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[PATCH] FUSE - device functions

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This adds the FUSE device handling functions.

This contains the following files:

 o dev.c
    - fuse device operations (read, write, release, poll)
    - registers misc device
    - support for sending requests to userspace

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Miklos Szeredi 2005-09-09 13:10:27 -07:00 committed by Linus Torvalds
parent d8a5ba4545
commit 334f485df8
6 changed files with 1537 additions and 7 deletions
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341
Documentation/filesystems/fuse.txt Normal file
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Definitions
~~~~~~~~~~~
Userspace filesystem:
A filesystem in which data and metadata are provided by an ordinary
userspace process. The filesystem can be accessed normally through
the kernel interface.
Filesystem daemon:
The process(es) providing the data and metadata of the filesystem.
Non-privileged mount (or user mount):
A userspace filesystem mounted by a non-privileged (non-root) user.
The filesystem daemon is running with the privileges of the mounting
user. NOTE: this is not the same as mounts allowed with the "user"
option in /etc/fstab, which is not discussed here.
Mount owner:
The user who does the mounting.
User:
The user who is performing filesystem operations.
What is FUSE?
~~~~~~~~~~~~~
FUSE is a userspace filesystem framework. It consists of a kernel
module (fuse.ko), a userspace library (libfuse.*) and a mount utility
(fusermount).
One of the most important features of FUSE is allowing secure,
non-privileged mounts. This opens up new possibilities for the use of
filesystems. A good example is sshfs: a secure network filesystem
using the sftp protocol.
The userspace library and utilities are available from the FUSE
homepage:
http://fuse.sourceforge.net/
Mount options
~~~~~~~~~~~~~
'fd=N'
The file descriptor to use for communication between the userspace
filesystem and the kernel. The file descriptor must have been
obtained by opening the FUSE device ('/dev/fuse').
'rootmode=M'
The file mode of the filesystem's root in octal representation.
'user_id=N'
The numeric user id of the mount owner.
'group_id=N'
The numeric group id of the mount owner.
'default_permissions'
By default FUSE doesn't check file access permissions, the
filesystem is free to implement it's access policy or leave it to
the underlying file access mechanism (e.g. in case of network
filesystems). This option enables permission checking, restricting
access based on file mode. This is option is usually useful
together with the 'allow_other' mount option.
'allow_other'
This option overrides the security measure restricting file access
to the user mounting the filesystem. This option is by default only
allowed to root, but this restriction can be removed with a
(userspace) configuration option.
'kernel_cache'
This option disables flushing the cache of the file contents on
every open(). This should only be enabled on filesystems, where the
file data is never changed externally (not through the mounted FUSE
filesystem). Thus it is not suitable for network filesystems and
other "intermediate" filesystems.
NOTE: if this option is not specified (and neither 'direct_io') data
is still cached after the open(), so a read() system call will not
always initiate a read operation.
'direct_io'
This option disables the use of page cache (file content cache) in
the kernel for this filesystem. This has several affects:
- Each read() or write() system call will initiate one or more
read or write operations, data will not be cached in the
kernel.
- The return value of the read() and write() system calls will
correspond to the return values of the read and write
operations. This is useful for example if the file size is not
known in advance (before reading it).
'max_read=N'
With this option the maximum size of read operations can be set.
The default is infinite. Note that the size of read requests is
limited anyway to 32 pages (which is 128kbyte on i386).
How do non-privileged mounts work?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Since the mount() system call is a privileged operation, a helper
program (fusermount) is needed, which is installed setuid root.
The implication of providing non-privileged mounts is that the mount
owner must not be able to use this capability to compromise the
system. Obvious requirements arising from this are:
A) mount owner should not be able to get elevated privileges with the
help of the mounted filesystem
B) mount owner should not get illegitimate access to information from
other users' and the super user's processes
C) mount owner should not be able to induce undesired behavior in
other users' or the super user's processes
How are requirements fulfilled?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A) The mount owner could gain elevated privileges by either:
1) creating a filesystem containing a device file, then opening
this device
2) creating a filesystem containing a suid or sgid application,
then executing this application
The solution is not to allow opening device files and ignore
setuid and setgid bits when executing programs. To ensure this
fusermount always adds "nosuid" and "nodev" to the mount options
for non-privileged mounts.
B) If another user is accessing files or directories in the
filesystem, the filesystem daemon serving requests can record the
exact sequence and timing of operations performed. This
information is otherwise inaccessible to the mount owner, so this
counts as an information leak.
The solution to this problem will be presented in point 2) of C).
C) There are several ways in which the mount owner can induce
undesired behavior in other users' processes, such as:
1) mounting a filesystem over a file or directory which the mount
owner could otherwise not be able to modify (or could only
make limited modifications).
This is solved in fusermount, by checking the access
permissions on the mountpoint and only allowing the mount if
the mount owner can do unlimited modification (has write
access to the mountpoint, and mountpoint is not a "sticky"
directory)
2) Even if 1) is solved the mount owner can change the behavior
of other users' processes.
i) It can slow down or indefinitely delay the execution of a
filesystem operation creating a DoS against the user or the
whole system. For example a suid application locking a
system file, and then accessing a file on the mount owner's
filesystem could be stopped, and thus causing the system
file to be locked forever.
ii) It can present files or directories of unlimited length, or
directory structures of unlimited depth, possibly causing a
system process to eat up diskspace, memory or other
resources, again causing DoS.
The solution to this as well as B) is not to allow processes
to access the filesystem, which could otherwise not be
monitored or manipulated by the mount owner. Since if the
mount owner can ptrace a process, it can do all of the above
without using a FUSE mount, the same criteria as used in
ptrace can be used to check if a process is allowed to access
the filesystem or not.
