/*
   *  linux/fs/nfs/file.c
   *
   *  Copyright (C) 1992  Rick Sladkey
   *
   *  Changes Copyright (C) 1994 by Florian La Roche
   *   - Do not copy data too often around in the kernel.
   *   - In nfs_file_read the return value of kmalloc wasn't checked.
   *   - Put in a better version of read look-ahead buffering. Original idea
   *     and implementation by Wai S Kok elekokws@ee.nus.sg.
   *
   *  Expire cache on write to a file by Wai S Kok (Oct 1994).
   *
   *  Total rewrite of read side for new NFS buffer cache.. Linus.
   *
   *  nfs regular file handling functions
   */
  
  #include <linux/module.h>
  #include <linux/time.h>
  #include <linux/kernel.h>
  #include <linux/errno.h>
  #include <linux/fcntl.h>
  #include <linux/stat.h>
  #include <linux/nfs_fs.h>
  #include <linux/nfs_mount.h>
  #include <linux/mm.h>
  #include <linux/pagemap.h>
  #include <linux/aio.h>
  #include <linux/gfp.h>
  #include <linux/swap.h>
  
  #include <asm/uaccess.h>
  
  #include "delegation.h"
  #include "internal.h"
  #include "iostat.h"
  #include "fscache.h"
  
  #include "nfstrace.h"
  
  #define NFSDBG_FACILITY		NFSDBG_FILE
  
  static const struct vm_operations_struct nfs_file_vm_ops;
  
  /* Hack for future NFS swap support */
  #ifndef IS_SWAPFILE
  # define IS_SWAPFILE(inode)	(0)
  #endif
  
  int nfs_check_flags(int flags)
  {
  	if ((flags & (O_APPEND | O_DIRECT)) == (O_APPEND | O_DIRECT))
  		return -EINVAL;
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(nfs_check_flags);
  
  /*
   * Open file
   */
  static int
  nfs_file_open(struct inode *inode, struct file *filp)
  {
  	int res;
  
  	dprintk("NFS: open file(%pD2)
  ", filp);
  
  	nfs_inc_stats(inode, NFSIOS_VFSOPEN);
  	res = nfs_check_flags(filp->f_flags);
  	if (res)
  		return res;
  
  	res = nfs_open(inode, filp);
  	return res;
  }
  
  int
  nfs_file_release(struct inode *inode, struct file *filp)
  {
  	dprintk("NFS: release(%pD2)
  ", filp);
  
  	nfs_inc_stats(inode, NFSIOS_VFSRELEASE);
  	return nfs_release(inode, filp);
  }
  EXPORT_SYMBOL_GPL(nfs_file_release);
  
  /**
   * nfs_revalidate_size - Revalidate the file size
   * @inode - pointer to inode struct
   * @file - pointer to struct file
   *
   * Revalidates the file length. This is basically a wrapper around
   * nfs_revalidate_inode() that takes into account the fact that we may
   * have cached writes (in which case we don't care about the server's
   * idea of what the file length is), or O_DIRECT (in which case we
   * shouldn't trust the cache).
   */
  static int nfs_revalidate_file_size(struct inode *inode, struct file *filp)
  {
  	struct nfs_server *server = NFS_SERVER(inode);
  	struct nfs_inode *nfsi = NFS_I(inode);
  
  	if (nfs_have_delegated_attributes(inode))
  		goto out_noreval;
  
  	if (filp->f_flags & O_DIRECT)
  		goto force_reval;
  	if (nfsi->cache_validity & NFS_INO_REVAL_PAGECACHE)
  		goto force_reval;
  	if (nfs_attribute_timeout(inode))
  		goto force_reval;
  out_noreval:
  	return 0;
  force_reval:
  	return __nfs_revalidate_inode(server, inode);
  }
  
  loff_t nfs_file_llseek(struct file *filp, loff_t offset, int whence)
  {
  	dprintk("NFS: llseek file(%pD2, %lld, %d)
  ",
  			filp, offset, whence);
  
  	/*
  	 * whence == SEEK_END || SEEK_DATA || SEEK_HOLE => we must revalidate
  	 * the cached file length
  	 */
  	if (whence != SEEK_SET && whence != SEEK_CUR) {
  		struct inode *inode = filp->f_mapping->host;
  
  		int retval = nfs_revalidate_file_size(inode, filp);
  		if (retval < 0)
  			return (loff_t)retval;
  	}
  
  	return generic_file_llseek(filp, offset, whence);
  }
  EXPORT_SYMBOL_GPL(nfs_file_llseek);
  
