在 2025/5/28 16:35, Gao Xiang 写道:
Hi Zizhi,
On 2025/5/28 16:07, Zizhi Wo wrote:
Currently, in on-demand loading mode, cachefiles first calls
cachefiles_create_tmpfile() to generate a tmpfile, and only during the
exit
process does it call
cachefiles_commit_object->cachefiles_commit_tmpfile to
create the actual dentry and making it visible to users.
If the cache write is interrupted unexpectedly (e.g., by system crash or
power loss), during the next startup process, cachefiles_look_up_object()
will determine that no corresponding dentry has been generated and will
recreate the tmpfile and pull the complete data again!
The current implementation mechanism appears to provide per-file
atomicity.
For scenarios involving large image files (where significant amount of
cache data needs to be written), this re-pulling process after an
interruption seems considerable overhead?
In previous kernel versions, cache dentry were generated during the
LOOK_UP_OBJECT process of the object state machine. Even if power was
lost
midway, the next startup process could continue pulling data based on the
previously downloaded cache data on disk.
What would be the recommended way to handle this situation? Or am I
thinking about this incorrectly? Would appreciate any feedback and
guidance
from the community.
As you can see, EROFS fscache feature was marked as deprecated
since per-content hooks already support the same use case.
the EROFS fscache support will be removed after I make
per-content hooks work in erofs-utils, which needs some time
because currently I don't have enough time to work on the
community stuff.
Thanks,
Gao Xiang
Thanks for your reply.
Indeed, the subsequent implementations have moved to using fanotify.
Moreover, based on evaluation, this approach could indeed lead to
performance improvements.
However, in our current use case, we are still working with a kernel
version that only supports the fscache-based approach, so this issue
still exists for us. :(
Thanks,
Zizhi Wo
Thanks,
Zizhi Wo