Note that the ptrace check is not strictly necessary to
prevent B/2/i, it is enough to check if mount owner has enough
privilege to send signal to the process accessing the
filesystem, since SIGSTOP can be used to get a similar effect.
I think these limitations are unacceptable?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If a sysadmin trusts the users enough, or can ensure through other
measures, that system processes will never enter non-privileged
mounts, it can relax the last limitation with a "user_allow_other"
config option. If this config option is set, the mounting user can
add the "allow_other" mount option which disables the check for other
users' processes.
Kernel - userspace interface
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The following diagram shows how a filesystem operation (in this
example unlink) is performed in FUSE.
NOTE: everything in this description is greatly simplified
| "rm /mnt/fuse/file" | FUSE filesystem daemon
| |
| | >sys_read()
| | >fuse_dev_read()
| | >request_wait()
| | [sleep on fc->waitq]
| |
| >sys_unlink() |
| >fuse_unlink() |
| [get request from |
| fc->unused_list] |
| >request_send() |
| [queue req on fc->pending] |
| [wake up fc->waitq] | [woken up]
| >request_wait_answer() |
| [sleep on req->waitq] |
| | <request_wait()
| | [remove req from fc->pending]
| | [copy req to read buffer]
| | [add req to fc->processing]
| | <fuse_dev_read()
| | <sys_read()
| |
| | [perform unlink]
| |
| | >sys_write()
| | >fuse_dev_write()
| | [look up req in fc->processing]
| | [remove from fc->processing]
| | [copy write buffer to req]
| [woken up] | [wake up req->waitq]
| | <fuse_dev_write()
| | <sys_write()
| <request_wait_answer() |
| <request_send() |
| [add request to |
| fc->unused_list] |
| <fuse_unlink() |
| <sys_unlink() |
There are a couple of ways in which to deadlock a FUSE filesystem.
Since we are talking about unprivileged userspace programs,
something must be done about these.
Scenario 1 - Simple deadlock
-----------------------------
| "rm /mnt/fuse/file" | FUSE filesystem daemon
| |
| >sys_unlink("/mnt/fuse/file") |
| [acquire inode semaphore |
| for "file"] |
| >fuse_unlink() |
| [sleep on req->waitq] |
| | <sys_read()
| | >sys_unlink("/mnt/fuse/file")
| | [acquire inode semaphore
| | for "file"]
| | *DEADLOCK*
The solution for this is to allow requests to be interrupted while
they are in userspace:
| [interrupted by signal] |
| <fuse_unlink() |
| [release semaphore] | [semaphore acquired]
| <sys_unlink() |
| | >fuse_unlink()
| | [queue req on fc->pending]
| | [wake up fc->waitq]
| | [sleep on req->waitq]
If the filesystem daemon was single threaded, this will stop here,
since there's no other thread to dequeue and execute the request.
In this case the solution is to kill the FUSE daemon as well. If
there are multiple serving threads, you just have to kill them as
long as any remain.
Moral: a filesystem which deadlocks, can soon find itself dead.
Scenario 2 - Tricky deadlock
----------------------------
This one needs a carefully crafted filesystem. It's a variation on
the above, only the call back to the filesystem is not explicit,
but is caused by a pagefault.
| Kamikaze filesystem thread 1 | Kamikaze filesystem thread 2
| |
| [fd = open("/mnt/fuse/file")] | [request served normally]
| [mmap fd to 'addr'] |
| [close fd] | [FLUSH triggers 'magic' flag]
| [read a byte from addr] |
| >do_page_fault() |
| [find or create page] |
| [lock page] |
| >fuse_readpage() |
| [queue READ request] |
| [sleep on req->waitq] |
| | [read request to buffer]
| | [create reply header before addr]
| | >sys_write(addr - headerlength)
| | >fuse_dev_write()
| | [look up req in fc->processing]
| | [remove from fc->processing]
| | [copy write buffer to req]
| | >do_page_fault()
| | [find or create page]
| | [lock page]
| | * DEADLOCK *
Solution is again to let the the request be interrupted (not
elaborated further).
An additional problem is that while the write buffer is being
copied to the request, the request must not be interrupted. This
is because the destination address of the copy may not be valid
after the request is interrupted.
This is solved with doing the copy atomically, and allowing
interruption while the page(s) belonging to the write buffer are
faulted with get_user_pages(). The 'req->locked' flag indicates
when the copy is taking place, and interruption is delayed until
this flag is unset.

2
fs/fuse/Makefile
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@ -4,4 +4,4 @@
obj-$(CONFIG_FUSE_FS) += fuse.o
fuse-objs := inode.o
fuse-objs := dev.o inode.o

884
fs/fuse/dev.c Normal file
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/*
FUSE: Filesystem in Userspace
Copyright (C) 2001-2005 Miklos Szeredi <miklos@szeredi.hu>
This program can be distributed under the terms of the GNU GPL.
See the file COPYING.
