linux-toradex.git/fs/configfs, branch tegra-9.12.7

Revert "configfs: Silence lockdep on mkdir(), rmdir() and configfs_depend_item()"

2009-02-04T17:46:25+00:00

This reverts commit 0e0333429a6280e6eb3c98845e4eed90d5f8078a.

I committed this by accident - Joel and Louis are working with the lockdep
maintainer to provide a better solution than just turning lockdep off.

Signed-off-by: Mark Fasheh 
Acked-by:

configfs: Silence lockdep on mkdir(), rmdir() and configfs_depend_item()

2009-02-02T22:20:18+00:00

When attaching default groups (subdirs) of a new group (in mkdir() or
in configfs_register()), configfs recursively takes inode's mutexes
along the path from the parent of the new group to the default
subdirs. This is needed to ensure that the VFS will not race with
operations on these sub-dirs. This is safe for the following reasons:

- the VFS allows one to lock first an inode and second one of its
  children (The lock subclasses for this pattern are respectively
  I_MUTEX_PARENT and I_MUTEX_CHILD);
- from this rule any inode path can be recursively locked in
  descending order as long as it stays under a single mountpoint and
  does not follow symlinks.

Unfortunately lockdep does not know (yet?) how to handle such
recursion.

I've tried to use Peter Zijlstra's lock_set_subclass() helper to
upgrade i_mutexes from I_MUTEX_CHILD to I_MUTEX_PARENT when we know
that we might recursively lock some of their descendant, but this
usage does not seem to fit the purpose of lock_set_subclass() because
it leads to several i_mutex locked with subclass I_MUTEX_PARENT by
the same task.

>From inside configfs it is not possible to serialize those recursive
locking with a top-level one, because mkdir() and rmdir() are already
called with inodes locked by the VFS. So using some
mutex_lock_nest_lock() is not an option.

I am proposing two solutions:
1) one that wraps recursive mutex_lock()s with
   lockdep_off()/lockdep_on().
2) (as suggested earlier by Peter Zijlstra) one that puts the
   i_mutexes recursively locked in different classes based on their
   depth from the top-level config_group created. This
   induces an arbitrary limit (MAX_LOCK_DEPTH - 2 == 46) on the
   nesting of configfs default groups whenever lockdep is activated
   but this limit looks reasonably high. Unfortunately, this alos
   isolates VFS operations on configfs default groups from the others
   and thus lowers the chances to detect locking issues.

This patch implements solution 1).

Solution 2) looks better from lockdep's point of view, but fails with
configfs_depend_item(). This needs to rework the locking
scheme of configfs_depend_item() by removing the variable lock recursion
depth, and I think that it's doable thanks to the configfs_dirent_lock.
For now, let's stick to solution 1).

Signed-off-by: Louis Rilling 
Acked-by: Joel Becker 
Signed-off-by: Mark Fasheh

fs/Kconfig: move configfs out

2009-01-22T10:15:56+00:00

Signed-off-by: Alexey Dobriyan

zero i_uid/i_gid on inode allocation

2009-01-05T16:54:28+00:00

... and don't bother in callers.  Don't bother with zeroing i_blocks,
while we are at it - it's already been zeroed.

i_mode is not worth the effort; it has no common default value.

Signed-off-by: Al Viro

[PATCH] assorted path_lookup() -> kern_path() conversions

2008-10-23T09:12:52+00:00

more nameidata eviction

Signed-off-by: Al Viro

[PATCH] configfs: Consolidate locking around configfs_detach_prep() in configfs_rmdir()

2008-08-22T18:09:02+00:00

It appears that configfs_rmdir() can protect configfs_detach_prep() retries with
less calls to {spin,mutex}_{lock,unlock}, and a cleaner code.

This patch does not change any behavior, except that it removes two useless
lock/unlock pairs having nothing inside to protect and providing a useless
barrier.

Signed-off-by: Louis Rilling 
Signed-off-by: Joel Becker 
Signed-off-by: Mark Fasheh

[PATCH] configfs: Pin configfs subsystems separately from new config_items.

2008-07-31T23:21:13+00:00

configfs_mkdir() creates a new item by calling its parent's
->make_item/group() functions.  Once that object is created,
configfs_mkdir() calls try_module_get() on the new item's module.  If it
succeeds, the module owning the new item cannot be unloaded, and
configfs is safe to reference the item.

If the item and the subsystem it belongs to are part of the same module,
the subsystem is also pinned.  This is the common case.

