/*
   * linux/fs/nfs/read.c
   *
   * Block I/O for NFS
   *
   * Partial copy of Linus' read cache modifications to fs/nfs/file.c
   * modified for async RPC by okir@monad.swb.de

   */

  #include <linux/time.h>
  #include <linux/kernel.h>
  #include <linux/errno.h>
  #include <linux/fcntl.h>
  #include <linux/stat.h>
  #include <linux/mm.h>
  #include <linux/slab.h>
  #include <linux/pagemap.h>
  #include <linux/sunrpc/clnt.h>
  #include <linux/nfs_fs.h>
  #include <linux/nfs_page.h>

  #include <linux/module.h>

  
  #include <asm/system.h>

  #include "pnfs.h"

  #include "nfs4_fs.h"

  #include "internal.h"

  #include "iostat.h"

  #include "fscache.h"

  #define NFSDBG_FACILITY		NFSDBG_PAGECACHE

  static const struct nfs_pageio_ops nfs_pageio_read_ops;

  static const struct rpc_call_ops nfs_read_partial_ops;
  static const struct rpc_call_ops nfs_read_full_ops;

  static struct kmem_cache *nfs_rdata_cachep;

  struct nfs_read_data *nfs_readdata_alloc(unsigned int pagecount)

  {

  	struct nfs_read_data *p;

  	p = kmem_cache_zalloc(nfs_rdata_cachep, GFP_KERNEL);

  	if (p) {

  		INIT_LIST_HEAD(&p->pages);

  		p->npages = pagecount;

  		if (pagecount <= ARRAY_SIZE(p->page_array))
  			p->pagevec = p->page_array;

  		else {

  			p->pagevec = kcalloc(pagecount, sizeof(struct page *), GFP_KERNEL);

  			if (!p->pagevec) {

  				kmem_cache_free(nfs_rdata_cachep, p);

  				p = NULL;
  			}
  		}
  	}
  	return p;
  }

  void nfs_readdata_free(struct nfs_read_data *p)

  {
  	if (p && (p->pagevec != &p->page_array[0]))
  		kfree(p->pagevec);

  	kmem_cache_free(nfs_rdata_cachep, p);

  }

  void nfs_readdata_release(struct nfs_read_data *rdata)

  {

  	put_lseg(rdata->lseg);

  	put_nfs_open_context(rdata->args.context);
  	nfs_readdata_free(rdata);

  }
  
  static

  int nfs_return_empty_page(struct page *page)
  {

  	zero_user(page, 0, PAGE_CACHE_SIZE);

  	SetPageUptodate(page);
  	unlock_page(page);
  	return 0;
  }

  static void nfs_readpage_truncate_uninitialised_page(struct nfs_read_data *data)
  {
  	unsigned int remainder = data->args.count - data->res.count;
  	unsigned int base = data->args.pgbase + data->res.count;
  	unsigned int pglen;
  	struct page **pages;
  
  	if (data->res.eof == 0 || remainder == 0)
  		return;
  	/*
  	 * Note: "remainder" can never be negative, since we check for
  	 * 	this in the XDR code.
  	 */
  	pages = &data->args.pages[base >> PAGE_CACHE_SHIFT];
  	base &= ~PAGE_CACHE_MASK;
  	pglen = PAGE_CACHE_SIZE - base;

  	for (;;) {
  		if (remainder <= pglen) {

  			zero_user(*pages, base, remainder);

  			break;
  		}

  		zero_user(*pages, base, pglen);

  		pages++;
  		remainder -= pglen;
  		pglen = PAGE_CACHE_SIZE;
  		base = 0;
  	}

  }

  void nfs_pageio_init_read_mds(struct nfs_pageio_descriptor *pgio,

  		struct inode *inode)
  {
  	nfs_pageio_init(pgio, inode, &nfs_pageio_read_ops,
  			NFS_SERVER(inode)->rsize, 0);
  }

  void nfs_pageio_reset_read_mds(struct nfs_pageio_descriptor *pgio)
  {
  	pgio->pg_ops = &nfs_pageio_read_ops;
  	pgio->pg_bsize = NFS_SERVER(pgio->pg_inode)->rsize;
  }