*/
#include "fuse_i.h"
#include <linux/init.h>
#include <linux/module.h>
#include <linux/poll.h>
#include <linux/uio.h>
#include <linux/miscdevice.h>
#include <linux/pagemap.h>
#include <linux/file.h>
#include <linux/slab.h>
MODULE_ALIAS_MISCDEV(FUSE_MINOR);
static kmem_cache_t *fuse_req_cachep;
static inline struct fuse_conn *fuse_get_conn(struct file *file)
{
struct fuse_conn *fc;
spin_lock(&fuse_lock);
fc = file->private_data;
if (fc && !fc->sb)
fc = NULL;
spin_unlock(&fuse_lock);
return fc;
}
static inline void fuse_request_init(struct fuse_req *req)
{
memset(req, 0, sizeof(*req));
INIT_LIST_HEAD(&req->list);
init_waitqueue_head(&req->waitq);
atomic_set(&req->count, 1);
}
struct fuse_req *fuse_request_alloc(void)
{
struct fuse_req *req = kmem_cache_alloc(fuse_req_cachep, SLAB_KERNEL);
if (req)
fuse_request_init(req);
return req;
}
void fuse_request_free(struct fuse_req *req)
{
kmem_cache_free(fuse_req_cachep, req);
}
static inline void block_sigs(sigset_t *oldset)
{
sigset_t mask;
siginitsetinv(&mask, sigmask(SIGKILL));
sigprocmask(SIG_BLOCK, &mask, oldset);
}
static inline void restore_sigs(sigset_t *oldset)
{
sigprocmask(SIG_SETMASK, oldset, NULL);
}
void fuse_reset_request(struct fuse_req *req)
{
int preallocated = req->preallocated;
BUG_ON(atomic_read(&req->count) != 1);
fuse_request_init(req);
req->preallocated = preallocated;
}
static void __fuse_get_request(struct fuse_req *req)
{
atomic_inc(&req->count);
}
/* Must be called with > 1 refcount */
static void __fuse_put_request(struct fuse_req *req)
{
BUG_ON(atomic_read(&req->count) < 2);
atomic_dec(&req->count);
}
static struct fuse_req *do_get_request(struct fuse_conn *fc)
{
struct fuse_req *req;
spin_lock(&fuse_lock);
BUG_ON(list_empty(&fc->unused_list));
req = list_entry(fc->unused_list.next, struct fuse_req, list);
list_del_init(&req->list);
spin_unlock(&fuse_lock);
fuse_request_init(req);
req->preallocated = 1;
req->in.h.uid = current->fsuid;
req->in.h.gid = current->fsgid;
req->in.h.pid = current->pid;
return req;
}
struct fuse_req *fuse_get_request(struct fuse_conn *fc)
{
if (down_interruptible(&fc->outstanding_sem))
return NULL;
return do_get_request(fc);
}
/*
* Non-interruptible version of the above function is for operations
* which can't legally return -ERESTART{SYS,NOINTR}. This can still
* return NULL, but only in case the signal is SIGKILL.
*/
struct fuse_req *fuse_get_request_nonint(struct fuse_conn *fc)
{
int intr;
sigset_t oldset;
block_sigs(&oldset);
intr = down_interruptible(&fc->outstanding_sem);
restore_sigs(&oldset);
return intr ? NULL : do_get_request(fc);
}
static void fuse_putback_request(struct fuse_conn *fc, struct fuse_req *req)
{
spin_lock(&fuse_lock);
if (req->preallocated)
list_add(&req->list, &fc->unused_list);
else
fuse_request_free(req);
/* If we are in debt decrease that first */
if (fc->outstanding_debt)
fc->outstanding_debt--;
else
up(&fc->outstanding_sem);
spin_unlock(&fuse_lock);
}
void fuse_put_request(struct fuse_conn *fc, struct fuse_req *req)
{
if (atomic_dec_and_test(&req->count))
fuse_putback_request(fc, req);
}
/*
* This function is called when a request is finished. Either a reply
* has arrived or it was interrupted (and not yet sent) or some error
* occured during communication with userspace, or the device file was
* closed. It decreases the referece count for the request. In case
* of a background request the referece to the stored objects are
* released. The requester thread is woken up (if still waiting), and
* finally the request is either freed or put on the unused_list
*
* Called with fuse_lock, unlocks it
*/
static void request_end(struct fuse_conn *fc, struct fuse_req *req)
{
int putback;
req->finished = 1;
putback = atomic_dec_and_test(&req->count);
spin_unlock(&fuse_lock);
if (req->background) {
if (req->inode)
iput(req->inode);
if (req->inode2)
iput(req->inode2);
if (req->file)
fput(req->file);
}
wake_up(&req->waitq);
if (req->in.h.opcode == FUSE_INIT) {
int i;
if (req->misc.init_in_out.major != FUSE_KERNEL_VERSION)
fc->conn_error = 1;
/* After INIT reply is received other requests can go
out. So do (FUSE_MAX_OUTSTANDING - 1) number of
up()s on outstanding_sem. The last up() is done in
fuse_putback_request() */
for (i = 1; i < FUSE_MAX_OUTSTANDING; i++)
up(&fc->outstanding_sem);
}
if (putback)
fuse_putback_request(fc, req);
}
static void background_request(struct fuse_req *req)
{
/* Need to get hold of the inode(s) and/or file used in the
request, so FORGET and RELEASE are not sent too early */
req->background = 1;
if (req->inode)
req->inode = igrab(req->inode);
if (req->inode2)
req->inode2 = igrab(req->inode2);
if (req->file)
get_file(req->file);
}
