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Roman Pen a8f324a46f debugfs: fix inode i_nlink references for automount dentry 
Directory inodes should start off with i_nlink == 2 (one extra ref
for "." entry).  debugfs_create_automount() increases neither the
i_nlink reference for current inode nor for parent inode.

On attempt to remove the automount dentry, kernel complains:

  [   86.288070] WARNING: CPU: 1 PID: 3616 at fs/inode.c:273 drop_nlink+0x3e/0x50()
  [   86.288461] Modules linked in: debugfs_example2(O-)
  [   86.288745] CPU: 1 PID: 3616 Comm: rmmod Tainted: G           O    4.4.0-rc3-next-20151207+ #135
  [   86.289197] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.8.2-20150617_082717-anatol 04/01/2014
  [   86.289696]  ffffffff81be05c9 ffff8800b9e6fda0 ffffffff81352e2c 0000000000000000
  [   86.290110]  ffff8800b9e6fdd8 ffffffff81065142 ffff8801399175e8 ffff8800bb78b240
  [   86.290507]  ffff8801399175e8 ffff8800b73d7898 ffff8800b73d7840 ffff8800b9e6fde8
  [   86.290933] Call Trace:
  [   86.291080]  [<ffffffff81352e2c>] dump_stack+0x4e/0x82
  [   86.291340]  [<ffffffff81065142>] warn_slowpath_common+0x82/0xc0
  [   86.291640]  [<ffffffff8106523a>] warn_slowpath_null+0x1a/0x20
  [   86.291932]  [<ffffffff811ae62e>] drop_nlink+0x3e/0x50
  [   86.292208]  [<ffffffff811ba35b>] simple_unlink+0x4b/0x60
  [   86.292481]  [<ffffffff811ba3a7>] simple_rmdir+0x37/0x50
  [   86.292748]  [<ffffffff812d9808>] __debugfs_remove.part.16+0xa8/0xd0
  [   86.293082]  [<ffffffff812d9a0b>] debugfs_remove_recursive+0xdb/0x1c0
  [   86.293406]  [<ffffffffa00004dd>] cleanup_module+0x2d/0x3b [debugfs_example2]
  [   86.293762]  [<ffffffff810d959b>] SyS_delete_module+0x16b/0x220
  [   86.294077]  [<ffffffff818ef857>] entry_SYSCALL_64_fastpath+0x12/0x6a
  [   86.294405] ---[ end trace c9fc53353fe14a36 ]---
  [   86.294639] ------------[ cut here ]------------

To reproduce the issue it is enough to invoke these lines:

     autom = debugfs_create_automount("automount", NULL, vfsmount_cb, data);
     BUG_ON(IS_ERR_OR_NULL(autom));
     debugfs_remove(autom);

The issue is fixed by increasing inode i_nlink references for current
and parent inodes.

Signed-off-by: Roman Pen <r.peniaev@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-03-29 10:11:44 -07:00
..
9p
wrappers for ->i_mutex access
2016-01-22 18:04:28 -05:00
adfs
fs/adfs/adfs.h: tidy up comments
2016-01-20 17:09:18 -08:00
affs
affs_do_readpage_ofs(): just use kmap_atomic() around memcpy()
2016-02-20 00:15:51 -05:00
afs
wrappers for ->i_mutex access
2016-01-22 18:04:28 -05:00
autofs4
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
2016-03-19 18:52:29 -07:00
befs
kmemcg: account certain kmem allocations to memcg
2016-01-14 16:00:49 -08:00
bfs
kmemcg: account certain kmem allocations to memcg
2016-01-14 16:00:49 -08:00
btrfs
Merge branch 'for-linus-4.6' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs
2016-03-21 18:12:42 -07:00
cachefiles
CacheFiles: Provide read-and-reset release counters for cachefilesd
2016-02-01 12:30:10 -05:00
ceph
ceph: use kmem_cache_zalloc
2016-03-25 18:51:56 +01:00
cifs
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
2016-03-19 18:52:29 -07:00
coda
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
2016-01-23 12:24:56 -08:00
configfs
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