However, if the subsystem is made up of multiple modules, this may not
pin the subsystem.  Thus, it would be possible to unload the toplevel
subsystem module while there is still a child item.  Thus, we now
try_module_get() the subsystem's module.  This only really affects
children of the toplevel subsystem group.  Deeper children already have
their parents pinned.

Signed-off-by: Joel Becker 
Signed-off-by: Mark Fasheh

[PATCH] configfs: Fix open directory making rmdir() fail

2008-07-31T23:21:13+00:00

When checking for user-created elements under an item to be removed by rmdir(),
configfs_detach_prep() counts fake configfs_dirents created by dir_open() as
user-created and fails when finding one. It is however perfectly valid to remove
a directory that is open.

Simply make configfs_detach_prep() skip fake configfs_dirent, like it already
does for attributes, and like detach_groups() does.

Signed-off-by: Louis Rilling 
Signed-off-by: Joel Becker 
Signed-off-by: Mark Fasheh

[PATCH] configfs: Lock new directory inodes before removing on cleanup after failure

2008-07-31T23:21:13+00:00

Once a new configfs directory is created by configfs_attach_item() or
configfs_attach_group(), a failure in the remaining initialization steps leads
to removing a directory which inode the VFS may have already accessed.

This commit adds the necessary inode locking to safely remove configfs
directories while cleaning up after a failure. As an advantage, the locking
rules of populate_groups() and detach_groups() become the same: the caller must
have the group's inode mutex locked.

Signed-off-by: Louis Rilling 
Signed-off-by: Joel Becker 
Signed-off-by: Mark Fasheh

[PATCH] configfs: Prevent userspace from creating new entries under attaching directories

2008-07-31T23:21:13+00:00

process 1: 					process 2:
configfs_mkdir("A")
  attach_group("A")
    attach_item("A")
      d_instantiate("A")
    populate_groups("A")
      mutex_lock("A")
      attach_group("A/B")
        attach_item("A")
          d_instantiate("A/B")
						mkdir("A/B/C")
						  do_path_lookup("A/B/C", LOOKUP_PARENT)
						    ok
						  lookup_create("A/B/C")
						    mutex_lock("A/B")
						    ok
						  configfs_mkdir("A/B/C")
						    ok
      attach_group("A/C")
        attach_item("A/C")
          d_instantiate("A/C")
        populate_groups("A/C")
          mutex_lock("A/C")
          attach_group("A/C/D")
            attach_item("A/C/D")
              failure
          mutex_unlock("A/C")
          detach_groups("A/C")
            nothing to do
						mkdir("A/C/E")
						  do_path_lookup("A/C/E", LOOKUP_PARENT)
						    ok
						  lookup_create("A/C/E")
						    mutex_lock("A/C")
						    ok
						  configfs_mkdir("A/C/E")
						    ok
        detach_item("A/C")
        d_delete("A/C")
      mutex_unlock("A")
      detach_groups("A")
        mutex_lock("A/B")
        detach_group("A/B")
	  detach_groups("A/B")
	    nothing since no _default_ group
          detach_item("A/B")
        mutex_unlock("A/B")
        d_delete("A/B")
    detach_item("A")
    d_delete("A")

Two bugs:

1/ "A/B/C" and "A/C/E" are created, but never removed while their parent are
removed in the end. The same could happen with symlink() instead of mkdir().

2/ "A" and "A/C" inodes are not locked while detach_item() is called on them,
   which may probably confuse VFS.

This commit fixes 1/, tagging new directories with CONFIGFS_USET_CREATING before
building the inode and instantiating the dentry, and validating the whole
group+default groups hierarchy in a second pass by clearing
CONFIGFS_USET_CREATING.
	mkdir(), symlink(), lookup(), and dir_open() simply return -ENOENT if
called in (or linking to) a directory tagged with CONFIGFS_USET_CREATING. This
does not prevent userspace from calling stat() successfuly on such directories,
but this prevents userspace from adding (children to | symlinking from/to |
read/write attributes of | listing the contents of) not validated items. In
other words, userspace will not interact with the subsystem on a new item until
the new item creation completes correctly.
	It was first proposed to re-use CONFIGFS_USET_IN_MKDIR instead of a new
flag CONFIGFS_USET_CREATING, but this generated conflicts when checking the
target of a new symlink: a valid target directory in the middle of attaching
a new user-created child item could be wrongly detected as being attached.

2/ is fixed by next commit.

Signed-off-by: Louis Rilling 
Signed-off-by: Joel Becker 
Signed-off-by: Mark Fasheh