Now that we never use the backing_dev_info pointer in struct address_space
we can simply remove it and save 4 to 8 bytes in every inode.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Reviewed-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>
Since "BDI: Provide backing device capability information [try #3]" the
backing_dev_info structure also provides flags for the kind of mmap
operation available in a nommu environment, which is entirely unrelated
to it's original purpose.
Introduce a new nommu-only file operation to provide this information to
the nommu mmap code instead. Splitting this from the backing_dev_info
structure allows to remove lots of backing_dev_info instance that aren't
otherwise needed, and entirely gets rid of the concept of providing a
backing_dev_info for a character device. It also removes the need for
the mtd_inodefs filesystem.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Tejun Heo <tj@kernel.org>
Acked-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Add pr_fmt based on module name.
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix function parameter documentation
EXPORT_SYMBOLS moved after corresponding functions
Small coding style and checkpatch warning fixes
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Acked-by: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
A race window in configfs, it starts from one dentry is UNHASHED and end
before configfs_d_iput is called. In this window, if a lookup happen,
since the original dentry was UNHASHED, so a new dentry will be
allocated, and then in configfs_attach_attr(), sd->s_dentry will be
updated to the new dentry. Then in configfs_d_iput(),
BUG_ON(sd->s_dentry != dentry) will be triggered and system panic.
sys_open: sys_close:
... fput
dput
dentry_kill
__d_drop <--- dentry unhashed here,
but sd->dentry still point
to this dentry.
lookup_real
configfs_lookup
configfs_attach_attr---> update sd->s_dentry
to new allocated dentry here.
d_kill
configfs_d_iput <--- BUG_ON(sd->s_dentry != dentry)
triggered here.
To fix it, change configfs_d_iput to not update sd->s_dentry if
sd->s_count > 2, that means there are another dentry is using the sd
beside the one that is going to be put. Use configfs_dirent_lock in
configfs_attach_attr to sync with configfs_d_iput.
With the following steps, you can reproduce the bug.
1. enable ocfs2, this will mount configfs at /sys/kernel/config and
fill configure in it.
2. run the following script.
while [ 1 ]; do cat /sys/kernel/config/cluster/$your_cluster_name/idle_timeout_ms > /dev/null; done &
while [ 1 ]; do cat /sys/kernel/config/cluster/$your_cluster_name/idle_timeout_ms > /dev/null; done &
Signed-off-by: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Rename simple_delete_dentry() to always_delete_dentry() and export it.
Export simple_dentry_operations, while we are at it, and get rid of
their duplicates
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Pull more vfs stuff from Al Viro:
"O_TMPFILE ABI changes, Oleg's fput() series, misc cleanups, including
making simple_lookup() usable for filesystems with non-NULL s_d_op,
which allows us to get rid of quite a bit of ugliness"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
sunrpc: now we can just set ->s_d_op
cgroup: we can use simple_lookup() now
efivarfs: we can use simple_lookup() now
make simple_lookup() usable for filesystems that set ->s_d_op
configfs: don't open-code d_alloc_name()
__rpc_lookup_create_exclusive: pass string instead of qstr
rpc_create_*_dir: don't bother with qstr
llist: llist_add() can use llist_add_batch()
llist: fix/simplify llist_add() and llist_add_batch()
fput: turn "list_head delayed_fput_list" into llist_head
fs/file_table.c:fput(): add comment
Safer ABI for O_TMPFILE
Pull third set of VFS updates from Al Viro:
"Misc stuff all over the place. There will be one more pile in a
couple of days"
This is an "evil merge" that also uses the new d_count helper in
fs/configfs/dir.c, missed by commit 84d08fa888 ("helper for reading
->d_count")
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
ncpfs: fix error return code in ncp_parse_options()
locks: move file_lock_list to a set of percpu hlist_heads and convert file_lock_lock to an lglock
seq_file: add seq_list_*_percpu helpers
f2fs: fix readdir incorrectness
mode_t whack-a-mole...
lustre: kill the pointless wrapper
helper for reading ->d_count
The difference between "count" and "len" is that "len" is capped at
4095. Changing it like this makes it match how sysfs_write_file() is
implemented.
