sysfs and configfs setattr functions have error cases after the generic inode's
attributes have been changed. Fix consistency by changing the generic inode
attributes only when it is guaranteed to succeed.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Convert simple filesystems: ramfs, configfs, sysfs, block_dev to new truncate
sequence.
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
1) i_flags simply doesn't work for mount/unlink race prevention;
we may have many links to file and rm on one of those obviously
shouldn't prevent bind on top of another later on. To fix it
right way we need to mark _dentry_ as unsuitable for mounting
upon; new flag (DCACHE_CANT_MOUNT) is protected by d_flags and
i_mutex on the inode in question. Set it (with dont_mount(dentry))
in unlink/rmdir/etc., check (with cant_mount(dentry)) in places
in namespace.c that used to check for S_DEAD. Setting S_DEAD
is still needed in places where we used to set it (for directories
getting killed), since we rely on it for readdir/rmdir race
prevention.
2) rename()/mount() protection has another bogosity - we unhash
the target before we'd checked that it's not a mountpoint. Fixed.
3) ancient bogosity in pivot_root() - we locked i_mutex on the
right directory, but checked S_DEAD on the different (and wrong)
one. Noticed and fixed.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
percpu.h is included by sched.h and module.h and thus ends up being
included when building most .c files. percpu.h includes slab.h which
in turn includes gfp.h making everything defined by the two files
universally available and complicating inclusion dependencies.
percpu.h -> slab.h dependency is about to be removed. Prepare for
this change by updating users of gfp and slab facilities include those
headers directly instead of assuming availability. As this conversion
needs to touch large number of source files, the following script is
used as the basis of conversion.
http://userweb.kernel.org/~tj/misc/slabh-sweep.py
The script does the followings.
* Scan files for gfp and slab usages and update includes such that
only the necessary includes are there. ie. if only gfp is used,
gfp.h, if slab is used, slab.h.
* When the script inserts a new include, it looks at the include
blocks and try to put the new include such that its order conforms
to its surrounding. It's put in the include block which contains
core kernel includes, in the same order that the rest are ordered -
alphabetical, Christmas tree, rev-Xmas-tree or at the end if there
doesn't seem to be any matching order.
* If the script can't find a place to put a new include (mostly
because the file doesn't have fitting include block), it prints out
an error message indicating which .h file needs to be added to the
file.
The conversion was done in the following steps.
1. The initial automatic conversion of all .c files updated slightly
over 4000 files, deleting around 700 includes and adding ~480 gfp.h
and ~3000 slab.h inclusions. The script emitted errors for ~400
files.
2. Each error was manually checked. Some didn't need the inclusion,
some needed manual addition while adding it to implementation .h or
embedding .c file was more appropriate for others. This step added
inclusions to around 150 files.
3. The script was run again and the output was compared to the edits
from #2 to make sure no file was left behind.
4. Several build tests were done and a couple of problems were fixed.
e.g. lib/decompress_*.c used malloc/free() wrappers around slab
APIs requiring slab.h to be added manually.
5. The script was run on all .h files but without automatically
editing them as sprinkling gfp.h and slab.h inclusions around .h
files could easily lead to inclusion dependency hell. Most gfp.h
inclusion directives were ignored as stuff from gfp.h was usually
wildly available and often used in preprocessor macros. Each
slab.h inclusion directive was examined and added manually as
necessary.
6. percpu.h was updated not to include slab.h.
7. Build test were done on the following configurations and failures
were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my
distributed build env didn't work with gcov compiles) and a few
more options had to be turned off depending on archs to make things
build (like ipr on powerpc/64 which failed due to missing writeq).
* x86 and x86_64 UP and SMP allmodconfig and a custom test config.
* powerpc and powerpc64 SMP allmodconfig
* sparc and sparc64 SMP allmodconfig
* ia64 SMP allmodconfig
* s390 SMP allmodconfig
* alpha SMP allmodconfig
* um on x86_64 SMP allmodconfig
8. percpu.h modifications were reverted so that it could be applied as
a separate patch and serve as bisection point.
Given the fact that I had only a couple of failures from tests on step
6, I'm fairly confident about the coverage of this conversion patch.
If there is a breakage, it's likely to be something in one of the arch
headers which should be easily discoverable easily on most builds of
the specific arch.
Signed-off-by: Tejun Heo <tj@kernel.org>
Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
This enables us to track who does what and print info. Its main use
is catching dirty inodes on the default_backing_dev_info, so we can
fix that up.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
configfs_depend_item() recursively locks all inodes mutex from configfs root to
the target item, which makes lockdep unhappy. The purpose of this recursive
locking is to ensure that the item tree can be safely parsed and that the target
item, if found, is not about to leave.
This patch reworks configfs_depend_item() locking using configfs_dirent_lock.
Since configfs_dirent_lock protects all changes to the configfs_dirent tree, and
protects tagging of items to be removed, this lock can be used instead of the
inodes mutex lock chain.
This needs that the check for dependents be done atomically with
CONFIGFS_USET_DROPPING tagging.
Now lockdep looks happy with configfs.
