Hi,

when I try to load a sparse file via ext4load, I am getting the error message 'invalid extent'

After a deeper look in the code, it seems to be an issue in the function ext4fs_get_extent_block in fs/ext4/ext4_common.c:

The file starts with 1k of zeros. The blocksize is 1024. So the first extend block contains the following information:

eh_entries: 1 eh_depth: 1 ei_block 1

When the upper layer (ext4fs_read_file) asks for fileblock 0, we are running in the 'invalid extent' error message. For me it seems, that the code is not prepared for handling a sparse block at the beginning of the file. The following change, solved my problem:

diff --git a/fs/ext4/ext4_common.c b/fs/ext4/ext4_common.c index 67e2471bd3..7c8080d740 100644 --- a/fs/ext4/ext4_common.c +++ b/fs/ext4/ext4_common.c @@ -1546,8 +1546,10 @@ static struct ext4_extent_header *ext4fs_get_extent_block break; } while (fileblock >= le32_to_cpu(index[i].ei_block));

- if (--i < 0) - return NULL; + /* if first logical block number is higher than requested fileblock, + it is a sparse file. This is handled on upper layer */ + if (i > 0) + i--;

block = le16_to_cpu(index[i].ei_leaf_hi); block = (block << 32) + le32_to_cpu(index[i].ei_leaf_lo);

I am really not an expert in ext4 filesystems. Can somebody please have a look at this issue and give me a feedback, if I am totally wrong or not?