Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ryusuke/nilfs2

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ryusuke/nilfs2:
  nilfs2: fix oopses with doubly mounted snapshots
  nilfs2: missing a read lock for segment writer in nilfs_attach_checkpoint()

fs/nilfs2/super.c

@@ -416,8 +416,10 @@ int nilfs_attach_checkpoint(struct nilfs_sb_info *sbi, __u64 cno)
 	if (unlikely(err))
 		goto failed;
 
+	down_read(&nilfs->ns_segctor_sem);
 	err = nilfs_cpfile_get_checkpoint(nilfs->ns_cpfile, cno, 0, &raw_cp,
 					  &bh_cp);
+	up_read(&nilfs->ns_segctor_sem);
 	if (unlikely(err)) {
 		if (err == -ENOENT || err == -EINVAL) {
 			printk(KERN_ERR

fs/nilfs2/the_nilfs.h

@@ -253,7 +253,7 @@ nilfs_detach_writer(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi)
 
 static inline void nilfs_put_sbinfo(struct nilfs_sb_info *sbi)
 {
-	if (!atomic_dec_and_test(&sbi->s_count))
+	if (atomic_dec_and_test(&sbi->s_count))
 		kfree(sbi);
 }