2016-03-19 18:52:29 -07:00
cramfs
don't put symlink bodies in pagecache into highmem
2015-12-08 22:41:36 -05:00
crypto
f2fs/crypto: fix xts_tweak initialization
2016-03-26 10:13:05 -07:00
debugfs
debugfs: fix inode i_nlink references for automount dentry
2016-03-29 10:11:44 -07:00
devpts
pty: make sure super_block is still valid in final /dev/tty close
2016-02-06 23:45:46 -08:00
dlm
dlm for 4.6
2016-03-17 16:38:36 -07:00
ecryptfs
Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6
2016-03-23 06:12:39 -07:00
efivarfs
efi: Make efivarfs entries immutable by default
2016-02-10 16:25:52 +00:00
efs
kmemcg: account certain kmem allocations to memcg
2016-01-14 16:00:49 -08:00
exofs
wrappers for ->i_mutex access
2016-01-22 18:04:28 -05:00
exportfs
wrappers for ->i_mutex access
2016-01-22 18:04:28 -05:00
ext2
Performance improvements in SEEK_DATA and xattr scalability
2016-03-17 16:31:18 -07:00
ext4
ext4: in ext4_dir_llseek, check syscall bitness directly
2016-03-22 15:36:02 -07:00
f2fs
f2fs: submit node page write bios when really required
2016-03-17 21:19:47 -07:00
fat
fat: add config option to set UTF-8 mount option by default
2016-03-22 15:36:02 -07:00
freevxfs
don't put symlink bodies in pagecache into highmem
2015-12-08 22:41:36 -05:00
fscache
FS-Cache: Handle a write to the page immediately beyond the EOF marker
2015-11-11 02:11:02 -05:00
fuse
fuse: return patrial success from fuse_direct_io()
2016-03-16 14:38:31 +01:00
gfs2
GFS2: merge window
2016-03-17 16:51:32 -07:00
hfs
wrappers for ->i_mutex access
2016-01-22 18:04:28 -05:00
hfsplus
wrappers for ->i_mutex access
2016-01-22 18:04:28 -05:00
hostfs
wrappers for ->i_mutex access
2016-01-22 18:04:28 -05:00
hpfs
hpfs: don't truncate the file when delete fails
2016-02-27 19:15:51 -05:00
hugetlbfs
wrappers for ->i_mutex access
2016-01-22 18:04:28 -05:00
isofs
kmemcg: account certain kmem allocations to memcg
2016-01-14 16:00:49 -08:00
jbd2
jbd2: do not fail journal because of frozen_buffer allocation failure
2016-03-13 17:38:20 -04:00
jffs2
MTD updates for v4.6
2016-03-24 19:57:15 -07:00
jfs
wrappers for ->i_mutex access
2016-01-22 18:04:28 -05:00
kernfs
Merge branch 'for-4.6-ns' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
2016-03-21 10:05:13 -07:00
lockd
lockd: constify nlmsvc_binding structure
2016-01-07 10:10:50 -05:00
logfs
wrappers for ->i_mutex access
2016-01-22 18:04:28 -05:00
minix
kmemcg: account certain kmem allocations to memcg
2016-01-14 16:00:49 -08:00
ncpfs
ncpfs: fix a braino in OOM handling in ncp_fill_cache()
2016-03-07 22:25:16 -05:00
nfs
Various bugfixes, a RDMA update from Chuck Lever, and support for a new
2016-03-24 19:50:32 -07:00
nfs_common
lockd: NLM grace period shouldn't block NFSv4 opens
2015-08-13 10:22:06 -04:00
nfsd
Various bugfixes, a RDMA update from Chuck Lever, and support for a new
2016-03-24 19:50:32 -07:00
nilfs2
mm: introduce page reference manipulation functions
2016-03-17 15:09:34 -07:00
nls
…
notify
fsnotify: turn fsnotify reaper thread into a workqueue job
2016-02-18 16:23:24 -08:00
ntfs
wrappers for ->i_mutex access
2016-01-22 18:04:28 -05:00
ocfs2
ocfs2: extend enough credits for freeing one truncate record while replaying truncate records
2016-03-25 16:37:42 -07:00
omfs
…
openpromfs
kmemcg: account certain kmem allocations to memcg
2016-01-14 16:00:49 -08:00
orangefs