This is a static analysis patch. I haven't found any store_attribute()
functions where this change makes a difference.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Modify the request_module to prefix the file system type with "fs-"
and add aliases to all of the filesystems that can be built as modules
to match.
A common practice is to build all of the kernel code and leave code
that is not commonly needed as modules, with the result that many
users are exposed to any bug anywhere in the kernel.
Looking for filesystems with a fs- prefix limits the pool of possible
modules that can be loaded by mount to just filesystems trivially
making things safer with no real cost.
Using aliases means user space can control the policy of which
filesystem modules are auto-loaded by editing /etc/modprobe.d/*.conf
with blacklist and alias directives. Allowing simple, safe,
well understood work-arounds to known problematic software.
This also addresses a rare but unfortunate problem where the filesystem
name is not the same as it's module name and module auto-loading
would not work. While writing this patch I saw a handful of such
cases. The most significant being autofs that lives in the module
autofs4.
This is relevant to user namespaces because we can reach the request
module in get_fs_type() without having any special permissions, and
people get uncomfortable when a user specified string (in this case
the filesystem type) goes all of the way to request_module.
After having looked at this issue I don't think there is any
particular reason to perform any filtering or permission checks beyond
making it clear in the module request that we want a filesystem
module. The common pattern in the kernel is to call request_module()
without regards to the users permissions. In general all a filesystem
module does once loaded is call register_filesystem() and go to sleep.
Which means there is not much attack surface exposed by loading a
filesytem module unless the filesystem is mounted. In a user
namespace filesystems are not mounted unless .fs_flags = FS_USERNS_MOUNT,
which most filesystems do not set today.
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Acked-by: Kees Cook <keescook@chromium.org>
Reported-by: Kees Cook <keescook@google.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Pull vfs pile (part one) from Al Viro:
"Assorted stuff - cleaning namei.c up a bit, fixing ->d_name/->d_parent
locking violations, etc.
The most visible changes here are death of FS_REVAL_DOT (replaced with
"has ->d_weak_revalidate()") and a new helper getting from struct file
to inode. Some bits of preparation to xattr method interface changes.
Misc patches by various people sent this cycle *and* ocfs2 fixes from
several cycles ago that should've been upstream right then.
PS: the next vfs pile will be xattr stuff."
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (46 commits)
saner proc_get_inode() calling conventions
proc: avoid extra pde_put() in proc_fill_super()
fs: change return values from -EACCES to -EPERM
fs/exec.c: make bprm_mm_init() static
ocfs2/dlm: use GFP_ATOMIC inside a spin_lock
ocfs2: fix possible use-after-free with AIO
ocfs2: Fix oops in ocfs2_fast_symlink_readpage() code path
get_empty_filp()/alloc_file() leave both ->f_pos and ->f_version zero
target: writev() on single-element vector is pointless
export kernel_write(), convert open-coded instances
fs: encode_fh: return FILEID_INVALID if invalid fid_type
kill f_vfsmnt
vfs: kill FS_REVAL_DOT by adding a d_weak_revalidate dentry op
nfsd: handle vfs_getattr errors in acl protocol
switch vfs_getattr() to struct path
default SET_PERSONALITY() in linux/elf.h
ceph: prepopulate inodes only when request is aborted
d_hash_and_lookup(): export, switch open-coded instances
9p: switch v9fs_set_create_acl() to inode+fid, do it before d_instantiate()
9p: split dropping the acls from v9fs_set_create_acl()
...
The dereference should be moved below the NULL test.
spatch with a semantic match is used to found this.
(http://coccinelle.lip6.fr/)
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
But the kernel decided to call it "origin" instead. Fix most of the
sites.