[ Lifted the setting of s_type into configfs_new_dirent() to satisfy the
atomic setting of CONFIGFS_USET_CREATING -- Joel ]
Signed-off-by: Louis Rilling <louis.rilling@kerlabs.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
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 also
isolates VFS operations on configfs default groups from the others
and thus lowers the chances to detect locking issues.
Nobody likes solution 1), which I can understand.
This patch implements solution 2). However lockdep is still not happy with
configfs_depend_item(). Next patch reworks the locking of
configfs_depend_item() and finally makes lockdep happy.
[ Note: This hides a few locking interactions with the VFS from lockdep.
That was my big concern, because we like lockdep's protection. However,
the current state always dumps a spurious warning. The locking is
correct, so I tell people to ignore the warning and that we'll keep
our eyes on the locking to make sure it stays correct. With this patch,
we eliminate the warning. We do lose some of the lockdep protections,
but this only means that we still have to keep our eyes on the locking.
We're going to do that anyway. -- Joel ]
Signed-off-by: Louis Rilling <louis.rilling@kerlabs.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
I observed the following build warning with fs/configfs/symlink.c:
fs/configfs/symlink.c: In function 'configfs_symlink':
fs/configfs/symlink.c:138: warning: 'target_item' may be used uninitialized in this function
Here is a small fix for this.
Cc: Patrick Mochel <mochel@osdl.org>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: Sachin P Sant <sachinp@linux.vnet.ibm.com>
Signed-Off-By: Subrata Modak <subrata@linux.vnet.ibm.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
This reverts commit 0e0333429a.
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 <mfasheh@suse.com>
Acked-by: <Joel Becker <joel.becker@oracle.com>
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 <louis.rilling@kerlabs.com>
Acked-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>
... 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 <viro@zeniv.linux.org.uk>
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 <louis.rilling@kerlabs.com>
Signed-off-by: Joel Becker <Joel.Becker@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>
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 <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>
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 <louis.rilling@kerlabs.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>
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 <louis.rilling@kerlabs.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>
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 <louis.rilling@kerlabs.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>
On a similar pattern as mkdir() vs rmdir(), a failing symlink() may make rmdir()
fail for the symlink's parent and the symlink's target as well.
failing symlink() making target's rmdir() fail:
process 1: process 2:
symlink("A/S" -> "B")
allow_link()
create_link()
attach to "B" links list
rmdir("B")
detach_prep("B")
error because of new link
configfs_create_link("A", "S")
error (eg -ENOMEM)
failing symlink() making parent's rmdir() fail:
process 1: process 2:
symlink("A/D/S" -> "B")
allow_link()
create_link()
attach to "B" links list
configfs_create_link("A/D", "S")
make_dirent("A/D", "S")
rmdir("A")
detach_prep("A")
detach_prep("A/D")
error because of "S"
create("S")
error (eg -ENOMEM)
We cannot use the same solution as for mkdir() vs rmdir(), since rmdir() on the
target cannot wait on the i_mutex of the new symlink's parent without risking a
deadlock (with other symlink() or sys_rename()). Instead we define a global
mutex protecting all configfs symlinks attachment, so that rmdir() can avoid the
races above.
Signed-off-by: Louis Rilling <louis.rilling@kerlabs.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>
The rule for configfs symlinks is that symlinks always point to valid
config_items, and prevent the target from being removed. However,
configfs_symlink() only checks that it can grab a reference on the target item,
without ensuring that it remains alive until the symlink is correctly attached.
This patch makes configfs_symlink() fail whenever the target is being removed,
using the CONFIGFS_USET_DROPPING flag set by configfs_detach_prep() and
protected by configfs_dirent_lock.
This patch introduces a similar (weird?) behavior as with mkdir failures making
rmdir fail: if symlink() races with rmdir() of the parent directory (or its
youngest user-created ancestor if parent is a default group) or rmdir() of the
target directory, and then fails in configfs_create(), this can make the racing
rmdir() fail despite the concerned directory having no user-created entry (resp.
no symlink pointing to it or one of its default groups) in the end.
This behavior is fixed in later patches.
Signed-off-by: Louis Rilling <louis.rilling@kerlabs.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>
We now use PTR_ERR() in the ->make_item() and ->make_group() operations.
Folks including configfs.h need err.h.
Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>
The configfs operations ->make_item() and ->make_group() currently
return a new item/group. A return of NULL signifies an error. Because
of this, -ENOMEM is the only return code bubbled up the stack.
Multiple folks have requested the ability to return specific error codes
when these operations fail. This patch adds that ability by changing the
->make_item/group() ops to return ERR_PTR() values. These errors are
bubbled up appropriately. NULL returns are changed to -ENOMEM for
compatibility.
Also updated are the in-kernel users of configfs.
This is a rework of reverted commit 11c3b79218.
Signed-off-by: Joel Becker <joel.becker@oracle.com>
Nick Piggin
Al Viro
Tejun Heo
Jens Axboe
Louis Rilling
Subrata Modak
Mark Fasheh
Joel Becker
Alexey Dobriyan