static int request_wait_answer_nonint(struct fuse_req *req)
{
int err;
sigset_t oldset;
block_sigs(&oldset);
err = wait_event_interruptible(req->waitq, req->finished);
restore_sigs(&oldset);
return err;
}
/* Called with fuse_lock held. Releases, and then reacquires it. */
static void request_wait_answer(struct fuse_req *req, int interruptible)
{
int intr;
spin_unlock(&fuse_lock);
if (interruptible)
intr = wait_event_interruptible(req->waitq, req->finished);
else
intr = request_wait_answer_nonint(req);
spin_lock(&fuse_lock);
if (intr && interruptible && req->sent) {
/* If request is already in userspace, only allow KILL
signal to interrupt */
spin_unlock(&fuse_lock);
intr = request_wait_answer_nonint(req);
spin_lock(&fuse_lock);
}
if (!intr)
return;
if (!interruptible || req->sent)
req->out.h.error = -EINTR;
else
req->out.h.error = -ERESTARTNOINTR;
req->interrupted = 1;
if (req->locked) {
/* This is uninterruptible sleep, because data is
being copied to/from the buffers of req. During
locked state, there mustn't be any filesystem
operation (e.g. page fault), since that could lead
to deadlock */
spin_unlock(&fuse_lock);
wait_event(req->waitq, !req->locked);
spin_lock(&fuse_lock);
}
if (!req->sent && !list_empty(&req->list)) {
list_del(&req->list);
__fuse_put_request(req);
} else if (!req->finished && req->sent)
background_request(req);
}
static unsigned len_args(unsigned numargs, struct fuse_arg *args)
{
unsigned nbytes = 0;
unsigned i;
for (i = 0; i < numargs; i++)
nbytes += args[i].size;
return nbytes;
}
static void queue_request(struct fuse_conn *fc, struct fuse_req *req)
{
fc->reqctr++;
/* zero is special */
if (fc->reqctr == 0)
fc->reqctr = 1;
req->in.h.unique = fc->reqctr;
req->in.h.len = sizeof(struct fuse_in_header) +
len_args(req->in.numargs, (struct fuse_arg *) req->in.args);
if (!req->preallocated) {
/* If request is not preallocated (either FORGET or
RELEASE), then still decrease outstanding_sem, so
user can't open infinite number of files while not
processing the RELEASE requests. However for
efficiency do it without blocking, so if down()
would block, just increase the debt instead */
if (down_trylock(&fc->outstanding_sem))
fc->outstanding_debt++;
}
list_add_tail(&req->list, &fc->pending);
wake_up(&fc->waitq);
}
static void request_send_wait(struct fuse_conn *fc, struct fuse_req *req,
int interruptible)
{
req->isreply = 1;
spin_lock(&fuse_lock);
if (!fc->file)
req->out.h.error = -ENOTCONN;
else if (fc->conn_error)
req->out.h.error = -ECONNREFUSED;
else {
queue_request(fc, req);
/* acquire extra reference, since request is still needed
after request_end() */
__fuse_get_request(req);
request_wait_answer(req, interruptible);
}
spin_unlock(&fuse_lock);
}
void request_send(struct fuse_conn *fc, struct fuse_req *req)
{
request_send_wait(fc, req, 1);
}
/*
* Non-interruptible version of the above function is for operations
* which can't legally return -ERESTART{SYS,NOINTR}. This can still
* be interrupted but only with SIGKILL.
*/
void request_send_nonint(struct fuse_conn *fc, struct fuse_req *req)
{
request_send_wait(fc, req, 0);
}
static void request_send_nowait(struct fuse_conn *fc, struct fuse_req *req)
{
spin_lock(&fuse_lock);
if (fc->file) {
queue_request(fc, req);
spin_unlock(&fuse_lock);
} else {
req->out.h.error = -ENOTCONN;
request_end(fc, req);
}
}
void request_send_noreply(struct fuse_conn *fc, struct fuse_req *req)
{
req->isreply = 0;
request_send_nowait(fc, req);
}
void request_send_background(struct fuse_conn *fc, struct fuse_req *req)
{
req->isreply = 1;
background_request(req);
request_send_nowait(fc, req);
}
void fuse_send_init(struct fuse_conn *fc)
{
/* This is called from fuse_read_super() so there's guaranteed
to be a request available */
struct fuse_req *req = do_get_request(fc);
struct fuse_init_in_out *arg = &req->misc.init_in_out;
arg->major = FUSE_KERNEL_VERSION;
arg->minor = FUSE_KERNEL_MINOR_VERSION;
req->in.h.opcode = FUSE_INIT;
req->in.numargs = 1;
req->in.args[0].size = sizeof(*arg);
req->in.args[0].value = arg;
req->out.numargs = 1;
req->out.args[0].size = sizeof(*arg);
req->out.args[0].value = arg;
request_send_background(fc, req);
}
/*
* Lock the request. Up to the next unlock_request() there mustn't be
* anything that could cause a page-fault. If the request was already
* interrupted bail out.
*/
static inline int lock_request(struct fuse_req *req)
{
int err = 0;
if (req) {
spin_lock(&fuse_lock);
if (req->interrupted)
err = -ENOENT;
else
req->locked = 1;
spin_unlock(&fuse_lock);
}
return err;
}
/*
* Unlock request. If it was interrupted during being locked, the
* requester thread is currently waiting for it to be unlocked, so
* wake it up.
