linux/fs/fuse/dev.c

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/*
FUSE: Filesystem in Userspace
Copyright (C) 2001-2008 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 struct kmem_cache *fuse_req_cachep;
static struct fuse_conn *fuse_get_conn(struct file *file)
{
/*
* Lockless access is OK, because file->private data is set
* once during mount and is valid until the file is released.
*/
return file->private_data;
}
static void fuse_request_init(struct fuse_req *req)
{
memset(req, 0, sizeof(*req));
INIT_LIST_HEAD(&req->list);
INIT_LIST_HEAD(&req->intr_entry);
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, GFP_KERNEL);
if (req)
fuse_request_init(req);
return req;
}
fuse: support writable mmap Quoting Linus (3 years ago, FUSE inclusion discussions): "User-space filesystems are hard to get right. I'd claim that they are almost impossible, unless you limit them somehow (shared writable mappings are the nastiest part - if you don't have those, you can reasonably limit your problems by limiting the number of dirty pages you accept through normal "write()" calls)." Instead of attempting the impossible, I've just waited for the dirty page accounting infrastructure to materialize (thanks to Peter Zijlstra and others). This nicely solved the biggest problem: limiting the number of pages used for write caching. Some small details remained, however, which this largish patch attempts to address. It provides a page writeback implementation for fuse, which is completely safe against VM related deadlocks. Performance may not be very good for certain usage patterns, but generally it should be acceptable. It has been tested extensively with fsx-linux and bash-shared-mapping. Fuse page writeback design -------------------------- fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM. It copies the contents of the original page, and queues a WRITE request to the userspace filesystem using this temp page. The writeback is finished instantly from the MM's point of view: the page is removed from the radix trees, and the PageDirty and PageWriteback flags are cleared. For the duration of the actual write, the NR_WRITEBACK_TEMP counter is incremented. The per-bdi writeback count is not decremented until the actual write completes. On dirtying the page, fuse waits for a previous write to finish before proceeding. This makes sure, there can only be one temporary page used at a time for one cached page. This approach is wasteful in both memory and CPU bandwidth, so why is this complication needed? The basic problem is that there can be no guarantee about the time in which the userspace filesystem will complete a write. It may be buggy or even malicious, and fail to complete WRITE requests. We don't want unrelated parts of the system to grind to a halt in such cases. Also a filesystem may need additional resources (particularly memory) to complete a WRITE request. There's a great danger of a deadlock if that allocation may wait for the writepage to finish. Currently there are several cases where the kernel can block on page writeback: - allocation order is larger than PAGE_ALLOC_COSTLY_ORDER - page migration - throttle_vm_writeout (through NR_WRITEBACK) - sync(2) Of course in some cases (fsync, msync) we explicitly want to allow blocking. So for these cases new code has to be added to fuse, since the VM is not tracking writeback pages for us any more. As an extra safetly measure, the maximum dirty ratio allocated to a single fuse filesystem is set to 1% by default. This way one (or several) buggy or malicious fuse filesystems cannot slow down the rest of the system by hogging dirty memory. With appropriate privileges, this limit can be raised through '/sys/class/bdi/<bdi>/max_ratio'. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 07:54:41 +00:00
struct fuse_req *fuse_request_alloc_nofs(void)
{
struct fuse_req *req = kmem_cache_alloc(fuse_req_cachep, GFP_NOFS);
if (req)
fuse_request_init(req);
return req;
}
void fuse_request_free(struct fuse_req *req)
{
kmem_cache_free(fuse_req_cachep, req);
}
static void block_sigs(sigset_t *oldset)
{
sigset_t mask;
siginitsetinv(&mask, sigmask(SIGKILL));
sigprocmask(SIG_BLOCK, &mask, oldset);
}
static void restore_sigs(sigset_t *oldset)
{
sigprocmask(SIG_SETMASK, oldset, NULL);
}
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 void fuse_req_init_context(struct fuse_req *req)
{
req->in.h.uid = current->fsuid;
req->in.h.gid = current->fsgid;
req->in.h.pid = current->pid;
}
struct fuse_req *fuse_get_req(struct fuse_conn *fc)
{
struct fuse_req *req;
sigset_t oldset;
int intr;
int err;
atomic_inc(&fc->num_waiting);
block_sigs(&oldset);
intr = wait_event_interruptible(fc->blocked_waitq, !fc->blocked);
restore_sigs(&oldset);
err = -EINTR;
if (intr)
goto out;
err = -ENOTCONN;
if (!fc->connected)
goto out;
req = fuse_request_alloc();
err = -ENOMEM;
if (!req)
goto out;
fuse_req_init_context(req);
req->waiting = 1;
return req;
out:
atomic_dec(&fc->num_waiting);
return ERR_PTR(err);
}
/*
* Return request in fuse_file->reserved_req. However that may
* currently be in use. If that is the case, wait for it to become
* available.
