cifs: delay super block destruction until all cifsFileInfo objects are gone
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>
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index cab0054..0898d99 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -265,6 +265,8 @@
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*/
@@ -293,7 +295,8 @@
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);
@@ -345,6 +348,7 @@
cifs_put_tlink(cifs_file->tlink);
dput(cifs_file->dentry);
+ cifs_sb_deactive(sb);
kfree(cifs_file);
}