/*
   * 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 {
  	struct timespec	mtime;
  	loff_t          size;
  };
  
  struct fscache_netfs ceph_cache_netfs = {
  	.name		= "ceph",
  	.version	= 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;
  	uint16_t klen;
  
  	klen = sizeof(fsc->client->fsid);
  	if (klen > maxbuf)
  		return 0;
  
  	memcpy(buffer, &fsc->client->fsid, klen);
  	return klen;
  }
  
  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)
  {
  	fsc->fscache = fscache_acquire_cookie(ceph_cache_netfs.primary_index,
  					      &ceph_fscache_fsid_object_def,
  					      fsc, true);
  
  	if (fsc->fscache == NULL) {
  		pr_err("Unable to resgister fsid: %p fscache cookie", fsc);
  		return 0;
  	}
  
  	fsc->revalidate_wq = alloc_workqueue("ceph-revalidate", 0, 1);
  	if (fsc->revalidate_wq == NULL)
  		return -ENOMEM;
  
  	return 0;
  }
  
  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.mtime = inode->i_mtime;
  	aux.size = inode->i_size;
  
  	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;
  	const struct inode* inode = &ci->vfs_inode;
  
  	*size = inode->i_size;
  }
  
  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.mtime = inode->i_mtime;
  	aux.size = inode->i_size;
  
  	if (memcmp(data, &aux, sizeof(aux)) != 0)
  		return FSCACHE_CHECKAUX_OBSOLETE;
  
  	dout("ceph inode 0x%p cached okay", ci);
  	return FSCACHE_CHECKAUX_OKAY;
  }
  
  static void ceph_fscache_inode_now_uncached(void* cookie_netfs_data)
  {
  	struct ceph_inode_info* ci = cookie_netfs_data;
  	struct pagevec pvec;
  	pgoff_t first;
  	int loop, nr_pages;
  
  	pagevec_init(&pvec, 0);
  	first = 0;
  
  	dout("ceph inode 0x%p now uncached", ci);
  
  	while (1) {
  		nr_pages = pagevec_lookup(&pvec, ci->vfs_inode.i_mapping, first,
  					  PAGEVEC_SIZE - pagevec_count(&pvec));
  
  		if (!nr_pages)
  			break;
  
  		for (loop = 0; loop < nr_pages; loop++)
  			ClearPageFsCache(pvec.pages[loop]);
  
  		first = pvec.pages[nr_pages - 1]->index + 1;
  
  		pvec.nr = nr_pages;
  		pagevec_release(&pvec);
  		cond_resched();
  	}
  }
  
  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,
  	.now_uncached	= ceph_fscache_inode_now_uncached,
  };
  
  void ceph_fscache_register_inode_cookie(struct ceph_fs_client* fsc,
  					struct ceph_inode_info* ci)
  {
  	struct inode* inode = &ci->vfs_inode;
  
  	/* No caching for filesystem */
  	if (fsc->fscache == NULL)
  		return;
  
  	/* Only cache for regular files that are read only */
  	if ((ci->vfs_inode.i_mode & S_IFREG) == 0)
  		return;
  
  	/* Avoid multiple racing open requests */
  	mutex_lock(&inode->i_mutex);
  
  	if (ci->fscache)
  		goto done;
  
  	ci->fscache = fscache_acquire_cookie(fsc->fscache,
  					     &ceph_fscache_inode_object_def,
  					     ci, true);
  	fscache_check_consistency(ci->fscache);
  done:
  	mutex_unlock(&inode->i_mutex);
  
  }
  
  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 void ceph_vfs_readpage_complete(struct page *page, void *data, int error)
  {
  	if (!error)
  		SetPageUptodate(page);
  }
  
  static void ceph_vfs_readpage_complete_unlock(struct page *page, void *data, int error)
  {
  	if (!error)
  		SetPageUptodate(page);
  
  	unlock_page(page);
  }
  
  static inline int cache_valid(struct ceph_inode_info *ci)
  {
  	return ((ceph_caps_issued(ci) & CEPH_CAP_FILE_CACHE) &&
  		(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_vfs_readpage_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_vfs_readpage_complete_unlock,
  					  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 (fsc->revalidate_wq)
  		destroy_workqueue(fsc->revalidate_wq);
  
  	fscache_relinquish_cookie(fsc->fscache, 0);
  	fsc->fscache = NULL;
  }
  
  static void ceph_revalidate_work(struct work_struct *work)
  {
  	int issued;
  	u32 orig_gen;
  	struct ceph_inode_info *ci = container_of(work, struct ceph_inode_info,
  						  i_revalidate_work);
  	struct inode *inode = &ci->vfs_inode;
  
  	spin_lock(&ci->i_ceph_lock);
  	issued = __ceph_caps_issued(ci, NULL);
  	orig_gen = ci->i_rdcache_gen;
  	spin_unlock(&ci->i_ceph_lock);
  
  	if (!(issued & CEPH_CAP_FILE_CACHE)) {
  		dout("revalidate_work lost cache before validation %p
  ",
  		     inode);
  		goto out;
  	}
  
  	if (!fscache_check_consistency(ci->fscache))
  		fscache_invalidate(ci->fscache);
  
  	spin_lock(&ci->i_ceph_lock);
  	/* Update the new valid generation (backwards sanity check too) */
  	if (orig_gen > ci->i_fscache_gen) {
  		ci->i_fscache_gen = orig_gen;
  	}
  	spin_unlock(&ci->i_ceph_lock);
  
  out:
  	iput(&ci->vfs_inode);
  }
  
  void ceph_queue_revalidate(struct inode *inode)
  {
  	struct ceph_fs_client *fsc = ceph_sb_to_client(inode->i_sb);
  	struct ceph_inode_info *ci = ceph_inode(inode);
  
  	if (fsc->revalidate_wq == NULL || ci->fscache == NULL)
  		return;
  
  	ihold(inode);
  
  	if (queue_work(ceph_sb_to_client(inode->i_sb)->revalidate_wq,
  		       &ci->i_revalidate_work)) {
  		dout("ceph_queue_revalidate %p
  ", inode);
  	} else {
  		dout("ceph_queue_revalidate %p failed
  )", inode);
  		iput(inode);
  	}
  }
  
  void ceph_fscache_inode_init(struct ceph_inode_info *ci)
  {
  	ci->fscache = NULL;
  	/* The first load is verifed cookie open time */
  	ci->i_fscache_gen = 1;
  	INIT_WORK(&ci->i_revalidate_work, ceph_revalidate_work);
  }