Re: [PATCH] Btrfs: fill ->last_trans for delayed inode in btrfs_fill_inode.

[Miao Xie <miaoxie@huawei.com>]

On Thu, 09 Apr 2015 12:08:43 +0800, Dongsheng Yang wrote:
> We need to fill inode when we found a node for it in delayed_nodes_tree.
> But we did not fill the ->last_trans currently, it will cause the test
> of xfstest/generic/311 fail. Scenario of the 311 is shown as below:
> 
> Problem:
> 	(1). test_fd = open(fname, O_RDWR|O_DIRECT)
> 	(2). pwrite(test_fd, buf, 4096, 0)
> 	(3). close(test_fd)
> 	(4). drop_all_caches()	<-------- "echo 3 > /proc/sys/vm/drop_caches"
> 	(5). test_fd = open(fname, O_RDWR|O_DIRECT)
> 	(6). fsync(test_fd);
> 				<-------- we did not get the correct log entry for the file
> Reason:
> 	When we re-open this file in (5), we would find a node
> in delayed_nodes_tree and fill the inode we are lookup with the
> information. But the ->last_trans is not filled, then the fsync()
> will check the ->last_trans and found it's 0 then say this inode
> is already in our tree which is commited, not recording the extents
> for it.
> 
> Fix:
> 	This patch fill the ->last_trans properly and set the
> runtime_flags if needed in this situation. Then we can get the
> log entries we expected after (6) and generic/311 passed.
> 
> Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>

Good catch!

Reviewed-by: Miao Xie <miaoxie@huawei.com>

> ---
>  fs/btrfs/delayed-inode.c |  2 ++
>  fs/btrfs/inode.c         | 21 ++++++++++++---------
>  2 files changed, 14 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/btrfs/delayed-inode.c b/fs/btrfs/delayed-inode.c
> index 82f0c7c..9e8b435 100644
> --- a/fs/btrfs/delayed-inode.c
> +++ b/fs/btrfs/delayed-inode.c
> @@ -1801,6 +1801,8 @@ int btrfs_fill_inode(struct inode *inode, u32 *rdev)
>  	set_nlink(inode, btrfs_stack_inode_nlink(inode_item));
>  	inode_set_bytes(inode, btrfs_stack_inode_nbytes(inode_item));
>  	BTRFS_I(inode)->generation = btrfs_stack_inode_generation(inode_item);
> +        BTRFS_I(inode)->last_trans = btrfs_stack_inode_transid(inode_item);
> +
>  	inode->i_version = btrfs_stack_inode_sequence(inode_item);
>  	inode->i_rdev = 0;
>  	*rdev = btrfs_stack_inode_rdev(inode_item);
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index d2e732d..b132936 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -3628,25 +3628,28 @@ static void btrfs_read_locked_inode(struct inode *inode)
>  	BTRFS_I(inode)->generation = btrfs_inode_generation(leaf, inode_item);
>  	BTRFS_I(inode)->last_trans = btrfs_inode_transid(leaf, inode_item);
>  
> +	inode->i_version = btrfs_inode_sequence(leaf, inode_item);
> +	inode->i_generation = BTRFS_I(inode)->generation;
> +	inode->i_rdev = 0;
> +	rdev = btrfs_inode_rdev(leaf, inode_item);
> +
> +	BTRFS_I(inode)->index_cnt = (u64)-1;
> +	BTRFS_I(inode)->flags = btrfs_inode_flags(leaf, inode_item);
> +
> +cache_index:
>  	/*
>  	 * If we were modified in the current generation and evicted from memory
>  	 * and then re-read we need to do a full sync since we don't have any
>  	 * idea about which extents were modified before we were evicted from
>  	 * cache.
> +	 *
> +	 * This is required for both inode re-read from disk and delayed inode
> +	 * in delayed_nodes_tree.
>  	 */
>  	if (BTRFS_I(inode)->last_trans == root->fs_info->generation)
>  		set_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
>  			&BTRFS_I(inode)->runtime_flags);
>  
> -	inode->i_version = btrfs_inode_sequence(leaf, inode_item);
> -	inode->i_generation = BTRFS_I(inode)->generation;
> -	inode->i_rdev = 0;
> -	rdev = btrfs_inode_rdev(leaf, inode_item);
> -
> -	BTRFS_I(inode)->index_cnt = (u64)-1;
> -	BTRFS_I(inode)->flags = btrfs_inode_flags(leaf, inode_item);
> -
> -cache_index:
>  	path->slots[0]++;
>  	if (inode->i_nlink != 1 ||
>  	    path->slots[0] >= btrfs_header_nritems(leaf))
>