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/pagemap.h>
  #include <linux/slab.h>
  #include <linux/kernel.h>
  #include <linux/sched.h>
  
  static const struct file_operations fuse_direct_io_file_operations;
  
  static int fuse_send_open(struct inode *inode, struct file *file, int isdir,
                            struct fuse_open_out *outargp)
  {
          struct fuse_conn *fc = get_fuse_conn(inode);
          struct fuse_open_in inarg;
          struct fuse_req *req;
          int err;
  
          req = fuse_get_req(fc);
          if (IS_ERR(req))
                  return PTR_ERR(req);
  
          memset(&inarg, 0, sizeof(inarg));
          inarg.flags = file->f_flags & ~(O_CREAT | O_EXCL | O_NOCTTY);
          if (!fc->atomic_o_trunc)
                  inarg.flags &= ~O_TRUNC;
          req->in.h.opcode = isdir ? FUSE_OPENDIR : FUSE_OPEN;
          req->in.h.nodeid = get_node_id(inode);
          req->in.numargs = 1;
          req->in.args[0].size = sizeof(inarg);
          req->in.args[0].value = &inarg;
          req->out.numargs = 1;
          req->out.args[0].size = sizeof(*outargp);
          req->out.args[0].value = outargp;
          request_send(fc, req);
          err = req->out.h.error;
          fuse_put_request(fc, req);
  
          return err;
  }
  
  struct fuse_file *fuse_file_alloc(void)
  {
          struct fuse_file *ff;
          ff = kmalloc(sizeof(struct fuse_file), GFP_KERNEL);
          if (ff) {
                  ff->reserved_req = fuse_request_alloc();
                  if (!ff->reserved_req) {
                          kfree(ff);
                          ff = NULL;
                  } else {
                          INIT_LIST_HEAD(&ff->write_entry);
                          atomic_set(&ff->count, 0);
                  }
          }
          return ff;
  }
  
  void fuse_file_free(struct fuse_file *ff)
  {
          fuse_request_free(ff->reserved_req);
          kfree(ff);
  }
  
  static struct fuse_file *fuse_file_get(struct fuse_file *ff)
  {
          atomic_inc(&ff->count);
          return ff;
  }
  
  static void fuse_release_end(struct fuse_conn *fc, struct fuse_req *req)
  {
          dput(req->misc.release.dentry);
          mntput(req->misc.release.vfsmount);
          fuse_put_request(fc, req);
  }
  
  static void fuse_file_put(struct fuse_file *ff)
  {
          if (atomic_dec_and_test(&ff->count)) {
                  struct fuse_req *req = ff->reserved_req;
                  struct inode *inode = req->misc.release.dentry->d_inode;
                  struct fuse_conn *fc = get_fuse_conn(inode);
                  req->end = fuse_release_end;
                  request_send_background(fc, req);
                  kfree(ff);
          }
  }
  
  void fuse_finish_open(struct inode *inode, struct file *file,
                        struct fuse_file *ff, struct fuse_open_out *outarg)
  {
         if (outarg->open_flags & FOPEN_DIRECT_IO)
                 file->f_op = &fuse_direct_io_file_operations;
         if (!(outarg->open_flags & FOPEN_KEEP_CACHE))
                 invalidate_inode_pages2(inode->i_mapping);
         if (outarg->open_flags & FOPEN_NONSEEKABLE)
                 nonseekable_open(inode, file);
         ff->fh = outarg->fh;
         file->private_data = fuse_file_get(ff);
 }
 
 int fuse_open_common(struct inode *inode, struct file *file, int isdir)
 {
         struct fuse_open_out outarg;
         struct fuse_file *ff;
         int err;
 
         /* VFS checks this, but only _after_ ->open() */
         if (file->f_flags & O_DIRECT)
                 return -EINVAL;
 
         err = generic_file_open(inode, file);
         if (err)
                 return err;
 
         ff = fuse_file_alloc();
         if (!ff)
                 return -ENOMEM;
 
         err = fuse_send_open(inode, file, isdir, &outarg);
         if (err)
                 fuse_file_free(ff);
         else {
                 if (isdir)
                         outarg.open_flags &= ~FOPEN_DIRECT_IO;
                 fuse_finish_open(inode, file, ff, &outarg);
         }
 
         return err;
 }
 
 void fuse_release_fill(struct fuse_file *ff, u64 nodeid, int flags, int opcode)
 {
         struct fuse_req *req = ff->reserved_req;
         struct fuse_release_in *inarg = &req->misc.release.in;
 
         inarg->fh = ff->fh;
         inarg->flags = flags;
         req->in.h.opcode = opcode;
         req->in.h.nodeid = nodeid;
         req->in.numargs = 1;
         req->in.args[0].size = sizeof(struct fuse_release_in);
         req->in.args[0].value = inarg;
 }
 
 int fuse_release_common(struct inode *inode, struct file *file, int isdir)
 {
         struct fuse_file *ff = file->private_data;
         if (ff) {
                 struct fuse_conn *fc = get_fuse_conn(inode);
                 struct fuse_req *req = ff->reserved_req;
 
                 fuse_release_fill(ff, get_node_id(inode), file->f_flags,
                                   isdir ? FUSE_RELEASEDIR : FUSE_RELEASE);
 
                 /* Hold vfsmount and dentry until release is finished */
                 req->misc.release.vfsmount = mntget(file->f_path.mnt);
                 req->misc.release.dentry = dget(file->f_path.dentry);
 
                 spin_lock(&fc->lock);
                 list_del(&ff->write_entry);
                 spin_unlock(&fc->lock);
                 /*
                  * Normally this will send the RELEASE request,
                  * however if some asynchronous READ or WRITE requests
                  * are outstanding, the sending will be delayed
                  */
                 fuse_file_put(ff);
         }
 
         /* Return value is ignored by VFS */
         return 0;
 }
 
 static int fuse_open(struct inode *inode, struct file *file)
 {
         return fuse_open_common(inode, file, 0);
 }
 
 static int fuse_release(struct inode *inode, struct file *file)
 {
         return fuse_release_common(inode, file, 0);
 }
 
