// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * mmap.c
 *
 * Code to deal with the mess that is clustered mmap.
 *
 * Copyright (C) 2002, 2004 Oracle.  All rights reserved.
 */

#include <linux/fs.h>
#include <linux/types.h>
#include <linux/highmem.h>
#include <linux/pagemap.h>
#include <linux/uio.h>
#include <linux/signal.h>
#include <linux/rbtree.h>

#include <cluster/masklog.h>

#include "ocfs2.h"

#include "aops.h"
#include "dlmglue.h"
#include "file.h"
#include "inode.h"
#include "mmap.h"
#include "super.h"
#include "ocfs2_trace.h"


static vm_fault_t ocfs2_fault(struct vm_fault *vmf)
{
        struct vm_area_struct *vma = vmf->vma;
        sigset_t oldset;
        vm_fault_t ret;

        ocfs2_block_signals(&oldset);
        ret = filemap_fault(vmf);
        ocfs2_unblock_signals(&oldset);

        trace_ocfs2_fault(OCFS2_I(vma->vm_file->f_mapping->host)->ip_blkno,
                          vma, vmf->page, vmf->pgoff);
        return ret;
}

static vm_fault_t __ocfs2_page_mkwrite(struct file *file,
                        struct buffer_head *di_bh, struct folio *folio)
{
        int err;
        vm_fault_t ret = VM_FAULT_NOPAGE;
        struct inode *inode = file_inode(file);
        struct address_space *mapping = inode->i_mapping;
        loff_t pos = folio_pos(folio);
        unsigned int len = PAGE_SIZE;
        pgoff_t last_index;
        struct folio *locked_folio = NULL;
        void *fsdata;
        loff_t size = i_size_read(inode);

        last_index = (size - 1) >> PAGE_SHIFT;

        /*
         * There are cases that lead to the page no longer belonging to the
         * mapping.
         * 1) pagecache truncates locally due to memory pressure.
         * 2) pagecache truncates when another is taking EX lock against 
         * inode lock. see ocfs2_data_convert_worker.
         * 
         * The i_size check doesn't catch the case where nodes truncated and
         * then re-extended the file. We'll re-check the page mapping after
         * taking the page lock inside of ocfs2_write_begin_nolock().
         *
         * Let VM retry with these cases.
         */
        if ((folio->mapping != inode->i_mapping) ||
            !folio_test_uptodate(folio) ||
            (pos >= size))
                goto out;

        /*
         * Call ocfs2_write_begin() and ocfs2_write_end() to take
         * advantage of the allocation code there. We pass a write
         * length of the whole page (chopped to i_size) to make sure
         * the whole thing is allocated.
         *
         * Since we know the page is up to date, we don't have to
         * worry about ocfs2_write_begin() skipping some buffer reads
         * because the "write" would invalidate their data.
         */
        if (folio->index == last_index)
                len = ((size - 1) & ~PAGE_MASK) + 1;

        err = ocfs2_write_begin_nolock(mapping, pos, len, OCFS2_WRITE_MMAP,
                                       &locked_folio, &fsdata, di_bh, folio);
        if (err) {
                if (err != -ENOSPC)
                        mlog_errno(err);
                ret = vmf_error(err);
                goto out;
        }

        if (!locked_folio) {
                ret = VM_FAULT_NOPAGE;
                goto out;
        }
        err = ocfs2_write_end_nolock(mapping, pos, len, len, fsdata);
        BUG_ON(err != len);
        ret = VM_FAULT_LOCKED;
out:
        return ret;
}

static vm_fault_t ocfs2_page_mkwrite(struct vm_fault *vmf)
{
        struct folio *folio = page_folio(vmf->page);
        struct inode *inode = file_inode(vmf->vma->vm_file);
        struct buffer_head *di_bh = NULL;
        sigset_t oldset;
        int err;
        vm_fault_t ret;

        sb_start_pagefault(inode->i_sb);
        ocfs2_block_signals(&oldset);

        /*
         * The cluster locks taken will block a truncate from another
         * node. Taking the data lock will also ensure that we don't
         * attempt page truncation as part of a downconvert.
         */
        err = ocfs2_inode_lock(inode, &di_bh, 1);
        if (err < 0) {
                mlog_errno(err);
                ret = vmf_error(err);
                goto out;
        }

        /*
         * The alloc sem should be enough to serialize with
         * ocfs2_truncate_file() changing i_size as well as any thread
         * modifying the inode btree.
         */
        down_write(&OCFS2_I(inode)->ip_alloc_sem);

        ret = __ocfs2_page_mkwrite(vmf->vma->vm_file, di_bh, folio);

        up_write(&OCFS2_I(inode)->ip_alloc_sem);

        brelse(di_bh);
        ocfs2_inode_unlock(inode, 1);

out:
        ocfs2_unblock_signals(&oldset);
        sb_end_pagefault(inode->i_sb);
        return ret;
}

static const struct vm_operations_struct ocfs2_file_vm_ops = {
        .fault          = ocfs2_fault,
        .page_mkwrite   = ocfs2_page_mkwrite,
};

int ocfs2_mmap_prepare(struct vm_area_desc *desc)
{
        struct file *file = desc->file;
        int ret = 0, lock_level = 0;

        ret = ocfs2_inode_lock_atime(file_inode(file),
                                    file->f_path.mnt, &lock_level, 1);
        if (ret < 0) {
                mlog_errno(ret);
                goto out;
        }
        ocfs2_inode_unlock(file_inode(file), lock_level);
out:
        desc->vm_ops = &ocfs2_file_vm_ops;
        return 0;
}