  EXPORT_SYMBOL_GPL(nfs_pageio_reset_read_mds);

  static void nfs_pageio_init_read(struct nfs_pageio_descriptor *pgio,
  		struct inode *inode)
  {
  	if (!pnfs_pageio_init_read(pgio, inode))
  		nfs_pageio_init_read_mds(pgio, inode);
  }

  int nfs_readpage_async(struct nfs_open_context *ctx, struct inode *inode,
  		       struct page *page)

  {

  	struct nfs_page	*new;
  	unsigned int len;

  	struct nfs_pageio_descriptor pgio;

  	len = nfs_page_length(page);

  	if (len == 0)
  		return nfs_return_empty_page(page);
  	new = nfs_create_request(ctx, inode, page, 0, len);
  	if (IS_ERR(new)) {
  		unlock_page(page);
  		return PTR_ERR(new);
  	}
  	if (len < PAGE_CACHE_SIZE)

  		zero_user_segment(page, len, PAGE_CACHE_SIZE);

  	nfs_pageio_init_read(&pgio, inode);

  	nfs_pageio_add_request(&pgio, new);

  	nfs_pageio_complete(&pgio);

  	return 0;
  }
  
  static void nfs_readpage_release(struct nfs_page *req)
  {

  	struct inode *d_inode = req->wb_context->dentry->d_inode;

  
  	if (PageUptodate(req->wb_page))
  		nfs_readpage_to_fscache(d_inode, req->wb_page, 0);

  	unlock_page(req->wb_page);

  	dprintk("NFS: read done (%s/%Ld %d@%Ld)
  ",

  			req->wb_context->dentry->d_inode->i_sb->s_id,
  			(long long)NFS_FILEID(req->wb_context->dentry->d_inode),

  			req->wb_bytes,
  			(long long)req_offset(req));

  	nfs_release_request(req);

  }

  int nfs_initiate_read(struct nfs_read_data *data, struct rpc_clnt *clnt,

  		      const struct rpc_call_ops *call_ops)

  {

  	struct inode *inode = data->inode;

  	int swap_flags = IS_SWAPFILE(inode) ? NFS_RPC_SWAPFLAGS : 0;

  	struct rpc_task *task;

  	struct rpc_message msg = {
  		.rpc_argp = &data->args,
  		.rpc_resp = &data->res,

  		.rpc_cred = data->cred,

  	};

  	struct rpc_task_setup task_setup_data = {

  		.task = &data->task,

  		.rpc_client = clnt,

  		.rpc_message = &msg,

  		.callback_ops = call_ops,
  		.callback_data = data,

  		.workqueue = nfsiod_workqueue,

  		.flags = RPC_TASK_ASYNC | swap_flags,
  	};

  	/* Set up the initial task struct. */
  	NFS_PROTO(inode)->read_setup(data, &msg);
  
  	dprintk("NFS: %5u initiated read call (req %s/%lld, %u bytes @ "
  			"offset %llu)
  ",
  			data->task.tk_pid,
  			inode->i_sb->s_id,
  			(long long)NFS_FILEID(inode),
  			data->args.count,
  			(unsigned long long)data->args.offset);
  
  	task = rpc_run_task(&task_setup_data);
  	if (IS_ERR(task))
  		return PTR_ERR(task);
  	rpc_put_task(task);
  	return 0;
  }

  EXPORT_SYMBOL_GPL(nfs_initiate_read);

  
  /*
   * Set up the NFS read request struct
   */

  static void nfs_read_rpcsetup(struct nfs_page *req, struct nfs_read_data *data,
  		unsigned int count, unsigned int offset)