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Just the flags; only NFS cares even about that, but there are
legitimate uses for such argument. And getting rid of that
completely would require splitting ->lookup() into a couple
of methods (at least), so let's leave that alone for now...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
vfs_mkdir() gets int, but immediately drops everything that might not
fit into umode_t and that's the only caller of ->mkdir()...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
There are numerous broken references to Documentation files (in other
Documentation files, in comments, etc.). These broken references are
caused by typo's in the references, and by renames or removals of the
Documentation files. Some broken references are simply odd.
Fix these broken references, sometimes by dropping the irrelevant text
they were part of.
Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
configfs does not have problems with references to unlinked directories.
CC: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Sage Weil <sage@newdream.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6: (25 commits)
cifs: remove unnecessary dentry_unhash on rmdir/rename_dir
ocfs2: remove unnecessary dentry_unhash on rmdir/rename_dir
exofs: remove unnecessary dentry_unhash on rmdir/rename_dir
nfs: remove unnecessary dentry_unhash on rmdir/rename_dir
ext2: remove unnecessary dentry_unhash on rmdir/rename_dir
ext3: remove unnecessary dentry_unhash on rmdir/rename_dir
ext4: remove unnecessary dentry_unhash on rmdir/rename_dir
btrfs: remove unnecessary dentry_unhash in rmdir/rename_dir
ceph: remove unnecessary dentry_unhash calls
vfs: clean up vfs_rename_other
vfs: clean up vfs_rename_dir
vfs: clean up vfs_rmdir
vfs: fix vfs_rename_dir for FS_RENAME_DOES_D_MOVE filesystems
libfs: drop unneeded dentry_unhash
vfs: update dentry_unhash() comment
vfs: push dentry_unhash on rename_dir into file systems
vfs: push dentry_unhash on rmdir into file systems
vfs: remove dget() from dentry_unhash()
vfs: dentry_unhash immediately prior to rmdir
vfs: Block mmapped writes while the fs is frozen
...
Only a few file systems need this. Start by pushing it down into each
fs rmdir method (except gfs2 and xfs) so it can be dealt with on a per-fs
basis.
This does not change behavior for any in-tree file systems.
Acked-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sage Weil <sage@newdream.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
configfs_readdir() will use the existing inode numbers of inodes in the
dcache, but it makes them up for attribute files that aren't currently
instantiated. There is a race where a closing attribute file can be
tearing down at the same time as configfs_readdir() is trying to get its
inode number.
We want to get the inode number of open attribute files, because they
should match while instantiated. We can't lock down the transition
where dentry->d_inode is set to NULL, so we just check for NULL there.
We can, however, ensure that an inode we find isn't iput() in
configfs_d_iput() until after we've accessed it.
Signed-off-by: Joel Becker <jlbec@evilplan.org>
When configfs is faking mkdir() on its subsystem or default group
objects, it starts by adding a negative dentry. It then tries to
instantiate the group. If that should fail, it must clean up after
itself.
I was using d_delete() here, but configfs_attach_group() promises to
return an empty dentry on error. d_delete() explodes with the entry
dentry. Let's try d_drop() instead. The unhashing is what we want for
our dentry.
Signed-off-by: Joel Becker <jlbec@evilplan.org>
This patch changes configfs to select SYSFS to fix the following:
warning: (TARGET_CORE && GFS2_FS) selects CONFIGFS_FS which has unmet direct dependencies (SYSFS)
Reported-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Nicholas A. Bellinger <nab@linux-iscsi.org>
Acked-by: Joel Becker <jlbec@evilplan.org>
Reduce some branches and memory accesses in dcache lookup by adding dentry
flags to indicate common d_ops are set, rather than having to check them.
This saves a pointer memory access (dentry->d_op) in common path lookup
situations, and saves another pointer load and branch in cases where we
have d_op but not the particular operation.
Patched with:
git grep -E '[.>]([[:space:]])*d_op([[:space:]])*=' | xargs sed -e 's/\([^\t ]*\)->d_op = \(.*\);/d_set_d_op(\1, \2);/' -e 's/\([^\t ]*\)\.d_op = \(.*\);/d_set_d_op(\&\1, \2);/' -i
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
dget_locked was a shortcut to avoid the lazy lru manipulation when we already
held dcache_lock (lru manipulation was relatively cheap at that point).
