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Commit d7c15171 authored by Zhao Lei's avatar Zhao Lei Committed by Chris Mason
Browse files

btrfs: Fix NO_SPACE bug caused by delayed-iput 



Steps to reproduce:
  while true; do
    dd if=/dev/zero of=/btrfs_dir/file count=[fs_size * 75%]
    rm /btrfs_dir/file
    sync
  done

  And we'll see dd failed because btrfs return NO_SPACE.

Reason:
  Normally, btrfs_commit_transaction() call btrfs_run_delayed_iputs()
  in end to free fs space for next write, but sometimes it hadn't
  done work on time, because btrfs-cleaner thread get delayed-iputs
  from list before, but do iput() after next write.

  This is log:
  [ 2569.050776] comm=btrfs-cleaner func=btrfs_evict_inode() begin

  [ 2569.084280] comm=sync func=btrfs_commit_transaction() call btrfs_run_delayed_iputs()
  [ 2569.085418] comm=sync func=btrfs_commit_transaction() done btrfs_run_delayed_iputs()
  [ 2569.087554] comm=sync func=btrfs_commit_transaction() end

  [ 2569.191081] comm=dd begin
  [ 2569.790112] comm=dd func=__btrfs_buffered_write() ret=-28

  [ 2569.847479] comm=btrfs-cleaner func=add_pinned_bytes() 0 + 32677888 = 32677888
  [ 2569.849530] comm=btrfs-cleaner func=add_pinned_bytes() 32677888 + 23834624 = 56512512
  ...
  [ 2569.903893] comm=btrfs-cleaner func=add_pinned_bytes() 943976448 + 21762048 = 965738496
  [ 2569.908270] comm=btrfs-cleaner func=btrfs_evict_inode() end

Fix:
  Make btrfs_commit_transaction() wait current running btrfs-cleaner's
  delayed-iputs() done in end.

Test:
  Use script similar to above(more complex),
  before patch:
    7 failed in 100 * 20 loop.
  after patch:
    0 failed in 100 * 20 loop.

Signed-off-by: default avatarZhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: default avatarChris Mason <clm@fb.com>
parent 18d018ad

fs/btrfs/ctree.h

+1 −0
Original line number Diff line number Diff line
@@ -1538,6 +1538,7 @@ struct btrfs_fs_info { 


	spinlock_t delayed_iput_lock;

	struct list_head delayed_iputs;

	struct rw_semaphore delayed_iput_sem;



	/* this protects tree_mod_seq_list */

	spinlock_t tree_mod_seq_lock;

fs/btrfs/disk-io.c

+2 −1
Original line number Diff line number Diff line
@@ -2487,11 +2487,12 @@ int open_ctree(struct super_block *sb, 
	spin_lock_init(&fs_info->qgroup_op_lock);

	spin_lock_init(&fs_info->buffer_lock);

	spin_lock_init(&fs_info->unused_bgs_lock);

	mutex_init(&fs_info->unused_bg_unpin_mutex);

	rwlock_init(&fs_info->tree_mod_log_lock);

	mutex_init(&fs_info->unused_bg_unpin_mutex);

	mutex_init(&fs_info->reloc_mutex);

	mutex_init(&fs_info->delalloc_root_mutex);

	seqlock_init(&fs_info->profiles_lock);

	init_rwsem(&fs_info->delayed_iput_sem);



	init_completion(&fs_info->kobj_unregister);

	INIT_LIST_HEAD(&fs_info->dirty_cowonly_roots);

fs/btrfs/extent-tree.c

+6 −0
Original line number Diff line number Diff line
@@ -3950,6 +3950,12 @@ int btrfs_check_data_free_space(struct inode *inode, u64 bytes) 
				ret = btrfs_commit_transaction(trans, root);

				if (ret)

					return ret;

				/*

				 * make sure that all running delayed iput are

				 * done

				 */

				down_write(&root->fs_info->delayed_iput_sem);

				up_write(&root->fs_info->delayed_iput_sem);

				goto again;

			} else {

				btrfs_end_transaction(trans, root);

fs/btrfs/inode.c

+4 −0
Original line number Diff line number Diff line
@@ -3111,6 +3111,8 @@ void btrfs_run_delayed_iputs(struct btrfs_root *root) 
	if (empty)

		return;



	down_read(&fs_info->delayed_iput_sem);



	spin_lock(&fs_info->delayed_iput_lock);

	list_splice_init(&fs_info->delayed_iputs, &list);

	spin_unlock(&fs_info->delayed_iput_lock);
@@ -3121,6 +3123,8 @@ void btrfs_run_delayed_iputs(struct btrfs_root *root) 
		iput(delayed->inode);

		kfree(delayed);

	}



	up_read(&root->fs_info->delayed_iput_sem);

}



/*