  {

  	struct inode *inode = req->wb_context->dentry->d_inode;

  	data->req	  = req;

  	data->inode	  = inode;

  	data->cred	  = req->wb_context->cred;

  
  	data->args.fh     = NFS_FH(inode);
  	data->args.offset = req_offset(req) + offset;
  	data->args.pgbase = req->wb_pgbase + offset;
  	data->args.pages  = data->pagevec;
  	data->args.count  = count;

  	data->args.context = get_nfs_open_context(req->wb_context);

  	data->args.lock_context = req->wb_lock_context;

  
  	data->res.fattr   = &data->fattr;
  	data->res.count   = count;
  	data->res.eof     = 0;

  	nfs_fattr_init(&data->fattr);

  }

  static int nfs_do_read(struct nfs_read_data *data,

  		const struct rpc_call_ops *call_ops)

  {

  	struct inode *inode = data->args.context->dentry->d_inode;

  	return nfs_initiate_read(data, NFS_CLIENT(inode), call_ops);

  }

  static int
  nfs_do_multiple_reads(struct list_head *head,

  		const struct rpc_call_ops *call_ops)

  {
  	struct nfs_read_data *data;
  	int ret = 0;
  
  	while (!list_empty(head)) {
  		int ret2;
  
  		data = list_entry(head->next, struct nfs_read_data, list);
  		list_del_init(&data->list);

  		ret2 = nfs_do_read(data, call_ops);

  		if (ret == 0)
  			ret = ret2;
  	}
  	return ret;
  }

  static void
  nfs_async_read_error(struct list_head *head)
  {
  	struct nfs_page	*req;
  
  	while (!list_empty(head)) {
  		req = nfs_list_entry(head->next);
  		nfs_list_remove_request(req);

  		nfs_readpage_release(req);
  	}
  }
  
  /*

   * Generate multiple requests to fill a single page.
   *
   * We optimize to reduce the number of read operations on the wire.  If we
   * detect that we're reading a page, or an area of a page, that is past the
   * end of file, we do not generate NFS read operations but just clear the
   * parts of the page that would have come back zero from the server anyway.
   *
   * We rely on the cached value of i_size to make this determination; another
   * client can fill pages on the server past our cached end-of-file, but we
   * won't see the new data until our attribute cache is updated.  This is more
   * or less conventional NFS client behavior.
   */

  static int nfs_pagein_multi(struct nfs_pageio_descriptor *desc, struct list_head *res)

  {

  	struct nfs_page *req = nfs_list_entry(desc->pg_list.next);

  	struct page *page = req->wb_page;
  	struct nfs_read_data *data;

  	size_t rsize = desc->pg_bsize, nbytes;

  	unsigned int offset;

  	int requests = 0;

  	int ret = 0;

  
  	nfs_list_remove_request(req);

  	offset = 0;

  	nbytes = desc->pg_count;

  	do {
  		size_t len = min(nbytes,rsize);

  		data = nfs_readdata_alloc(1);

  		if (!data)
  			goto out_bad;

  		data->pagevec[0] = page;
  		nfs_read_rpcsetup(req, data, len, offset);
  		list_add(&data->list, res);

  		requests++;

  		nbytes -= len;

  		offset += len;

  	} while(nbytes != 0);

  	atomic_set(&req->wb_complete, requests);

  	desc->pg_rpc_callops = &nfs_read_partial_ops;

  	return ret;

  out_bad:

  	while (!list_empty(res)) {
  		data = list_entry(res->next, struct nfs_read_data, list);

  		list_del(&data->list);

  		nfs_readdata_free(data);
  	}

  	nfs_readpage_release(req);
  	return -ENOMEM;
  }

  static int nfs_pagein_one(struct nfs_pageio_descriptor *desc, struct list_head *res)

  {
  	struct nfs_page		*req;
  	struct page		**pages;
  	struct nfs_read_data	*data;

  	struct list_head *head = &desc->pg_list;

  	int ret = 0;

  	data = nfs_readdata_alloc(nfs_page_array_len(desc->pg_base,
  						     desc->pg_count));

  	if (!data) {
  		nfs_async_read_error(head);

  		ret = -ENOMEM;

  		goto out;
  	}

  	pages = data->pagevec;

  	while (!list_empty(head)) {
  		req = nfs_list_entry(head->next);
  		nfs_list_remove_request(req);
  		nfs_list_add_request(req, &data->pages);

