On 2024/6/21 17:37, Hongbo Li wrote:
On 2024/6/21 17:14, Gao Xiang wrote:
On 2024/6/21 14:18, Hongbo Li wrote:
Erofs over fscache need CONFIG_CACHEFILES_ONDEMAND in cachefiles
module. We cannot know whether it is supported from userspace, so
we export this feature to user by sysfs interface.
[Before]
$ cat /sys/fs/cachefiles/features/cachefiles_ondemand
cat: /sys/fs/cachefiles/features/cachefiles_ondemand: No such file or directory
[After]
$ cat /sys/fs/cachefiles/features/cachefiles_ondemand
supported
Signed-off-by: Hongbo Li <[email protected]>
I don't think such sysfs is needed, you could just use
`bind ondemand` to check if it is supported:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/fs/cachefiles/daemon.c?h=v6.9#n780
Thanks for reply!
`bind ondemand` can check if it is supported, but it requires a more
complicated procedure for user to implement. For example, a serial of system
call (open, ioctl, close) are need.The containerd snapshotter daemon relies on
these feature, only use a simple check method is usable in product environment.
The snapshotter developers may know how cachefiles works, but for snapshotter
users, a simple way to check whether snapshotter can be launched is useful.
Even though they do not know how cachefiles works.
I don't think it needs to be considered as long as userspace
has a way to check since you could wrap up these as a helper
(I will do in the official erofs-utils later or if you have
some interest you could help too) and even some erofs-utils
binary for this.
sysfs maintainence just for some random feature doesn't
sound good to me (similar to ext4/xfs on-disk features) and
even if works, you cannot use this way for 5.19~6.10
upstream kernels.
Thanks,
Gao Xiang
Thanks,
Hongbo
Thanks,
Gao Xiang
