Re: [PATCH v2] Btrfs: add missing inode item update in fallocate()

[Liu Bo <bo.li.liu@oracle.com>]

On Thu, Mar 12, 2015 at 11:23:13PM +0000, Filipe Manana wrote:
> If we fallocate(), without the keep size flag, into an area already covered
> by an extent previously fallocated, we were updating the inode's i_size but
> we weren't updating the inode item in the fs/subvol tree. A following umount
> + mount would result in a loss of the inode's size (and an fsync would miss
> too the fact that the inode changed).
> 
> Reproducer:
> 
>   $ mkfs.btrfs -f /dev/sdd
>   $ mount /dev/sdd /mnt
>   $ fallocate -n -l 1M /mnt/foobar
>   $ fallocate -l 512K /mnt/foobar
>   $ umount /mnt
>   $ mount /dev/sdd /mnt
>   $ od -t x1 /mnt/foobar
>   0000000
> 
> The expected result is:
> 
>   $ od -t x1 /mnt/foobar
>   0000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>   *
>   2000000
> 
> A test case for fstests follows soon.

Looks good.

Reviewed-by: Liu Bo <bo.li.liu@oracle.com>

> 
> Signed-off-by: Filipe Manana <fdmanana@suse.com>
> ---
> 
> V2: Update the inode's sizes and ctime while holding a transaction
>     open.
> 
>  fs/btrfs/file.c | 29 ++++++++++++++++++++---------
>  1 file changed, 20 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
> index 8f256b1..c261ff0 100644
> --- a/fs/btrfs/file.c
> +++ b/fs/btrfs/file.c
> @@ -2677,23 +2677,34 @@ static long btrfs_fallocate(struct file *file, int mode,
>  							1 << inode->i_blkbits,
>  							offset + len,
>  							&alloc_hint);
> -
> -			if (ret < 0) {
> -				free_extent_map(em);
> -				break;
> -			}
>  		} else if (actual_end > inode->i_size &&
>  			   !(mode & FALLOC_FL_KEEP_SIZE)) {
> +			struct btrfs_trans_handle *trans;
> +
>  			/*
>  			 * We didn't need to allocate any more space, but we
>  			 * still extended the size of the file so we need to
> -			 * update i_size.
> +			 * update i_size and the inode item.
>  			 */
> -			inode->i_ctime = CURRENT_TIME;
> -			i_size_write(inode, actual_end);
> -			btrfs_ordered_update_i_size(inode, actual_end, NULL);
> +			trans = btrfs_start_transaction(root, 1);
> +			if (IS_ERR(trans)) {
> +				ret = PTR_ERR(trans);
> +			} else {
> +				inode->i_ctime = CURRENT_TIME;
> +				i_size_write(inode, actual_end);
> +				btrfs_ordered_update_i_size(inode, actual_end,
> +							    NULL);
> +				ret = btrfs_update_inode(trans, root, inode);
> +				if (ret)
> +					btrfs_end_transaction(trans, root);
> +				else
> +					ret = btrfs_end_transaction(trans,
> +								    root);
> +			}
>  		}
>  		free_extent_map(em);
> +		if (ret < 0)
> +			break;
>  
>  		cur_offset = last_byte;
>  		if (cur_offset >= alloc_end) {
> -- 
> 2.1.3
> 
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