*/
static struct fuse_req *get_reserved_req(struct fuse_conn *fc,
struct file *file)
{
struct fuse_req *req = NULL;
struct fuse_file *ff = file->private_data;
do {
wait_event(fc->reserved_req_waitq, ff->reserved_req);
spin_lock(&fc->lock);
if (ff->reserved_req) {
req = ff->reserved_req;
ff->reserved_req = NULL;
get_file(file);
req->stolen_file = file;
}
spin_unlock(&fc->lock);
} while (!req);
return req;
}
/*
* Put stolen request back into fuse_file->reserved_req
*/
static void put_reserved_req(struct fuse_conn *fc, struct fuse_req *req)
{
struct file *file = req->stolen_file;
struct fuse_file *ff = file->private_data;
spin_lock(&fc->lock);
fuse_request_init(req);
BUG_ON(ff->reserved_req);
ff->reserved_req = req;
wake_up_all(&fc->reserved_req_waitq);
spin_unlock(&fc->lock);
fput(file);
}
/*
* Gets a requests for a file operation, always succeeds
*
* This is used for sending the FLUSH request, which must get to
* userspace, due to POSIX locks which may need to be unlocked.
*
* If allocation fails due to OOM, use the reserved request in
* fuse_file.
*
* This is very unlikely to deadlock accidentally, since the
* filesystem should not have it's own file open. If deadlock is
* intentional, it can still be broken by "aborting" the filesystem.
*/
struct fuse_req *fuse_get_req_nofail(struct fuse_conn *fc, struct file *file)
{
struct fuse_req *req;
atomic_inc(&fc->num_waiting);
wait_event(fc->blocked_waitq, !fc->blocked);
req = fuse_request_alloc();
if (!req)
req = get_reserved_req(fc, file);
fuse_req_init_context(req);
req->waiting = 1;
return req;
}
void fuse_put_request(struct fuse_conn *fc, struct fuse_req *req)
{
if (atomic_dec_and_test(&req->count)) {
if (req->waiting)
atomic_dec(&fc->num_waiting);
if (req->stolen_file)
put_reserved_req(fc, req);
else
fuse_request_free(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 u64 fuse_get_unique(struct fuse_conn *fc)
{
fc->reqctr++;
/* zero is special */
if (fc->reqctr == 0)
fc->reqctr = 1;
return fc->reqctr;
}
static void queue_request(struct fuse_conn *fc, struct fuse_req *req)
{
req->in.h.unique = fuse_get_unique(fc);
req->in.h.len = sizeof(struct fuse_in_header) +
len_args(req->in.numargs, (struct fuse_arg *) req->in.args);
list_add_tail(&req->list, &fc->pending);
req->state = FUSE_REQ_PENDING;
if (!req->waiting) {
req->waiting = 1;
atomic_inc(&fc->num_waiting);
}
wake_up(&fc->waitq);
kill_fasync(&fc->fasync, SIGIO, POLL_IN);
}
static void flush_bg_queue(struct fuse_conn *fc)
{
while (fc->active_background < FUSE_MAX_BACKGROUND &&
!list_empty(&fc->bg_queue)) {
