On Tue, Oct 08, 2024 at 10:13:31AM GMT, Gao Xiang wrote: > Hi Christian, > > On 2024/10/7 19:35, Christian Brauner wrote: > > On Sat, Oct 05, 2024 at 10:41:10PM GMT, Gao Xiang wrote: > > ... > > > > > > > Hi Christian, if possible, could you give some other > > > idea to handle this case better? Many thanks! > > Thanks for the reply! > > > > > (1) Require that the path be qualified like: > > > > fsconfig(<fd>, FSCONFIG_SET_STRING, "source", "file:/home/lis/src/mountcfs/cfs", 0) > > > > and match on it in either erofs_*_get_tree() or by adding a custom > > function for the Opt_source/"source" parameter. > > IMHO, Users could create names with the prefix `file:`, > it's somewhat strange to define a fixed prefix by the > definition of source path fc->source. > > Although there could be some escape character likewise > way, but I'm not sure if it's worthwhile to work out > this in kernel. > > > > > (2) Add a erofs specific "source-file" mount option. IOW, check that > > either "source-file" or "source" was specified but not both. You > > could even set fc->source to "source-file" value and fail if > > fc->source is already set. You get the idea. > > I once thought to add a new mount option too, yet from > the user perpertive, I think users may not care about > the source type of an arbitary path, and the kernel also > can parse the type of the source path directly... so.. > > > So.. I wonder if it's possible to add a new VFS interface > like get_tree_bdev_by_dev() for filesystems to specify a > device number rather than hardcoded hard-coded source path > way, e.g. I could see the potential benefits other than > the EROFS use case: > > - Filesystems can have other ways to get a bdev-based sb > in addition to the current hard-coded source path way; > > - Some pseudo fs can use this way to generate a fs from a > bdev. > > - Just like get_tree_nodev(), it doesn't strictly tie to > fc->source too. > > Also EROFS could lookup_bdev() (this kAPI is already > exported) itself to check if it uses get_tree_bdev_by_dev() > or get_tree_nodev()... Does it sounds good? Many thanks! Sounds fair to me.