 /*
  * Scramble the ID space with XTEA, so that the value of the files_struct
  * pointer is not exposed to userspace.
  */
 u64 fuse_lock_owner_id(struct fuse_conn *fc, fl_owner_t id)
 {
         u32 *k = fc->scramble_key;
         u64 v = (unsigned long) id;
         u32 v0 = v;
         u32 v1 = v >> 32;
         u32 sum = 0;
         int i;
 
         for (i = 0; i < 32; i++) {
                 v0 += ((v1 << 4 ^ v1 >> 5) + v1) ^ (sum + k[sum & 3]);
                 sum += 0x9E3779B9;
                 v1 += ((v0 << 4 ^ v0 >> 5) + v0) ^ (sum + k[sum>>11 & 3]);
         }
 
         return (u64) v0 + ((u64) v1 << 32);
 }
 
 /*
  * Check if page is under writeback
  *
  * This is currently done by walking the list of writepage requests
  * for the inode, which can be pretty inefficient.
  */
 static bool fuse_page_is_writeback(struct inode *inode, pgoff_t index)
 {
         struct fuse_conn *fc = get_fuse_conn(inode);
         struct fuse_inode *fi = get_fuse_inode(inode);
         struct fuse_req *req;
         bool found = false;
 
         spin_lock(&fc->lock);
         list_for_each_entry(req, &fi->writepages, writepages_entry) {
                 pgoff_t curr_index;
 
                 BUG_ON(req->inode != inode);
                 curr_index = req->misc.write.in.offset >> PAGE_CACHE_SHIFT;
                 if (curr_index == index) {
                         found = true;
                         break;
                 }
         }
         spin_unlock(&fc->lock);
 
         return found;
 }
 
 /*
  * Wait for page writeback to be completed.
  *
  * Since fuse doesn't rely on the VM writeback tracking, this has to
  * use some other means.
  */
 static int fuse_wait_on_page_writeback(struct inode *inode, pgoff_t index)
 {
         struct fuse_inode *fi = get_fuse_inode(inode);
 
         wait_event(fi->page_waitq, !fuse_page_is_writeback(inode, index));
         return 0;
 }
 
 static int fuse_flush(struct file *file, fl_owner_t id)
 {
         struct inode *inode = file->f_path.dentry->d_inode;
         struct fuse_conn *fc = get_fuse_conn(inode);
         struct fuse_file *ff = file->private_data;
         struct fuse_req *req;
         struct fuse_flush_in inarg;
         int err;
 
         if (is_bad_inode(inode))
                 return -EIO;
 
         if (fc->no_flush)
                 return 0;
 
         req = fuse_get_req_nofail(fc, file);
         memset(&inarg, 0, sizeof(inarg));
         inarg.fh = ff->fh;
         inarg.lock_owner = fuse_lock_owner_id(fc, id);
         req->in.h.opcode = FUSE_FLUSH;
         req->in.h.nodeid = get_node_id(inode);
         req->in.numargs = 1;
         req->in.args[0].size = sizeof(inarg);
         req->in.args[0].value = &inarg;
         req->force = 1;
         request_send(fc, req);
         err = req->out.h.error;
         fuse_put_request(fc, req);
         if (err == -ENOSYS) {
                 fc->no_flush = 1;
                 err = 0;
         }
         return err;
 }
 
 /*
  * Wait for all pending writepages on the inode to finish.
  *
  * This is currently done by blocking further writes with FUSE_NOWRITE
  * and waiting for all sent writes to complete.
  *
  * This must be called under i_mutex, otherwise the FUSE_NOWRITE usage
  * could conflict with truncation.
  */
 static void fuse_sync_writes(struct inode *inode)
 {
         fuse_set_nowrite(inode);
         fuse_release_nowrite(inode);
 }
 
 int fuse_fsync_common(struct file *file, struct dentry *de, int datasync,
                       int isdir)
 {
         struct inode *inode = de->d_inode;
         struct fuse_conn *fc = get_fuse_conn(inode);
         struct fuse_file *ff = file->private_data;
         struct fuse_req *req;
         struct fuse_fsync_in inarg;
         int err;
 
         if (is_bad_inode(inode))
                 return -EIO;
 
         if ((!isdir && fc->no_fsync) || (isdir && fc->no_fsyncdir))
                 return 0;
 
         /*
          * Start writeback against all dirty pages of the inode, then
          * wait for all outstanding writes, before sending the FSYNC
          * request.
          */
         err = write_inode_now(inode, 0);
         if (err)
                 return err;
 
         fuse_sync_writes(inode);
 
         req = fuse_get_req(fc);
         if (IS_ERR(req))
                 return PTR_ERR(req);
 
         memset(&inarg, 0, sizeof(inarg));
         inarg.fh = ff->fh;
         inarg.fsync_flags = datasync ? 1 : 0;
         req->in.h.opcode = isdir ? FUSE_FSYNCDIR : FUSE_FSYNC;
         req->in.h.nodeid = get_node_id(inode);
         req->in.numargs = 1;
         req->in.args[0].size = sizeof(inarg);
         req->in.args[0].value = &inarg;
         request_send(fc, req);
         err = req->out.h.error;
         fuse_put_request(fc, req);
         if (err == -ENOSYS) {
                 if (isdir)
                         fc->no_fsyncdir = 1;
                 else
                         fc->no_fsync = 1;
                 err = 0;
         }
         return err;
 }
 
 static int fuse_fsync(struct file *file, struct dentry *de, int datasync)
 {
         return fuse_fsync_common(file, de, datasync, 0);
 }
 
 void fuse_read_fill(struct fuse_req *req, struct file *file,
                     struct inode *inode, loff_t pos, size_t count, int opcode)
 {
         struct fuse_read_in *inarg = &req->misc.read.in;
         struct fuse_file *ff = file->private_data;
 