  /*
   * Flush all dirty pages, and check for write errors.
   */
  int
  nfs_file_flush(struct file *file, fl_owner_t id)
  {
  	struct inode	*inode = file_inode(file);
  
  	dprintk("NFS: flush(%pD2)
  ", file);
  
  	nfs_inc_stats(inode, NFSIOS_VFSFLUSH);
  	if ((file->f_mode & FMODE_WRITE) == 0)
  		return 0;
  
  	/*
  	 * If we're holding a write delegation, then just start the i/o
  	 * but don't wait for completion (or send a commit).
  	 */
  	if (NFS_PROTO(inode)->have_delegation(inode, FMODE_WRITE))
  		return filemap_fdatawrite(file->f_mapping);
  
  	/* Flush writes to the server and return any errors */
  	return vfs_fsync(file, 0);
  }
  EXPORT_SYMBOL_GPL(nfs_file_flush);
  
  ssize_t
  nfs_file_read(struct kiocb *iocb, const struct iovec *iov,
  		unsigned long nr_segs, loff_t pos)
  {
  	struct inode *inode = file_inode(iocb->ki_filp);
  	ssize_t result;
  
  	if (iocb->ki_filp->f_flags & O_DIRECT)
  		return nfs_file_direct_read(iocb, iov, nr_segs, pos, true);
  
  	dprintk("NFS: read(%pD2, %lu@%lu)
  ",
  		iocb->ki_filp,
  		(unsigned long) iov_length(iov, nr_segs), (unsigned long) pos);
  
  	result = nfs_revalidate_mapping(inode, iocb->ki_filp->f_mapping);
  	if (!result) {
  		result = generic_file_aio_read(iocb, iov, nr_segs, pos);
  		if (result > 0)
  			nfs_add_stats(inode, NFSIOS_NORMALREADBYTES, result);
  	}
  	return result;
  }
  EXPORT_SYMBOL_GPL(nfs_file_read);
  
  ssize_t
  nfs_file_splice_read(struct file *filp, loff_t *ppos,
  		     struct pipe_inode_info *pipe, size_t count,
  		     unsigned int flags)
  {
  	struct inode *inode = file_inode(filp);
  	ssize_t res;
  
  	dprintk("NFS: splice_read(%pD2, %lu@%Lu)
  ",
  		filp, (unsigned long) count, (unsigned long long) *ppos);
  
  	res = nfs_revalidate_mapping(inode, filp->f_mapping);
  	if (!res) {
  		res = generic_file_splice_read(filp, ppos, pipe, count, flags);
  		if (res > 0)
  			nfs_add_stats(inode, NFSIOS_NORMALREADBYTES, res);
  	}
  	return res;
  }
  EXPORT_SYMBOL_GPL(nfs_file_splice_read);
  
  int
  nfs_file_mmap(struct file * file, struct vm_area_struct * vma)
  {
  	struct inode *inode = file_inode(file);
  	int	status;
  
  	dprintk("NFS: mmap(%pD2)
  ", file);
  
  	/* Note: generic_file_mmap() returns ENOSYS on nommu systems
  	 *       so we call that before revalidating the mapping
  	 */
  	status = generic_file_mmap(file, vma);
  	if (!status) {
  		vma->vm_ops = &nfs_file_vm_ops;
  		status = nfs_revalidate_mapping(inode, file->f_mapping);
  	}
  	return status;
  }
  EXPORT_SYMBOL_GPL(nfs_file_mmap);
  