struct fuse_req *req;
req = list_entry(fc->bg_queue.next, struct fuse_req, list);
list_del(&req->list);
fc->active_background++;
queue_request(fc, req);
}
}
/*
* This function is called when a request is finished. Either a reply
* has arrived or it was aborted (and not yet sent) or some error
* occurred during communication with userspace, or the device file
* was closed. The requester thread is woken up (if still waiting),
* the 'end' callback is called if given, else the reference to the
* request is released
*
* Called with fc->lock, unlocks it
*/
static void request_end(struct fuse_conn *fc, struct fuse_req *req)
__releases(fc->lock)
{
void (*end) (struct fuse_conn *, struct fuse_req *) = req->end;
req->end = NULL;
list_del(&req->list);
list_del(&req->intr_entry);
req->state = FUSE_REQ_FINISHED;
if (req->background) {
if (fc->num_background == FUSE_MAX_BACKGROUND) {
fc->blocked = 0;
wake_up_all(&fc->blocked_waitq);
}
if (fc->num_background == FUSE_CONGESTION_THRESHOLD) {
clear_bdi_congested(&fc->bdi, READ);
clear_bdi_congested(&fc->bdi, WRITE);
}
fc->num_background--;
fc->active_background--;
flush_bg_queue(fc);
}
spin_unlock(&fc->lock);
wake_up(&req->waitq);
if (end)
end(fc, req);
fuse_put_request(fc, req);
}
static void wait_answer_interruptible(struct fuse_conn *fc,
struct fuse_req *req)
__releases(fc->lock) __acquires(fc->lock)
{
if (signal_pending(current))
return;
spin_unlock(&fc->lock);
wait_event_interruptible(req->waitq, req->state == FUSE_REQ_FINISHED);
spin_lock(&fc->lock);
}
static void queue_interrupt(struct fuse_conn *fc, struct fuse_req *req)
{
list_add_tail(&req->intr_entry, &fc->interrupts);
wake_up(&fc->waitq);
kill_fasync(&fc->fasync, SIGIO, POLL_IN);
}
static void request_wait_answer(struct fuse_conn *fc, struct fuse_req *req)
__releases(fc->lock) __acquires(fc->lock)
{
if (!fc->no_interrupt) {
/* Any signal may interrupt this */
wait_answer_interruptible(fc, req);
if (req->aborted)
goto aborted;
if (req->state == FUSE_REQ_FINISHED)
return;
req->interrupted = 1;
if (req->state == FUSE_REQ_SENT)
queue_interrupt(fc, req);
}
if (!req->force) {
sigset_t oldset;
/* Only fatal signals may interrupt this */
block_sigs(&oldset);
wait_answer_interruptible(fc, req);
restore_sigs(&oldset);
if (req->aborted)
goto aborted;
if (req->state == FUSE_REQ_FINISHED)
return;
/* Request is not yet in userspace, bail out */
if (req->state == FUSE_REQ_PENDING) {
list_del(&req->list);
__fuse_put_request(req);
req->out.h.error = -EINTR;
return;
}
}
/*
* Either request is already in userspace, or it was forced.
* Wait it out.
