nilfs2: get rid of bd_mount_sem use from nilfs

This will remove every bd_mount_sem use in nilfs.

The intended exclusion control was replaced by the previous patch
("nilfs2: correct exclusion control in nilfs_remount function") for
nilfs_remount(), and this patch will replace remains with a new mutex
that this inserts in nilfs object.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

4 files changed, 12 insertions, 9 deletions

diff --git a/fs/nilfs2/cpfile.c b/fs/nilfs2/cpfile.c
index 300f1cdfa86..cadd36b14d0 100644
--- a/fs/nilfs2/cpfile.c
+++ b/fs/nilfs2/cpfile.c
@@ -864,11 +864,11 @@ int nilfs_cpfile_change_cpmode(struct inode *cpfile, __u64 cno, int mode)
         case NILFS_CHECKPOINT:
                 /*
                  * Check for protecting existing snapshot mounts:
-                 * bd_mount_sem is used to make this operation atomic and
+                 * ns_mount_mutex is used to make this operation atomic and
                  * exclusive with a new mount job.  Though it doesn't cover
                  * umount, it's enough for the purpose.
                  */
-                down(&nilfs->ns_bdev->bd_mount_sem);
+                mutex_lock(&nilfs->ns_mount_mutex);
                 if (nilfs_checkpoint_is_mounted(nilfs, cno, 1)) {
                         /* Current implementation does not have to protect
                            plain read-only mounts since they are exclusive
@@ -877,7 +877,7 @@ int nilfs_cpfile_change_cpmode(struct inode *cpfile, __u64 cno, int mode)
                         ret = -EBUSY;
                 } else
                         ret = nilfs_cpfile_clear_snapshot(cpfile, cno);
-                up(&nilfs->ns_bdev->bd_mount_sem);
+                mutex_unlock(&nilfs->ns_mount_mutex);
                 return ret;
         case NILFS_SNAPSHOT:
                 return nilfs_cpfile_set_snapshot(cpfile, cno);
diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
index f02762fa8ea..1777a3467bd 100644
--- a/fs/nilfs2/super.c
+++ b/fs/nilfs2/super.c
@@ -764,7 +764,7 @@ int nilfs_store_magic_and_option(struct super_block *sb,
  * @silent: silent mode flag
  * @nilfs: the_nilfs struct
  *
- * This function is called exclusively by bd_mount_mutex.
+ * This function is called exclusively by nilfs->ns_mount_mutex.
  * So, the recovery process is protected from other simultaneous mounts.
  */
 static int
@@ -1105,7 +1105,7 @@ nilfs_get_sb(struct file_system_type *fs_type, int flags,
                 goto failed;
         }
 
-        down(&sd.bdev->bd_mount_sem);
+        mutex_lock(&nilfs->ns_mount_mutex);
 
         if (!sd.cno) {
                 /*
@@ -1164,7 +1164,7 @@ nilfs_get_sb(struct file_system_type *fs_type, int flags,
                 need_to_close = 0;
         }
 
-        up(&sd.bdev->bd_mount_sem);
+        mutex_unlock(&nilfs->ns_mount_mutex);
         put_nilfs(nilfs);
         if (need_to_close)
                 close_bdev_exclusive(sd.bdev, flags);
@@ -1172,7 +1172,7 @@ nilfs_get_sb(struct file_system_type *fs_type, int flags,
         return 0;
 
  failed_unlock:
-        up(&sd.bdev->bd_mount_sem);
+        mutex_unlock(&nilfs->ns_mount_mutex);
         put_nilfs(nilfs);
  failed:
         close_bdev_exclusive(sd.bdev, flags);
@@ -1181,14 +1181,14 @@ nilfs_get_sb(struct file_system_type *fs_type, int flags,
 
  cancel_new:
         /* Abandoning the newly allocated superblock */
-        up(&sd.bdev->bd_mount_sem);
+        mutex_unlock(&nilfs->ns_mount_mutex);
         put_nilfs(nilfs);
         up_write(&s->s_umount);
         deactivate_super(s);
         /*
          * deactivate_super() invokes close_bdev_exclusive().
          * We must finish all post-cleaning before this call;
-         * put_nilfs() and unlocking bd_mount_sem need the block device.
+         * put_nilfs() needs the block device.
          */
         return err;
 }
diff --git a/fs/nilfs2/the_nilfs.c b/fs/nilfs2/the_nilfs.c
index 06e8dfd538d..e4e5c78bcc9 100644
--- a/fs/nilfs2/the_nilfs.c
+++ b/fs/nilfs2/the_nilfs.c
@@ -73,6 +73,7 @@ static struct the_nilfs *alloc_nilfs(struct block_device *bdev)
         atomic_set(&nilfs->ns_ndirtyblks, 0);
         init_rwsem(&nilfs->ns_sem);
         init_rwsem(&nilfs->ns_super_sem);
+        mutex_init(&nilfs->ns_mount_mutex);
         mutex_init(&nilfs->ns_writer_mutex);
         INIT_LIST_HEAD(&nilfs->ns_list);
         INIT_LIST_HEAD(&nilfs->ns_supers);
diff --git a/fs/nilfs2/the_nilfs.h b/fs/nilfs2/the_nilfs.h
index d0cf4fb7c9c..e8adbffc626 100644
--- a/fs/nilfs2/the_nilfs.h
+++ b/fs/nilfs2/the_nilfs.h
@@ -49,6 +49,7 @@ enum {
  * @ns_writer: back pointer to writable nilfs_sb_info
  * @ns_sem: semaphore for shared states
  * @ns_super_sem: semaphore for global operations across super block instances
+ * @ns_mount_mutex: mutex protecting mount process of nilfs
  * @ns_writer_mutex: mutex protecting ns_writer attach/detach
  * @ns_writer_refcount: number of referrers on ns_writer
  * @ns_current: back pointer to current mount
@@ -98,6 +99,7 @@ struct the_nilfs {
         struct nilfs_sb_info   *ns_writer;
         struct rw_semaphore     ns_sem;
         struct rw_semaphore     ns_super_sem;
+        struct mutex            ns_mount_mutex;
         struct mutex            ns_writer_mutex;
         atomic_t                ns_writer_refcount;