         inarg->fh = ff->fh;
         inarg->offset = pos;
         inarg->size = count;
         inarg->flags = file->f_flags;
         req->in.h.opcode = opcode;
         req->in.h.nodeid = get_node_id(inode);
         req->in.numargs = 1;
         req->in.args[0].size = sizeof(struct fuse_read_in);
         req->in.args[0].value = inarg;
         req->out.argpages = 1;
         req->out.argvar = 1;
         req->out.numargs = 1;
         req->out.args[0].size = count;
 }
 
 static size_t fuse_send_read(struct fuse_req *req, struct file *file,
                              struct inode *inode, loff_t pos, size_t count,
                              fl_owner_t owner)
 {
         struct fuse_conn *fc = get_fuse_conn(inode);
 
         fuse_read_fill(req, file, inode, pos, count, FUSE_READ);
         if (owner != NULL) {
                 struct fuse_read_in *inarg = &req->misc.read.in;
 
                 inarg->read_flags |= FUSE_READ_LOCKOWNER;
                 inarg->lock_owner = fuse_lock_owner_id(fc, owner);
         }
         request_send(fc, req);
         return req->out.args[0].size;
 }
 
 static void fuse_read_update_size(struct inode *inode, loff_t size,
                                   u64 attr_ver)
 {
         struct fuse_conn *fc = get_fuse_conn(inode);
         struct fuse_inode *fi = get_fuse_inode(inode);
 
         spin_lock(&fc->lock);
         if (attr_ver == fi->attr_version && size < inode->i_size) {
                 fi->attr_version = ++fc->attr_version;
                 i_size_write(inode, size);
         }
         spin_unlock(&fc->lock);
 }
 
 static int fuse_readpage(struct file *file, struct page *page)
 {
         struct inode *inode = page->mapping->host;
         struct fuse_conn *fc = get_fuse_conn(inode);
         struct fuse_req *req;
         size_t num_read;
         loff_t pos = page_offset(page);
         size_t count = PAGE_CACHE_SIZE;
         u64 attr_ver;
         int err;
 
         err = -EIO;
         if (is_bad_inode(inode))
                 goto out;
 
         /*
          * Page writeback can extend beyond the liftime of the
          * page-cache page, so make sure we read a properly synced
          * page.
          */
         fuse_wait_on_page_writeback(inode, page->index);
 
         req = fuse_get_req(fc);
         err = PTR_ERR(req);
         if (IS_ERR(req))
                 goto out;
 
         attr_ver = fuse_get_attr_version(fc);
 
         req->out.page_zeroing = 1;
         req->num_pages = 1;
         req->pages[0] = page;
         num_read = fuse_send_read(req, file, inode, pos, count, NULL);
         err = req->out.h.error;
         fuse_put_request(fc, req);
 
         if (!err) {
                 /*
                  * Short read means EOF.  If file size is larger, truncate it
                  */
                 if (num_read < count)
                         fuse_read_update_size(inode, pos + num_read, attr_ver);
 
                 SetPageUptodate(page);
         }
 
         fuse_invalidate_attr(inode); /* atime changed */
  out:
         unlock_page(page);
         return err;
 }
 
 static void fuse_readpages_end(struct fuse_conn *fc, struct fuse_req *req)
 {
         int i;
         size_t count = req->misc.read.in.size;
         size_t num_read = req->out.args[0].size;
         struct inode *inode = req->pages[0]->mapping->host;
 
         /*
          * Short read means EOF.  If file size is larger, truncate it
          */
         if (!req->out.h.error && num_read < count) {
                 loff_t pos = page_offset(req->pages[0]) + num_read;
                 fuse_read_update_size(inode, pos, req->misc.read.attr_ver);
         }
 
         fuse_invalidate_attr(inode); /* atime changed */
 
         for (i = 0; i < req->num_pages; i++) {
                 struct page *page = req->pages[i];
                 if (!req->out.h.error)
                         SetPageUptodate(page);
                 else
                         SetPageError(page);
                 unlock_page(page);
         }
         if (req->ff)
                 fuse_file_put(req->ff);
         fuse_put_request(fc, req);
 }
 
 static void fuse_send_readpages(struct fuse_req *req, struct file *file,
                                 struct inode *inode)
 {
         struct fuse_conn *fc = get_fuse_conn(inode);
         loff_t pos = page_offset(req->pages[0]);
         size_t count = req->num_pages << PAGE_CACHE_SHIFT;
         req->out.page_zeroing = 1;
         fuse_read_fill(req, file, inode, pos, count, FUSE_READ);
         req->misc.read.attr_ver = fuse_get_attr_version(fc);
         if (fc->async_read) {
                 struct fuse_file *ff = file->private_data;
                 req->ff = fuse_file_get(ff);
                 req->end = fuse_readpages_end;
                 request_send_background(fc, req);
         } else {
                 request_send(fc, req);
                 fuse_readpages_end(fc, req);
         }
 }
 
 struct fuse_fill_data {
         struct fuse_req *req;
         struct file *file;
         struct inode *inode;
 };
 
 static int fuse_readpages_fill(void *_data, struct page *page)
 {
         struct fuse_fill_data *data = _data;
         struct fuse_req *req = data->req;
         struct inode *inode = data->inode;
         struct fuse_conn *fc = get_fuse_conn(inode);
 
         fuse_wait_on_page_writeback(inode, page->index);
 
         if (req->num_pages &&
             (req->num_pages == FUSE_MAX_PAGES_PER_REQ ||
              (req->num_pages + 1) * PAGE_CACHE_SIZE > fc->max_read ||
              req->pages[req->num_pages - 1]->index + 1 != page->index)) {
                 fuse_send_readpages(req, data->file, inode);
                 data->req = req = fuse_get_req(fc);
                 if (IS_ERR(req)) {
                         unlock_page(page);
                         return PTR_ERR(req);
                 }
         }
         req->pages[req->num_pages] = page;
         req->num_pages ++;
         return 0;
 }
 
 static int fuse_readpages(struct file *file, struct address_space *mapping,
                           struct list_head *pages, unsigned nr_pages)
 {
         struct inode *inode = mapping->host;
         struct fuse_conn *fc = get_fuse_conn(inode);
         struct fuse_fill_data data;
         int err;
 
