/*
 * GPL HEADER START
 *
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 only,
 * 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 version 2 for more details (a copy is included
 * in the LICENSE file that accompanied this code).
 *
 * You should have received a copy of the GNU General Public License
 * version 2 along with this program; If not, see
 * http://www.gnu.org/licenses/gpl-2.0.html
 *
 * GPL HEADER END
 */
/*
 * Copyright (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved.
 * Use is subject to license terms.
 *
 * Copyright (c) 2011, 2012, Intel Corporation.
 */
/*
 * This file is part of Lustre, http://www.lustre.org/
 * Lustre is a trademark of Sun Microsystems, Inc.
 *
 * lustre/lustre/llite/rw26.c
 *
 * Lustre Lite I/O page cache routines for the 2.5/2.6 kernel version
 */

#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/stat.h>
#include <linux/errno.h>
#include <linux/unistd.h>
#include <linux/uaccess.h>

#include <linux/migrate.h>
#include <linux/fs.h>
#include <linux/buffer_head.h>
#include <linux/mpage.h>
#include <linux/writeback.h>
#include <linux/pagemap.h>

#define DEBUG_SUBSYSTEM S_LLITE

#include "llite_internal.h"

/**
 * Implements Linux VM address_space::invalidatepage() method. This method is
 * called when the page is truncate from a file, either as a result of
 * explicit truncate, or when inode is removed from memory (as a result of
 * final iput(), umount, or memory pressure induced icache shrinking).
 *
 * [0, offset] bytes of the page remain valid (this is for a case of not-page
 * aligned truncate). Lustre leaves partially truncated page in the cache,
 * relying on struct inode::i_size to limit further accesses.
 */
static void ll_invalidatepage(struct page *vmpage, unsigned int offset,
			      unsigned int length)
{
	struct inode     *inode;
	struct lu_env    *env;
	struct cl_page   *page;
	struct cl_object *obj;

	int refcheck;

	LASSERT(PageLocked(vmpage));
	LASSERT(!PageWriteback(vmpage));

	/*
	 * It is safe to not check anything in invalidatepage/releasepage
	 * below because they are run with page locked and all our io is
	 * happening with locked page too
	 */
	if (offset == 0 && length == PAGE_SIZE) {
		env = cl_env_get(&refcheck);
		if (!IS_ERR(env)) {
			inode = vmpage->mapping->host;
			obj = ll_i2info(inode)->lli_clob;
			if (obj) {
				page = cl_vmpage_page(vmpage, obj);
				if (page) {
					cl_page_delete(env, page);
					cl_page_put(env, page);
				}
			} else {
				LASSERT(vmpage->private == 0);
			}
			cl_env_put(env, &refcheck);
		}
	}
}

static int ll_releasepage(struct page *vmpage, gfp_t gfp_mask)
{
	struct lu_env     *env;
	void			*cookie;
	struct cl_object  *obj;
	struct cl_page    *page;
	struct address_space *mapping;
	int result = 0;

	LASSERT(PageLocked(vmpage));
	if (PageWriteback(vmpage) || PageDirty(vmpage))
		return 0;

	mapping = vmpage->mapping;
	if (!mapping)
		return 1;

	obj = ll_i2info(mapping->host)->lli_clob;
	if (!obj)
		return 1;

	/* 1 for caller, 1 for cl_page and 1 for page cache */
	if (page_count(vmpage) > 3)
		return 0;

	page = cl_vmpage_page(vmpage, obj);
	if (!page)
		return 1;

	cookie = cl_env_reenter();
	env = cl_env_percpu_get();
	LASSERT(!IS_ERR(env));

	if (!cl_page_in_use(page)) {
		result = 1;
		cl_page_delete(env, page);
	}

	/* To use percpu env array, the call path can not be rescheduled;
	 * otherwise percpu array will be messed if ll_releaspage() called
	 * again on the same CPU.
	 *
	 * If this page holds the last refc of cl_object, the following
	 * call path may cause reschedule:
	 *   cl_page_put -> cl_page_free -> cl_object_put ->
	 *     lu_object_put -> lu_object_free -> lov_delete_raid0.
	 *
	 * However, the kernel can't get rid of this inode until all pages have
	 * been cleaned up. Now that we hold page lock here, it's pretty safe
	 * that we won't get into object delete path.
	 */
	LASSERT(cl_object_refc(obj) > 1);
	cl_page_put(env, page);

	cl_env_percpu_put(env);
	cl_env_reexit(cookie);
	return result;
}

#define MAX_DIRECTIO_SIZE (2 * 1024 * 1024 * 1024UL)

static inline int ll_get_user_pages(int rw, unsigned long user_addr,
				    size_t size, struct page ***pages,
				    int *max_pages)
{
	int result = -ENOMEM;

