commit
24261fc23db950951760d00c188ba63cc756b932 upstream.
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>
Reported-and-Tested-by: Ben Greear <greearb@candelatech.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
[xr: Backported to 3.4: adjust context]
Signed-off-by: Rui Xiang <rui.xiang@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
struct workqueue_struct *cifsiod_wq;
+/*
+ * Bumps refcount for cifs super block.
+ * Note that it should be only called if a referece to VFS super block is
+ * already held, e.g. in open-type syscalls context. Otherwise it can race with
+ * atomic_dec_and_test in deactivate_locked_super.
+ */
+void
+cifs_sb_active(struct super_block *sb)
+{
+ struct cifs_sb_info *server = CIFS_SB(sb);
+
+ if (atomic_inc_return(&server->active) == 1)
+ atomic_inc(&sb->s_active);
+}
+
+void
+cifs_sb_deactive(struct super_block *sb)
+{
+ struct cifs_sb_info *server = CIFS_SB(sb);
+
+ if (atomic_dec_and_test(&server->active))
+ deactivate_super(sb);
+}
+
static int
cifs_read_super(struct super_block *sb)
{
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 *);
mutex_init(&pCifsFile->fh_mutex);
INIT_WORK(&pCifsFile->oplock_break, cifs_oplock_break);
+ cifs_sb_active(inode->i_sb);
+
spin_lock(&cifs_file_list_lock);
list_add(&pCifsFile->tlist, &(tlink_tcon(tlink)->openFileList));
/* if readable file instance put first in list*/
struct inode *inode = cifs_file->dentry->d_inode;
struct cifs_tcon *tcon = tlink_tcon(cifs_file->tlink);
struct cifsInodeInfo *cifsi = CIFS_I(inode);
- struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
+ struct super_block *sb = inode->i_sb;
+ struct cifs_sb_info *cifs_sb = CIFS_SB(sb);
struct cifsLockInfo *li, *tmp;
spin_lock(&cifs_file_list_lock);
cifs_put_tlink(cifs_file->tlink);
dput(cifs_file->dentry);
+ cifs_sb_deactive(sb);
kfree(cifs_file);
}