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author | Miklos Szeredi <miklos@szeredi.hu> | 2004-09-02 18:13:57 +0000 |
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committer | Miklos Szeredi <miklos@szeredi.hu> | 2004-09-02 18:13:57 +0000 |
commit | 12085102bf932dbcda6114cdfc42209de3037656 (patch) | |
tree | f58686cacde83bf9c2ce6ecb763eefe97a7d5a01 /doc | |
parent | 22ea3dc045ca3bfc67b3cbb8e33e8f63a6f46a5e (diff) |
fix
Diffstat (limited to 'doc')
-rw-r--r-- | doc/how-fuse-works | 54 |
1 files changed, 54 insertions, 0 deletions
diff --git a/doc/how-fuse-works b/doc/how-fuse-works new file mode 100644 index 0000000..2e5d05c --- /dev/null +++ b/doc/how-fuse-works @@ -0,0 +1,54 @@ + How Fuse-1.3 Works + +[Written by Terje Oseberg] + +1. The fuse library. + +When your user mode program calls fuse_main() (lib/helper.c), +fuse_main() parses the arguments passed to your user mode program, +then calls fuse_mount() (lib/mount.c). + +fuse_mount() creates a UNIX domain socket, then forks and execs +fusermount (util/fusermount.c) passing it one end of the socket in the +FUSE_COMMFD_ENV environment variable. + +fusermount (util/fusermount.c) makes sure that the fuse module is +loaded. fusermount then open /proc/fs/fuse/dev and send the file +handle over a UNIX domain socket back to fuse_mount(). + +fuse_mount() returns the filehandle for /proc/fs/fuse/dev to fuse_main(). + +fuse_main() calls fuse_new() (lib/fuse.c) which allocates the struct +fuse datastructure that stores and maintains a cached image of the +filesystem data. + +Lastly, fuse_main() calls either fuse_loop() (lib/fuse.c) or +fuse_loop_mt() (lib/fuse_mt.c) which both start to read the filesystem +system calls from the /proc/fs/fuse/dev, call the usermode functions +stored in struct fuse_operations datastructure before calling +fuse_main(). The results of those calls are then written back to the +/proc/fs/fuse/dev file where they can be forwarded back to the system +calls. + +2. The kernel module. + +The kernel module consists of two parts. First the proc filesystem +component in kernel/dev.c -and second the filesystem system calls +kernel/file.c, kernel/inode.c, and kernel/dir.c + +All the system calls in kernel/file.c, kernel/inode.c, and +kernel/dir.c make calls to either request_send(), +request_send_noreply(), or request_send_nonblock(). Most of the calls +(all but 2) are to request_send(). request_send() adds the request to, +"list of requests" structure (fc->pending), then waits for a response. +request_send_noreply() and request_send_nonblock() are both similar in +function to request_send() except that one is non-blocking, and the +other does not respond with a reply. + +The proc filesystem component in kernel/dev.c responds to file io +requests to the file /proc/fs/fuse/dev. fuse_dev_read() handles the +file reads and returns commands from the "list of requests" structure +to the calling program. fuse_dev_write() handles file writes and takes +the data written and places them into the req->out datastructure where +they can be returned to the system call through the "list of requests" +structure and request_send(). |