On 5/13/25 15:17, Gao Xiang wrote:
On 2025/5/13 15:06, Hongbo Li wrote:
On 2025/4/8 20:23, Sheng Yong wrote:
From: Sheng Yong <[email protected]>
When attempting to use an archive file, such as APEX on android,
as a file-backed mount source, it fails because EROFS image within
the archive file does not start at offset 0. As a result, a loop
device is still needed to attach the image file at an appropriate
offset first. Similarly, if an EROFS image within a block device
does not start at offset 0, it cannot be mounted directly either.
To address this issue, this patch adds a new mount option `fsoffset=x'
to accept a start offset for both file-backed and bdev-based mounts.
The offset should be aligned to block size. EROFS will add this offset
Hi Yong,
Why the offset should be aligned to block size? I mean, we can use the
original offset directly during read, and then add this offset after
reading.
Currently metabuf and bio are all block-based I/Os (otherwise
taking metadata for example, it could cross page boundary), I
Hi, Hongbo and Xiang,
I agree that "we cannot handle cross page/block" is the main reason. And
for use case, e.g APEX file, to achieve a better performance and make it
easy to extract filesystem image from a APEX file, the fs image is used
to put at page/block-size-aligned position.
thanks,
shengyong
uess it's complex to support unaligned offsets. Also it seems
lack of use cases?
Thanks,
Gao Xiang
Thanks,
Hongbo
