/* NFS filesystem cache interface
   *
   * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
   * Written by David Howells (dhowells@redhat.com)
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public Licence
   * as published by the Free Software Foundation; either version
   * 2 of the Licence, or (at your option) any later version.
   */
  
  #include <linux/init.h>
  #include <linux/kernel.h>
  #include <linux/sched.h>
  #include <linux/mm.h>
  #include <linux/nfs_fs.h>
  #include <linux/nfs_fs_sb.h>
  #include <linux/in6.h>
  #include <linux/seq_file.h>
  #include <linux/slab.h>
  
  #include "internal.h"
  #include "iostat.h"
  #include "fscache.h"
  
  #define NFSDBG_FACILITY		NFSDBG_FSCACHE
  
  static struct rb_root nfs_fscache_keys = RB_ROOT;
  static DEFINE_SPINLOCK(nfs_fscache_keys_lock);
  
  /*
   * Get the per-client index cookie for an NFS client if the appropriate mount
   * flag was set
   * - We always try and get an index cookie for the client, but get filehandle
   *   cookies on a per-superblock basis, depending on the mount flags
   */
  void nfs_fscache_get_client_cookie(struct nfs_client *clp)
  {
  	/* create a cache index for looking up filehandles */
  	clp->fscache = fscache_acquire_cookie(nfs_fscache_netfs.primary_index,
  					      &nfs_fscache_server_index_def,
  					      clp, true);
  	dfprintk(FSCACHE, "NFS: get client cookie (0x%p/0x%p)
  ",
  		 clp, clp->fscache);
  }
  
  /*
   * Dispose of a per-client cookie
   */
  void nfs_fscache_release_client_cookie(struct nfs_client *clp)
  {
  	dfprintk(FSCACHE, "NFS: releasing client cookie (0x%p/0x%p)
  ",
  		 clp, clp->fscache);
  
  	fscache_relinquish_cookie(clp->fscache, 0);
  	clp->fscache = NULL;
  }
  
  /*
   * Get the cache cookie for an NFS superblock.  We have to handle
   * uniquification here because the cache doesn't do it for us.
   *
   * The default uniquifier is just an empty string, but it may be overridden
   * either by the 'fsc=xxx' option to mount, or by inheriting it from the parent
   * superblock across an automount point of some nature.
   */
  void nfs_fscache_get_super_cookie(struct super_block *sb, const char *uniq, int ulen)
  {
  	struct nfs_fscache_key *key, *xkey;
  	struct nfs_server *nfss = NFS_SB(sb);
  	struct rb_node **p, *parent;
  	int diff;
  
  	if (!uniq) {
  		uniq = "";
  		ulen = 1;
  	}
  
  	key = kzalloc(sizeof(*key) + ulen, GFP_KERNEL);
  	if (!key)
  		return;
  
  	key->nfs_client = nfss->nfs_client;
  	key->key.super.s_flags = sb->s_flags & NFS_MS_MASK;
  	key->key.nfs_server.flags = nfss->flags;
  	key->key.nfs_server.rsize = nfss->rsize;
  	key->key.nfs_server.wsize = nfss->wsize;
  	key->key.nfs_server.acregmin = nfss->acregmin;
  	key->key.nfs_server.acregmax = nfss->acregmax;
  	key->key.nfs_server.acdirmin = nfss->acdirmin;
  	key->key.nfs_server.acdirmax = nfss->acdirmax;
  	key->key.nfs_server.fsid = nfss->fsid;
  	key->key.rpc_auth.au_flavor = nfss->client->cl_auth->au_flavor;
  
  	key->key.uniq_len = ulen;
  	memcpy(key->key.uniquifier, uniq, ulen);
  
  	spin_lock(&nfs_fscache_keys_lock);
  	p = &nfs_fscache_keys.rb_node;
  	parent = NULL;
  	while (*p) {
  		parent = *p;
  		xkey = rb_entry(parent, struct nfs_fscache_key, node);
  
  		if (key->nfs_client < xkey->nfs_client)
  			goto go_left;
  		if (key->nfs_client > xkey->nfs_client)
  			goto go_right;
  
