cifs: delay super block destruction until all cifsFileInfo objects are gone
cifsFileInfo objects hold references to dentries and it is possible that
these will still be around in workqueues when VFS decides to kill super
block during unmount.
This results in panics like this one:
BUG: Dentry ffff88001f5e76c0{i=66b4a,n=1M-2} still in use (1) [unmount of cifs cifs]
------------[ cut here ]------------
kernel BUG at fs/dcache.c:943!
[..]
Process umount (pid: 1781, threadinfo ffff88003d6e8000, task ffff880035eeaec0)
[..]
Call Trace:
[<ffffffff811b44f3>] shrink_dcache_for_umount+0x33/0x60
[<ffffffff8119f7fc>] generic_shutdown_super+0x2c/0xe0
[<ffffffff8119f946>] kill_anon_super+0x16/0x30
[<ffffffffa036623a>] cifs_kill_sb+0x1a/0x30 [cifs]
[<ffffffff8119fcc7>] deactivate_locked_super+0x57/0x80
[<ffffffff811a085e>] deactivate_super+0x4e/0x70
[<ffffffff811bb417>] mntput_no_expire+0xd7/0x130
[<ffffffff811bc30c>] sys_umount+0x9c/0x3c0
[<ffffffff81657c19>] system_call_fastpath+0x16/0x1b
Fix this by making each cifsFileInfo object hold a reference to cifs
super block, which implicitly keeps VFS super block around as well.
Signed-off-by: Mateusz Guzik <mguzik@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Cc: <stable@vger.kernel.org>
Reported-and-Tested-by: Ben Greear <greearb@candelatech.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
diff --git a/fs/cifs/cifsfs.h b/fs/cifs/cifsfs.h
index 7163419..0e32c34 100644
--- a/fs/cifs/cifsfs.h
+++ b/fs/cifs/cifsfs.h
@@ -41,6 +41,10 @@
extern const struct address_space_operations cifs_addr_ops;
extern const struct address_space_operations cifs_addr_ops_smallbuf;
+/* Functions related to super block operations */
+extern void cifs_sb_active(struct super_block *sb);
+extern void cifs_sb_deactive(struct super_block *sb);
+
/* Functions related to inodes */
extern const struct inode_operations cifs_dir_inode_ops;
extern struct inode *cifs_root_iget(struct super_block *);