From 28813390bf99b818801105328fbc2da466a9974d Mon Sep 17 00:00:00 2001 From: Daniel Rosenberg Date: Fri, 22 Apr 2016 00:00:48 -0700 Subject: [PATCH] fuse: Add support for d_canonical_path Allows FUSE to report to inotify that it is acting as a layered filesystem. The userspace component returns a string representing the location of the underlying file. If the string cannot be resolved into a path, the top level path is returned instead. bug: 23904372 Change-Id: Iabdca0bbedfbff59e9c820c58636a68ef9683d9f Signed-off-by: Daniel Rosenberg --- fs/fuse/dev.c | 5 +++++ fs/fuse/dir.c | 45 +++++++++++++++++++++++++++++++++++++++ fs/fuse/fuse_i.h | 3 +++ include/uapi/linux/fuse.h | 1 + 4 files changed, 54 insertions(+) diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index 175fcdeabe4c..8932c06e40c1 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -13,6 +13,7 @@ #include #include #include +#include #include #include #include @@ -1935,6 +1936,10 @@ static ssize_t fuse_dev_do_write(struct fuse_dev *fud, cs->move_pages = 0; err = copy_out_args(cs, &req->out, nbytes); + if (req->in.h.opcode == FUSE_CANONICAL_PATH) { + req->out.h.error = kern_path((char *)req->out.args[0].value, 0, + req->canonical_path); + } fuse_copy_finish(cs); spin_lock(&fpq->lock); diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index 5e2e08712d3b..24df0a5df675 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -267,6 +267,50 @@ invalid: goto out; } +/* + * Get the canonical path. Since we must translate to a path, this must be done + * in the context of the userspace daemon, however, the userspace daemon cannot + * look up paths on its own. Instead, we handle the lookup as a special case + * inside of the write request. + */ +static void fuse_dentry_canonical_path(const struct path *path, struct path *canonical_path) { + struct inode *inode = path->dentry->d_inode; + struct fuse_conn *fc = get_fuse_conn(inode); + struct fuse_req *req; + int err; + char *path_name; + + req = fuse_get_req(fc, 1); + err = PTR_ERR(req); + if (IS_ERR(req)) + goto default_path; + + path_name = (char*)__get_free_page(GFP_KERNEL); + if (!path_name) { + fuse_put_request(fc, req); + goto default_path; + } + + req->in.h.opcode = FUSE_CANONICAL_PATH; + req->in.h.nodeid = get_node_id(inode); + req->in.numargs = 0; + req->out.numargs = 1; + req->out.args[0].size = PATH_MAX; + req->out.args[0].value = path_name; + req->canonical_path = canonical_path; + req->out.argvar = 1; + fuse_request_send(fc, req); + err = req->out.h.error; + fuse_put_request(fc, req); + free_page((unsigned long)path_name); + if (!err) + return; +default_path: + canonical_path->dentry = path->dentry; + canonical_path->mnt = path->mnt; + path_get(canonical_path); +} + static int invalid_nodeid(u64 nodeid) { return !nodeid || nodeid == FUSE_ROOT_ID; @@ -274,6 +318,7 @@ static int invalid_nodeid(u64 nodeid) const struct dentry_operations fuse_dentry_operations = { .d_revalidate = fuse_dentry_revalidate, + .d_canonical_path = fuse_dentry_canonical_path, }; int fuse_valid_type(int m) diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h index 604cd42dafef..644687ae04bd 100644 --- a/fs/fuse/fuse_i.h +++ b/fs/fuse/fuse_i.h @@ -372,6 +372,9 @@ struct fuse_req { /** Inode used in the request or NULL */ struct inode *inode; + /** Path used for completing d_canonical_path */ + struct path *canonical_path; + /** AIO control block */ struct fuse_io_priv *io; diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h index c9aca042e61d..8485dd4300b8 100644 --- a/include/uapi/linux/fuse.h +++ b/include/uapi/linux/fuse.h @@ -358,6 +358,7 @@ enum fuse_opcode { FUSE_FALLOCATE = 43, FUSE_READDIRPLUS = 44, FUSE_RENAME2 = 45, + FUSE_CANONICAL_PATH= 2016, /* CUSE specific operations */ CUSE_INIT = 4096, -- 2.34.1