/*
 * 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) 2004, 2010, Oracle and/or its affiliates. All rights reserved.
 * Use is subject to license terms.
 *
 * Copyright (c) 2011, 2015, Intel Corporation.
 */
/*
 * This file is part of Lustre, http://www.lustre.org/
 * Lustre is a trademark of Sun Microsystems, Inc.
 */

#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/fs.h>
#include <linux/pagemap.h>

#define DEBUG_SUBSYSTEM S_LLITE

#include "llite_internal.h"

static const struct vm_operations_struct ll_file_vm_ops;

void policy_from_vma(ldlm_policy_data_t *policy,
                     struct vm_area_struct *vma, unsigned long addr,
                     size_t count)
{
        policy->l_extent.start = ((addr - vma->vm_start) & PAGE_MASK) +
                                 (vma->vm_pgoff << PAGE_SHIFT);
        policy->l_extent.end = (policy->l_extent.start + count - 1) |
                               ~PAGE_MASK;
}

struct vm_area_struct *our_vma(struct mm_struct *mm, unsigned long addr,
                               size_t count)
{
        struct vm_area_struct *vma, *ret = NULL;

        /* mmap_sem must have been held by caller. */
        LASSERT(!down_write_trylock(&mm->mmap_sem));

        for (vma = find_vma(mm, addr);
            vma && vma->vm_start < (addr + count); vma = vma->vm_next) {
                if (vma->vm_ops && vma->vm_ops == &ll_file_vm_ops &&
                    vma->vm_flags & VM_SHARED) {
                        ret = vma;
                        break;
                }
        }
        return ret;
}

/**
 * API independent part for page fault initialization.
 * \param vma - virtual memory area addressed to page fault
 * \param env - corespondent lu_env to processing
 * \param nest - nested level
 * \param index - page index corespondent to fault.
 * \parm ra_flags - vma readahead flags.
 *
 * \return allocated and initialized env for fault operation.
 * \retval EINVAL if env can't allocated
 * \return other error codes from cl_io_init.
 */
static struct cl_io *
ll_fault_io_init(struct vm_area_struct *vma, struct lu_env **env_ret,
                 struct cl_env_nest *nest, pgoff_t index,
                 unsigned long *ra_flags)
{
        struct file            *file = vma->vm_file;
        struct inode           *inode = file_inode(file);
        struct cl_io           *io;
        struct cl_fault_io     *fio;
        struct lu_env          *env;
        int                     rc;

        *env_ret = NULL;
        if (ll_file_nolock(file))
                return ERR_PTR(-EOPNOTSUPP);

        /*
         * page fault can be called when lustre IO is
         * already active for the current thread, e.g., when doing read/write
         * against user level buffer mapped from Lustre buffer. To avoid
         * stomping on existing context, optionally force an allocation of a new
         * one.
         */
        env = cl_env_nested_get(nest);
        if (IS_ERR(env))
                return ERR_PTR(-EINVAL);

        *env_ret = env;

restart:
        io = vvp_env_thread_io(env);
        io->ci_obj = ll_i2info(inode)->lli_clob;
        LASSERT(io->ci_obj);

        fio = &io->u.ci_fault;
        fio->ft_index      = index;
        fio->ft_executable = vma->vm_flags & VM_EXEC;

        /*
         * disable VM_SEQ_READ and use VM_RAND_READ to make sure that
         * the kernel will not read other pages not covered by ldlm in
         * filemap_nopage. we do our readahead in ll_readpage.
         */
        if (ra_flags)
                *ra_flags = vma->vm_flags & (VM_RAND_READ | VM_SEQ_READ);
        vma->vm_flags &= ~VM_SEQ_READ;
        vma->vm_flags |= VM_RAND_READ;

        CDEBUG(D_MMAP, "vm_flags: %lx (%lu %d)\n", vma->vm_flags,
               fio->ft_index, fio->ft_executable);

        rc = cl_io_init(env, io, CIT_FAULT, io->ci_obj);
        if (rc == 0) {
                struct vvp_io *vio = vvp_env_io(env);
                struct ll_file_data *fd = LUSTRE_FPRIVATE(file);

                LASSERT(vio->vui_cl.cis_io == io);