  /*
   * Flush any dirty pages for this process, and check for write errors.
   * The return status from this call provides a reliable indication of
   * whether any write errors occurred for this process.
   *
   * Notice that it clears the NFS_CONTEXT_ERROR_WRITE before synching to
   * disk, but it retrieves and clears ctx->error after synching, despite
   * the two being set at the same time in nfs_context_set_write_error().
   * This is because the former is used to notify the _next_ call to
   * nfs_file_write() that a write error occurred, and hence cause it to
   * fall back to doing a synchronous write.
   */
  int
  nfs_file_fsync_commit(struct file *file, loff_t start, loff_t end, int datasync)
  {
  	struct nfs_open_context *ctx = nfs_file_open_context(file);
  	struct inode *inode = file_inode(file);
  	int have_error, do_resend, status;
  	int ret = 0;
  
  	dprintk("NFS: fsync file(%pD2) datasync %d
  ", file, datasync);
  
  	nfs_inc_stats(inode, NFSIOS_VFSFSYNC);
  	do_resend = test_and_clear_bit(NFS_CONTEXT_RESEND_WRITES, &ctx->flags);
  	have_error = test_and_clear_bit(NFS_CONTEXT_ERROR_WRITE, &ctx->flags);
  	status = nfs_commit_inode(inode, FLUSH_SYNC);
  	have_error |= test_bit(NFS_CONTEXT_ERROR_WRITE, &ctx->flags);
  	if (have_error) {
  		ret = xchg(&ctx->error, 0);
  		if (ret)
  			goto out;
  	}
  	if (status < 0) {
  		ret = status;
  		goto out;
  	}
  	do_resend |= test_bit(NFS_CONTEXT_RESEND_WRITES, &ctx->flags);
  	if (do_resend)
  		ret = -EAGAIN;
  out:
  	return ret;
  }
  EXPORT_SYMBOL_GPL(nfs_file_fsync_commit);
  
  static int
  nfs_file_fsync(struct file *file, loff_t start, loff_t end, int datasync)
  {
  	int ret;
  	struct inode *inode = file_inode(file);
  
  	trace_nfs_fsync_enter(inode);
  
  	do {
  		ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
  		if (ret != 0)
  			break;
  		mutex_lock(&inode->i_mutex);
  		ret = nfs_file_fsync_commit(file, start, end, datasync);
  		mutex_unlock(&inode->i_mutex);
  		/*
  		 * If nfs_file_fsync_commit detected a server reboot, then
  		 * resend all dirty pages that might have been covered by
  		 * the NFS_CONTEXT_RESEND_WRITES flag
  		 */
  		start = 0;
  		end = LLONG_MAX;
  	} while (ret == -EAGAIN);
  
  	trace_nfs_fsync_exit(inode, ret);
  	return ret;
  }
  
  /*
   * Decide whether a read/modify/write cycle may be more efficient
   * then a modify/write/read cycle when writing to a page in the
   * page cache.
   *
   * The modify/write/read cycle may occur if a page is read before
   * being completely filled by the writer.  In this situation, the
   * page must be completely written to stable storage on the server
   * before it can be refilled by reading in the page from the server.
   * This can lead to expensive, small, FILE_SYNC mode writes being
   * done.
   *
   * It may be more efficient to read the page first if the file is
   * open for reading in addition to writing, the page is not marked
   * as Uptodate, it is not dirty or waiting to be committed,
   * indicating that it was previously allocated and then modified,
   * that there were valid bytes of data in that range of the file,
   * and that the new data won't completely replace the old data in
   * that range of the file.
   */
  static int nfs_want_read_modify_write(struct file *file, struct page *page,
  			loff_t pos, unsigned len)
  {
  	unsigned int pglen = nfs_page_length(page);
  	unsigned int offset = pos & (PAGE_CACHE_SIZE - 1);
  	unsigned int end = offset + len;
  
  	if ((file->f_mode & FMODE_READ) &&	/* open for read? */
  	    !PageUptodate(page) &&		/* Uptodate? */
  	    !PagePrivate(page) &&		/* i/o request already? */
  	    pglen &&				/* valid bytes of file? */
  	    (end < pglen || offset))		/* replace all valid bytes? */
  		return 1;
  	return 0;
  }
  