	/* set an arbitrary limit to prevent arithmetic overflow */
	if (size > MAX_DIRECTIO_SIZE) {
		*pages = NULL;
		return -EFBIG;
	}

	*max_pages = (user_addr + size + PAGE_SIZE - 1) >> PAGE_SHIFT;
	*max_pages -= user_addr >> PAGE_SHIFT;

	*pages = libcfs_kvzalloc(*max_pages * sizeof(**pages), GFP_NOFS);
	if (*pages) {
		result = get_user_pages_fast(user_addr, *max_pages,
					     (rw == READ), *pages);
		if (unlikely(result <= 0))
			kvfree(*pages);
	}

	return result;
}

/*  ll_free_user_pages - tear down page struct array
 *  @pages: array of page struct pointers underlying target buffer
 */
static void ll_free_user_pages(struct page **pages, int npages, int do_dirty)
{
	int i;

	for (i = 0; i < npages; i++) {
		if (do_dirty)
			set_page_dirty_lock(pages[i]);
		put_page(pages[i]);
	}
	kvfree(pages);
}

ssize_t ll_direct_rw_pages(const struct lu_env *env, struct cl_io *io,
			   int rw, struct inode *inode,
			   struct ll_dio_pages *pv)
{
	struct cl_page    *clp;
	struct cl_2queue  *queue;
	struct cl_object  *obj = io->ci_obj;
	int i;
	ssize_t rc = 0;
	loff_t file_offset  = pv->ldp_start_offset;
	size_t size = pv->ldp_size;
	int page_count      = pv->ldp_nr;
	struct page **pages = pv->ldp_pages;
	size_t page_size = cl_page_size(obj);
	bool do_io;
	int  io_pages       = 0;

	queue = &io->ci_queue;
	cl_2queue_init(queue);
	for (i = 0; i < page_count; i++) {
		if (pv->ldp_offsets)
			file_offset = pv->ldp_offsets[i];

		LASSERT(!(file_offset & (page_size - 1)));
		clp = cl_page_find(env, obj, cl_index(obj, file_offset),
				   pv->ldp_pages[i], CPT_TRANSIENT);
		if (IS_ERR(clp)) {
			rc = PTR_ERR(clp);
			break;
		}

		rc = cl_page_own(env, io, clp);
		if (rc) {
			LASSERT(clp->cp_state == CPS_FREEING);
			cl_page_put(env, clp);
			break;
		}

		do_io = true;

		/* check the page type: if the page is a host page, then do
		 * write directly
		 */
		if (clp->cp_type == CPT_CACHEABLE) {
			struct page *vmpage = cl_page_vmpage(clp);
			struct page *src_page;
			struct page *dst_page;
			void       *src;
			void       *dst;

			src_page = (rw == WRITE) ? pages[i] : vmpage;
			dst_page = (rw == WRITE) ? vmpage : pages[i];

			src = kmap_atomic(src_page);
			dst = kmap_atomic(dst_page);
			memcpy(dst, src, min(page_size, size));
			kunmap_atomic(dst);
			kunmap_atomic(src);

			/* make sure page will be added to the transfer by
			 * cl_io_submit()->...->vvp_page_prep_write().
			 */
			if (rw == WRITE)
				set_page_dirty(vmpage);

			if (rw == READ) {
				/* do not issue the page for read, since it
				 * may reread a ra page which has NOT uptodate
				 * bit set.
				 */
				cl_page_disown(env, io, clp);
				do_io = false;
			}
		}

		if (likely(do_io)) {
			/*
			 * Add a page to the incoming page list of 2-queue.
			 */
			cl_page_list_add(&queue->c2_qin, clp);

			/*
			 * Set page clip to tell transfer formation engine
			 * that page has to be sent even if it is beyond KMS.
			 */
			cl_page_clip(env, clp, 0, min(size, page_size));