                /* mmap lock must be MANDATORY it has to cache pages. */
                io->ci_lockreq = CILR_MANDATORY;
                vio->vui_fd = fd;
        } else {
                LASSERT(rc < 0);
                cl_io_fini(env, io);
                if (io->ci_need_restart)
                        goto restart;

                cl_env_nested_put(nest, env);
                io = ERR_PTR(rc);
        }

        return io;
}

/* Sharing code of page_mkwrite method for rhel5 and rhel6 */
static int ll_page_mkwrite0(struct vm_area_struct *vma, struct page *vmpage,
                            bool *retry)
{
        struct lu_env      *env;
        struct cl_io        *io;
        struct vvp_io      *vio;
        struct cl_env_nest       nest;
        int                   result;
        sigset_t             set;
        struct inode         *inode;
        struct ll_inode_info     *lli;

        io = ll_fault_io_init(vma, &env,  &nest, vmpage->index, NULL);
        if (IS_ERR(io)) {
                result = PTR_ERR(io);
                goto out;
        }

        result = io->ci_result;
        if (result < 0)
                goto out_io;

        io->u.ci_fault.ft_mkwrite = 1;
        io->u.ci_fault.ft_writable = 1;

        vio = vvp_env_io(env);
        vio->u.fault.ft_vma    = vma;
        vio->u.fault.ft_vmpage = vmpage;

        set = cfs_block_sigsinv(sigmask(SIGKILL) | sigmask(SIGTERM));

        inode = vvp_object_inode(io->ci_obj);
        lli = ll_i2info(inode);

        result = cl_io_loop(env, io);

        cfs_restore_sigs(set);

        if (result == 0) {
                struct inode *inode = file_inode(vma->vm_file);
                struct ll_inode_info *lli = ll_i2info(inode);

                lock_page(vmpage);
                if (!vmpage->mapping) {
                        unlock_page(vmpage);

                        /* page was truncated and lock was cancelled, return
                         * ENODATA so that VM_FAULT_NOPAGE will be returned
                         * to handle_mm_fault().
                         */
                        if (result == 0)
                                result = -ENODATA;
                } else if (!PageDirty(vmpage)) {
                        /* race, the page has been cleaned by ptlrpcd after
                         * it was unlocked, it has to be added into dirty
                         * cache again otherwise this soon-to-dirty page won't
                         * consume any grants, even worse if this page is being
                         * transferred because it will break RPC checksum.
                         */
                        unlock_page(vmpage);

                        CDEBUG(D_MMAP, "Race on page_mkwrite %p/%lu, page has been written out, retry.\n",
                               vmpage, vmpage->index);

                        *retry = true;
                        result = -EAGAIN;
                }

                if (result == 0) {
                        spin_lock(&lli->lli_lock);
                        lli->lli_flags |= LLIF_DATA_MODIFIED;
                        spin_unlock(&lli->lli_lock);
                }
        }

out_io:
        cl_io_fini(env, io);
        cl_env_nested_put(&nest, env);
out:
        CDEBUG(D_MMAP, "%s mkwrite with %d\n", current->comm, result);
        LASSERT(ergo(result == 0, PageLocked(vmpage)));

        return result;
}

static inline int to_fault_error(int result)
{
        switch (result) {
        case 0:
                result = VM_FAULT_LOCKED;
                break;
        case -EFAULT:
                result = VM_FAULT_NOPAGE;
                break;
        case -ENOMEM:
                result = VM_FAULT_OOM;
                break;
        default:
                result = VM_FAULT_SIGBUS;
                break;
        }
        return result;
}

/**
 * Lustre implementation of a vm_operations_struct::fault() method, called by
 * VM to server page fault (both in kernel and user space).
 *
 * \param vma - is virtual area struct related to page fault
 * \param vmf - structure which describe type and address where hit fault
 *
 * \return allocated and filled _locked_ page for address
 * \retval VM_FAULT_ERROR on general error
 * \retval NOPAGE_OOM not have memory for allocate new page
 */
static int ll_fault0(struct vm_area_struct *vma, struct vm_fault *vmf)
{
        struct lu_env      *env;
        struct cl_io        *io;
        struct vvp_io      *vio = NULL;
        struct page          *vmpage;
        unsigned long       ra_flags;
        struct cl_env_nest       nest;
        int                   result;
        int                   fault_ret = 0;

        io = ll_fault_io_init(vma, &env,  &nest, vmf->pgoff, &ra_flags);
        if (IS_ERR(io))
                return to_fault_error(PTR_ERR(io));

        result = io->ci_result;
        if (result == 0) {
                vio = vvp_env_io(env);
                vio->u.fault.ft_vma       = vma;
                vio->u.fault.ft_vmpage    = NULL;
                vio->u.fault.ft_vmf = vmf;
                vio->u.fault.ft_flags = 0;
                vio->u.fault.ft_flags_valid = false;

                /* May call ll_readpage() */
                ll_cl_add(vma->vm_file, env, io);

                result = cl_io_loop(env, io);

                ll_cl_remove(vma->vm_file, env);

                /* ft_flags are only valid if we reached
                 * the call to filemap_fault
                 */
                if (vio->u.fault.ft_flags_valid)
                        fault_ret = vio->u.fault.ft_flags;

                vmpage = vio->u.fault.ft_vmpage;
                if (result != 0 && vmpage) {
                        put_page(vmpage);
                        vmf->page = NULL;
                }
        }
        cl_io_fini(env, io);
        cl_env_nested_put(&nest, env);

        vma->vm_flags |= ra_flags;
        if (result != 0 && !(fault_ret & VM_FAULT_RETRY))
                fault_ret |= to_fault_error(result);