         err = -EIO;
         if (is_bad_inode(inode))
                 goto out;
 
         data.file = file;
         data.inode = inode;
         data.req = fuse_get_req(fc);
         err = PTR_ERR(data.req);
         if (IS_ERR(data.req))
                 goto out;
 
         err = read_cache_pages(mapping, pages, fuse_readpages_fill, &data);
         if (!err) {
                 if (data.req->num_pages)
                         fuse_send_readpages(data.req, file, inode);
                 else
                         fuse_put_request(fc, data.req);
         }
 out:
         return err;
 }
 
 static ssize_t fuse_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
                                   unsigned long nr_segs, loff_t pos)
 {
         struct inode *inode = iocb->ki_filp->f_mapping->host;
 
         if (pos + iov_length(iov, nr_segs) > i_size_read(inode)) {
                 int err;
                 /*
                  * If trying to read past EOF, make sure the i_size
                  * attribute is up-to-date.
                  */
                 err = fuse_update_attributes(inode, NULL, iocb->ki_filp, NULL);
                 if (err)
                         return err;
         }
 
         return generic_file_aio_read(iocb, iov, nr_segs, pos);
 }
 
 static void fuse_write_fill(struct fuse_req *req, struct file *file,
                             struct fuse_file *ff, struct inode *inode,
                             loff_t pos, size_t count, int writepage)
 {
         struct fuse_conn *fc = get_fuse_conn(inode);
         struct fuse_write_in *inarg = &req->misc.write.in;
         struct fuse_write_out *outarg = &req->misc.write.out;
 
         memset(inarg, 0, sizeof(struct fuse_write_in));
         inarg->fh = ff->fh;
         inarg->offset = pos;
         inarg->size = count;
         inarg->write_flags = writepage ? FUSE_WRITE_CACHE : 0;
         inarg->flags = file ? file->f_flags : 0;
         req->in.h.opcode = FUSE_WRITE;
         req->in.h.nodeid = get_node_id(inode);
         req->in.argpages = 1;
         req->in.numargs = 2;
         if (fc->minor < 9)
                 req->in.args[0].size = FUSE_COMPAT_WRITE_IN_SIZE;
         else
                 req->in.args[0].size = sizeof(struct fuse_write_in);
         req->in.args[0].value = inarg;
         req->in.args[1].size = count;
         req->out.numargs = 1;
         req->out.args[0].size = sizeof(struct fuse_write_out);
         req->out.args[0].value = outarg;
 }
 
 static size_t fuse_send_write(struct fuse_req *req, struct file *file,
                               struct inode *inode, loff_t pos, size_t count,
                               fl_owner_t owner)
 {
         struct fuse_conn *fc = get_fuse_conn(inode);
         fuse_write_fill(req, file, file->private_data, inode, pos, count, 0);
         if (owner != NULL) {
                 struct fuse_write_in *inarg = &req->misc.write.in;
                 inarg->write_flags |= FUSE_WRITE_LOCKOWNER;
                 inarg->lock_owner = fuse_lock_owner_id(fc, owner);
         }
         request_send(fc, req);
         return req->misc.write.out.size;
 }
 
 static int fuse_write_begin(struct file *file, struct address_space *mapping,
                         loff_t pos, unsigned len, unsigned flags,
                         struct page **pagep, void **fsdata)
 {
         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
 
         *pagep = __grab_cache_page(mapping, index);
         if (!*pagep)
                 return -ENOMEM;
         return 0;
 }
 
 static void fuse_write_update_size(struct inode *inode, loff_t pos)
 {
         struct fuse_conn *fc = get_fuse_conn(inode);
         struct fuse_inode *fi = get_fuse_inode(inode);
 
         spin_lock(&fc->lock);
         fi->attr_version = ++fc->attr_version;
         if (pos > inode->i_size)
                 i_size_write(inode, pos);
         spin_unlock(&fc->lock);
 }
 
 static int fuse_buffered_write(struct file *file, struct inode *inode,
                                loff_t pos, unsigned count, struct page *page)
 {
         int err;
         size_t nres;
         struct fuse_conn *fc = get_fuse_conn(inode);
         unsigned offset = pos & (PAGE_CACHE_SIZE - 1);
         struct fuse_req *req;
 
         if (is_bad_inode(inode))
                 return -EIO;
 
         /*
          * Make sure writepages on the same page are not mixed up with
          * plain writes.
          */
         fuse_wait_on_page_writeback(inode, page->index);
 
         req = fuse_get_req(fc);
         if (IS_ERR(req))
                 return PTR_ERR(req);
 
         req->num_pages = 1;
         req->pages[0] = page;
         req->page_offset = offset;
         nres = fuse_send_write(req, file, inode, pos, count, NULL);
         err = req->out.h.error;
         fuse_put_request(fc, req);
         if (!err && !nres)
                 err = -EIO;
         if (!err) {
                 pos += nres;
                 fuse_write_update_size(inode, pos);
                 if (count == PAGE_CACHE_SIZE)
                         SetPageUptodate(page);
         }
         fuse_invalidate_attr(inode);
         return err ? err : nres;
 }
 
 static int fuse_write_end(struct file *file, struct address_space *mapping,
                         loff_t pos, unsigned len, unsigned copied,
                         struct page *page, void *fsdata)
 {
         struct inode *inode = mapping->host;
         int res = 0;
 
         if (copied)
                 res = fuse_buffered_write(file, inode, pos, copied, page);
 
         unlock_page(page);
         page_cache_release(page);
         return res;
 }
 
 static size_t fuse_send_write_pages(struct fuse_req *req, struct file *file,
                                     struct inode *inode, loff_t pos,
                                     size_t count)
 {
         size_t res;
         unsigned offset;
         unsigned i;
 
         for (i = 0; i < req->num_pages; i++)
                 fuse_wait_on_page_writeback(inode, req->pages[i]->index);
 
         res = fuse_send_write(req, file, inode, pos, count, NULL);
 
         offset = req->page_offset;
         count = res;
         for (i = 0; i < req->num_pages; i++) {
                 struct page *page = req->pages[i];
 
