/*
   * Ceph cache definitions.
   *
   *  Copyright (C) 2013 by Adfin Solutions, Inc. All Rights Reserved.
   *  Written by Milosz Tanski (milosz@adfin.com)
   *
   *  This program is free software; you can redistribute it and/or modify
   *  it under the terms of the GNU General Public License version 2
   *  as published by the Free Software Foundation.
   *
   *  This program is distributed in the hope that it will be useful,
   *  but WITHOUT ANY WARRANTY; without even the implied warranty of
   *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   *  GNU General Public License for more details.
   *
   *  You should have received a copy of the GNU General Public License
   *  along with this program; if not, write to:
   *  Free Software Foundation
   *  51 Franklin Street, Fifth Floor
   *  Boston, MA  02111-1301  USA
   *
   */

  #include "super.h"
  #include "cache.h"
  
  struct ceph_aux_inode {

  	u64 		version;

  	struct timespec	mtime;
  	loff_t          size;
  };
  
  struct fscache_netfs ceph_cache_netfs = {
  	.name		= "ceph",
  	.version	= 0,
  };

  static DEFINE_MUTEX(ceph_fscache_lock);
  static LIST_HEAD(ceph_fscache_list);
  
  struct ceph_fscache_entry {
  	struct list_head list;
  	struct fscache_cookie *fscache;
  	struct ceph_fsid fsid;
  	size_t uniq_len;
  	char uniquifier[0];
  };

  static uint16_t ceph_fscache_session_get_key(const void *cookie_netfs_data,
  					     void *buffer, uint16_t maxbuf)
  {
  	const struct ceph_fs_client* fsc = cookie_netfs_data;

  	const char *fscache_uniq = fsc->mount_options->fscache_uniq;
  	uint16_t fsid_len, uniq_len;

  	fsid_len = sizeof(fsc->client->fsid);
  	uniq_len = fscache_uniq ? strlen(fscache_uniq) : 0;
  	if (fsid_len + uniq_len > maxbuf)

  		return 0;

  	memcpy(buffer, &fsc->client->fsid, fsid_len);
  	if (uniq_len)
  		memcpy(buffer + fsid_len, fscache_uniq, uniq_len);
  
  	return fsid_len + uniq_len;

  }
  
  static const struct fscache_cookie_def ceph_fscache_fsid_object_def = {
  	.name		= "CEPH.fsid",
  	.type		= FSCACHE_COOKIE_TYPE_INDEX,
  	.get_key	= ceph_fscache_session_get_key,
  };

  int ceph_fscache_register(void)

  {
  	return fscache_register_netfs(&ceph_cache_netfs);
  }

  void ceph_fscache_unregister(void)

  {
  	fscache_unregister_netfs(&ceph_cache_netfs);
  }
  
  int ceph_fscache_register_fs(struct ceph_fs_client* fsc)
  {

  	const struct ceph_fsid *fsid = &fsc->client->fsid;
  	const char *fscache_uniq = fsc->mount_options->fscache_uniq;
  	size_t uniq_len = fscache_uniq ? strlen(fscache_uniq) : 0;
  	struct ceph_fscache_entry *ent;
  	int err = 0;
  
  	mutex_lock(&ceph_fscache_lock);
  	list_for_each_entry(ent, &ceph_fscache_list, list) {
  		if (memcmp(&ent->fsid, fsid, sizeof(*fsid)))
  			continue;
  		if (ent->uniq_len != uniq_len)
  			continue;
  		if (uniq_len && memcmp(ent->uniquifier, fscache_uniq, uniq_len))
  			continue;
  
  		pr_err("fscache cookie already registered for fsid %pU
  ", fsid);
  		pr_err("  use fsc=%%s mount option to specify a uniquifier
  ");
  		err = -EBUSY;
  		goto out_unlock;
  	}
  
  	ent = kzalloc(sizeof(*ent) + uniq_len, GFP_KERNEL);
  	if (!ent) {
  		err = -ENOMEM;
  		goto out_unlock;
  	}

  	fsc->fscache = fscache_acquire_cookie(ceph_cache_netfs.primary_index,
  					      &ceph_fscache_fsid_object_def,

  					      fsc, true);

  	if (fsc->fscache) {
  		memcpy(&ent->fsid, fsid, sizeof(*fsid));
  		if (uniq_len > 0) {
  			memcpy(&ent->uniquifier, fscache_uniq, uniq_len);
  			ent->uniq_len = uniq_len;
  		}
  		ent->fscache = fsc->fscache;
  		list_add_tail(&ent->list, &ceph_fscache_list);
  	} else {
  		kfree(ent);
  		pr_err("unable to register fscache cookie for fsid %pU
  ",
  		       fsid);
  		/* all other fs ignore this error */
  	}
  out_unlock:
  	mutex_unlock(&ceph_fscache_lock);
  	return err;