  /*
   * This does the "real" work of the write. We must allocate and lock the
   * page to be sent back to the generic routine, which then copies the
   * data from user space.
   *
   * If the writer ends up delaying the write, the writer needs to
   * increment the page use counts until he is done with the page.
   */
  static int nfs_write_begin(struct file *file, struct address_space *mapping,
  			loff_t pos, unsigned len, unsigned flags,
  			struct page **pagep, void **fsdata)
  {
  	int ret;
  	pgoff_t index = pos >> PAGE_CACHE_SHIFT;
  	struct page *page;
  	int once_thru = 0;
  
  	dfprintk(PAGECACHE, "NFS: write_begin(%pD2(%lu), %u@%lld)
  ",
  		file, mapping->host->i_ino, len, (long long) pos);
  
  start:
  	/*
  	 * Prevent starvation issues if someone is doing a consistency
  	 * sync-to-disk
  	 */
  	ret = wait_on_bit(&NFS_I(mapping->host)->flags, NFS_INO_FLUSHING,
  			nfs_wait_bit_killable, TASK_KILLABLE);
  	if (ret)
  		return ret;
  
  	page = grab_cache_page_write_begin(mapping, index, flags);
  	if (!page)
  		return -ENOMEM;
  	*pagep = page;
  
  	ret = nfs_flush_incompatible(file, page);
  	if (ret) {
  		unlock_page(page);
  		page_cache_release(page);
  	} else if (!once_thru &&
  		   nfs_want_read_modify_write(file, page, pos, len)) {
  		once_thru = 1;
  		ret = nfs_readpage(file, page);
  		page_cache_release(page);
  		if (!ret)
  			goto start;
  	}
  	return ret;
  }
  
  static int nfs_write_end(struct file *file, struct address_space *mapping,
  			loff_t pos, unsigned len, unsigned copied,
  			struct page *page, void *fsdata)
  {
  	unsigned offset = pos & (PAGE_CACHE_SIZE - 1);
  	struct nfs_open_context *ctx = nfs_file_open_context(file);
  	int status;
  
  	dfprintk(PAGECACHE, "NFS: write_end(%pD2(%lu), %u@%lld)
  ",
  		file, mapping->host->i_ino, len, (long long) pos);
  
  	/*
  	 * Zero any uninitialised parts of the page, and then mark the page
  	 * as up to date if it turns out that we're extending the file.
  	 */
  	if (!PageUptodate(page)) {
  		unsigned pglen = nfs_page_length(page);
  		unsigned end = offset + len;
  
  		if (pglen == 0) {
  			zero_user_segments(page, 0, offset,
  					end, PAGE_CACHE_SIZE);
  			SetPageUptodate(page);
  		} else if (end >= pglen) {
  			zero_user_segment(page, end, PAGE_CACHE_SIZE);
  			if (offset == 0)
  				SetPageUptodate(page);
  		} else
  			zero_user_segment(page, pglen, PAGE_CACHE_SIZE);
  	}
  
  	status = nfs_updatepage(file, page, offset, copied);
  
  	unlock_page(page);
  	page_cache_release(page);
  
  	if (status < 0)
  		return status;
  	NFS_I(mapping->host)->write_io += copied;
  
  	if (nfs_ctx_key_to_expire(ctx)) {
  		status = nfs_wb_all(mapping->host);
  		if (status < 0)
  			return status;
  	}
  
  	return copied;
  }
  
  /*
   * Partially or wholly invalidate a page
   * - Release the private state associated with a page if undergoing complete
   *   page invalidation
   * - Called if either PG_private or PG_fscache is set on the page
   * - Caller holds page lock
   */
  static void nfs_invalidate_page(struct page *page, unsigned int offset,
  				unsigned int length)
  {
  	dfprintk(PAGECACHE, "NFS: invalidate_page(%p, %u, %u)
  ",
  		 page, offset, length);
  
  	if (offset != 0 || length < PAGE_CACHE_SIZE)
  		return;
  	/* Cancel any unstarted writes on this page */
  	nfs_wb_page_cancel(page_file_mapping(page)->host, page);
  
  	nfs_fscache_invalidate_page(page, page->mapping->host);
  }
  
  /*
   * Attempt to release the private state associated with a page
   * - Called if either PG_private or PG_fscache is set on the page
   * - Caller holds page lock
   * - Return true (may release page) or false (may not)
   */
  static int nfs_release_page(struct page *page, gfp_t gfp)
  {
  	struct address_space *mapping = page->mapping;
  
  	dfprintk(PAGECACHE, "NFS: release_page(%p)
  ", page);
  
  	/* Only do I/O if gfp is a superset of GFP_KERNEL, and we're not
  	 * doing this memory reclaim for a fs-related allocation.
  	 */
  	if (mapping && (gfp & GFP_KERNEL) == GFP_KERNEL &&
  	    !(current->flags & PF_FSTRANS)) {
  		int how = FLUSH_SYNC;
  