*/
spin_unlock(&fc->lock);
wait_event(req->waitq, req->state == FUSE_REQ_FINISHED);
spin_lock(&fc->lock);
if (!req->aborted)
return;
aborted:
BUG_ON(req->state != FUSE_REQ_FINISHED);
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(&fc->lock);
wait_event(req->waitq, !req->locked);
spin_lock(&fc->lock);
}
}
void request_send(struct fuse_conn *fc, struct fuse_req *req)
{
req->isreply = 1;
spin_lock(&fc->lock);
if (!fc->connected)
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(fc, req);
}
spin_unlock(&fc->lock);
}
static void request_send_nowait_locked(struct fuse_conn *fc,
struct fuse_req *req)
{
req->background = 1;
fc->num_background++;
if (fc->num_background == FUSE_MAX_BACKGROUND)
fc->blocked = 1;
if (fc->num_background == FUSE_CONGESTION_THRESHOLD) {
set_bdi_congested(&fc->bdi, READ);
set_bdi_congested(&fc->bdi, WRITE);
}
list_add_tail(&req->list, &fc->bg_queue);
flush_bg_queue(fc);
}
static void request_send_nowait(struct fuse_conn *fc, struct fuse_req *req)
{
spin_lock(&fc->lock);
if (fc->connected) {
request_send_nowait_locked(fc, req);
spin_unlock(&fc->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;
request_send_nowait(fc, req);
}
fuse: support writable mmap Quoting Linus (3 years ago, FUSE inclusion discussions): "User-space filesystems are hard to get right. I'd claim that they are almost impossible, unless you limit them somehow (shared writable mappings are the nastiest part - if you don't have those, you can reasonably limit your problems by limiting the number of dirty pages you accept through normal "write()" calls)." Instead of attempting the impossible, I've just waited for the dirty page accounting infrastructure to materialize (thanks to Peter Zijlstra and others). This nicely solved the biggest problem: limiting the number of pages used for write caching. Some small details remained, however, which this largish patch attempts to address. It provides a page writeback implementation for fuse, which is completely safe against VM related deadlocks. Performance may not be very good for certain usage patterns, but generally it should be acceptable. It has been tested extensively with fsx-linux and bash-shared-mapping. Fuse page writeback design -------------------------- fuse_writepage() allocates a new temporary page with GFP_NOFS|__GFP_HIGHMEM. It copies the contents of the original page, and queues a WRITE request to the userspace filesystem using this temp page. The writeback is finished instantly from the MM's point of view: the page is removed from the radix trees, and the PageDirty and PageWriteback flags are cleared. For the duration of the actual write, the NR_WRITEBACK_TEMP counter is incremented. The per-bdi writeback count is not decremented until the actual write completes. On dirtying the page, fuse waits for a previous write to finish before proceeding. This makes sure, there can only be one temporary page used at a time for one cached page. This approach is wasteful in both memory and CPU bandwidth, so why is this complication needed? The basic problem is that there can be no guarantee about the time in which the userspace filesystem will complete a write. It may be buggy or even malicious, and fail to complete WRITE requests. We don't want unrelated parts of the system to grind to a halt in such cases. Also a filesystem may need additional resources (particularly memory) to complete a WRITE request. There's a great danger of a deadlock if that allocation may wait for the writepage to finish. Currently there are several cases where the kernel can block on page writeback: - allocation order is larger than PAGE_ALLOC_COSTLY_ORDER - page migration - throttle_vm_writeout (through NR_WRITEBACK) - sync(2) Of course in some cases (fsync, msync) we explicitly want to allow blocking. So for these cases new code has to be added to fuse, since the VM is not tracking writeback pages for us any more. As an extra safetly measure, the maximum dirty ratio allocated to a single fuse filesystem is set to 1% by default. This way one (or several) buggy or malicious fuse filesystems cannot slow down the rest of the system by hogging dirty memory. With appropriate privileges, this limit can be raised through '/sys/class/bdi/<bdi>/max_ratio'. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-30 07:54:41 +00:00
/*
* Called under fc->lock
*
* fc->connected must have been checked previously
*/
void request_send_background_locked(struct fuse_conn *fc, struct fuse_req *req)
{
req->isreply = 1;
request_send_nowait_locked(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
* aborted bail out.