orangefs: fix orangefs_superblock locking
2016-03-26 07:22:00 -04:00
overlayfs
ovl: cleanup unused var in rename2
2016-03-21 17:31:46 +01:00
proc
Merge branch 'for-4.6-ns' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
2016-03-21 10:05:13 -07:00
pstore
pstore: Add support for 64 Bit address space
2016-03-10 09:43:36 -08:00
qnx4
kmemcg: account certain kmem allocations to memcg
2016-01-14 16:00:49 -08:00
qnx6
kmemcg: account certain kmem allocations to memcg
2016-01-14 16:00:49 -08:00
quota
Merge branch 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs
2016-03-21 12:22:37 -07:00
ramfs
don't put symlink bodies in pagecache into highmem
2015-12-08 22:41:36 -05:00
reiserfs
quota: Add support for ->get_nextdqblk() for VFS quota
2016-02-09 13:05:23 +01:00
romfs
kmemcg: account certain kmem allocations to memcg
2016-01-14 16:00:49 -08:00
squashfs
kmemcg: account certain kmem allocations to memcg
2016-01-14 16:00:49 -08:00
sysfs
platform/chrome: Branch for v4.4
2015-11-13 21:53:18 -08:00
sysv
kmemcg: account certain kmem allocations to memcg
2016-01-14 16:00:49 -08:00
tracefs
wrappers for ->i_mutex access
2016-01-22 18:04:28 -05:00
ubifs
ubifs: Remove unused header
2016-03-20 21:37:46 +01:00
udf
udf: Merge linux specific translation into CS0 conversion function
2016-02-09 13:05:23 +01:00
ufs
kmemcg: account certain kmem allocations to memcg
2016-01-14 16:00:49 -08:00
xfs
Various bugfixes, a RDMA update from Chuck Lever, and support for a new
2016-03-24 19:50:32 -07:00
aio.c
mm: move ->mremap() from file_operations to vm_operations_struct
2015-09-04 16:54:41 -07:00
anon_inodes.c
…
attr.c
wrappers for ->i_mutex access
2016-01-22 18:04:28 -05:00
bad_inode.c
fs/bad_inode.c: is_bad_inode can be boolean
2015-12-06 21:17:14 -05:00
binfmt_aout.c
…
binfmt_elf_fdpic.c
libnvdimm for 4.4:
2015-11-10 12:07:22 -08:00
binfmt_elf.c
mm: ASLR: use get_random_long()
2016-02-27 10:28:52 -08:00
binfmt_em86.c
…
binfmt_flat.c
…
binfmt_misc.c
wrappers for ->i_mutex access
2016-01-22 18:04:28 -05:00
binfmt_script.c
…
block_dev.c
Merge branch 'for-4.6/core' of git://git.kernel.dk/linux-block
2016-03-18 16:43:11 -07:00
buffer.c
mm: simplify lock_page_memcg()
2016-03-15 16:55:16 -07:00
char_dev.c
chrdev: emit a warning when we go below dynamic major range
2016-03-29 10:11:44 -07:00
compat_binfmt_elf.c
…
compat_ioctl.c
Merge 4.5-rc4 into char-misc-next
2016-02-14 14:25:59 -08:00
compat.c
saner calling conventions for copy_mount_options()
2016-01-04 10:28:32 -05:00
coredump.c
fs/coredump: prevent fsuid=0 dumps into user-controlled directories
2016-03-22 15:36:02 -07:00
dax.c
xfs: Changes for 4.6-rc1
2016-03-21 11:53:05 -07:00
dcache.c
dcache.c: new helper: __d_add()
2016-03-14 00:17:38 -04:00
dcookies.c
…
direct-io.c
xfs: Changes for 4.6-rc1
2016-03-21 11:53:05 -07:00
drop_caches.c
inode: convert inode_sb_list_lock to per-sb
2015-08-17 18:39:46 -04:00
eventfd.c
eventfd: document lockless access in eventfd_poll
2016-03-22 15:36:02 -07:00
eventpoll.c
timer: convert timer_slack_ns from unsigned long to u64
2016-03-17 15:09:34 -07:00
exec.c
Merge branch 'mm-pkeys-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
2016-03-20 19:08:56 -07:00
fcntl.c
fcntl: allow to set O_DIRECT flag on pipe
2016-01-09 02:55:37 -05:00
fhandle.c
fs/coredump: prevent fsuid=0 dumps into user-controlled directories
2016-03-22 15:36:02 -07:00