  }
  
  static uint16_t ceph_fscache_inode_get_key(const void *cookie_netfs_data,
  					   void *buffer, uint16_t maxbuf)
  {
  	const struct ceph_inode_info* ci = cookie_netfs_data;
  	uint16_t klen;

  	/* use ceph virtual inode (id + snapshot) */

  	klen = sizeof(ci->i_vino);
  	if (klen > maxbuf)
  		return 0;
  
  	memcpy(buffer, &ci->i_vino, klen);
  	return klen;
  }
  
  static uint16_t ceph_fscache_inode_get_aux(const void *cookie_netfs_data,
  					   void *buffer, uint16_t bufmax)
  {
  	struct ceph_aux_inode aux;
  	const struct ceph_inode_info* ci = cookie_netfs_data;
  	const struct inode* inode = &ci->vfs_inode;
  
  	memset(&aux, 0, sizeof(aux));

  	aux.version = ci->i_version;

  	aux.mtime = inode->i_mtime;

  	aux.size = i_size_read(inode);

  
  	memcpy(buffer, &aux, sizeof(aux));
  
  	return sizeof(aux);
  }
  
  static void ceph_fscache_inode_get_attr(const void *cookie_netfs_data,
  					uint64_t *size)
  {
  	const struct ceph_inode_info* ci = cookie_netfs_data;

  	*size = i_size_read(&ci->vfs_inode);

  }
  
  static enum fscache_checkaux ceph_fscache_inode_check_aux(
  	void *cookie_netfs_data, const void *data, uint16_t dlen)
  {
  	struct ceph_aux_inode aux;
  	struct ceph_inode_info* ci = cookie_netfs_data;
  	struct inode* inode = &ci->vfs_inode;
  
  	if (dlen != sizeof(aux))
  		return FSCACHE_CHECKAUX_OBSOLETE;
  
  	memset(&aux, 0, sizeof(aux));

  	aux.version = ci->i_version;

  	aux.mtime = inode->i_mtime;

  	aux.size = i_size_read(inode);

  
  	if (memcmp(data, &aux, sizeof(aux)) != 0)
  		return FSCACHE_CHECKAUX_OBSOLETE;
  
  	dout("ceph inode 0x%p cached okay", ci);
  	return FSCACHE_CHECKAUX_OKAY;
  }

  static const struct fscache_cookie_def ceph_fscache_inode_object_def = {
  	.name		= "CEPH.inode",
  	.type		= FSCACHE_COOKIE_TYPE_DATAFILE,
  	.get_key	= ceph_fscache_inode_get_key,
  	.get_attr	= ceph_fscache_inode_get_attr,
  	.get_aux	= ceph_fscache_inode_get_aux,
  	.check_aux	= ceph_fscache_inode_check_aux,

  };

  void ceph_fscache_register_inode_cookie(struct inode *inode)

  {

  	struct ceph_inode_info *ci = ceph_inode(inode);
  	struct ceph_fs_client *fsc = ceph_inode_to_client(inode);

  
  	/* No caching for filesystem */

  	if (!fsc->fscache)

  		return;
  
  	/* Only cache for regular files that are read only */

  	if (!S_ISREG(inode->i_mode))

  		return;

  	inode_lock_nested(inode, I_MUTEX_CHILD);
  	if (!ci->fscache) {
  		ci->fscache = fscache_acquire_cookie(fsc->fscache,
  					&ceph_fscache_inode_object_def,
  					ci, false);
  	}

  	inode_unlock(inode);

  }
  
  void ceph_fscache_unregister_inode_cookie(struct ceph_inode_info* ci)
  {
  	struct fscache_cookie* cookie;
  
  	if ((cookie = ci->fscache) == NULL)
  		return;
  
  	ci->fscache = NULL;
  
  	fscache_uncache_all_inode_pages(cookie, &ci->vfs_inode);
  	fscache_relinquish_cookie(cookie, 0);
  }

  static bool ceph_fscache_can_enable(void *data)
  {
  	struct inode *inode = data;
  	return !inode_is_open_for_write(inode);
  }
  
  void ceph_fscache_file_set_cookie(struct inode *inode, struct file *filp)
  {
  	struct ceph_inode_info *ci = ceph_inode(inode);
  
  	if (!fscache_cookie_valid(ci->fscache))
  		return;
  
  	if (inode_is_open_for_write(inode)) {
  		dout("fscache_file_set_cookie %p %p disabling cache
  ",
  		     inode, filp);
  		fscache_disable_cookie(ci->fscache, false);
  		fscache_uncache_all_inode_pages(ci->fscache, inode);
  	} else {
  		fscache_enable_cookie(ci->fscache, ceph_fscache_can_enable,
  				inode);
  		if (fscache_cookie_enabled(ci->fscache)) {

  			dout("fscache_file_set_cookie %p %p enabling cache
  ",

  			     inode, filp);
  		}
  	}
  }

  static void ceph_readpage_from_fscache_complete(struct page *page, void *data, int error)