*/
static int lock_request(struct fuse_conn *fc, struct fuse_req *req)
{
int err = 0;
if (req) {
spin_lock(&fc->lock);
if (req->aborted)
err = -ENOENT;
else
req->locked = 1;
spin_unlock(&fc->lock);
}
return err;
}
/*
* Unlock request. If it was aborted during being locked, the
* requester thread is currently waiting for it to be unlocked, so
* wake it up.
*/
static void unlock_request(struct fuse_conn *fc, struct fuse_req *req)
{
if (req) {
spin_lock(&fc->lock);
req->locked = 0;
if (req->aborted)
wake_up(&req->waitq);
spin_unlock(&fc->lock);
}
}
struct fuse_copy_state {
struct fuse_conn *fc;
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, struct fuse_conn *fc,
int write, struct fuse_req *req,
const struct iovec *iov, unsigned long nr_segs)
{
memset(cs, 0, sizeof(*cs));
cs->fc = fc;
cs->write = write;
cs->req = req;
cs->iov = iov;
cs->nr_segs = nr_segs;
}
/* Unmap and put previous page of userspace buffer */
static 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->fc, 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->fc, cs->req);
}
/* Do as much copy to/from userspace buffer as we can */
static 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 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) {
if (!cs->len) {
int err = fuse_copy_fill(cs);
if (err)
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) {
if (!cs->len) {
int err = fuse_copy_fill(cs);
if (err)
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;
}
static int request_pending(struct fuse_conn *fc)
{
return !list_empty(&fc->pending) || !list_empty(&fc->interrupts);
}
/* 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->connected && !request_pending(fc)) {
set_current_state(TASK_INTERRUPTIBLE);
if (signal_pending(current))
break;
spin_unlock(&fc->lock);
schedule();
spin_lock(&fc->lock);
}
set_current_state(TASK_RUNNING);
remove_wait_queue(&fc->waitq, &wait);
}
/*
* Transfer an interrupt request to userspace
*
* Unlike other requests this is assembled on demand, without a need
* to allocate a separate fuse_req structure.
*
* Called with fc->lock held, releases it
*/
static int fuse_read_interrupt(struct fuse_conn *fc, struct fuse_req *req,
const struct iovec *iov, unsigned long nr_segs)
__releases(fc->lock)
{
struct fuse_copy_state cs;
struct fuse_in_header ih;
struct fuse_interrupt_in arg;
unsigned reqsize = sizeof(ih) + sizeof(arg);
int err;
list_del_init(&req->intr_entry);
req->intr_unique = fuse_get_unique(fc);
memset(&ih, 0, sizeof(ih));
memset(&arg, 0, sizeof(arg));
ih.len = reqsize;
ih.opcode = FUSE_INTERRUPT;
ih.unique = req->intr_unique;
arg.unique = req->in.h.unique;
spin_unlock(&fc->lock);
if (iov_length(iov, nr_segs) < reqsize)
return -EINVAL;
fuse_copy_init(&cs, fc, 1, NULL, iov, nr_segs);
err = fuse_copy_one(&cs, &ih, sizeof(ih));
if (!err)
err = fuse_copy_one(&cs, &arg, sizeof(arg));
fuse_copy_finish(&cs);
return err ? err : reqsize;
}
/*
* 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 aborted 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_read(struct kiocb *iocb, const struct iovec *iov,
unsigned long nr_segs, loff_t pos)
{
int err;
struct fuse_req *req;
struct fuse_in *in;
struct fuse_copy_state cs;
unsigned reqsize;
struct file *file = iocb->ki_filp;
struct fuse_conn *fc = fuse_get_conn(file);
if (!fc)
return -EPERM;
restart:
spin_lock(&fc->lock);
err = -EAGAIN;
if ((file->f_flags & O_NONBLOCK) && fc->connected &&
!request_pending(fc))
goto err_unlock;
request_wait(fc);
err = -ENODEV;
if (!fc->connected)
goto err_unlock;
err = -ERESTARTSYS;
if (!request_pending(fc))
goto err_unlock;
if (!list_empty(&fc->interrupts)) {
req = list_entry(fc->interrupts.next, struct fuse_req,
intr_entry);
return fuse_read_interrupt(fc, req, iov, nr_segs);
}