  		diff = memcmp(&key->key, &xkey->key, sizeof(key->key));
  		if (diff < 0)
  			goto go_left;
  		if (diff > 0)
  			goto go_right;
  
  		if (key->key.uniq_len == 0)
  			goto non_unique;
  		diff = memcmp(key->key.uniquifier,
  			      xkey->key.uniquifier,
  			      key->key.uniq_len);
  		if (diff < 0)
  			goto go_left;
  		if (diff > 0)
  			goto go_right;
  		goto non_unique;
  
  	go_left:
  		p = &(*p)->rb_left;
  		continue;
  	go_right:
  		p = &(*p)->rb_right;
  	}
  
  	rb_link_node(&key->node, parent, p);
  	rb_insert_color(&key->node, &nfs_fscache_keys);
  	spin_unlock(&nfs_fscache_keys_lock);
  	nfss->fscache_key = key;
  
  	/* create a cache index for looking up filehandles */
  	nfss->fscache = fscache_acquire_cookie(nfss->nfs_client->fscache,
  					       &nfs_fscache_super_index_def,
  					       nfss, true);
  	dfprintk(FSCACHE, "NFS: get superblock cookie (0x%p/0x%p)
  ",
  		 nfss, nfss->fscache);
  	return;
  
  non_unique:
  	spin_unlock(&nfs_fscache_keys_lock);
  	kfree(key);
  	nfss->fscache_key = NULL;
  	nfss->fscache = NULL;
  	printk(KERN_WARNING "NFS:"
  	       " Cache request denied due to non-unique superblock keys
  ");
  }
  
  /*
   * release a per-superblock cookie
   */
  void nfs_fscache_release_super_cookie(struct super_block *sb)
  {
  	struct nfs_server *nfss = NFS_SB(sb);
  
  	dfprintk(FSCACHE, "NFS: releasing superblock cookie (0x%p/0x%p)
  ",
  		 nfss, nfss->fscache);
  
  	fscache_relinquish_cookie(nfss->fscache, 0);
  	nfss->fscache = NULL;
  
  	if (nfss->fscache_key) {
  		spin_lock(&nfs_fscache_keys_lock);
  		rb_erase(&nfss->fscache_key->node, &nfs_fscache_keys);
  		spin_unlock(&nfs_fscache_keys_lock);
  		kfree(nfss->fscache_key);
  		nfss->fscache_key = NULL;
  	}
  }
  
  /*
   * Initialise the per-inode cache cookie pointer for an NFS inode.
   */
  void nfs_fscache_init_inode(struct inode *inode)
  {
  	struct nfs_inode *nfsi = NFS_I(inode);
  
  	nfsi->fscache = NULL;
  	if (!S_ISREG(inode->i_mode))
  		return;
  	nfsi->fscache = fscache_acquire_cookie(NFS_SB(inode->i_sb)->fscache,
  					       &nfs_fscache_inode_object_def,
  					       nfsi, false);
  }
  
  /*
   * Release a per-inode cookie.
   */
  void nfs_fscache_clear_inode(struct inode *inode)
  {
  	struct nfs_inode *nfsi = NFS_I(inode);
  	struct fscache_cookie *cookie = nfs_i_fscache(inode);
  
  	dfprintk(FSCACHE, "NFS: clear cookie (0x%p/0x%p)
  ", nfsi, cookie);
  
  	fscache_relinquish_cookie(cookie, false);
  	nfsi->fscache = NULL;
  }
  
  static bool nfs_fscache_can_enable(void *data)
  {
  	struct inode *inode = data;
  
  	return !inode_is_open_for_write(inode);
  }
  
  /*
   * Enable or disable caching for a file that is being opened as appropriate.
   * The cookie is allocated when the inode is initialised, but is not enabled at
   * that time.  Enablement is deferred to file-open time to avoid stat() and
   * access() thrashing the cache.
   *
   * For now, with NFS, only regular files that are open read-only will be able
   * to use the cache.
   *
   * We enable the cache for an inode if we open it read-only and it isn't
   * currently open for writing.  We disable the cache if the inode is open
   * write-only.
   *
   * The caller uses the file struct to pin i_writecount on the inode before
   * calling us when a file is opened for writing, so we can make use of that.
   *
   * Note that this may be invoked multiple times in parallel by parallel
   * nfs_open() functions.
   */
  void nfs_fscache_open_file(struct inode *inode, struct file *filp)
  {
  	struct nfs_inode *nfsi = NFS_I(inode);
  	struct fscache_cookie *cookie = nfs_i_fscache(inode);
  