                 if (!req->out.h.error && !offset && count >= PAGE_CACHE_SIZE)
                         SetPageUptodate(page);
 
                 if (count > PAGE_CACHE_SIZE - offset)
                         count -= PAGE_CACHE_SIZE - offset;
                 else
                         count = 0;
                 offset = 0;
 
                 unlock_page(page);
                 page_cache_release(page);
         }
 
         return res;
 }
 
 static ssize_t fuse_fill_write_pages(struct fuse_req *req,
                                struct address_space *mapping,
                                struct iov_iter *ii, loff_t pos)
 {
         struct fuse_conn *fc = get_fuse_conn(mapping->host);
         unsigned offset = pos & (PAGE_CACHE_SIZE - 1);
         size_t count = 0;
         int err;
 
         req->page_offset = offset;
 
         do {
                 size_t tmp;
                 struct page *page;
                 pgoff_t index = pos >> PAGE_CACHE_SHIFT;
                 size_t bytes = min_t(size_t, PAGE_CACHE_SIZE - offset,
                                      iov_iter_count(ii));
 
                 bytes = min_t(size_t, bytes, fc->max_write - count);
 
  again:
                 err = -EFAULT;
                 if (iov_iter_fault_in_readable(ii, bytes))
                         break;
 
                 err = -ENOMEM;
                 page = __grab_cache_page(mapping, index);
                 if (!page)
                         break;
 
                 pagefault_disable();
                 tmp = iov_iter_copy_from_user_atomic(page, ii, offset, bytes);
                 pagefault_enable();
                 flush_dcache_page(page);
 
                 if (!tmp) {
                         unlock_page(page);
                         page_cache_release(page);
                         bytes = min(bytes, iov_iter_single_seg_count(ii));
                         goto again;
                 }
 
                 err = 0;
                 req->pages[req->num_pages] = page;
                 req->num_pages++;
 
                 iov_iter_advance(ii, tmp);
                 count += tmp;
                 pos += tmp;
                 offset += tmp;
                 if (offset == PAGE_CACHE_SIZE)
                         offset = 0;
 
                 if (!fc->big_writes)
                         break;
         } while (iov_iter_count(ii) && count < fc->max_write &&
                  req->num_pages < FUSE_MAX_PAGES_PER_REQ && offset == 0);
 
         return count > 0 ? count : err;
 }
 
 static ssize_t fuse_perform_write(struct file *file,
                                   struct address_space *mapping,
                                   struct iov_iter *ii, loff_t pos)
 {
         struct inode *inode = mapping->host;
         struct fuse_conn *fc = get_fuse_conn(inode);
         int err = 0;
         ssize_t res = 0;
 
         if (is_bad_inode(inode))
                 return -EIO;
 
         do {
                 struct fuse_req *req;
                 ssize_t count;
 
                 req = fuse_get_req(fc);
                 if (IS_ERR(req)) {
                         err = PTR_ERR(req);
                         break;
                 }
 
                 count = fuse_fill_write_pages(req, mapping, ii, pos);
                 if (count <= 0) {
                         err = count;
                 } else {
                         size_t num_written;
 
                         num_written = fuse_send_write_pages(req, file, inode,
                                                             pos, count);
                         err = req->out.h.error;
                         if (!err) {
                                 res += num_written;
                                 pos += num_written;
 
                                 /* break out of the loop on short write */
                                 if (num_written != count)
                                         err = -EIO;
                         }
                 }
                 fuse_put_request(fc, req);
         } while (!err && iov_iter_count(ii));
 
         if (res > 0)
                 fuse_write_update_size(inode, pos);
 
         fuse_invalidate_attr(inode);
 
         return res > 0 ? res : err;
 }
 
 static ssize_t fuse_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
                                    unsigned long nr_segs, loff_t pos)
 {
         struct file *file = iocb->ki_filp;
         struct address_space *mapping = file->f_mapping;
         size_t count = 0;
         ssize_t written = 0;
         struct inode *inode = mapping->host;
         ssize_t err;
         struct iov_iter i;
 
         WARN_ON(iocb->ki_pos != pos);
 
         err = generic_segment_checks(iov, &nr_segs, &count, VERIFY_READ);
         if (err)
                 return err;
 
         mutex_lock(&inode->i_mutex);
         vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
 
         /* We can write back this queue in page reclaim */
         current->backing_dev_info = mapping->backing_dev_info;
 
         err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
         if (err)
                 goto out;
 
         if (count == 0)
                 goto out;
 
         err = file_remove_suid(file);
         if (err)
                 goto out;
 
         file_update_time(file);
 
         iov_iter_init(&i, iov, nr_segs, count, 0);
         written = fuse_perform_write(file, mapping, &i, pos);
         if (written >= 0)
                 iocb->ki_pos = pos + written;
 
 out:
         current->backing_dev_info = NULL;
         mutex_unlock(&inode->i_mutex);
 
         return written ? written : err;
 }
 
 static void fuse_release_user_pages(struct fuse_req *req, int write)
 {
         unsigned i;
 
         for (i = 0; i < req->num_pages; i++) {
                 struct page *page = req->pages[i];
                 if (write)
                         set_page_dirty_lock(page);
                 put_page(page);
         }
 }
 
 static int fuse_get_user_pages(struct fuse_req *req, const char __user *buf,
                                unsigned nbytes, int write)
 {
         unsigned long user_addr = (unsigned long) buf;
         unsigned offset = user_addr & ~PAGE_MASK;
         int npages;
 