  {
  	if (!error)
  		SetPageUptodate(page);
  
  	unlock_page(page);
  }

  static inline bool cache_valid(struct ceph_inode_info *ci)

  {

  	return ci->i_fscache_gen == ci->i_rdcache_gen;

  }
  
  
  /* Atempt to read from the fscache,
   *
   * This function is called from the readpage_nounlock context. DO NOT attempt to
   * unlock the page here (or in the callback).
   */
  int ceph_readpage_from_fscache(struct inode *inode, struct page *page)
  {
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	int ret;
  
  	if (!cache_valid(ci))
  		return -ENOBUFS;
  
  	ret = fscache_read_or_alloc_page(ci->fscache, page,

  					 ceph_readpage_from_fscache_complete, NULL,

  					 GFP_KERNEL);
  
  	switch (ret) {
  		case 0: /* Page found */
  			dout("page read submitted
  ");
  			return 0;
  		case -ENOBUFS: /* Pages were not found, and can't be */
  		case -ENODATA: /* Pages were not found */
  			dout("page/inode not in cache
  ");
  			return ret;
  		default:
  			dout("%s: unknown error ret = %i
  ", __func__, ret);
  			return ret;
  	}
  }
  
  int ceph_readpages_from_fscache(struct inode *inode,
  				  struct address_space *mapping,
  				  struct list_head *pages,
  				  unsigned *nr_pages)
  {
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	int ret;
  
  	if (!cache_valid(ci))
  		return -ENOBUFS;
  
  	ret = fscache_read_or_alloc_pages(ci->fscache, mapping, pages, nr_pages,

  					  ceph_readpage_from_fscache_complete,

  					  NULL, mapping_gfp_mask(mapping));
  
  	switch (ret) {
  		case 0: /* All pages found */
  			dout("all-page read submitted
  ");
  			return 0;
  		case -ENOBUFS: /* Some pages were not found, and can't be */
  		case -ENODATA: /* some pages were not found */
  			dout("page/inode not in cache
  ");
  			return ret;
  		default:
  			dout("%s: unknown error ret = %i
  ", __func__, ret);
  			return ret;
  	}
  }
  
  void ceph_readpage_to_fscache(struct inode *inode, struct page *page)
  {
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	int ret;

  	if (!PageFsCache(page))
  		return;

  	if (!cache_valid(ci))
  		return;
  
  	ret = fscache_write_page(ci->fscache, page, GFP_KERNEL);
  	if (ret)
  		 fscache_uncache_page(ci->fscache, page);
  }
  
  void ceph_invalidate_fscache_page(struct inode* inode, struct page *page)
  {
  	struct ceph_inode_info *ci = ceph_inode(inode);

  	if (!PageFsCache(page))
  		return;

  	fscache_wait_on_page_write(ci->fscache, page);
  	fscache_uncache_page(ci->fscache, page);
  }
  
  void ceph_fscache_unregister_fs(struct ceph_fs_client* fsc)
  {

  	if (fscache_cookie_valid(fsc->fscache)) {
  		struct ceph_fscache_entry *ent;
  		bool found = false;
  
  		mutex_lock(&ceph_fscache_lock);
  		list_for_each_entry(ent, &ceph_fscache_list, list) {
  			if (ent->fscache == fsc->fscache) {
  				list_del(&ent->list);
  				kfree(ent);
  				found = true;
  				break;
  			}
  		}
  		WARN_ON_ONCE(!found);
  		mutex_unlock(&ceph_fscache_lock);
  
  		__fscache_relinquish_cookie(fsc->fscache, 0);
  	}

  	fsc->fscache = NULL;
  }

  /*
   * caller should hold CEPH_CAP_FILE_{RD,CACHE}
   */
  void ceph_fscache_revalidate_cookie(struct ceph_inode_info *ci)

  {

  	if (cache_valid(ci))

  		return;

  	/* resue i_truncate_mutex. There should be no pending
  	 * truncate while the caller holds CEPH_CAP_FILE_RD */
  	mutex_lock(&ci->i_truncate_mutex);
  	if (!cache_valid(ci)) {
  		if (fscache_check_consistency(ci->fscache))
  			fscache_invalidate(ci->fscache);
  		spin_lock(&ci->i_ceph_lock);
  		ci->i_fscache_gen = ci->i_rdcache_gen;
  		spin_unlock(&ci->i_ceph_lock);

  	}

  	mutex_unlock(&ci->i_truncate_mutex);

  }