  	if (!fscache_cookie_valid(cookie))
  		return;
  
  	if (inode_is_open_for_write(inode)) {
  		dfprintk(FSCACHE, "NFS: nfsi 0x%p disabling cache
  ", nfsi);
  		clear_bit(NFS_INO_FSCACHE, &nfsi->flags);
  		fscache_disable_cookie(cookie, true);
  		fscache_uncache_all_inode_pages(cookie, inode);
  	} else {
  		dfprintk(FSCACHE, "NFS: nfsi 0x%p enabling cache
  ", nfsi);
  		fscache_enable_cookie(cookie, nfs_fscache_can_enable, inode);
  		if (fscache_cookie_enabled(cookie))
  			set_bit(NFS_INO_FSCACHE, &NFS_I(inode)->flags);
  	}
  }
  EXPORT_SYMBOL_GPL(nfs_fscache_open_file);
  
  /*
   * Release the caching state associated with a page, if the page isn't busy
   * interacting with the cache.
   * - Returns true (can release page) or false (page busy).
   */
  int nfs_fscache_release_page(struct page *page, gfp_t gfp)
  {
  	if (PageFsCache(page)) {
  		struct fscache_cookie *cookie = nfs_i_fscache(page->mapping->host);
  
  		BUG_ON(!cookie);
  		dfprintk(FSCACHE, "NFS: fscache releasepage (0x%p/0x%p/0x%p)
  ",
  			 cookie, page, NFS_I(page->mapping->host));
  
  		if (!fscache_maybe_release_page(cookie, page, gfp))
  			return 0;
  
  		nfs_add_fscache_stats(page->mapping->host,
  				      NFSIOS_FSCACHE_PAGES_UNCACHED, 1);
  	}
  
  	return 1;
  }
  
  /*
   * Release the caching state associated with a page if undergoing complete page
   * invalidation.
   */
  void __nfs_fscache_invalidate_page(struct page *page, struct inode *inode)
  {
  	struct fscache_cookie *cookie = nfs_i_fscache(inode);
  
  	BUG_ON(!cookie);
  
  	dfprintk(FSCACHE, "NFS: fscache invalidatepage (0x%p/0x%p/0x%p)
  ",
  		 cookie, page, NFS_I(inode));
  
  	fscache_wait_on_page_write(cookie, page);
  
  	BUG_ON(!PageLocked(page));
  	fscache_uncache_page(cookie, page);
  	nfs_add_fscache_stats(page->mapping->host,
  			      NFSIOS_FSCACHE_PAGES_UNCACHED, 1);
  }
  
  /*
   * Handle completion of a page being read from the cache.
   * - Called in process (keventd) context.
   */
  static void nfs_readpage_from_fscache_complete(struct page *page,
  					       void *context,
  					       int error)
  {
  	dfprintk(FSCACHE,
  		 "NFS: readpage_from_fscache_complete (0x%p/0x%p/%d)
  ",
  		 page, context, error);
  
  	/* if the read completes with an error, we just unlock the page and let
  	 * the VM reissue the readpage */
  	if (!error) {
  		SetPageUptodate(page);
  		unlock_page(page);
  	} else {
  		error = nfs_readpage_async(context, page->mapping->host, page);
  		if (error)
  			unlock_page(page);
  	}
  }
  
