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ANDROID: fuse: Add support for d_canonical_path

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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
Bug: 171780975
Test: Pixel 4.19
Change-Id: Iabdca0bbedfbff59e9c820c58636a68ef9683d9f
Signed-off-by: Daniel Rosenberg <drosen@google.com>
Signed-off-by: Alessio Balsini <balsini@google.com>
This commit is contained in:
Daniel Rosenberg
2016-04-22 00:00:48 -07:00
committed by Alessio Balsini
parent 54b41388f5
commit fa199896a3
4 changed files with 55 additions and 0 deletions
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9
fs/fuse/dev.c
View File

@@ -14,6 +14,7 @@
#include <linux/sched/signal.h>
#include <linux/uio.h>
#include <linux/miscdevice.h>
#include <linux/namei.h>
#include <linux/pagemap.h>
#include <linux/file.h>
#include <linux/slab.h>
@@ -573,6 +574,7 @@ ssize_t fuse_simple_request(struct fuse_conn *fc, struct fuse_args *args)
req->out.numargs = args->out.numargs;
memcpy(req->out.args, args->out.args,
args->out.numargs * sizeof(struct fuse_arg));
req->out.canonical_path = args->out.canonical_path;
fuse_request_send(fc, req);
ret = req->out.h.error;
if (!ret && args->out.argvar) {
@@ -1932,6 +1934,13 @@ static ssize_t fuse_dev_do_write(struct fuse_dev *fud,
err = copy_out_args(cs, &req->out, nbytes);
fuse_copy_finish(cs);
if (!err && req->in.h.opcode == FUSE_CANONICAL_PATH) {
char *path = (char *)req->out.args[0].value;
path[req->out.args[0].size - 1] = 0;
req->out.h.error = kern_path(path, 0, req->out.canonical_path);
}
spin_lock(&fpq->lock);
clear_bit(FR_LOCKED, &req->flags);
if (!fpq->connected)

39
fs/fuse/dir.c
View File

@@ -281,10 +281,49 @@ static void fuse_dentry_release(struct dentry *dentry)
kfree_rcu(fd, rcu);
}
/*
* 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 = d_inode(path->dentry);
struct fuse_conn *fc = get_fuse_conn(inode);
FUSE_ARGS(args);
char *path_name;
int err;
path_name = (char *)__get_free_page(GFP_KERNEL);
if (!path_name)
goto default_path;
args.in.h.opcode = FUSE_CANONICAL_PATH;
args.in.h.nodeid = get_node_id(inode);
args.in.numargs = 0;
args.out.numargs = 1;
args.out.args[0].size = PATH_MAX;
args.out.args[0].value = path_name;
args.out.argvar = 1;
args.out.canonical_path = canonical_path;
err = fuse_simple_request(fc, &args);
free_page((unsigned long)path_name);
if (err > 0)
return;
default_path:
canonical_path->dentry = path->dentry;
canonical_path->mnt = path->mnt;
path_get(canonical_path);
}
const struct dentry_operations fuse_dentry_operations = {
.d_revalidate = fuse_dentry_revalidate,
.d_init = fuse_dentry_init,
.d_release = fuse_dentry_release,
.d_canonical_path = fuse_dentry_canonical_path,
};
const struct dentry_operations fuse_root_dentry_operations = {

6
fs/fuse/fuse_i.h
View File

@@ -213,6 +213,9 @@ struct fuse_out {
/** Array of arguments */
struct fuse_arg args[2];
/* Path used for completing d_canonical_path */
struct path *canonical_path;
};
/** FUSE page descriptor */
@@ -235,6 +238,9 @@ struct fuse_args {
unsigned argvar:1;
unsigned numargs;
struct fuse_arg args[2];
/* Path used for completing d_canonical_path */
struct path *canonical_path;
} out;
};

1
include/uapi/linux/fuse.h
View File

@@ -383,6 +383,7 @@ enum fuse_opcode {
FUSE_READDIRPLUS = 44,
FUSE_RENAME2 = 45,
FUSE_LSEEK = 46,
FUSE_CANONICAL_PATH= 2016,
/* CUSE specific operations */
CUSE_INIT = 4096,