  		*pages++ = req->wb_page;

  	}
  	req = nfs_list_entry(data->pages.next);

  	nfs_read_rpcsetup(req, data, desc->pg_count, 0);

  	list_add(&data->list, res);

  	desc->pg_rpc_callops = &nfs_read_full_ops;

  out:

  	return ret;

  }

  int nfs_generic_pagein(struct nfs_pageio_descriptor *desc, struct list_head *head)
  {
  	if (desc->pg_bsize < PAGE_CACHE_SIZE)
  		return nfs_pagein_multi(desc, head);
  	return nfs_pagein_one(desc, head);
  }
  
  static int nfs_generic_pg_readpages(struct nfs_pageio_descriptor *desc)

  {

  	LIST_HEAD(head);
  	int ret;

  	ret = nfs_generic_pagein(desc, &head);

  	if (ret == 0)

  		ret = nfs_do_multiple_reads(&head, desc->pg_rpc_callops);

  	return ret;

  }

  
  static const struct nfs_pageio_ops nfs_pageio_read_ops = {
  	.pg_test = nfs_generic_pg_test,
  	.pg_doio = nfs_generic_pg_readpages,
  };

  /*

   * This is the callback from RPC telling us whether a reply was
   * received or some error occurred (timeout or socket shutdown).
   */
  int nfs_readpage_result(struct rpc_task *task, struct nfs_read_data *data)
  {
  	int status;

  	dprintk("NFS: %s: %5u, (status %d)
  ", __func__, task->tk_pid,

  			task->tk_status);
  
  	status = NFS_PROTO(data->inode)->read_done(task, data);
  	if (status != 0)
  		return status;
  
  	nfs_add_stats(data->inode, NFSIOS_SERVERREADBYTES, data->res.count);
  
  	if (task->tk_status == -ESTALE) {

  		set_bit(NFS_INO_STALE, &NFS_I(data->inode)->flags);

  		nfs_mark_for_revalidate(data->inode);
  	}

  	return 0;
  }

  static void nfs_readpage_retry(struct rpc_task *task, struct nfs_read_data *data)

  {
  	struct nfs_readargs *argp = &data->args;
  	struct nfs_readres *resp = &data->res;
  
  	if (resp->eof || resp->count == argp->count)

  		return;

  
  	/* This is a short read! */
  	nfs_inc_stats(data->inode, NFSIOS_SHORTREAD);
  	/* Has the server at least made some progress? */
  	if (resp->count == 0)

  		return;

  
  	/* Yes, so retry the read at the end of the data */

  	data->mds_offset += resp->count;

  	argp->offset += resp->count;
  	argp->pgbase += resp->count;
  	argp->count -= resp->count;

  	rpc_restart_call_prepare(task);

  }
  
  /*

   * Handle a read reply that fills part of a page.
   */

  static void nfs_readpage_result_partial(struct rpc_task *task, void *calldata)

  {

  	struct nfs_read_data *data = calldata;

  	if (nfs_readpage_result(task, data) != 0)
  		return;

  	if (task->tk_status < 0)
  		return;

  	nfs_readpage_truncate_uninitialised_page(data);
  	nfs_readpage_retry(task, data);
  }
  
  static void nfs_readpage_release_partial(void *calldata)
  {
  	struct nfs_read_data *data = calldata;
  	struct nfs_page *req = data->req;
  	struct page *page = req->wb_page;
  	int status = data->task.tk_status;
  
  	if (status < 0)

  		set_bit(PG_PARTIAL_READ_FAILED, &req->wb_flags);

  	if (atomic_dec_and_test(&req->wb_complete)) {

  		if (!test_bit(PG_PARTIAL_READ_FAILED, &req->wb_flags))

  			SetPageUptodate(page);
  		nfs_readpage_release(req);
  	}

  	nfs_readdata_release(calldata);