			++io_pages;
		}

		/* drop the reference count for cl_page_find */
		cl_page_put(env, clp);
		size -= page_size;
		file_offset += page_size;
	}

	if (rc == 0 && io_pages) {
		rc = cl_io_submit_sync(env, io,
				       rw == READ ? CRT_READ : CRT_WRITE,
				       queue, 0);
	}
	if (rc == 0)
		rc = pv->ldp_size;

	cl_2queue_discard(env, io, queue);
	cl_2queue_disown(env, io, queue);
	cl_2queue_fini(env, queue);
	return rc;
}
EXPORT_SYMBOL(ll_direct_rw_pages);

static ssize_t ll_direct_IO_26_seg(const struct lu_env *env, struct cl_io *io,
				   int rw, struct inode *inode,
				   struct address_space *mapping,
				   size_t size, loff_t file_offset,
				   struct page **pages, int page_count)
{
	struct ll_dio_pages pvec = {
		.ldp_pages	= pages,
		.ldp_nr		= page_count,
		.ldp_size	= size,
		.ldp_offsets	= NULL,
		.ldp_start_offset = file_offset
	};

	return ll_direct_rw_pages(env, io, rw, inode, &pvec);
}

/* This is the maximum size of a single O_DIRECT request, based on the
 * kmalloc limit.  We need to fit all of the brw_page structs, each one
 * representing PAGE_SIZE worth of user data, into a single buffer, and
 * then truncate this to be a full-sized RPC.  For 4kB PAGE_SIZE this is
 * up to 22MB for 128kB kmalloc and up to 682MB for 4MB kmalloc.
 */
#define MAX_DIO_SIZE ((KMALLOC_MAX_SIZE / sizeof(struct brw_page) *	  \
		       PAGE_SIZE) & ~(DT_MAX_BRW_SIZE - 1))
static ssize_t ll_direct_IO_26(struct kiocb *iocb, struct iov_iter *iter)
{
	struct lu_env *env;
	struct cl_io *io;
	struct file *file = iocb->ki_filp;
	struct inode *inode = file->f_mapping->host;
	loff_t file_offset = iocb->ki_pos;
	ssize_t count = iov_iter_count(iter);
	ssize_t tot_bytes = 0, result = 0;
	struct ll_inode_info *lli = ll_i2info(inode);
	long size = MAX_DIO_SIZE;
	int refcheck;

	if (!lli->lli_has_smd)
		return -EBADF;

	/* Check EOF by ourselves */
	if (iov_iter_rw(iter) == READ && file_offset >= i_size_read(inode))
		return 0;

	/* FIXME: io smaller than PAGE_SIZE is broken on ia64 ??? */
	if ((file_offset & ~PAGE_MASK) || (count & ~PAGE_MASK))
		return -EINVAL;

	CDEBUG(D_VFSTRACE, "VFS Op:inode="DFID"(%p), size=%zd (max %lu), offset=%lld=%llx, pages %zd (max %lu)\n",
	       PFID(ll_inode2fid(inode)), inode, count, MAX_DIO_SIZE,
	       file_offset, file_offset, count >> PAGE_SHIFT,
	       MAX_DIO_SIZE >> PAGE_SHIFT);

	/* Check that all user buffers are aligned as well */
	if (iov_iter_alignment(iter) & ~PAGE_MASK)
		return -EINVAL;

	env = cl_env_get(&refcheck);
	LASSERT(!IS_ERR(env));
	io = vvp_env_io(env)->vui_cl.cis_io;
	LASSERT(io);

	while (iov_iter_count(iter)) {
		struct page **pages;
		size_t offs;

		count = min_t(size_t, iov_iter_count(iter), size);
		if (iov_iter_rw(iter) == READ) {
			if (file_offset >= i_size_read(inode))
				break;
			if (file_offset + count > i_size_read(inode))
				count = i_size_read(inode) - file_offset;
		}

		result = iov_iter_get_pages_alloc(iter, &pages, count, &offs);
		if (likely(result > 0)) {
			int n = DIV_ROUND_UP(result + offs, PAGE_SIZE);