*/
static inline void unlock_request(struct fuse_req *req)
{
if (req) {
spin_lock(&fuse_lock);
req->locked = 0;
if (req->interrupted)
wake_up(&req->waitq);
spin_unlock(&fuse_lock);
}
}
struct fuse_copy_state {
int write;
struct fuse_req *req;
const struct iovec *iov;
unsigned long nr_segs;
unsigned long seglen;
unsigned long addr;
struct page *pg;
void *mapaddr;
void *buf;
unsigned len;
};
static void fuse_copy_init(struct fuse_copy_state *cs, int write,
struct fuse_req *req, const struct iovec *iov,
unsigned long nr_segs)
{
memset(cs, 0, sizeof(*cs));
cs->write = write;
cs->req = req;
cs->iov = iov;
cs->nr_segs = nr_segs;
}
/* Unmap and put previous page of userspace buffer */
static inline void fuse_copy_finish(struct fuse_copy_state *cs)
{
if (cs->mapaddr) {
kunmap_atomic(cs->mapaddr, KM_USER0);
if (cs->write) {
flush_dcache_page(cs->pg);
set_page_dirty_lock(cs->pg);
}
put_page(cs->pg);
cs->mapaddr = NULL;
}
}
/*
* Get another pagefull of userspace buffer, and map it to kernel
* address space, and lock request
*/
static int fuse_copy_fill(struct fuse_copy_state *cs)
{
unsigned long offset;
int err;
unlock_request(cs->req);
fuse_copy_finish(cs);
if (!cs->seglen) {
BUG_ON(!cs->nr_segs);
cs->seglen = cs->iov[0].iov_len;
cs->addr = (unsigned long) cs->iov[0].iov_base;
cs->iov ++;
cs->nr_segs --;
}
down_read(&current->mm->mmap_sem);
err = get_user_pages(current, current->mm, cs->addr, 1, cs->write, 0,
&cs->pg, NULL);
up_read(&current->mm->mmap_sem);
if (err < 0)
return err;
BUG_ON(err != 1);
offset = cs->addr % PAGE_SIZE;
cs->mapaddr = kmap_atomic(cs->pg, KM_USER0);
cs->buf = cs->mapaddr + offset;
cs->len = min(PAGE_SIZE - offset, cs->seglen);
cs->seglen -= cs->len;
cs->addr += cs->len;
return lock_request(cs->req);
}
/* Do as much copy to/from userspace buffer as we can */
static inline int fuse_copy_do(struct fuse_copy_state *cs, void **val,
unsigned *size)
{
unsigned ncpy = min(*size, cs->len);
if (val) {
if (cs->write)
memcpy(cs->buf, *val, ncpy);
else
memcpy(*val, cs->buf, ncpy);
*val += ncpy;
}
*size -= ncpy;
cs->len -= ncpy;
cs->buf += ncpy;
return ncpy;
}
/*
* Copy a page in the request to/from the userspace buffer. Must be
* done atomically
*/
static inline int fuse_copy_page(struct fuse_copy_state *cs, struct page *page,
unsigned offset, unsigned count, int zeroing)
{
if (page && zeroing && count < PAGE_SIZE) {
void *mapaddr = kmap_atomic(page, KM_USER1);
memset(mapaddr, 0, PAGE_SIZE);
kunmap_atomic(mapaddr, KM_USER1);
}
while (count) {
int err;
if (!cs->len && (err = fuse_copy_fill(cs)))
return err;
if (page) {
void *mapaddr = kmap_atomic(page, KM_USER1);
void *buf = mapaddr + offset;
offset += fuse_copy_do(cs, &buf, &count);
kunmap_atomic(mapaddr, KM_USER1);
} else
offset += fuse_copy_do(cs, NULL, &count);
}
if (page && !cs->write)
flush_dcache_page(page);
return 0;
}
/* Copy pages in the request to/from userspace buffer */
static int fuse_copy_pages(struct fuse_copy_state *cs, unsigned nbytes,
int zeroing)
{
unsigned i;
struct fuse_req *req = cs->req;
unsigned offset = req->page_offset;
unsigned count = min(nbytes, (unsigned) PAGE_SIZE - offset);
for (i = 0; i < req->num_pages && (nbytes || zeroing); i++) {
struct page *page = req->pages[i];
int err = fuse_copy_page(cs, page, offset, count, zeroing);
if (err)
return err;
nbytes -= count;
count = min(nbytes, (unsigned) PAGE_SIZE);
offset = 0;
}
return 0;
}
/* Copy a single argument in the request to/from userspace buffer */
static int fuse_copy_one(struct fuse_copy_state *cs, void *val, unsigned size)
{
while (size) {
int err;
if (!cs->len && (err = fuse_copy_fill(cs)))
return err;
fuse_copy_do(cs, &val, &size);
}
return 0;
}
/* Copy request arguments to/from userspace buffer */
static int fuse_copy_args(struct fuse_copy_state *cs, unsigned numargs,
unsigned argpages, struct fuse_arg *args,
int zeroing)
{
int err = 0;
unsigned i;
for (i = 0; !err && i < numargs; i++) {
struct fuse_arg *arg = &args[i];
if (i == numargs - 1 && argpages)
err = fuse_copy_pages(cs, arg->size, zeroing);
else
err = fuse_copy_one(cs, arg->value, arg->size);
}
return err;
}
/* Wait until a request is available on the pending list */
static void request_wait(struct fuse_conn *fc)
{
DECLARE_WAITQUEUE(wait, current);
add_wait_queue_exclusive(&fc->waitq, &wait);
while (fc->sb && list_empty(&fc->pending)) {
set_current_state(TASK_INTERRUPTIBLE);
if (signal_pending(current))
break;
spin_unlock(&fuse_lock);
schedule();
spin_lock(&fuse_lock);
}
set_current_state(TASK_RUNNING);
remove_wait_queue(&fc->waitq, &wait);
}
/*
* Read a single request into the userspace filesystem's buffer. This
* function waits until a request is available, then removes it from
* the pending list and copies request data to userspace buffer. If
* no reply is needed (FORGET) or request has been interrupted or
* there was an error during the copying then it's finished by calling
* request_end(). Otherwise add it to the processing list, and set
* the 'sent' flag.
