CIFS: Protect i_nlink from being negative

that can cause warning messages.  Pavel had initially
suggested a smaller patch around drop_nlink, after
a similar problem was discovered NFS.  Protecting
additional places where nlink is touched was
suggested by Jeff Layton and is included in this.

Reviewed-by: Pavel Shilovsky <pshilovsky@samba.org>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Signed-off-by: Steve French <smfrench@gmail.com>

2 files changed, 18 insertions, 8 deletions

diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index 7354877fa3bd..cb79c7edecb0 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -124,10 +124,10 @@ cifs_fattr_to_inode(struct inode *inode, struct cifs_fattr *fattr)
 {
         struct cifsInodeInfo *cifs_i = CIFS_I(inode);
         struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
-        unsigned long oldtime = cifs_i->time;
 
         cifs_revalidate_cache(inode, fattr);
 
+        spin_lock(&inode->i_lock);
         inode->i_atime = fattr->cf_atime;
         inode->i_mtime = fattr->cf_mtime;
         inode->i_ctime = fattr->cf_ctime;
@@ -148,9 +148,6 @@ cifs_fattr_to_inode(struct inode *inode, struct cifs_fattr *fattr)
         else
                 cifs_i->time = jiffies;
 
-        cFYI(1, "inode 0x%p old_time=%ld new_time=%ld", inode,
-                 oldtime, cifs_i->time);
-
         cifs_i->delete_pending = fattr->cf_flags & CIFS_FATTR_DELETE_PENDING;
 
         cifs_i->server_eof = fattr->cf_eof;
@@ -158,7 +155,6 @@ cifs_fattr_to_inode(struct inode *inode, struct cifs_fattr *fattr)
          * Can't safely change the file size here if the client is writing to
          * it due to potential races.
          */
-        spin_lock(&inode->i_lock);
         if (is_size_safe_to_change(cifs_i, fattr->cf_eof)) {
                 i_size_write(inode, fattr->cf_eof);
 
@@ -859,12 +855,14 @@ struct inode *cifs_root_iget(struct super_block *sb)
 
         if (rc && tcon->ipc) {
                 cFYI(1, "ipc connection - fake read inode");
+                spin_lock(&inode->i_lock);
                 inode->i_mode |= S_IFDIR;
                 set_nlink(inode, 2);
                 inode->i_op = &cifs_ipc_inode_ops;
                 inode->i_fop = &simple_dir_operations;
                 inode->i_uid = cifs_sb->mnt_uid;
                 inode->i_gid = cifs_sb->mnt_gid;
+                spin_unlock(&inode->i_lock);
         } else if (rc) {
                 iget_failed(inode);
                 inode = ERR_PTR(rc);
@@ -1110,6 +1108,15 @@ undo_setattr:
         goto out_close;
 }
 
+/* copied from fs/nfs/dir.c with small changes */
+static void
+cifs_drop_nlink(struct inode *inode)
+{
+        spin_lock(&inode->i_lock);
+        if (inode->i_nlink > 0)
+                drop_nlink(inode);
+        spin_unlock(&inode->i_lock);
+}
 
 /*
  * If dentry->d_inode is null (usually meaning the cached dentry
@@ -1166,13 +1173,13 @@ retry_std_delete:
 psx_del_no_retry:
         if (!rc) {
                 if (inode)
-                        drop_nlink(inode);
+                        cifs_drop_nlink(inode);
         } else if (rc == -ENOENT) {
                 d_drop(dentry);
         } else if (rc == -ETXTBSY) {
                 rc = cifs_rename_pending_delete(full_path, dentry, xid);
                 if (rc == 0)
-                        drop_nlink(inode);
+                        cifs_drop_nlink(inode);
         } else if ((rc == -EACCES) && (dosattr == 0) && inode) {
                 attrs = kzalloc(sizeof(*attrs), GFP_KERNEL);
                 if (attrs == NULL) {
@@ -1241,9 +1248,10 @@ cifs_mkdir_qinfo(struct inode *inode, struct dentry *dentry, umode_t mode,
          * setting nlink not necessary except in cases where we failed to get it
          * from the server or was set bogus
          */
+        spin_lock(&dentry->d_inode->i_lock);
         if ((dentry->d_inode) && (dentry->d_inode->i_nlink < 2))
                 set_nlink(dentry->d_inode, 2);
-
+        spin_unlock(&dentry->d_inode->i_lock);
         mode &= ~current_umask();
         /* must turn on setgid bit if parent dir has it */
         if (inode->i_mode & S_ISGID)
diff --git a/fs/cifs/link.c b/fs/cifs/link.c
index 09e4b3ae4564..e6ce3b112875 100644
--- a/fs/cifs/link.c
+++ b/fs/cifs/link.c
@@ -433,7 +433,9 @@ cifs_hardlink(struct dentry *old_file, struct inode *inode,
         if (old_file->d_inode) {
                 cifsInode = CIFS_I(old_file->d_inode);
                 if (rc == 0) {
+                        spin_lock(&old_file->d_inode->i_lock);
                         inc_nlink(old_file->d_inode);
+                        spin_unlock(&old_file->d_inode->i_lock);
 /* BB should we make this contingent on superblock flag NOATIME? */
 /*                      old_file->d_inode->i_ctime = CURRENT_TIME;*/
                         /* parent dir timestamps will update from srv