  		/* Don't let kswapd deadlock waiting for OOM RPC calls */
  		if (current_is_kswapd())
  			how = 0;
  		nfs_commit_inode(mapping->host, how);
  	}
  	/* If PagePrivate() is set, then the page is not freeable */
  	if (PagePrivate(page))
  		return 0;
  	return nfs_fscache_release_page(page, gfp);
  }
  
  static void nfs_check_dirty_writeback(struct page *page,
  				bool *dirty, bool *writeback)
  {
  	struct nfs_inode *nfsi;
  	struct address_space *mapping = page_file_mapping(page);
  
  	if (!mapping || PageSwapCache(page))
  		return;
  
  	/*
  	 * Check if an unstable page is currently being committed and
  	 * if so, have the VM treat it as if the page is under writeback
  	 * so it will not block due to pages that will shortly be freeable.
  	 */
  	nfsi = NFS_I(mapping->host);
  	if (test_bit(NFS_INO_COMMIT, &nfsi->flags)) {
  		*writeback = true;
  		return;
  	}
  
  	/*
  	 * If PagePrivate() is set, then the page is not freeable and as the
  	 * inode is not being committed, it's not going to be cleaned in the
  	 * near future so treat it as dirty
  	 */
  	if (PagePrivate(page))
  		*dirty = true;
  }
  
  /*
   * Attempt to clear the private state associated with a page when an error
   * occurs that requires the cached contents of an inode to be written back or
   * destroyed
   * - Called if either PG_private or fscache is set on the page
   * - Caller holds page lock
   * - Return 0 if successful, -error otherwise
   */
  static int nfs_launder_page(struct page *page)
  {
  	struct inode *inode = page_file_mapping(page)->host;
  	struct nfs_inode *nfsi = NFS_I(inode);
  
  	dfprintk(PAGECACHE, "NFS: launder_page(%ld, %llu)
  ",
  		inode->i_ino, (long long)page_offset(page));
  
  	nfs_fscache_wait_on_page_write(nfsi, page);
  	return nfs_wb_page(inode, page);
  }
  
  #ifdef CONFIG_NFS_SWAP
  static int nfs_swap_activate(struct swap_info_struct *sis, struct file *file,
  						sector_t *span)
  {
  	*span = sis->pages;
  	return xs_swapper(NFS_CLIENT(file->f_mapping->host)->cl_xprt, 1);
  }
  
  static void nfs_swap_deactivate(struct file *file)
  {
  	xs_swapper(NFS_CLIENT(file->f_mapping->host)->cl_xprt, 0);
  }
  #endif
  
  const struct address_space_operations nfs_file_aops = {
  	.readpage = nfs_readpage,
  	.readpages = nfs_readpages,
  	.set_page_dirty = __set_page_dirty_nobuffers,
  	.writepage = nfs_writepage,
  	.writepages = nfs_writepages,
  	.write_begin = nfs_write_begin,
  	.write_end = nfs_write_end,
  	.invalidatepage = nfs_invalidate_page,
  	.releasepage = nfs_release_page,
  	.direct_IO = nfs_direct_IO,
  	.migratepage = nfs_migrate_page,
  	.launder_page = nfs_launder_page,
  	.is_dirty_writeback = nfs_check_dirty_writeback,
  	.error_remove_page = generic_error_remove_page,
  #ifdef CONFIG_NFS_SWAP
  	.swap_activate = nfs_swap_activate,
  	.swap_deactivate = nfs_swap_deactivate,
  #endif
  };
  
  /*
   * Notification that a PTE pointing to an NFS page is about to be made
   * writable, implying that someone is about to modify the page through a
   * shared-writable mapping
   */
  static int nfs_vm_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
  {
  	struct page *page = vmf->page;
  	struct file *filp = vma->vm_file;
  	struct inode *inode = file_inode(filp);
  	unsigned pagelen;
  	int ret = VM_FAULT_NOPAGE;
  	struct address_space *mapping;
  
  	dfprintk(PAGECACHE, "NFS: vm_page_mkwrite(%pD2(%lu), offset %lld)
  ",
  		filp, filp->f_mapping->host->i_ino,
  		(long long)page_offset(page));
  