         /* This doesn't work with nfsd */
         if (!current->mm)
                 return -EPERM;
 
         nbytes = min(nbytes, (unsigned) FUSE_MAX_PAGES_PER_REQ << PAGE_SHIFT);
         npages = (nbytes + offset + PAGE_SIZE - 1) >> PAGE_SHIFT;
         npages = clamp(npages, 1, FUSE_MAX_PAGES_PER_REQ);
         down_read(&current->mm->mmap_sem);
         npages = get_user_pages(current, current->mm, user_addr, npages, write,
                                 0, req->pages, NULL);
         up_read(&current->mm->mmap_sem);
         if (npages < 0)
                 return npages;
 
         req->num_pages = npages;
         req->page_offset = offset;
         return 0;
 }
 
 static ssize_t fuse_direct_io(struct file *file, const char __user *buf,
                               size_t count, loff_t *ppos, int write)
 {
         struct inode *inode = file->f_path.dentry->d_inode;
         struct fuse_conn *fc = get_fuse_conn(inode);
         size_t nmax = write ? fc->max_write : fc->max_read;
         loff_t pos = *ppos;
         ssize_t res = 0;
         struct fuse_req *req;
 
         if (is_bad_inode(inode))
                 return -EIO;
 
         req = fuse_get_req(fc);
         if (IS_ERR(req))
                 return PTR_ERR(req);
 
         while (count) {
                 size_t nres;
                 size_t nbytes_limit = min(count, nmax);
                 size_t nbytes;
                 int err = fuse_get_user_pages(req, buf, nbytes_limit, !write);
                 if (err) {
                         res = err;
                         break;
                 }
                 nbytes = (req->num_pages << PAGE_SHIFT) - req->page_offset;
                 nbytes = min(nbytes_limit, nbytes);
                 if (write)
                         nres = fuse_send_write(req, file, inode, pos, nbytes,
                                                current->files);
                 else
                         nres = fuse_send_read(req, file, inode, pos, nbytes,
                                               current->files);
                 fuse_release_user_pages(req, !write);
                 if (req->out.h.error) {
                         if (!res)
                                 res = req->out.h.error;
                         break;
                 } else if (nres > nbytes) {
                         res = -EIO;
                         break;
                 }
                 count -= nres;
                 res += nres;
                 pos += nres;
                buf += nres;
                if (nres != nbytes)
                        break;
                if (count) {
                        fuse_put_request(fc, req);
                        req = fuse_get_req(fc);
                        if (IS_ERR(req))
                                break;
                }
        }
        fuse_put_request(fc, req);
        if (res > 0) {
                if (write)
                        fuse_write_update_size(inode, pos);
                *ppos = pos;
        }
        fuse_invalidate_attr(inode);

        return res;
}

static ssize_t fuse_direct_read(struct file *file, char __user *buf,
                                     size_t count, loff_t *ppos)
{
        return fuse_direct_io(file, buf, count, ppos, 0);
}

static ssize_t fuse_direct_write(struct file *file, const char __user *buf,
                                 size_t count, loff_t *ppos)
{
        struct inode *inode = file->f_path.dentry->d_inode;
        ssize_t res;
        /* Don't allow parallel writes to the same file */
        mutex_lock(&inode->i_mutex);
        res = generic_write_checks(file, ppos, &count, 0);
        if (!res)
                res = fuse_direct_io(file, buf, count, ppos, 1);
        mutex_unlock(&inode->i_mutex);
        return res;
}

static void fuse_writepage_free(struct fuse_conn *fc, struct fuse_req *req)
{
        __free_page(req->pages[0]);
        fuse_file_put(req->ff);
        fuse_put_request(fc, req);
}

static void fuse_writepage_finish(struct fuse_conn *fc, struct fuse_req *req)
{
        struct inode *inode = req->inode;
        struct fuse_inode *fi = get_fuse_inode(inode);
        struct backing_dev_info *bdi = inode->i_mapping->backing_dev_info;

        list_del(&req->writepages_entry);
        dec_bdi_stat(bdi, BDI_WRITEBACK);
        dec_zone_page_state(req->pages[0], NR_WRITEBACK_TEMP);
        bdi_writeout_inc(bdi);
        wake_up(&fi->page_waitq);
}

/* Called under fc->lock, may release and reacquire it */
static void fuse_send_writepage(struct fuse_conn *fc, struct fuse_req *req)
{
        struct fuse_inode *fi = get_fuse_inode(req->inode);
        loff_t size = i_size_read(req->inode);
        struct fuse_write_in *inarg = &req->misc.write.in;

        if (!fc->connected)
                goto out_free;

        if (inarg->offset + PAGE_CACHE_SIZE <= size) {
                inarg->size = PAGE_CACHE_SIZE;
        } else if (inarg->offset < size) {
                inarg->size = size & (PAGE_CACHE_SIZE - 1);
        } else {
                /* Got truncated off completely */
                goto out_free;
        }

        req->in.args[1].size = inarg->size;
        fi->writectr++;
        request_send_background_locked(fc, req);
        return;

 out_free:
        fuse_writepage_finish(fc, req);
        spin_unlock(&fc->lock);
        fuse_writepage_free(fc, req);
        spin_lock(&fc->lock);
}

/*
 * If fi->writectr is positive (no truncate or fsync going on) send
 * all queued writepage requests.
 *
 * Called with fc->lock
 */
void fuse_flush_writepages(struct inode *inode)
{
        struct fuse_conn *fc = get_fuse_conn(inode);
        struct fuse_inode *fi = get_fuse_inode(inode);
        struct fuse_req *req;

        while (fi->writectr >= 0 && !list_empty(&fi->queued_writes)) {
                req = list_entry(fi->queued_writes.next, struct fuse_req, list);
                list_del_init(&req->list);
                fuse_send_writepage(fc, req);
        }
}

static void fuse_writepage_end(struct fuse_conn *fc, struct fuse_req *req)
{
        struct inode *inode = req->inode;
        struct fuse_inode *fi = get_fuse_inode(inode);

        mapping_set_error(inode->i_mapping, req->out.h.error);
        spin_lock(&fc->lock);
        fi->writectr--;
        fuse_writepage_finish(fc, req);
        spin_unlock(&fc->lock);
        fuse_writepage_free(fc, req);
}

static int fuse_writepage_locked(struct page *page)
{
        struct address_space *mapping = page->mapping;
        struct inode *inode = mapping->host;
        struct fuse_conn *fc = get_fuse_conn(inode);
        struct fuse_inode *fi = get_fuse_inode(inode);
        struct fuse_req *req;
        struct fuse_file *ff;
        struct page *tmp_page;