			result = ll_direct_IO_26_seg(env, io, iov_iter_rw(iter),
						     inode, file->f_mapping,
						     result, file_offset, pages,
						     n);
			ll_free_user_pages(pages, n, iov_iter_rw(iter) == READ);
		}
		if (unlikely(result <= 0)) {
			/* If we can't allocate a large enough buffer
			 * for the request, shrink it to a smaller
			 * PAGE_SIZE multiple and try again.
			 * We should always be able to kmalloc for a
			 * page worth of page pointers = 4MB on i386.
			 */
			if (result == -ENOMEM &&
			    size > (PAGE_SIZE / sizeof(*pages)) *
			    PAGE_SIZE) {
				size = ((((size / 2) - 1) |
					 ~PAGE_MASK) + 1) &
					PAGE_MASK;
				CDEBUG(D_VFSTRACE, "DIO size now %lu\n",
				       size);
				continue;
			}

			goto out;
		}
		iov_iter_advance(iter, result);
		tot_bytes += result;
		file_offset += result;
	}
out:
	if (tot_bytes > 0) {
		struct vvp_io *vio = vvp_env_io(env);

		/* no commit async for direct IO */
		vio->u.write.vui_written += tot_bytes;
	}

	cl_env_put(env, &refcheck);
	return tot_bytes ? tot_bytes : result;
}

/**
 * Prepare partially written-to page for a write.
 */
static int ll_prepare_partial_page(const struct lu_env *env, struct cl_io *io,
				   struct cl_page *pg)
{
	struct cl_attr *attr   = vvp_env_thread_attr(env);
	struct cl_object *obj  = io->ci_obj;
	struct vvp_page *vpg   = cl_object_page_slice(obj, pg);
	loff_t          offset = cl_offset(obj, vvp_index(vpg));
	int             result;

	cl_object_attr_lock(obj);
	result = cl_object_attr_get(env, obj, attr);
	cl_object_attr_unlock(obj);
	if (result == 0) {
		/*
		 * If are writing to a new page, no need to read old data.
		 * The extent locking will have updated the KMS, and for our
		 * purposes here we can treat it like i_size.
		 */
		if (attr->cat_kms <= offset) {
			char *kaddr = kmap_atomic(vpg->vpg_page);

			memset(kaddr, 0, cl_page_size(obj));
			kunmap_atomic(kaddr);
		} else if (vpg->vpg_defer_uptodate) {
			vpg->vpg_ra_used = 1;
		} else {
			result = ll_page_sync_io(env, io, pg, CRT_READ);
		}
	}
	return result;
}

static int ll_write_begin(struct file *file, struct address_space *mapping,
			  loff_t pos, unsigned len, unsigned flags,
			  struct page **pagep, void **fsdata)
{
	struct ll_cl_context *lcc;
	const struct lu_env  *env;
	struct cl_io   *io;
	struct cl_page *page;
	struct cl_object *clob = ll_i2info(mapping->host)->lli_clob;
	pgoff_t index = pos >> PAGE_SHIFT;
	struct page *vmpage = NULL;
	unsigned int from = pos & (PAGE_SIZE - 1);
	unsigned int to = from + len;
	int result = 0;

	CDEBUG(D_VFSTRACE, "Writing %lu of %d to %d bytes\n", index, from, len);

	lcc = ll_cl_find(file);
	if (!lcc) {
		result = -EIO;
		goto out;
	}

	env = lcc->lcc_env;
	io  = lcc->lcc_io;

	/* To avoid deadlock, try to lock page first. */
	vmpage = grab_cache_page_nowait(mapping, index);
	if (unlikely(!vmpage || PageDirty(vmpage) || PageWriteback(vmpage))) {
		struct vvp_io *vio = vvp_env_io(env);
		struct cl_page_list *plist = &vio->u.write.vui_queue;

		/* if the page is already in dirty cache, we have to commit
		 * the pages right now; otherwise, it may cause deadlock
		 * because it holds page lock of a dirty page and request for
		 * more grants. It's okay for the dirty page to be the first
		 * one in commit page list, though.
		 */
		if (vmpage && plist->pl_nr > 0) {
			unlock_page(vmpage);
			put_page(vmpage);
			vmpage = NULL;
		}