req = list_entry(fc->pending.next, struct fuse_req, list);
req->state = FUSE_REQ_READING;
list_move(&req->list, &fc->io);
in = &req->in;
reqsize = in->h.len;
/* If request is too large, reply with an error and restart the read */
if (iov_length(iov, nr_segs) < reqsize) {
req->out.h.error = -EIO;
/* SETXATTR is special, since it may contain too large data */
if (in->h.opcode == FUSE_SETXATTR)
req->out.h.error = -E2BIG;
request_end(fc, req);
goto restart;
}
spin_unlock(&fc->lock);
fuse_copy_init(&cs, fc, 1, req, iov, nr_segs);
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(&fc->lock);
req->locked = 0;
if (req->aborted) {
request_end(fc, req);
return -ENODEV;
}
if (err) {
req->out.h.error = -EIO;
request_end(fc, req);
return err;
}
if (!req->isreply)
request_end(fc, req);
else {
req->state = FUSE_REQ_SENT;
list_move_tail(&req->list, &fc->processing);
if (req->interrupted)
queue_interrupt(fc, req);
spin_unlock(&fc->lock);
}
return reqsize;
err_unlock:
spin_unlock(&fc->lock);
return err;
}
static int fuse_notify(struct fuse_conn *fc, enum fuse_notify_code code,
unsigned int size, struct fuse_copy_state *cs)
{
switch (code) {
default:
return -EINVAL;
}
}
/* 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 || req->intr_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_write(struct kiocb *iocb, const struct iovec *iov,
unsigned long nr_segs, loff_t pos)
{
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(iocb->ki_filp);
if (!fc)
return -EPERM;
fuse_copy_init(&cs, fc, 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.len != nbytes)
goto err_finish;
/*
* Zero oh.unique indicates unsolicited notification message
* and error contains notification code.
*/
if (!oh.unique) {
err = fuse_notify(fc, oh.error, nbytes - sizeof(oh), &cs);
fuse_copy_finish(&cs);
return err ? err : nbytes;
}
err = -EINVAL;
if (oh.error <= -1000 || oh.error > 0)
goto err_finish;
spin_lock(&fc->lock);
err = -ENOENT;
if (!fc->connected)
goto err_unlock;
req = request_find(fc, oh.unique);
if (!req)
goto err_unlock;
if (req->aborted) {
spin_unlock(&fc->lock);
fuse_copy_finish(&cs);
spin_lock(&fc->lock);
request_end(fc, req);
return -ENOENT;
}
/* Is it an interrupt reply? */
if (req->intr_unique == oh.unique) {
err = -EINVAL;
if (nbytes != sizeof(struct fuse_out_header))
goto err_unlock;
if (oh.error == -ENOSYS)
fc->no_interrupt = 1;
else if (oh.error == -EAGAIN)
queue_interrupt(fc, req);
spin_unlock(&fc->lock);
fuse_copy_finish(&cs);
return nbytes;
}
req->state = FUSE_REQ_WRITING;
list_move(&req->list, &fc->io);
req->out.h = oh;
req->locked = 1;
cs.req = req;
spin_unlock(&fc->lock);
err = copy_out_args(&cs, &req->out, nbytes);
fuse_copy_finish(&cs);
spin_lock(&fc->lock);
req->locked = 0;
if (!err) {
if (req->aborted)
err = -ENOENT;
} else if (!req->aborted)
req->out.h.error = -EIO;
request_end(fc, req);
return err ? err : nbytes;
err_unlock:
spin_unlock(&fc->lock);
err_finish:
fuse_copy_finish(&cs);
return err;
}
static unsigned fuse_dev_poll(struct file *file, poll_table *wait)
{
unsigned mask = POLLOUT | POLLWRNORM;
struct fuse_conn *fc = fuse_get_conn(file);
if (!fc)
return POLLERR;
poll_wait(file, &fc->waitq, wait);
spin_lock(&fc->lock);
if (!fc->connected)
mask = POLLERR;
else if (request_pending(fc))
mask |= POLLIN | POLLRDNORM;
spin_unlock(&fc->lock);
return mask;
}
/*
* Abort all requests on the given list (pending or processing)
*
* This function releases and reacquires fc->lock
*/
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);
req->out.h.error = -ECONNABORTED;
request_end(fc, req);
spin_lock(&fc->lock);
}
}
/*
* Abort requests under I/O
*
* The requests are set to aborted and finished, and the request
* waiter is woken up. This will make request_wait_answer() wait
* until the request is unlocked and then return.