*/
static ssize_t fuse_dev_readv(struct file *file, const struct iovec *iov,
unsigned long nr_segs, loff_t *off)
{
int err;
struct fuse_conn *fc;
struct fuse_req *req;
struct fuse_in *in;
struct fuse_copy_state cs;
unsigned reqsize;
spin_lock(&fuse_lock);
fc = file->private_data;
err = -EPERM;
if (!fc)
goto err_unlock;
request_wait(fc);
err = -ENODEV;
if (!fc->sb)
goto err_unlock;
err = -ERESTARTSYS;
if (list_empty(&fc->pending))
goto err_unlock;
req = list_entry(fc->pending.next, struct fuse_req, list);
list_del_init(&req->list);
spin_unlock(&fuse_lock);
in = &req->in;
reqsize = req->in.h.len;
fuse_copy_init(&cs, 1, req, iov, nr_segs);
err = -EINVAL;
if (iov_length(iov, nr_segs) >= reqsize) {
err = fuse_copy_one(&cs, &in->h, sizeof(in->h));
if (!err)
err = fuse_copy_args(&cs, in->numargs, in->argpages,
(struct fuse_arg *) in->args, 0);
}
fuse_copy_finish(&cs);
spin_lock(&fuse_lock);
req->locked = 0;
if (!err && req->interrupted)
err = -ENOENT;
if (err) {
if (!req->interrupted)
req->out.h.error = -EIO;
request_end(fc, req);
return err;
}
if (!req->isreply)
request_end(fc, req);
else {
req->sent = 1;
list_add_tail(&req->list, &fc->processing);
spin_unlock(&fuse_lock);
}
return reqsize;
err_unlock:
spin_unlock(&fuse_lock);
return err;
}
static ssize_t fuse_dev_read(struct file *file, char __user *buf,
size_t nbytes, loff_t *off)
{
struct iovec iov;
iov.iov_len = nbytes;
iov.iov_base = buf;
return fuse_dev_readv(file, &iov, 1, off);
}
/* Look up request on processing list by unique ID */
static struct fuse_req *request_find(struct fuse_conn *fc, u64 unique)
{
struct list_head *entry;
list_for_each(entry, &fc->processing) {
struct fuse_req *req;
req = list_entry(entry, struct fuse_req, list);
if (req->in.h.unique == unique)
return req;
}
return NULL;
}
static int copy_out_args(struct fuse_copy_state *cs, struct fuse_out *out,
unsigned nbytes)
{
unsigned reqsize = sizeof(struct fuse_out_header);
if (out->h.error)
return nbytes != reqsize ? -EINVAL : 0;
reqsize += len_args(out->numargs, out->args);
if (reqsize < nbytes || (reqsize > nbytes && !out->argvar))
return -EINVAL;
else if (reqsize > nbytes) {
struct fuse_arg *lastarg = &out->args[out->numargs-1];
unsigned diffsize = reqsize - nbytes;
if (diffsize > lastarg->size)
return -EINVAL;
lastarg->size -= diffsize;
}
return fuse_copy_args(cs, out->numargs, out->argpages, out->args,
out->page_zeroing);
}
/*
* Write a single reply to a request. First the header is copied from
* the write buffer. The request is then searched on the processing
* list by the unique ID found in the header. If found, then remove
* it from the list and copy the rest of the buffer to the request.
* The request is finished by calling request_end()
*/
static ssize_t fuse_dev_writev(struct file *file, const struct iovec *iov,
unsigned long nr_segs, loff_t *off)
{
int err;
unsigned nbytes = iov_length(iov, nr_segs);
struct fuse_req *req;
struct fuse_out_header oh;
struct fuse_copy_state cs;
struct fuse_conn *fc = fuse_get_conn(file);
if (!fc)
return -ENODEV;
fuse_copy_init(&cs, 0, NULL, iov, nr_segs);
if (nbytes < sizeof(struct fuse_out_header))
return -EINVAL;
err = fuse_copy_one(&cs, &oh, sizeof(oh));
if (err)
goto err_finish;
err = -EINVAL;
if (!oh.unique || oh.error <= -1000 || oh.error > 0 ||
oh.len != nbytes)
goto err_finish;
spin_lock(&fuse_lock);
req = request_find(fc, oh.unique);
err = -EINVAL;
if (!req)
goto err_unlock;
list_del_init(&req->list);
if (req->interrupted) {
request_end(fc, req);
fuse_copy_finish(&cs);
return -ENOENT;
}
req->out.h = oh;
req->locked = 1;
cs.req = req;
spin_unlock(&fuse_lock);
err = copy_out_args(&cs, &req->out, nbytes);
fuse_copy_finish(&cs);
spin_lock(&fuse_lock);
req->locked = 0;
if (!err) {
if (req->interrupted)
err = -ENOENT;
} else if (!req->interrupted)
req->out.h.error = -EIO;
request_end(fc, req);
return err ? err : nbytes;
err_unlock:
spin_unlock(&fuse_lock);
err_finish:
fuse_copy_finish(&cs);
return err;
}
static ssize_t fuse_dev_write(struct file *file, const char __user *buf,
size_t nbytes, loff_t *off)
{
struct iovec iov;
iov.iov_len = nbytes;
iov.iov_base = (char __user *) buf;
return fuse_dev_writev(file, &iov, 1, off);
}
static unsigned fuse_dev_poll(struct file *file, poll_table *wait)
{
struct fuse_conn *fc = fuse_get_conn(file);
unsigned mask = POLLOUT | POLLWRNORM;
if (!fc)
return -ENODEV;
poll_wait(file, &fc->waitq, wait);
spin_lock(&fuse_lock);
if (!list_empty(&fc->pending))
mask |= POLLIN | POLLRDNORM;
spin_unlock(&fuse_lock);
return mask;
}
/* Abort all requests on the given list (pending or processing) */
static void end_requests(struct fuse_conn *fc, struct list_head *head)
{
while (!list_empty(head)) {
struct fuse_req *req;
req = list_entry(head->next, struct fuse_req, list);
list_del_init(&req->list);
req->out.h.error = -ECONNABORTED;
request_end(fc, req);
spin_lock(&fuse_lock);
}
}
static int fuse_dev_release(struct inode *inode, struct file *file)
{
struct fuse_conn *fc;
spin_lock(&fuse_lock);
fc = file->private_data;
if (fc) {
fc->file = NULL;
end_requests(fc, &fc->pending);
end_requests(fc, &fc->processing);
fuse_release_conn(fc);
}
spin_unlock(&fuse_lock);
return 0;
}
struct file_operations fuse_dev_operations = {
.owner = THIS_MODULE,
.llseek = no_llseek,
.read = fuse_dev_read,
.readv = fuse_dev_readv,
.write = fuse_dev_write,
.writev = fuse_dev_writev,
.poll = fuse_dev_poll,
.release = fuse_dev_release,
};
static struct miscdevice fuse_miscdevice = {
.minor = FUSE_MINOR,
.name = "fuse",