		/* commit pages and then wait for page lock */
		result = vvp_io_write_commit(env, io);
		if (result < 0)
			goto out;

		if (!vmpage) {
			vmpage = grab_cache_page_write_begin(mapping, index,
							     flags);
			if (!vmpage) {
				result = -ENOMEM;
				goto out;
			}
		}
	}

	page = cl_page_find(env, clob, vmpage->index, vmpage, CPT_CACHEABLE);
	if (IS_ERR(page)) {
		result = PTR_ERR(page);
		goto out;
	}

	lcc->lcc_page = page;
	lu_ref_add(&page->cp_reference, "cl_io", io);

	cl_page_assume(env, io, page);
	if (!PageUptodate(vmpage)) {
		/*
		 * We're completely overwriting an existing page,
		 * so _don't_ set it up to date until commit_write
		 */
		if (from == 0 && to == PAGE_SIZE) {
			CL_PAGE_HEADER(D_PAGE, env, page, "full page write\n");
			POISON_PAGE(vmpage, 0x11);
		} else {
			/* TODO: can be optimized at OSC layer to check if it
			 * is a lockless IO. In that case, it's not necessary
			 * to read the data.
			 */
			result = ll_prepare_partial_page(env, io, page);
			if (result == 0)
				SetPageUptodate(vmpage);
		}
	}
	if (result < 0)
		cl_page_unassume(env, io, page);
out:
	if (result < 0) {
		if (vmpage) {
			unlock_page(vmpage);
			put_page(vmpage);
		}
	} else {
		*pagep = vmpage;
		*fsdata = lcc;
	}
	return result;
}

static int ll_write_end(struct file *file, struct address_space *mapping,
			loff_t pos, unsigned len, unsigned copied,
			struct page *vmpage, void *fsdata)
{
	struct ll_cl_context *lcc = fsdata;
	const struct lu_env *env;
	struct cl_io *io;
	struct vvp_io *vio;
	struct cl_page *page;
	unsigned from = pos & (PAGE_SIZE - 1);
	bool unplug = false;
	int result = 0;

	put_page(vmpage);

	env  = lcc->lcc_env;
	page = lcc->lcc_page;
	io   = lcc->lcc_io;
	vio  = vvp_env_io(env);

	LASSERT(cl_page_is_owned(page, io));
	if (copied > 0) {
		struct cl_page_list *plist = &vio->u.write.vui_queue;

		lcc->lcc_page = NULL; /* page will be queued */

		/* Add it into write queue */
		cl_page_list_add(plist, page);
		if (plist->pl_nr == 1) /* first page */
			vio->u.write.vui_from = from;
		else
			LASSERT(from == 0);
		vio->u.write.vui_to = from + copied;

		/*
		 * To address the deadlock in balance_dirty_pages() where
		 * this dirty page may be written back in the same thread.
		 */
		if (PageDirty(vmpage))
			unplug = true;

		/* We may have one full RPC, commit it soon */
		if (plist->pl_nr >= PTLRPC_MAX_BRW_PAGES)
			unplug = true;

		CL_PAGE_DEBUG(D_VFSTRACE, env, page,
			      "queued page: %d.\n", plist->pl_nr);
	} else {
		cl_page_disown(env, io, page);

		lcc->lcc_page = NULL;
		lu_ref_del(&page->cp_reference, "cl_io", io);
		cl_page_put(env, page);

		/* page list is not contiguous now, commit it now */
		unplug = true;
	}

	if (unplug ||
	    file->f_flags & O_SYNC || IS_SYNC(file_inode(file)))
		result = vvp_io_write_commit(env, io);

	return result >= 0 ? copied : result;
}

#ifdef CONFIG_MIGRATION
static int ll_migratepage(struct address_space *mapping,
			  struct page *newpage, struct page *page,
			  enum migrate_mode mode
		)
{
	/* Always fail page migration until we have a proper implementation */
	return -EIO;
}
#endif

const struct address_space_operations ll_aops = {
	.readpage	= ll_readpage,
	.direct_IO      = ll_direct_IO_26,
	.writepage      = ll_writepage,
	.writepages     = ll_writepages,
	.set_page_dirty = __set_page_dirty_nobuffers,
	.write_begin    = ll_write_begin,
	.write_end      = ll_write_end,
	.invalidatepage = ll_invalidatepage,
	.releasepage    = (void *)ll_releasepage,
#ifdef CONFIG_MIGRATION
	.migratepage    = ll_migratepage,
#endif
};