        CDEBUG(D_MMAP, "%s fault %d/%d\n",
               current->comm, fault_ret, result);
        return fault_ret;
}

static int ll_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
{
        int count = 0;
        bool printed = false;
        int result;
        sigset_t set;

        /* Only SIGKILL and SIGTERM are allowed for fault/nopage/mkwrite
         * so that it can be killed by admin but not cause segfault by
         * other signals.
         */
        set = cfs_block_sigsinv(sigmask(SIGKILL) | sigmask(SIGTERM));

restart:
        result = ll_fault0(vma, vmf);
        LASSERT(!(result & VM_FAULT_LOCKED));
        if (result == 0) {
                struct page *vmpage = vmf->page;

                /* check if this page has been truncated */
                lock_page(vmpage);
                if (unlikely(!vmpage->mapping)) { /* unlucky */
                        unlock_page(vmpage);
                        put_page(vmpage);
                        vmf->page = NULL;

                        if (!printed && ++count > 16) {
                                CWARN("the page is under heavy contention, maybe your app(%s) needs revising :-)\n",
                                      current->comm);
                                printed = true;
                        }

                        goto restart;
                }

                result = VM_FAULT_LOCKED;
        }
        cfs_restore_sigs(set);
        return result;
}

static int ll_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
{
        int count = 0;
        bool printed = false;
        bool retry;
        int result;

        do {
                retry = false;
                result = ll_page_mkwrite0(vma, vmf->page, &retry);

                if (!printed && ++count > 16) {
                        const struct dentry *de = vma->vm_file->f_path.dentry;

                        CWARN("app(%s): the page %lu of file "DFID" is under heavy contention\n",
                              current->comm, vmf->pgoff,
                              PFID(ll_inode2fid(de->d_inode)));
                        printed = true;
                }
        } while (retry);

        switch (result) {
        case 0:
                LASSERT(PageLocked(vmf->page));
                result = VM_FAULT_LOCKED;
                break;
        case -ENODATA:
        case -EFAULT:
                result = VM_FAULT_NOPAGE;
                break;
        case -ENOMEM:
                result = VM_FAULT_OOM;
                break;
        case -EAGAIN:
                result = VM_FAULT_RETRY;
                break;
        default:
                result = VM_FAULT_SIGBUS;
                break;
        }

        return result;
}

/**
 *  To avoid cancel the locks covering mmapped region for lock cache pressure,
 *  we track the mapped vma count in vvp_object::vob_mmap_cnt.
 */
static void ll_vm_open(struct vm_area_struct *vma)
{
        struct inode *inode    = file_inode(vma->vm_file);
        struct vvp_object *vob = cl_inode2vvp(inode);

        LASSERT(atomic_read(&vob->vob_mmap_cnt) >= 0);
        atomic_inc(&vob->vob_mmap_cnt);
}

/**
 * Dual to ll_vm_open().
 */
static void ll_vm_close(struct vm_area_struct *vma)
{
        struct inode      *inode = file_inode(vma->vm_file);
        struct vvp_object *vob   = cl_inode2vvp(inode);

        atomic_dec(&vob->vob_mmap_cnt);
        LASSERT(atomic_read(&vob->vob_mmap_cnt) >= 0);
}

/* XXX put nice comment here.  talk about __free_pte -> dirty pages and
 * nopage's reference passing to the pte
 */
int ll_teardown_mmaps(struct address_space *mapping, __u64 first, __u64 last)
{
        int rc = -ENOENT;

        LASSERTF(last > first, "last %llu first %llu\n", last, first);
        if (mapping_mapped(mapping)) {
                rc = 0;
                unmap_mapping_range(mapping, first + PAGE_SIZE - 1,
                                    last - first + 1, 0);
        }

        return rc;
}

static const struct vm_operations_struct ll_file_vm_ops = {
        .fault                  = ll_fault,
        .page_mkwrite           = ll_page_mkwrite,
        .open                   = ll_vm_open,
        .close                  = ll_vm_close,
};

int ll_file_mmap(struct file *file, struct vm_area_struct *vma)
{
        struct inode *inode = file_inode(file);
        int rc;

        if (ll_file_nolock(file))
                return -EOPNOTSUPP;

        ll_stats_ops_tally(ll_i2sbi(inode), LPROC_LL_MAP, 1);
        rc = generic_file_mmap(file, vma);
        if (rc == 0) {
                vma->vm_ops = &ll_file_vm_ops;
                vma->vm_ops->open(vma);
                /* update the inode's size and mtime */
                rc = ll_glimpse_size(inode);
        }

        return rc;
}