.fops = &fuse_dev_operations,
};
int __init fuse_dev_init(void)
{
int err = -ENOMEM;
fuse_req_cachep = kmem_cache_create("fuse_request",
sizeof(struct fuse_req),
0, 0, NULL, NULL);
if (!fuse_req_cachep)
goto out;
err = misc_register(&fuse_miscdevice);
if (err)
goto out_cache_clean;
return 0;
out_cache_clean:
kmem_cache_destroy(fuse_req_cachep);
out:
return err;
}
void fuse_dev_cleanup(void)
{
misc_deregister(&fuse_miscdevice);
kmem_cache_destroy(fuse_req_cachep);
}

223
fs/fuse/fuse_i.h
View File

@ -15,6 +15,12 @@
#include <linux/backing-dev.h>
#include <asm/semaphore.h>
/** Max number of pages that can be used in a single read request */
#define FUSE_MAX_PAGES_PER_REQ 32
/** If more requests are outstanding, then the operation will block */
#define FUSE_MAX_OUTSTANDING 10
/** FUSE inode */
struct fuse_inode {
/** Inode data */
@ -28,6 +34,123 @@ struct fuse_inode {
unsigned long i_time;
};
/** One input argument of a request */
struct fuse_in_arg {
unsigned size;
const void *value;
};
/** The request input */
struct fuse_in {
/** The request header */
struct fuse_in_header h;
/** True if the data for the last argument is in req->pages */
unsigned argpages:1;
/** Number of arguments */
unsigned numargs;
/** Array of arguments */
struct fuse_in_arg args[3];
};
/** One output argument of a request */
struct fuse_arg {
unsigned size;
void *value;
};
/** The request output */
struct fuse_out {
/** Header returned from userspace */
struct fuse_out_header h;
/** Last argument is variable length (can be shorter than
arg->size) */
unsigned argvar:1;
/** Last argument is a list of pages to copy data to */
unsigned argpages:1;
/** Zero partially or not copied pages */
unsigned page_zeroing:1;
/** Number or arguments */
unsigned numargs;
/** Array of arguments */
struct fuse_arg args[3];
};
struct fuse_req;
struct fuse_conn;
/**
* A request to the client
*/
struct fuse_req {
/** This can be on either unused_list, pending or processing
lists in fuse_conn */
struct list_head list;
/** refcount */
atomic_t count;
/** True if the request has reply */
unsigned isreply:1;
/** The request is preallocated */
unsigned preallocated:1;
/** The request was interrupted */
unsigned interrupted:1;
/** Request is sent in the background */
unsigned background:1;
/** Data is being copied to/from the request */
unsigned locked:1;
/** Request has been sent to userspace */
unsigned sent:1;
/** The request is finished */
unsigned finished:1;
/** The request input */
struct fuse_in in;
/** The request output */
struct fuse_out out;
/** Used to wake up the task waiting for completion of request*/
wait_queue_head_t waitq;
/** Data for asynchronous requests */
union {
struct fuse_init_in_out init_in_out;
} misc;
/** page vector */
struct page *pages[FUSE_MAX_PAGES_PER_REQ];
/** number of pages in vector */
unsigned num_pages;
/** offset of data on first page */
unsigned page_offset;
/** Inode used in the request */
struct inode *inode;
/** Second inode used in the request (or NULL) */
struct inode *inode2;
/** File used in the request (or NULL) */
struct file *file;
};
/**
* A Fuse connection.
*
@ -39,9 +162,37 @@ struct fuse_conn {
/** The superblock of the mounted filesystem */
struct super_block *sb;
/** The opened client device */
struct file *file;
/** The user id for this mount */
uid_t user_id;
/** Readers of the connection are waiting on this */
wait_queue_head_t waitq;
/** The list of pending requests */
struct list_head pending;
/** The list of requests being processed */
struct list_head processing;
/** Controls the maximum number of outstanding requests */
struct semaphore outstanding_sem;
/** This counts the number of outstanding requests if
outstanding_sem would go negative */
unsigned outstanding_debt;
/** The list of unused requests */
struct list_head unused_list;
/** The next unique request id */
u64 reqctr;
/** Connection failed (version mismatch) */
unsigned conn_error : 1;
/** Backing dev info */
struct backing_dev_info bdi;
};
@ -71,13 +222,20 @@ static inline u64 get_node_id(struct inode *inode)
return get_fuse_inode(inode)->nodeid;
}
/** Device operations */
extern struct file_operations fuse_dev_operations;
/**
* This is the single global spinlock which protects FUSE's structures
*
* The following data is protected by this lock:
*
* - the private_data field of the device file
* - the s_fs_info field of the super block
* - unused_list, pending, processing lists in fuse_conn
* - the unique request ID counter reqctr in fuse_conn
* - the sb (super_block) field in fuse_conn
* - the file (device file) field in fuse_conn
*/
extern spinlock_t fuse_lock;
@ -87,3 +245,68 @@ extern spinlock_t fuse_lock;
*/
void fuse_release_conn(struct fuse_conn *fc);
/**
* Initialize the client device
*/
int fuse_dev_init(void);
/**
* Cleanup the client device
*/
void fuse_dev_cleanup(void);
/**
* Allocate a request
*/
struct fuse_req *fuse_request_alloc(void);
/**
* Free a request
*/
void fuse_request_free(struct fuse_req *req);
/**
* Reinitialize a request, the preallocated flag is left unmodified
*/
void fuse_reset_request(struct fuse_req *req);
/**
* Reserve a preallocated request
*/
struct fuse_req *fuse_get_request(struct fuse_conn *fc);
/**
* Reserve a preallocated request, only interruptible by SIGKILL
*/
struct fuse_req *fuse_get_request_nonint(struct fuse_conn *fc);
/**
* Decrement reference count of a request. If count goes to zero put
* on unused list (preallocated) or free reqest (not preallocated).