However, how that the lru lock is an innermost one, we never hold it at any
caller, so the lock cost can now be avoided. We already have well working lazy
dcache LRU, so it should be fine to defer LRU manipulations to scan time.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Protect d_unhashed(dentry) condition with d_lock. This means keeping
DCACHE_UNHASHED bit in synch with hash manipulations.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Make d_count non-atomic and protect it with d_lock. This allows us to ensure a
0 refcount dentry remains 0 without dcache_lock. It is also fairly natural when
we start protecting many other dentry members with d_lock.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Change d_delete from a dentry deletion notification to a dentry caching
advise, more like ->drop_inode. Require it to be constant and idempotent,
and not take d_lock. This is how all existing filesystems use the callback
anyway.
This makes fine grained dentry locking of dput and dentry lru scanning
much simpler.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Switching d_op on a live dentry is racy in general, so avoid it. In this case
it is a negative dentry, which is safer, but there are still concurrent ops
which may be called on d_op in that case (eg. d_revalidate). So in general
a filesystem may not do this. Fix configfs so as not to do this.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Instead of always assigning an increasing inode number in new_inode
move the call to assign it into those callers that actually need it.
For now callers that need it is estimated conservatively, that is
the call is added to all filesystems that do not assign an i_ino
by themselves. For a few more filesystems we can avoid assigning
any inode number given that they aren't user visible, and for others
it could be done lazily when an inode number is actually needed,
but that's left for later patches.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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>
When allow_link() succeeds but create_link() fails, the subsystem is not
informed of the failure.
This patch fixes this by calling drop_link() on create_link() failures.
Signed-off-by: Louis Rilling <Louis.Rilling@kerlabs.com>
Signed-off-by: Joel Becker <joel.becker@oracle.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 an int.
Also updated are the in-kernel users of configfs.
Signed-off-by: Joel Becker <joel.becker@oracle.com>
When fixing the rename() vs rmdir() deadlock, we stopped locking default groups'
inodes in configfs_detach_prep(), letting racing mkdir() in default groups
proceed concurrently. This enables races like below happen, which leads to a
failing mkdir() making rmdir() fail, despite the group to remove having no
user-created directory under it in the end.
process A: process B:
/* PWD=A/B */
mkdir("C")
make_item("C")
attach_group("C")
rmdir("A")
detach_prep("A")
detach_prep("B")
error because of "C"
return -ENOTEMPTY
attach_group("C/D")
error (eg -ENOMEM)
return -ENOMEM
This patch prevents such scenarii by making rmdir() wait as long as
detach_prep() fails because a racing mkdir() is in the middle of attach_group().
To achieve this, mkdir() sets a flag CONFIGFS_USET_IN_MKDIR in parent's
configfs_dirent before calling attach_group(), and clears the flag once
attach_group() is done. detach_prep() fails with -EAGAIN whenever the flag is
hit and returns the guilty inode's mutex so that rmdir() can wait on it.
Signed-off-by: Louis Rilling <Louis.Rilling@kerlabs.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
This patch fixes the deadlock between racing sys_rename() and configfs_rmdir().
The idea is to avoid locking i_mutexes of default groups in
configfs_detach_prep(), and rely instead on the new configfs_dirent_lock to
protect against configfs_dirent's linkage mutations. To ensure that an mkdir()
racing with rmdir() will not create new items in a to-be-removed default group,
we make configfs_new_dirent() check for the CONFIGFS_USET_DROPPING flag right
before linking the new dirent, and return error if the flag is set. This makes
racing mkdir()/symlink()/dir_open() fail in places where errors could already
happen, resp. in (attach_item()|attach_group())/create_link()/new_dirent().
configfs_depend() remains safe since it locks all the path from configfs root,
and is thus mutually exclusive with rmdir().
