[3.5.y.z,extended,stable] Patch "cifs: delay super block destruction until all cifsFileInfo" has been added to staging queue

Message ID 1364234415-8380-1-git-send-email-luis.henriques@canonical.com
State New
Headers show

Commit Message

Luis Henriques March 25, 2013, 6 p.m.
This is a note to let you know that I have just added a patch titled

    cifs: delay super block destruction until all cifsFileInfo

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:


If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see



From bf20633835605ede14bc75464e769f38ad009596 Mon Sep 17 00:00:00 2001
From: Mateusz Guzik <mguzik@redhat.com>
Date: Fri, 8 Mar 2013 16:30:03 +0100
Subject: [PATCH] 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>
[ luis: adjust context ]
Luis Henriques <luis.henriques@canonical.com>
 fs/cifs/cifsfs.c | 24 ++++++++++++++++++++++++
 fs/cifs/cifsfs.h |  4 ++++
 fs/cifs/file.c   |  6 +++++-
 3 files changed, 33 insertions(+), 1 deletion(-)



diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 745c306..c552953 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -86,6 +86,30 @@  extern mempool_t *cifs_mid_poolp;

 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.
+ */
+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);
+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)
diff --git a/fs/cifs/cifsfs.h b/fs/cifs/cifsfs.h
index 6536535..f711765 100644
--- a/fs/cifs/cifsfs.h
+++ b/fs/cifs/cifsfs.h
@@ -41,6 +41,10 @@  extern struct file_system_type cifs_fs_type;
 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 *);
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 2cbda4e..8a0f553 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -266,6 +266,8 @@  cifs_new_fileinfo(__u16 fileHandle, struct file *file,
 	INIT_WORK(&pCifsFile->oplock_break, cifs_oplock_break);

+	cifs_sb_active(inode->i_sb);
 	list_add(&pCifsFile->tlist, &(tlink_tcon(tlink)->openFileList));
 	/* if readable file instance put first in list*/
@@ -303,7 +305,8 @@  void cifsFileInfo_put(struct cifsFileInfo *cifs_file)
 	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;

@@ -353,6 +356,7 @@  void cifsFileInfo_put(struct cifsFileInfo *cifs_file)

+	cifs_sb_deactive(sb);