*/
void fuse_put_request(struct fuse_conn *fc, struct fuse_req *req);
/**
* Send a request (synchronous, interruptible)
*/
void request_send(struct fuse_conn *fc, struct fuse_req *req);
/**
* Send a request (synchronous, non-interruptible except by SIGKILL)
*/
void request_send_nonint(struct fuse_conn *fc, struct fuse_req *req);
/**
* Send a request with no reply
*/
void request_send_noreply(struct fuse_conn *fc, struct fuse_req *req);
/**
* Send a request in the background
*/
void request_send_background(struct fuse_conn *fc, struct fuse_req *req);
/**
* Send the INIT message
*/
void fuse_send_init(struct fuse_conn *fc);

58
fs/fuse/inode.c
View File

@ -151,6 +151,8 @@ static void fuse_put_super(struct super_block *sb)
mount_count --;
fc->sb = NULL;
fc->user_id = 0;
/* Flush all readers on this fs */
wake_up_all(&fc->waitq);
fuse_release_conn(fc);
*get_fuse_conn_super_p(sb) = NULL;
spin_unlock(&fuse_lock);
@ -229,9 +231,22 @@ static int fuse_show_options(struct seq_file *m, struct vfsmount *mnt)
return 0;
}
static void free_conn(struct fuse_conn *fc)
{
while (!list_empty(&fc->unused_list)) {
struct fuse_req *req;
req = list_entry(fc->unused_list.next, struct fuse_req, list);
list_del(&req->list);
fuse_request_free(req);
}
kfree(fc);
}
/* Must be called with the fuse lock held */
void fuse_release_conn(struct fuse_conn *fc)
{
kfree(fc);
if (!fc->sb && !fc->file)
free_conn(fc);
}
static struct fuse_conn *new_conn(void)
@ -240,11 +255,27 @@ static struct fuse_conn *new_conn(void)
fc = kmalloc(sizeof(*fc), GFP_KERNEL);
if (fc != NULL) {
int i;
memset(fc, 0, sizeof(*fc));
fc->sb = NULL;
fc->file = NULL;
fc->user_id = 0;
init_waitqueue_head(&fc->waitq);
INIT_LIST_HEAD(&fc->pending);
INIT_LIST_HEAD(&fc->processing);
INIT_LIST_HEAD(&fc->unused_list);
sema_init(&fc->outstanding_sem, 0);
for (i = 0; i < FUSE_MAX_OUTSTANDING; i++) {
struct fuse_req *req = fuse_request_alloc();
if (!req) {
free_conn(fc);
return NULL;
}
list_add(&req->list, &fc->unused_list);
}
fc->bdi.ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
fc->bdi.unplug_io_fn = default_unplug_io_fn;
fc->reqctr = 0;
}
return fc;
}
@ -253,11 +284,20 @@ static struct fuse_conn *get_conn(struct file *file, struct super_block *sb)
{
struct fuse_conn *fc;
if (file->f_op != &fuse_dev_operations)
return ERR_PTR(-EINVAL);
fc = new_conn();
if (fc == NULL)
return NULL;
return ERR_PTR(-ENOMEM);
spin_lock(&fuse_lock);
fc->sb = sb;
if (file->private_data) {
free_conn(fc);
fc = ERR_PTR(-EINVAL);
} else {
file->private_data = fc;
fc->sb = sb;
fc->file = file;
}
spin_unlock(&fuse_lock);
return fc;
}
@ -315,8 +355,8 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
fc = get_conn(file, sb);
fput(file);
if (fc == NULL)
return -EINVAL;
if (IS_ERR(fc))
return PTR_ERR(fc);
fc->user_id = d.user_id;
@ -336,6 +376,7 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
iput(root);
goto err;
}
fuse_send_init(fc);
return 0;
err:
@ -411,8 +452,14 @@ static int __init fuse_init(void)
if (res)
goto err;
res = fuse_dev_init();
if (res)
goto err_fs_cleanup;
return 0;
err_fs_cleanup:
fuse_fs_cleanup();
err:
return res;
}
@ -422,6 +469,7 @@ static void __exit fuse_exit(void)
printk(KERN_DEBUG "fuse exit\n");
fuse_fs_cleanup();
fuse_dev_cleanup();
}
module_init(fuse_init);

36
include/linux/fuse.h
View File

@ -11,7 +11,7 @@
#include <asm/types.h>
/** Version number of this interface */
#define FUSE_KERNEL_VERSION 5
#define FUSE_KERNEL_VERSION 6
/** Minor version number of this interface */
#define FUSE_KERNEL_MINOR_VERSION 1
@ -19,6 +19,12 @@
/** The node ID of the root inode */
#define FUSE_ROOT_ID 1
/** The major number of the fuse character device */
#define FUSE_MAJOR 10
/** The minor number of the fuse character device */
#define FUSE_MINOR 229
struct fuse_attr {
__u64 ino;
__u64 size;
@ -36,3 +42,31 @@ struct fuse_attr {
__u32 rdev;
};
enum fuse_opcode {
FUSE_INIT = 26
};
/* Conservative buffer size for the client */
#define FUSE_MAX_IN 8192
struct fuse_init_in_out {
__u32 major;
__u32 minor;
};
struct fuse_in_header {
__u32 len;
__u32 opcode;
__u64 unique;
__u64 nodeid;
__u32 uid;
__u32 gid;
__u32 pid;
};
struct fuse_out_header {
__u32 len;
__s32 error;
__u64 unique;
};