An advantage of this is that now detach_groups() unconditionnaly takes the
default groups i_mutex, which makes it more consistent with populate_groups().
Signed-off-by: Louis Rilling <Louis.Rilling@kerlabs.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
This patch makes configfs_new_dirent return negative error code instead of NULL,
which will be useful in the next patch to differentiate ENOMEM from ENOENT.
Signed-off-by: Louis Rilling <Louis.Rilling@kerlabs.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
Symlinks to a config_item are listed under its configfs_dirent s_links, but the
list mutations are not protected by any common lock.
This patch uses the configfs_dirent_lock spinlock to add the necessary
protection.
Note: we should also protect the list_empty() test in configfs_detach_prep() but
1/ the lock should not be released immediately because nothing would prevent the
list from being filled after a successful list_empty() test, making the problem
tricky,
2/ this will be solved by the rmdir() vs rename() deadlock bugfix.
Signed-off-by: Louis Rilling <Louis.Rilling@kerlabs.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
This patch introduces configfs_dirent_lock spinlock to protect configfs_dirent
traversals against linkage mutations (add/del/move). This will allow
configfs_detach_prep() to avoid locking i_mutexes.
Locking rules for configfs_dirent linkage mutations are the same plus the
requirement of taking configfs_dirent_lock. For configfs_dirent walking, one can
either take appropriate i_mutex as before, or take configfs_dirent_lock.
The spinlock could actually be a mutex, but the critical sections are either
O(1) or should not be too long (default groups walking in last patch).
ChangeLog:
- Clarify the comment on configfs_dirent_lock usage
- Move sd->s_element init before linking the new dirent
- In lseek(), do not release configfs_dirent_lock before the dirent is
relinked.
Signed-off-by: Louis Rilling <Louis.Rilling@kerlabs.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
__FUNCTION__ is gcc-specific, use __func__
Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add a new BDI capability flag: BDI_CAP_NO_ACCT_WB. If this flag is
set, then don't update the per-bdi writeback stats from
test_set_page_writeback() and test_clear_page_writeback().
Misc cleanups:
- convert bdi_cap_writeback_dirty() and friends to static inline functions
- create a flag that includes all three dirty/writeback related flags,
since almst all users will want to have them toghether
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Add path_put() functions for releasing a reference to the dentry and
vfsmount of a struct path in the right order
* Switch from path_release(nd) to path_put(&nd->path)
* Rename dput_path() to path_put_conditional()
[akpm@linux-foundation.org: fix cifs]
Signed-off-by: Jan Blunck <jblunck@suse.de>
Signed-off-by: Andreas Gruenbacher <agruen@suse.de>
Acked-by: Christoph Hellwig <hch@lst.de>
Cc: <linux-fsdevel@vger.kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Steven French <sfrench@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This is the central patch of a cleanup series. In most cases there is no good
reason why someone would want to use a dentry for itself. This series reflects
that fact and embeds a struct path into nameidata.
Together with the other patches of this series
- it enforced the correct order of getting/releasing the reference count on
<dentry,vfsmount> pairs
- it prepares the VFS for stacking support since it is essential to have a
struct path in every place where the stack can be traversed
- it reduces the overall code size:
without patch series:
text data bss dec hex filename
5321639 858418 715768 6895825 6938d1 vmlinux
with patch series:
text data bss dec hex filename
5320026 858418 715768 6894212 693284 vmlinux
This patch:
Switch from nd->{dentry,mnt} to nd->path.{dentry,mnt} everywhere.
[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: fix cifs]
[akpm@linux-foundation.org: fix smack]
Signed-off-by: Jan Blunck <jblunck@suse.de>
Signed-off-by: Andreas Gruenbacher <agruen@suse.de>
Acked-by: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There is no need for kobject_unregister() anymore, thanks to Kay's
kobject cleanup changes, so replace all instances of it with
kobject_put().
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
kernel_kset does not need to be a kset, but a much simpler kobject now
that we have kobj_attributes.
We also rename kernel_kset to kernel_kobj to catch all users of this
symbol with a build error instead of an easy-to-ignore build warning.
