On Mon, Sep 1, 2014 at 6:07 AM, Vimal A R <arvimal@xxxxxxxx> wrote: > Hello fuse-devel / fs-cache / gluster-devel lists, > > I would like to propose the idea of implementing FS-Cache support in the > fuse kernel module, which I am planning to do as part of my UG university > course. This proposal is by no means final, since I have just started to > look into this. > > There are several user-space filesystems which are based on the FUSE > kernel module. As of now, if I understand correct, the only networked > filesystems having FS-Cache support are NFS and AFS. > > Implementing support hooks for fs-cache in the fuse module would provide > networked filesystems such as GlusterFS the benefit of a client-side > caching mechanism, which should decrease the access times. > If you are planning to test this with GlusterFS, note that one of the first challenges would be to have persistent filehandles in FUSE. While GlusterFS has a notion of a persistent handle (GFID, 128bit) which is constant across clients and remounts, the FUSE kernel module is presented a transient LONG (64/32 bit) which is specific to the mount instance (actually, the address of the userspace inode_t within glusterfs process - allows for constant time filehandle resolution). This would be a challenge with any FUSE based filesystem which has persistent filehandles larger than 64bit. Thanks > When enabled, FS-Cache would maintain a virtual indexing tree to cache the > data or object-types per network FS. Indices in the tree are used by > FS-Cache to find objects faster. The tree or index structure under the main > network FS index depends on the filesystem. Cookies are used to represent > the indices, the pages etc.. > > The tree structure would be as following: > > a) The virtual index tree maintained by fs-cache would look like: > > * FS-Cache master index -> The network-filesystem indice (NFS/AFS etc..) > -> per-share indices -> File-handle indices -> Page indices > > b) In case of FUSE-based filesystems, the tree would be similar to : > > * FS-Cache master index -> FUSE indice -> Per FS indices -> file-handle > indices -> page indices. > > c) In case of FUSE based filesystems as GlusterFS, the tree would as : > > * FS-Cache master index -> FUSE indice (fuse.glusterfs) -> GlusterFS > volume ID (a UUID exists for each volume) - > GlusterFS file-handle indices > (based on the GFID of a file) -> page indices. > > The idea is to enable FUSE to work with the FS-Cache network filesystem > API, which is documented at ' > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/filesystems/caching/netfs-api.txt > '. > > The implementation of FS-Cache support in NFS can be taken as a guideline > to understand and start off. > > I will reply to this mail with any other updates that would come up whilst > pursuing this further. I request any sort of feedback/suggestions, ideas, > any pitfalls etc.. that can help in taking this further. > > Thank you, > > Vimal > > References: > * > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/filesystems/caching/fscache.txt > * > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/filesystems/caching/netfs-api.txt > * > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/filesystems/caching/object.txt > * http://people.redhat.com/dhowells/fscache/FS-Cache.pdf > * http://people.redhat.com/steved/fscache/docs/HOWTO.txt > * https://en.wikipedia.org/wiki/CacheFS > * https://lwn.net/Articles/160122/ > * http://www.linux-mag.com/id/7378/ > _______________________________________________ > Gluster-devel mailing list > Gluster-devel@xxxxxxxxxxx > http://supercolony.gluster.org/mailman/listinfo/gluster-devel > -- Linux-cachefs mailing list Linux-cachefs@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/linux-cachefs
