nilfs2: add reader's lock for cno in nilfs_ioctl_sync

This adds reader's lock for the_nilfs->cno in nilfs_ioctl_sync,
for the_nilfs->cno should be proctected by segctor_sem when reading.

Signed-off-by: Jiro SEKIBA <jir@unicus.jp>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

1 files changed, 5 insertions, 1 deletions

diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c
index 8e5cad020c30..313d0a21da48 100644
--- a/fs/nilfs2/ioctl.c
+++ b/fs/nilfs2/ioctl.c
@@ -601,13 +601,17 @@ static int nilfs_ioctl_sync(struct inode *inode, struct file *filp,
 {
         __u64 cno;
         int ret;
+        struct the_nilfs *nilfs;
 
         ret = nilfs_construct_segment(inode->i_sb);
         if (ret < 0)
                 return ret;
 
         if (argp != NULL) {
-                cno = NILFS_SB(inode->i_sb)->s_nilfs->ns_cno - 1;
+                nilfs = NILFS_SB(inode->i_sb)->s_nilfs;
+                down_read(&nilfs->ns_segctor_sem);
+                cno = nilfs->ns_cno - 1;
+                up_read(&nilfs->ns_segctor_sem);
                 if (copy_to_user(argp, &cno, sizeof(cno)))
                         return -EFAULT;
         }