/*
 * 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 <linux/fscache.h>

#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()
{
	return fscache_register_netfs(&ceph_cache_netfs);
}

void ceph_fscache_unregister()
{
	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);

	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 + snaphot) */
	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);
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\n");
			return 0;
		case -ENOBUFS: /* Pages were not found, and can't be */
		case -ENODATA: /* Pages were not found */
			dout("page/inode not in cache\n");
			return ret;
		default:
			dout("%s: unknown error ret = %i\n", __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\n");
			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\n");
			return ret;
		default:
			dout("%s: unknown error ret = %i\n", __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 (!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);

	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\n",
		     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_inode_info *ci = ceph_inode(inode);

	ihold(inode);

	if (queue_work(ceph_sb_to_client(inode->i_sb)->revalidate_wq,
		       &ci->i_revalidate_work)) {
		dout("ceph_queue_revalidate %p\n", inode);
	} else {
		dout("ceph_queue_revalidate %p failed\n)", 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);
}