger is mounted on a dentry, when the follow_link method is called, the nameidata struct contains the vfsmount and mountpoint dentry of the parent mount while the dentry that is passed in is the root of the autofs trigger mount. I believe it is impossible to get the vfsmount of the trigger mount, within the follow_link method, when only the parent vfsmount and the root dentry of the trigger mount are known. The solution in this commit was to replace the path embedded in the parent's nameidata with the path of the link itself in __do_follow_link(). This is a relatively harmless misuse of the field, but union mounts ran into a bug during follow_link() caused by the nameidata containing the wrong path (we count on it being what it is all other places - the path of the parent). A cleaner and easier to understand solution is to save the necessary vfsmount in the autofs superblock info when it is mounted. Then we can easily update the vfsmount in autofs4_follow_link(). Signed-off-by: Jan Blunck <jblunck@xxxxxxx> Signed-off-by: Valerie Aurora <vaurora@xxxxxxxxxx> Acked-by: Ian Kent <raven@xxxxxxxxxx> Cc: autofs@xxxxxxxxxxxxxxxx Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx> --- fs/autofs4/autofs_i.h | 1 + fs/autofs4/init.c | 11 ++++++++++- fs/autofs4/root.c | 6 ++++++ fs/namei.c | 7 ++----- 4 files changed, 19 insertions(+), 6 deletions(-) diff --git a/fs/autofs4/autofs_i.h b/fs/autofs4/autofs_i.h index 3d283ab..de3af64 100644 --- a/fs/autofs4/autofs_i.h +++ b/fs/autofs4/autofs_i.h @@ -133,6 +133,7 @@ struct autofs_sb_info { int reghost_enabled; int needs_reghost; struct super_block *sb; + struct vfsmount *mnt; struct mutex wq_mutex; spinlock_t fs_lock; struct autofs_wait_queue *queues; /* Wait queue pointer */ diff --git a/fs/autofs4/init.c b/fs/autofs4/init.c index 9722e4b..5e0dcd7 100644 --- a/fs/autofs4/init.c +++ b/fs/autofs4/init.c @@ -17,7 +17,16 @@ static int autofs_get_sb(struct file_system_type *fs_type, int flags, const char *dev_name, void *data, struct vfsmount *mnt) { - return get_sb_nodev(fs_type, flags, data, autofs4_fill_super, mnt); + struct autofs_sb_info *sbi; + int ret; + + ret = get_sb_nodev(fs_type, flags, data, autofs4_fill_super, mnt); + if (ret) + return ret; + + sbi = autofs4_sbi(mnt->mnt_sb); + sbi->mnt = mnt; + return 0; } static struct file_system_type autofs_fs_type = { diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c index 109a6c6..54d2857 100644 --- a/fs/autofs4/root.c +++ b/fs/autofs4/root.c @@ -220,6 +220,12 @@ static void *autofs4_follow_link(struct dentry *dentry, struct nameidata *nd) DPRINTK("dentry=%p %.*s oz_mode=%d nd->flags=%d", dentry, dentry->d_name.len, dentry->d_name.name, oz_mode, nd->flags); + + dput(nd->path.dentry); + mntput(nd->path.mnt); + nd->path.mnt = mntget(sbi->mnt); + nd->path.dentry = dget(dentry); + /* * For an expire of a covered direct or offset mount we need * to break out of follow_down() at the autofs mount trigger diff --git a/fs/namei.c b/fs/namei.c index 219da2b..304aa05 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -538,11 +538,8 @@ __do_follow_link(struct path *path, struct nameidata *nd, void **p) touch_atime(path->mnt, dentry); nd_set_link(nd, NULL); - if (path->mnt != nd->path.mnt) { - path_to_nameidata(path, nd); - dget(dentry); - } - mntget(path->mnt); + if (path->mnt == nd->path.mnt) + mntget(nd->path.mnt); nd->last_type = LAST_BIND; *p = dentry->d_inode->i_op->follow_link(dentry, nd); error = PTR_ERR(*p); -- 1.6.3.3 -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