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Dynamically create the kset instead of declaring it statically. We also
rename kernel_subsys to kernel_kset to catch all users of this symbol
with a build error instead of an easy-to-ignore build warning.
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
We don't need a kset here, a simple kobject will do just fine, so
dynamically create the kobject and use it.
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
We don't need a "default" ktype for a kset. We should set this
explicitly every time for each kset. This change is needed so that we
can make ksets dynamic, and cleans up one of the odd, undocumented
assumption that the kset/kobject/ktype model has.
This patch is based on a lot of help from Kay Sievers.
Nasty bug in the block code was found by Dave Young
<hidave.darkstar@gmail.com>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: Dave Young <hidave.darkstar@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Why do we need r/o bind mounts?
This feature allows a read-only view into a read-write filesystem. In the
process of doing that, it also provides infrastructure for keeping track of
the number of writers to any given mount.
This has a number of uses. It allows chroots to have parts of filesystems
writable. It will be useful for containers in the future because users may
have root inside a container, but should not be allowed to write to
somefilesystems. This also replaces patches that vserver has had out of the
tree for several years.
It allows security enhancement by making sure that parts of your filesystem
read-only (such as when you don't trust your FTP server), when you don't want
to have entire new filesystems mounted, or when you want atime selectively
updated. I've been using the following script to test that the feature is
working as desired. It takes a directory and makes a regular bind and a r/o
bind mount of it. It then performs some normal filesystem operations on the
three directories, including ones that are expected to fail, like creating a
file on the r/o mount.
This patch:
Some filesystems forego the vfs and may_open() and create their own 'struct
file's.
This patch creates a couple of helper functions which can be used by these
filesystems, and will provide a unified place which the r/o bind mount code
may patch.
Also, rename an existing, static-scope init_file() to a less generic name.
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Implement new aops for some of the simpler filesystems.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Slab destructors were no longer supported after Christoph's
c59def9f22 change. They've been
BUGs for both slab and slub, and slob never supported them
either.
This rips out support for the dtor pointer from kmem_cache_create()
completely and fixes up every single callsite in the kernel (there were
about 224, not including the slab allocator definitions themselves,
or the documentation references).
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Sometimes other drivers depend on particular configfs items. For
example, ocfs2 mounts depend on a heartbeat region item. If that
region item is removed with rmdir(2), the ocfs2 mount must BUG or go
readonly. Not happy.
This provides two additional API calls: configfs_depend_item() and
configfs_undepend_item(). A client driver can call
configfs_depend_item() on an existing item to tell configfs that it is
depended on. configfs will then return -EBUSY from rmdir(2) for that
item. When the item is no longer depended on, the client driver calls
configfs_undepend_item() on it.
These API cannot be called underneath any configfs callbacks, as
they will conflict. They can block and allocate. A client driver
probably shouldn't calling them of its own gumption. Rather it should
be providing an API that external subsystems call.
How does this work? Imagine the ocfs2 mount process. When it mounts,
it asks for a heart region item. This is done via a call into the
heartbeat code. Inside the heartbeat code, the region item is looked
up. Here, the heartbeat code calls configfs_depend_item(). If it
succeeds, then heartbeat knows the region is safe to give to ocfs2.
If it fails, it was being torn down anyway, and heartbeat can gracefully
pass up an error.
[ Fixed some bad whitespace in configfs.txt. --Mark ]
Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
Add a notification callback, ops->disconnect_notify(). It has the same
prototype as ->drop_item(), but it will be called just before the item
linkage is broken. This way, configfs users who want to do work while
the object is still in the heirarchy have a chance.
Client drivers will still need to config_item_put() in their
->drop_item(), if they implement it. They need do nothing in
->disconnect_notify(). They don't have to provide it if they don't
care. But someone who wants to be notified before ci_parent is set to
NULL can now be notified.
Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
Seems copied from sysfs, but I don't see a reason here nor there to use
a semaphore instead of a mutex. Convert.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