        set_page_writeback(page);

        req = fuse_request_alloc_nofs();
        if (!req)
                goto err;

        tmp_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
        if (!tmp_page)
                goto err_free;

        spin_lock(&fc->lock);
        BUG_ON(list_empty(&fi->write_files));
        ff = list_entry(fi->write_files.next, struct fuse_file, write_entry);
        req->ff = fuse_file_get(ff);
        spin_unlock(&fc->lock);

        fuse_write_fill(req, NULL, ff, inode, page_offset(page), 0, 1);

        copy_highpage(tmp_page, page);
        req->num_pages = 1;
        req->pages[0] = tmp_page;
        req->page_offset = 0;
        req->end = fuse_writepage_end;
        req->inode = inode;

        inc_bdi_stat(mapping->backing_dev_info, BDI_WRITEBACK);
        inc_zone_page_state(tmp_page, NR_WRITEBACK_TEMP);
        end_page_writeback(page);

        spin_lock(&fc->lock);
        list_add(&req->writepages_entry, &fi->writepages);
        list_add_tail(&req->list, &fi->queued_writes);
        fuse_flush_writepages(inode);
        spin_unlock(&fc->lock);

        return 0;

err_free:
        fuse_request_free(req);
err:
        end_page_writeback(page);
        return -ENOMEM;
}

static int fuse_writepage(struct page *page, struct writeback_control *wbc)
{
        int err;

        err = fuse_writepage_locked(page);
        unlock_page(page);

        return err;
}

static int fuse_launder_page(struct page *page)
{
        int err = 0;
        if (clear_page_dirty_for_io(page)) {
                struct inode *inode = page->mapping->host;
                err = fuse_writepage_locked(page);
                if (!err)
                        fuse_wait_on_page_writeback(inode, page->index);
        }
        return err;
}

/*
 * Write back dirty pages now, because there may not be any suitable
 * open files later
 */
static void fuse_vma_close(struct vm_area_struct *vma)
{
        filemap_write_and_wait(vma->vm_file->f_mapping);
}

/*
 * Wait for writeback against this page to complete before allowing it
 * to be marked dirty again, and hence written back again, possibly
 * before the previous writepage completed.
 *
 * Block here, instead of in ->writepage(), so that the userspace fs
 * can only block processes actually operating on the filesystem.
 *
 * Otherwise unprivileged userspace fs would be able to block
 * unrelated:
 *
 * - page migration
 * - sync(2)
 * - try_to_free_pages() with order > PAGE_ALLOC_COSTLY_ORDER
 */
static int fuse_page_mkwrite(struct vm_area_struct *vma, struct page *page)
{
        /*
         * Don't use page->mapping as it may become NULL from a
         * concurrent truncate.
         */
        struct inode *inode = vma->vm_file->f_mapping->host;

        fuse_wait_on_page_writeback(inode, page->index);
        return 0;
}

static struct vm_operations_struct fuse_file_vm_ops = {
        .close                = fuse_vma_close,
        .fault                = filemap_fault,
        .page_mkwrite        = fuse_page_mkwrite,
};

static int fuse_file_mmap(struct file *file, struct vm_area_struct *vma)
{
        if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE)) {
                struct inode *inode = file->f_dentry->d_inode;
                struct fuse_conn *fc = get_fuse_conn(inode);
                struct fuse_inode *fi = get_fuse_inode(inode);
                struct fuse_file *ff = file->private_data;
                /*
                 * file may be written through mmap, so chain it onto the
                 * inodes's write_file list
                 */
                spin_lock(&fc->lock);
                if (list_empty(&ff->write_entry))
                        list_add(&ff->write_entry, &fi->write_files);
                spin_unlock(&fc->lock);
        }
        file_accessed(file);
        vma->vm_ops = &fuse_file_vm_ops;
        return 0;
}

static int convert_fuse_file_lock(const struct fuse_file_lock *ffl,
                                  struct file_lock *fl)
{
        switch (ffl->type) {
        case F_UNLCK:
                break;

        case F_RDLCK:
        case F_WRLCK:
                if (ffl->start > OFFSET_MAX || ffl->end > OFFSET_MAX ||
                    ffl->end < ffl->start)
                        return -EIO;

                fl->fl_start = ffl->start;
                fl->fl_end = ffl->end;
                fl->fl_pid = ffl->pid;
                break;

        default:
                return -EIO;
        }
        fl->fl_type = ffl->type;
        return 0;
}

static void fuse_lk_fill(struct fuse_req *req, struct file *file,
                         const struct file_lock *fl, int opcode, pid_t pid,
                         int flock)
{
        struct inode *inode = file->f_path.dentry->d_inode;
        struct fuse_conn *fc = get_fuse_conn(inode);
        struct fuse_file *ff = file->private_data;
        struct fuse_lk_in *arg = &req->misc.lk_in;

        arg->fh = ff->fh;
        arg->owner = fuse_lock_owner_id(fc, fl->fl_owner);
        arg->lk.start = fl->fl_start;
        arg->lk.end = fl->fl_end;
        arg->lk.type = fl->fl_type;
        arg->lk.pid = pid;
        if (flock)
                arg->lk_flags |= FUSE_LK_FLOCK;
        req->in.h.opcode = opcode;
        req->in.h.nodeid = get_node_id(inode);
        req->in.numargs = 1;
        req->in.args[0].size = sizeof(*arg);
        req->in.args[0].value = arg;
}

static int fuse_getlk(struct file *file, struct file_lock *fl)
{
        struct inode *inode = file->f_path.dentry->d_inode;
        struct fuse_conn *fc = get_fuse_conn(inode);
        struct fuse_req *req;
        struct fuse_lk_out outarg;
        int err;

        req = fuse_get_req(fc);
        if (IS_ERR(req))
                return PTR_ERR(req);

        fuse_lk_fill(req, file, fl, FUSE_GETLK, 0, 0);
        req->out.numargs = 1;
        req->out.args[0].size = sizeof(outarg);
        req->out.args[0].value = &outarg;
        request_send(fc, req);
        err = req->out.h.error;
        fuse_put_request(fc, req);
        if (!err)
                err = convert_fuse_file_lock(&outarg.lk, fl);

        return err;
}

static int fuse_setlk(struct file *file, struct file_lock *fl, int flock)
{
        struct inode *inode = file->f_path.dentry->d_inode;
        struct fuse_conn *fc = get_fuse_conn(inode);
        struct fuse_req *req;
        int opcode = (fl->fl_flags & FL_SLEEP) ? FUSE_SETLKW : FUSE_SETLK;
        pid_t pid = fl->fl_type != F_UNLCK ? current->tgid : 0;
        int err;

        if (fl->fl_lmops && fl->fl_lmops->fl_grant) {
                /* NLM needs asynchronous locks, which we don't support yet */
                return -ENOLCK;
        }