  	/* make sure the cache has finished storing the page */
  	nfs_fscache_wait_on_page_write(NFS_I(inode), page);
  
  	lock_page(page);
  	mapping = page_file_mapping(page);
  	if (mapping != inode->i_mapping)
  		goto out_unlock;
  
  	wait_on_page_writeback(page);
  
  	pagelen = nfs_page_length(page);
  	if (pagelen == 0)
  		goto out_unlock;
  
  	ret = VM_FAULT_LOCKED;
  	if (nfs_flush_incompatible(filp, page) == 0 &&
  	    nfs_updatepage(filp, page, 0, pagelen) == 0)
  		goto out;
  
  	ret = VM_FAULT_SIGBUS;
  out_unlock:
  	unlock_page(page);
  out:
  	return ret;
  }
  
  static const struct vm_operations_struct nfs_file_vm_ops = {
  	.fault = filemap_fault,
  	.page_mkwrite = nfs_vm_page_mkwrite,
  	.remap_pages = generic_file_remap_pages,
  };
  
  static int nfs_need_sync_write(struct file *filp, struct inode *inode)
  {
  	struct nfs_open_context *ctx;
  
  	if (IS_SYNC(inode) || (filp->f_flags & O_DSYNC))
  		return 1;
  	ctx = nfs_file_open_context(filp);
  	if (test_bit(NFS_CONTEXT_ERROR_WRITE, &ctx->flags) ||
  	    nfs_ctx_key_to_expire(ctx))
  		return 1;
  	return 0;
  }
  
  ssize_t nfs_file_write(struct kiocb *iocb, const struct iovec *iov,
  		       unsigned long nr_segs, loff_t pos)
  {
  	struct file *file = iocb->ki_filp;
  	struct inode *inode = file_inode(file);
  	unsigned long written = 0;
  	ssize_t result;
  	size_t count = iov_length(iov, nr_segs);
  
  	result = nfs_key_timeout_notify(file, inode);
  	if (result)
  		return result;
  
  	if (file->f_flags & O_DIRECT)
  		return nfs_file_direct_write(iocb, iov, nr_segs, pos, true);
  
  	dprintk("NFS: write(%pD2, %lu@%Ld)
  ",
  		file, (unsigned long) count, (long long) pos);
  
  	result = -EBUSY;
  	if (IS_SWAPFILE(inode))
  		goto out_swapfile;
  	/*
  	 * O_APPEND implies that we must revalidate the file length.
  	 */
  	if (file->f_flags & O_APPEND) {
  		result = nfs_revalidate_file_size(inode, file);
  		if (result)
  			goto out;
  	}
  
  	result = count;
  	if (!count)
  		goto out;
  
  	result = generic_file_aio_write(iocb, iov, nr_segs, pos);
  	if (result > 0)
  		written = result;
  
  	/* Return error values for O_DSYNC and IS_SYNC() */
  	if (result >= 0 && nfs_need_sync_write(file, inode)) {
  		int err = vfs_fsync(file, 0);
  		if (err < 0)
  			result = err;
  	}
  	if (result > 0)
  		nfs_add_stats(inode, NFSIOS_NORMALWRITTENBYTES, written);
  out:
  	return result;
  
  out_swapfile:
  	printk(KERN_INFO "NFS: attempt to write to active swap file!
  ");
  	goto out;
  }
  EXPORT_SYMBOL_GPL(nfs_file_write);
  
  ssize_t nfs_file_splice_write(struct pipe_inode_info *pipe,
  			      struct file *filp, loff_t *ppos,
  			      size_t count, unsigned int flags)
  {
  	struct inode *inode = file_inode(filp);
  	unsigned long written = 0;
  	ssize_t ret;
  
  	dprintk("NFS splice_write(%pD2, %lu@%llu)
  ",
  		filp, (unsigned long) count, (unsigned long long) *ppos);
  
