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
..
file.c	debugfs: Add debugfs_create_ulong()	2015-10-18 10:14:39 -07:00
inode.c	debugfs: fix inode i_nlink references for automount dentry	2016-03-29 10:11:44 -07:00
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