        /* Unlock on close is handled by the flush method */
        if (fl->fl_flags & FL_CLOSE)
                return 0;

        req = fuse_get_req(fc);
        if (IS_ERR(req))
                return PTR_ERR(req);

        fuse_lk_fill(req, file, fl, opcode, pid, flock);
        request_send(fc, req);
        err = req->out.h.error;
        /* locking is restartable */
        if (err == -EINTR)
                err = -ERESTARTSYS;
        fuse_put_request(fc, req);
        return err;
}

static int fuse_file_lock(struct file *file, int cmd, struct file_lock *fl)
{
        struct inode *inode = file->f_path.dentry->d_inode;
        struct fuse_conn *fc = get_fuse_conn(inode);
        int err;

        if (cmd == F_CANCELLK) {
                err = 0;
        } else if (cmd == F_GETLK) {
                if (fc->no_lock) {
                        posix_test_lock(file, fl);
                        err = 0;
                } else
                        err = fuse_getlk(file, fl);
        } else {
                if (fc->no_lock)
                        err = posix_lock_file(file, fl, NULL);
                else
                        err = fuse_setlk(file, fl, 0);
        }
        return err;
}

static int fuse_file_flock(struct file *file, int cmd, struct file_lock *fl)
{
        struct inode *inode = file->f_path.dentry->d_inode;
        struct fuse_conn *fc = get_fuse_conn(inode);
        int err;

        if (fc->no_lock) {
                err = flock_lock_file_wait(file, fl);
        } else {
                /* emulate flock with POSIX locks */
                fl->fl_owner = (fl_owner_t) file;
                err = fuse_setlk(file, fl, 1);
        }

        return err;
}

static sector_t fuse_bmap(struct address_space *mapping, sector_t block)
{
        struct inode *inode = mapping->host;
        struct fuse_conn *fc = get_fuse_conn(inode);
        struct fuse_req *req;
        struct fuse_bmap_in inarg;
        struct fuse_bmap_out outarg;
        int err;

        if (!inode->i_sb->s_bdev || fc->no_bmap)
                return 0;

        req = fuse_get_req(fc);
        if (IS_ERR(req))
                return 0;

        memset(&inarg, 0, sizeof(inarg));
        inarg.block = block;
        inarg.blocksize = inode->i_sb->s_blocksize;
        req->in.h.opcode = FUSE_BMAP;
        req->in.h.nodeid = get_node_id(inode);
        req->in.numargs = 1;
        req->in.args[0].size = sizeof(inarg);
        req->in.args[0].value = &inarg;
        req->out.numargs = 1;
        req->out.args[0].size = sizeof(outarg);
        req->out.args[0].value = &outarg;
        request_send(fc, req);
        err = req->out.h.error;
        fuse_put_request(fc, req);
        if (err == -ENOSYS)
                fc->no_bmap = 1;

        return err ? 0 : outarg.block;
}

static loff_t fuse_file_llseek(struct file *file, loff_t offset, int origin)
{
        loff_t retval;
        struct inode *inode = file->f_path.dentry->d_inode;

        mutex_lock(&inode->i_mutex);
        switch (origin) {
        case SEEK_END:
                retval = fuse_update_attributes(inode, NULL, file, NULL);
                if (retval)
                        return retval;
                offset += i_size_read(inode);
                break;
        case SEEK_CUR:
                offset += file->f_pos;
        }
        retval = -EINVAL;
        if (offset >= 0 && offset <= inode->i_sb->s_maxbytes) {
                if (offset != file->f_pos) {
                        file->f_pos = offset;
                        file->f_version = 0;
                }
                retval = offset;
        }
        mutex_unlock(&inode->i_mutex);
        return retval;
}

static const struct file_operations fuse_file_operations = {
        .llseek                = fuse_file_llseek,
        .read                = do_sync_read,
        .aio_read        = fuse_file_aio_read,
        .write                = do_sync_write,
        .aio_write        = fuse_file_aio_write,
        .mmap                = fuse_file_mmap,
        .open                = fuse_open,
        .flush                = fuse_flush,
        .release        = fuse_release,
        .fsync                = fuse_fsync,
        .lock                = fuse_file_lock,
        .flock                = fuse_file_flock,
        .splice_read        = generic_file_splice_read,
};

static const struct file_operations fuse_direct_io_file_operations = {
        .llseek                = fuse_file_llseek,
        .read                = fuse_direct_read,
        .write                = fuse_direct_write,
        .open                = fuse_open,
        .flush                = fuse_flush,
        .release        = fuse_release,
        .fsync                = fuse_fsync,
        .lock                = fuse_file_lock,
        .flock                = fuse_file_flock,
        /* no mmap and splice_read */
};

static const struct address_space_operations fuse_file_aops  = {
        .readpage        = fuse_readpage,
        .writepage        = fuse_writepage,
        .launder_page        = fuse_launder_page,
        .write_begin        = fuse_write_begin,
        .write_end        = fuse_write_end,
        .readpages        = fuse_readpages,
        .set_page_dirty        = __set_page_dirty_nobuffers,
        .bmap                = fuse_bmap,
};

void fuse_init_file_inode(struct inode *inode)
{
        inode->i_fop = &fuse_file_operations;
        inode->i_data.a_ops = &fuse_file_aops;
}