From 1c48fda3e5a88159130b4d4805fbdf367212afab Mon Sep 17 00:00:00 2001 From: Gero Schumacher Date: Tue, 26 Feb 2019 15:45:22 +0000 Subject: [PATCH] fs: ext4: Problem with ext4load and sparse files 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: 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? --- fs/ext4/ext4_common.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/fs/ext4/ext4_common.c b/fs/ext4/ext4_common.c index 59ad6c8f8c..feffbfa9a9 100644 --- a/fs/ext4/ext4_common.c +++ b/fs/ext4/ext4_common.c @@ -1547,8 +1547,12 @@ 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); -- 2.30.2