file_table.c
fs, file table: reinit files_stat.max_files after deferred memory initialisation
2015-08-07 04:39:40 +03:00
file.c
kmemcg: account certain kmem allocations to memcg
2016-01-14 16:00:49 -08:00
filesystems.c
find_filesystem(): simplify comparison
2016-01-19 12:02:23 -05:00
fs_pin.c
…
fs_struct.c
…
fs-writeback.c
writeback, cgroup: fix use of the wrong bdi_writeback which mismatches the inode
2016-03-20 09:44:20 -06:00
inode.c
writeback: initialize inode members that track writeback history
2016-02-16 14:57:21 -07:00
internal.h
Merge branch 'for-linus' into work.misc
2016-01-08 21:20:11 -05:00
ioctl.c
wrappers for ->i_mutex access
2016-01-22 18:04:28 -05:00
Kconfig
Merge tag 'ofs-pull-tag-1' of git://git.kernel.org/pub/scm/linux/kernel/git/hubcap/linux
2016-03-26 12:59:04 -07:00
Kconfig.binfmt
…
libfs.c
wrappers for ->i_mutex access
2016-01-22 18:04:28 -05:00
locks.c
wrappers for ->i_mutex access
2016-01-22 18:04:28 -05:00
Makefile
Merge tag 'ofs-pull-tag-1' of git://git.kernel.org/pub/scm/linux/kernel/git/hubcap/linux
2016-03-26 12:59:04 -07:00
mbcache.c
mbcache: add reusable flag to cache entries
2016-02-22 22:44:04 -05:00
mount.h
fs: use seq_open_private() for proc_mounts
2015-06-30 19:44:56 -07:00
mpage.c
fs/mpage.c:mpage_readpages(): use lru_to_page() helper
2016-03-15 16:55:16 -07:00
namei.c
kill dentry_unhash()
2016-03-14 00:16:33 -04:00
namespace.c
wrappers for ->i_mutex access
2016-01-22 18:04:28 -05:00
no-block.c
…
nsfs.c
fs/seq_file: convert int seq_vprint/seq_printf/etc... returns to void
2015-09-11 15:21:34 -07:00
open.c
fs/coredump: prevent fsuid=0 dumps into user-controlled directories
2016-03-22 15:36:02 -07:00
pipe.c
pipe: limit the per-user amount of pages allocated in pipes
2016-01-19 19:25:21 -05:00
pnode.c
fs/pnode.c: treat zero mnt_group_id-s as unequal
2016-02-20 00:15:52 -05:00
pnode.h
mnt: Clarify and correct the disconnect logic in umount_tree
2015-07-22 20:33:27 -05:00
posix_acl.c
xattr handlers: Simplify list operation
2015-12-13 19:46:12 -05:00
proc_namespace.c
vfs: show_vfsstat: do not ignore errors from show_devname method
2016-03-16 13:09:08 -04:00
read_write.c
Merge branches 'work.lookups', 'work.misc' and 'work.preadv2' into for-next
2016-03-18 16:07:38 -04:00
readdir.c
wrappers for ->i_mutex access
2016-01-22 18:04:28 -05:00
select.c
timer: convert timer_slack_ns from unsigned long to u64
2016-03-17 15:09:34 -07:00
seq_file.c
fs, seqfile: always allow oom killer
2015-11-06 17:50:42 -08:00
signalfd.c
signalfd: fix information leak in signalfd_copyinfo
2015-08-07 04:39:40 +03:00
splice.c
Merge branches 'work.lookups', 'work.misc' and 'work.preadv2' into for-next
2016-03-18 16:07:38 -04:00
stack.c
…
stat.c
fs/stat.c: drop the last new_valid_dev check
2016-01-16 11:17:23 -08:00
statfs.c
…
super.c
writeback: flush inode cgroup wb switches instead of pinning super_block
2016-03-03 14:42:50 -07:00
sync.c
fs/sync.c: make sync_file_range(2) use WB_SYNC_NONE writeback
2015-11-06 17:50:42 -08:00
timerfd.c
timerfd: Handle relative timers with CONFIG_TIME_LOW_RES proper
2016-01-17 11:13:55 +01:00
userfaultfd.c
userfaultfd: don't block on the last VM updates at exit time
2016-03-02 09:03:18 -08:00
utimes.c
wrappers for ->i_mutex access
2016-01-22 18:04:28 -05:00
xattr.c
xattr handlers: plug a lock leak in simple_xattr_list
2016-02-20 00:15:51 -05:00