  	/*
  	 * The combination of splice and an O_APPEND destination is disallowed.
  	 */
  
  	ret = generic_file_splice_write(pipe, filp, ppos, count, flags);
  	if (ret > 0)
  		written = ret;
  
  	if (ret >= 0 && nfs_need_sync_write(filp, inode)) {
  		int err = vfs_fsync(filp, 0);
  		if (err < 0)
  			ret = err;
  	}
  	if (ret > 0)
  		nfs_add_stats(inode, NFSIOS_NORMALWRITTENBYTES, written);
  	return ret;
  }
  EXPORT_SYMBOL_GPL(nfs_file_splice_write);
  
  static int
  do_getlk(struct file *filp, int cmd, struct file_lock *fl, int is_local)
  {
  	struct inode *inode = filp->f_mapping->host;
  	int status = 0;
  	unsigned int saved_type = fl->fl_type;
  
  	/* Try local locking first */
  	posix_test_lock(filp, fl);
  	if (fl->fl_type != F_UNLCK) {
  		/* found a conflict */
  		goto out;
  	}
  	fl->fl_type = saved_type;
  
  	if (NFS_PROTO(inode)->have_delegation(inode, FMODE_READ))
  		goto out_noconflict;
  
  	if (is_local)
  		goto out_noconflict;
  
  	status = NFS_PROTO(inode)->lock(filp, cmd, fl);
  out:
  	return status;
  out_noconflict:
  	fl->fl_type = F_UNLCK;
  	goto out;
  }
  
  static int do_vfs_lock(struct file *file, struct file_lock *fl)
  {
  	int res = 0;
  	switch (fl->fl_flags & (FL_POSIX|FL_FLOCK)) {
  		case FL_POSIX:
  			res = posix_lock_file_wait(file, fl);
  			break;
  		case FL_FLOCK:
  			res = flock_lock_file_wait(file, fl);
  			break;
  		default:
  			BUG();
  	}
  	return res;
  }
  
  static int
  do_unlk(struct file *filp, int cmd, struct file_lock *fl, int is_local)
  {
  	struct inode *inode = filp->f_mapping->host;
  	struct nfs_lock_context *l_ctx;
  	int status;
  
  	/*
  	 * Flush all pending writes before doing anything
  	 * with locks..
  	 */
  	nfs_sync_mapping(filp->f_mapping);
  
  	l_ctx = nfs_get_lock_context(nfs_file_open_context(filp));
  	if (!IS_ERR(l_ctx)) {
  		status = nfs_iocounter_wait(&l_ctx->io_count);
  		nfs_put_lock_context(l_ctx);
  		if (status < 0)
  			return status;
  	}
  
  	/* NOTE: special case
  	 * 	If we're signalled while cleaning up locks on process exit, we
  	 * 	still need to complete the unlock.
  	 */
  	/*
  	 * Use local locking if mounted with "-onolock" or with appropriate
  	 * "-olocal_lock="
  	 */
  	if (!is_local)
  		status = NFS_PROTO(inode)->lock(filp, cmd, fl);
  	else
  		status = do_vfs_lock(filp, fl);
  	return status;
  }
  
  static int
  is_time_granular(struct timespec *ts) {
  	return ((ts->tv_sec == 0) && (ts->tv_nsec <= 1000));
  }
  
  static int
  do_setlk(struct file *filp, int cmd, struct file_lock *fl, int is_local)
  {
  	struct inode *inode = filp->f_mapping->host;
  	int status;
  
  	/*
  	 * Flush all pending writes before doing anything
  	 * with locks..
  	 */
  	status = nfs_sync_mapping(filp->f_mapping);
  	if (status != 0)
  		goto out;
  
  	/*
  	 * Use local locking if mounted with "-onolock" or with appropriate
  	 * "-olocal_lock="
  	 */
  	if (!is_local)
  		status = NFS_PROTO(inode)->lock(filp, cmd, fl);
  	else
  		status = do_vfs_lock(filp, fl);
  	if (status < 0)
  		goto out;
  
  	/*
  	 * Revalidate the cache if the server has time stamps granular
  	 * enough to detect subsecond changes.  Otherwise, clear the
  	 * cache to prevent missing any changes.
  	 *
  	 * This makes locking act as a cache coherency point.
  	 */
  	nfs_sync_mapping(filp->f_mapping);
  	if (!NFS_PROTO(inode)->have_delegation(inode, FMODE_READ)) {
  		if (is_time_granular(&NFS_SERVER(inode)->time_delta))
  			__nfs_revalidate_inode(NFS_SERVER(inode), inode);
  		else
  			nfs_zap_caches(inode);
  	}
  out:
  	return status;
  }
  
