ClabureDB: Classified Bug-Reports Database

   /*
     FUSE: Filesystem in Userspace
     Copyright (C) 2001-2006  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;
  }
  
  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);
         else
                 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);
 }
 
 /*
  * 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) {
                 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;
 }
 
 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;
 }
 
 /* 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.unique || oh.error <= -1000 || oh.error > 0 ||
             oh.len != nbytes)
                 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;
                        /* The end function will consume this reference */
                        __fuse_get_request(req);
                        spin_unlock(&fc->lock);
                        wait_event(req->waitq, !req->locked);
                        end(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);
}