  /*
   * Retrieve a page from fscache
   */
  int __nfs_readpage_from_fscache(struct nfs_open_context *ctx,
  				struct inode *inode, struct page *page)
  {
  	int ret;
  
  	dfprintk(FSCACHE,
  		 "NFS: readpage_from_fscache(fsc:%p/p:%p(i:%lx f:%lx)/0x%p)
  ",
  		 nfs_i_fscache(inode), page, page->index, page->flags, inode);
  
  	ret = fscache_read_or_alloc_page(nfs_i_fscache(inode),
  					 page,
  					 nfs_readpage_from_fscache_complete,
  					 ctx,
  					 GFP_KERNEL);
  
  	switch (ret) {
  	case 0: /* read BIO submitted (page in fscache) */
  		dfprintk(FSCACHE,
  			 "NFS:    readpage_from_fscache: BIO submitted
  ");
  		nfs_add_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_OK, 1);
  		return ret;
  
  	case -ENOBUFS: /* inode not in cache */
  	case -ENODATA: /* page not in cache */
  		nfs_add_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_FAIL, 1);
  		dfprintk(FSCACHE,
  			 "NFS:    readpage_from_fscache %d
  ", ret);
  		return 1;
  
  	default:
  		dfprintk(FSCACHE, "NFS:    readpage_from_fscache %d
  ", ret);
  		nfs_add_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_FAIL, 1);
  	}
  	return ret;
  }
  
  /*
   * Retrieve a set of pages from fscache
   */
  int __nfs_readpages_from_fscache(struct nfs_open_context *ctx,
  				 struct inode *inode,
  				 struct address_space *mapping,
  				 struct list_head *pages,
  				 unsigned *nr_pages)
  {
  	unsigned npages = *nr_pages;
  	int ret;
  
  	dfprintk(FSCACHE, "NFS: nfs_getpages_from_fscache (0x%p/%u/0x%p)
  ",
  		 nfs_i_fscache(inode), npages, inode);
  
  	ret = fscache_read_or_alloc_pages(nfs_i_fscache(inode),
  					  mapping, pages, nr_pages,
  					  nfs_readpage_from_fscache_complete,
  					  ctx,
  					  mapping_gfp_mask(mapping));
  	if (*nr_pages < npages)
  		nfs_add_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_OK,
  				      npages);
  	if (*nr_pages > 0)
  		nfs_add_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_FAIL,
  				      *nr_pages);
  
  	switch (ret) {
  	case 0: /* read submitted to the cache for all pages */
  		BUG_ON(!list_empty(pages));
  		BUG_ON(*nr_pages != 0);
  		dfprintk(FSCACHE,
  			 "NFS: nfs_getpages_from_fscache: submitted
  ");
  
  		return ret;
  
  	case -ENOBUFS: /* some pages aren't cached and can't be */
  	case -ENODATA: /* some pages aren't cached */
  		dfprintk(FSCACHE,
  			 "NFS: nfs_getpages_from_fscache: no page: %d
  ", ret);
  		return 1;
  
  	default:
  		dfprintk(FSCACHE,
  			 "NFS: nfs_getpages_from_fscache: ret  %d
  ", ret);
  	}
  
  	return ret;
  }
  
  /*
   * Store a newly fetched page in fscache
   * - PG_fscache must be set on the page
   */
  void __nfs_readpage_to_fscache(struct inode *inode, struct page *page, int sync)
  {
  	int ret;
  
  	dfprintk(FSCACHE,
  		 "NFS: readpage_to_fscache(fsc:%p/p:%p(i:%lx f:%lx)/%d)
  ",
  		 nfs_i_fscache(inode), page, page->index, page->flags, sync);
  
  	ret = fscache_write_page(nfs_i_fscache(inode), page, GFP_KERNEL);
  	dfprintk(FSCACHE,
  		 "NFS:     readpage_to_fscache: p:%p(i:%lu f:%lx) ret %d
  ",
  		 page, page->index, page->flags, ret);
  
  	if (ret != 0) {
  		fscache_uncache_page(nfs_i_fscache(inode), page);
  		nfs_add_fscache_stats(inode,
  				      NFSIOS_FSCACHE_PAGES_WRITTEN_FAIL, 1);
  		nfs_add_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_UNCACHED, 1);
  	} else {
  		nfs_add_fscache_stats(inode,
  				      NFSIOS_FSCACHE_PAGES_WRITTEN_OK, 1);
  	}
  }