  /*
   * Lock a (portion of) a file
   */
  int nfs_lock(struct file *filp, int cmd, struct file_lock *fl)
  {
  	struct inode *inode = filp->f_mapping->host;
  	int ret = -ENOLCK;
  	int is_local = 0;
  
  	dprintk("NFS: lock(%pD2, t=%x, fl=%x, r=%lld:%lld)
  ",
  			filp, fl->fl_type, fl->fl_flags,
  			(long long)fl->fl_start, (long long)fl->fl_end);
  
  	nfs_inc_stats(inode, NFSIOS_VFSLOCK);
  
  	/* No mandatory locks over NFS */
  	if (__mandatory_lock(inode) && fl->fl_type != F_UNLCK)
  		goto out_err;
  
  	if (NFS_SERVER(inode)->flags & NFS_MOUNT_LOCAL_FCNTL)
  		is_local = 1;
  
  	if (NFS_PROTO(inode)->lock_check_bounds != NULL) {
  		ret = NFS_PROTO(inode)->lock_check_bounds(fl);
  		if (ret < 0)
  			goto out_err;
  	}
  
  	if (IS_GETLK(cmd))
  		ret = do_getlk(filp, cmd, fl, is_local);
  	else if (fl->fl_type == F_UNLCK)
  		ret = do_unlk(filp, cmd, fl, is_local);
  	else
  		ret = do_setlk(filp, cmd, fl, is_local);
  out_err:
  	return ret;
  }
  EXPORT_SYMBOL_GPL(nfs_lock);
  
  /*
   * Lock a (portion of) a file
   */
  int nfs_flock(struct file *filp, int cmd, struct file_lock *fl)
  {
  	struct inode *inode = filp->f_mapping->host;
  	int is_local = 0;
  
  	dprintk("NFS: flock(%pD2, t=%x, fl=%x)
  ",
  			filp, fl->fl_type, fl->fl_flags);
  
  	if (!(fl->fl_flags & FL_FLOCK))
  		return -ENOLCK;
  
  	/*
  	 * The NFSv4 protocol doesn't support LOCK_MAND, which is not part of
  	 * any standard. In principle we might be able to support LOCK_MAND
  	 * on NFSv2/3 since NLMv3/4 support DOS share modes, but for now the
  	 * NFS code is not set up for it.
  	 */
  	if (fl->fl_type & LOCK_MAND)
  		return -EINVAL;
  
  	if (NFS_SERVER(inode)->flags & NFS_MOUNT_LOCAL_FLOCK)
  		is_local = 1;
  
  	/* We're simulating flock() locks using posix locks on the server */
  	fl->fl_owner = (fl_owner_t)filp;
  	fl->fl_start = 0;
  	fl->fl_end = OFFSET_MAX;
  
  	if (fl->fl_type == F_UNLCK)
  		return do_unlk(filp, cmd, fl, is_local);
  	return do_setlk(filp, cmd, fl, is_local);
  }
  EXPORT_SYMBOL_GPL(nfs_flock);
  
  /*
   * There is no protocol support for leases, so we have no way to implement
   * them correctly in the face of opens by other clients.
   */
  int nfs_setlease(struct file *file, long arg, struct file_lock **fl)
  {
  	dprintk("NFS: setlease(%pD2, arg=%ld)
  ", file, arg);
  	return -EINVAL;
  }
  EXPORT_SYMBOL_GPL(nfs_setlease);
  
  const struct file_operations nfs_file_operations = {
  	.llseek		= nfs_file_llseek,
  	.read		= do_sync_read,
  	.write		= do_sync_write,
  	.aio_read	= nfs_file_read,
  	.aio_write	= nfs_file_write,
  	.mmap		= nfs_file_mmap,
  	.open		= nfs_file_open,
  	.flush		= nfs_file_flush,
  	.release	= nfs_file_release,
  	.fsync		= nfs_file_fsync,
  	.lock		= nfs_lock,
  	.flock		= nfs_flock,
  	.splice_read	= nfs_file_splice_read,
  	.splice_write	= nfs_file_splice_write,
  	.check_flags	= nfs_check_flags,
  	.setlease	= nfs_setlease,
  };
  EXPORT_SYMBOL_GPL(nfs_file_operations);