*
* If the request is asynchronous, then the end function needs to be
* called after waiting for the request to be unlocked (if it was
* locked).
*/
static void end_io_requests(struct fuse_conn *fc)
__releases(fc->lock) __acquires(fc->lock)
{
while (!list_empty(&fc->io)) {
struct fuse_req *req =
list_entry(fc->io.next, struct fuse_req, list);
void (*end) (struct fuse_conn *, struct fuse_req *) = req->end;
req->aborted = 1;
req->out.h.error = -ECONNABORTED;
req->state = FUSE_REQ_FINISHED;
list_del_init(&req->list);
wake_up(&req->waitq);
if (end) {
req->end = NULL;
__fuse_get_request(req);
spin_unlock(&fc->lock);
wait_event(req->waitq, !req->locked);
end(fc, req);
fuse_put_request(fc, req);
spin_lock(&fc->lock);
}
}
}
/*
* Abort all requests.
*
* Emergency exit in case of a malicious or accidental deadlock, or
* just a hung filesystem.
*
* The same effect is usually achievable through killing the
* filesystem daemon and all users of the filesystem. The exception
* is the combination of an asynchronous request and the tricky
* deadlock (see Documentation/filesystems/fuse.txt).
*
* During the aborting, progression of requests from the pending and
* processing lists onto the io list, and progression of new requests
* onto the pending list is prevented by req->connected being false.
*
* Progression of requests under I/O to the processing list is
* prevented by the req->aborted flag being true for these requests.
* For this reason requests on the io list must be aborted first.
*/
void fuse_abort_conn(struct fuse_conn *fc)
{
spin_lock(&fc->lock);
if (fc->connected) {
fc->connected = 0;
fc->blocked = 0;
end_io_requests(fc);
end_requests(fc, &fc->pending);
end_requests(fc, &fc->processing);
wake_up_all(&fc->waitq);
wake_up_all(&fc->blocked_waitq);
kill_fasync(&fc->fasync, SIGIO, POLL_IN);
}
spin_unlock(&fc->lock);
}
static int fuse_dev_release(struct inode *inode, struct file *file)
{
struct fuse_conn *fc = fuse_get_conn(file);
if (fc) {
spin_lock(&fc->lock);
fc->connected = 0;
end_requests(fc, &fc->pending);
end_requests(fc, &fc->processing);
spin_unlock(&fc->lock);
fuse_conn_put(fc);
}
return 0;
}
static int fuse_dev_fasync(int fd, struct file *file, int on)
{
struct fuse_conn *fc = fuse_get_conn(file);
if (!fc)
return -EPERM;
/* No locking - fasync_helper does its own locking */
return fasync_helper(fd, file, on, &fc->fasync);
}
const struct file_operations fuse_dev_operations = {
.owner = THIS_MODULE,
.llseek = no_llseek,
.read = do_sync_read,
.aio_read = fuse_dev_read,
.write = do_sync_write,
.aio_write = fuse_dev_write,
.poll = fuse_dev_poll,
.release = fuse_dev_release,
.fasync = fuse_dev_fasync,
};
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);
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);
}