  }

  #if defined(CONFIG_NFS_V4_1)
  void nfs_read_prepare(struct rpc_task *task, void *calldata)
  {
  	struct nfs_read_data *data = calldata;

  	if (nfs4_setup_sequence(NFS_SERVER(data->inode),

  				&data->args.seq_args, &data->res.seq_res,
  				0, task))
  		return;
  	rpc_call_start(task);
  }
  #endif /* CONFIG_NFS_V4_1 */

  static const struct rpc_call_ops nfs_read_partial_ops = {

  #if defined(CONFIG_NFS_V4_1)
  	.rpc_call_prepare = nfs_read_prepare,
  #endif /* CONFIG_NFS_V4_1 */

  	.rpc_call_done = nfs_readpage_result_partial,

  	.rpc_release = nfs_readpage_release_partial,

  };

  static void nfs_readpage_set_pages_uptodate(struct nfs_read_data *data)
  {
  	unsigned int count = data->res.count;
  	unsigned int base = data->args.pgbase;
  	struct page **pages;

  	if (data->res.eof)
  		count = data->args.count;

  	if (unlikely(count == 0))
  		return;
  	pages = &data->args.pages[base >> PAGE_CACHE_SHIFT];
  	base &= ~PAGE_CACHE_MASK;
  	count += base;
  	for (;count >= PAGE_CACHE_SIZE; count -= PAGE_CACHE_SIZE, pages++)
  		SetPageUptodate(*pages);

  	if (count == 0)
  		return;
  	/* Was this a short read? */
  	if (data->res.eof || data->res.count == data->args.count)

  		SetPageUptodate(*pages);
  }

  /*
   * This is the callback from RPC telling us whether a reply was
   * received or some error occurred (timeout or socket shutdown).
   */

  static void nfs_readpage_result_full(struct rpc_task *task, void *calldata)

  {

  	struct nfs_read_data *data = calldata;

  	if (nfs_readpage_result(task, data) != 0)
  		return;

  	if (task->tk_status < 0)
  		return;

  	/*

  	 * Note: nfs_readpage_retry may change the values of

  	 * data->args. In the multi-page case, we therefore need

  	 * to ensure that we call nfs_readpage_set_pages_uptodate()
  	 * first.

  	 */

  	nfs_readpage_truncate_uninitialised_page(data);
  	nfs_readpage_set_pages_uptodate(data);
  	nfs_readpage_retry(task, data);
  }
  
  static void nfs_readpage_release_full(void *calldata)
  {
  	struct nfs_read_data *data = calldata;

  	while (!list_empty(&data->pages)) {
  		struct nfs_page *req = nfs_list_entry(data->pages.next);

  		nfs_list_remove_request(req);

  		nfs_readpage_release(req);

  	}

  	nfs_readdata_release(calldata);

  }

  static const struct rpc_call_ops nfs_read_full_ops = {

  #if defined(CONFIG_NFS_V4_1)
  	.rpc_call_prepare = nfs_read_prepare,
  #endif /* CONFIG_NFS_V4_1 */

  	.rpc_call_done = nfs_readpage_result_full,

  	.rpc_release = nfs_readpage_release_full,

  };

  /*

   * Read a page over NFS.
   * We read the page synchronously in the following case:
   *  -	The error flag is set for this page. This happens only when a
   *	previous async read operation failed.
   */
  int nfs_readpage(struct file *file, struct page *page)
  {
  	struct nfs_open_context *ctx;
  	struct inode *inode = page->mapping->host;
  	int		error;
  
  	dprintk("NFS: nfs_readpage (%p %ld@%lu)
  ",
  		page, PAGE_CACHE_SIZE, page->index);

  	nfs_inc_stats(inode, NFSIOS_VFSREADPAGE);
  	nfs_add_stats(inode, NFSIOS_READPAGES, 1);

  	/*
  	 * Try to flush any pending writes to the file..
  	 *
  	 * NOTE! Because we own the page lock, there cannot
  	 * be any new pending writes generated at this point
  	 * for this page (other pages can be written to).
  	 */
  	error = nfs_wb_page(inode, page);
  	if (error)

  		goto out_unlock;
  	if (PageUptodate(page))
  		goto out_unlock;

  	error = -ESTALE;
  	if (NFS_STALE(inode))

  		goto out_unlock;

  	if (file == NULL) {

  		error = -EBADF;

  		ctx = nfs_find_open_context(inode, NULL, FMODE_READ);

  		if (ctx == NULL)

  			goto out_unlock;

  	} else

  		ctx = get_nfs_open_context(nfs_file_open_context(file));

  	if (!IS_SYNC(inode)) {
  		error = nfs_readpage_from_fscache(ctx, inode, page);
  		if (error == 0)
  			goto out;
  	}

  	error = nfs_readpage_async(ctx, inode, page);

  out:

  	put_nfs_open_context(ctx);
  	return error;

  out_unlock:

  	unlock_page(page);
  	return error;
  }
  
  struct nfs_readdesc {

  	struct nfs_pageio_descriptor *pgio;

  	struct nfs_open_context *ctx;
  };
  
  static int
  readpage_async_filler(void *data, struct page *page)
  {
  	struct nfs_readdesc *desc = (struct nfs_readdesc *)data;
  	struct inode *inode = page->mapping->host;
  	struct nfs_page *new;
  	unsigned int len;

  	int error;

  	len = nfs_page_length(page);

  	if (len == 0)
  		return nfs_return_empty_page(page);

  	new = nfs_create_request(desc->ctx, inode, page, 0, len);

  	if (IS_ERR(new))
  		goto out_error;

  	if (len < PAGE_CACHE_SIZE)

  		zero_user_segment(page, len, PAGE_CACHE_SIZE);

  	if (!nfs_pageio_add_request(desc->pgio, new)) {
  		error = desc->pgio->pg_error;
  		goto out_unlock;
  	}

  	return 0;

  out_error:
  	error = PTR_ERR(new);

  out_unlock:
  	unlock_page(page);
  	return error;

  }
  
  int nfs_readpages(struct file *filp, struct address_space *mapping,
  		struct list_head *pages, unsigned nr_pages)
  {

  	struct nfs_pageio_descriptor pgio;

  	struct nfs_readdesc desc = {

  		.pgio = &pgio,

  	};
  	struct inode *inode = mapping->host;

  	unsigned long npages;

  	int ret = -ESTALE;

  
  	dprintk("NFS: nfs_readpages (%s/%Ld %d)
  ",
  			inode->i_sb->s_id,
  			(long long)NFS_FILEID(inode),
  			nr_pages);

  	nfs_inc_stats(inode, NFSIOS_VFSREADPAGES);

  	if (NFS_STALE(inode))
  		goto out;

  	if (filp == NULL) {

  		desc.ctx = nfs_find_open_context(inode, NULL, FMODE_READ);

  		if (desc.ctx == NULL)
  			return -EBADF;
  	} else

  		desc.ctx = get_nfs_open_context(nfs_file_open_context(filp));

  
  	/* attempt to read as many of the pages as possible from the cache
  	 * - this returns -ENOBUFS immediately if the cookie is negative
  	 */
  	ret = nfs_readpages_from_fscache(desc.ctx, inode, mapping,
  					 pages, &nr_pages);
  	if (ret == 0)
  		goto read_complete; /* all pages were read */

  	nfs_pageio_init_read(&pgio, inode);

  	ret = read_cache_pages(mapping, pages, readpage_async_filler, &desc);

  
  	nfs_pageio_complete(&pgio);
  	npages = (pgio.pg_bytes_written + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
  	nfs_add_stats(inode, NFSIOS_READPAGES, npages);

  read_complete:

  	put_nfs_open_context(desc.ctx);

  out:

  	return ret;
  }

  int __init nfs_init_readpagecache(void)

  {
  	nfs_rdata_cachep = kmem_cache_create("nfs_read_data",
  					     sizeof(struct nfs_read_data),
  					     0, SLAB_HWCACHE_ALIGN,

  					     NULL);

  	if (nfs_rdata_cachep == NULL)
  		return -ENOMEM;

  	return 0;
  }

  void nfs_destroy_readpagecache(void)

  {

  	kmem_cache_destroy(nfs_rdata_cachep);

  }