/*
 * JFFS2 -- Journalling Flash File System, Version 2.
 *
 * Copyright © 2001-2007 Red Hat, Inc.
 * Copyright © 2004-2010 David Woodhouse <dwmw2@infradead.org>
 *
 * Created by David Woodhouse <dwmw2@infradead.org>
 *
 * For licensing information, see the file 'LICENCE' in this directory.
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/time.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/crc32.h>
#include <linux/jffs2.h>
#include "nodelist.h"

static int jffs2_write_end(struct file *filp, struct address_space *mapping,
                        loff_t pos, unsigned len, unsigned copied,
                        struct page *pg, void *fsdata);
static int jffs2_write_begin(struct file *filp, struct address_space *mapping,
                        loff_t pos, unsigned len, unsigned flags,
                        struct page **pagep, void **fsdata);
static int jffs2_readpage (struct file *filp, struct page *pg);

int jffs2_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
{
        struct inode *inode = filp->f_mapping->host;
        struct jffs2_sb_info *c = JFFS2_SB_INFO(inode->i_sb);
        int ret;

        ret = file_write_and_wait_range(filp, start, end);
        if (ret)
                return ret;

        inode_lock(inode);
        /* Trigger GC to flush any pending writes for this inode */
        jffs2_flush_wbuf_gc(c, inode->i_ino);
        inode_unlock(inode);

        return 0;
}

const struct file_operations jffs2_file_operations =
{
        .llseek =       generic_file_llseek,
        .open =         generic_file_open,
        .read_iter =    generic_file_read_iter,
        .write_iter =   generic_file_write_iter,
        .unlocked_ioctl=jffs2_ioctl,
        .mmap =         generic_file_readonly_mmap,
        .fsync =        jffs2_fsync,
        .splice_read =  generic_file_splice_read,
};

/* jffs2_file_inode_operations */

const struct inode_operations jffs2_file_inode_operations =
{
        .get_acl =      jffs2_get_acl,
        .set_acl =      jffs2_set_acl,
        .setattr =      jffs2_setattr,
        .listxattr =    jffs2_listxattr,
};

const struct address_space_operations jffs2_file_address_operations =
{
        .readpage =     jffs2_readpage,
        .write_begin =  jffs2_write_begin,
        .write_end =    jffs2_write_end,
};

static int jffs2_do_readpage_nolock (struct inode *inode, struct page *pg)
{
        struct jffs2_inode_info *f = JFFS2_INODE_INFO(inode);
        struct jffs2_sb_info *c = JFFS2_SB_INFO(inode->i_sb);
        unsigned char *pg_buf;
        int ret;

        jffs2_dbg(2, "%s(): ino #%lu, page at offset 0x%lx\n",
                  __func__, inode->i_ino, pg->index << PAGE_SHIFT);

        BUG_ON(!PageLocked(pg));

        pg_buf = kmap(pg);
        /* FIXME: Can kmap fail? */

        ret = jffs2_read_inode_range(c, f, pg_buf, pg->index << PAGE_SHIFT,
                                     PAGE_SIZE);

        if (ret) {
                ClearPageUptodate(pg);
                SetPageError(pg);
        } else {
                SetPageUptodate(pg);
                ClearPageError(pg);
        }

        flush_dcache_page(pg);
        kunmap(pg);

        jffs2_dbg(2, "readpage finished\n");
        return ret;
}

int jffs2_do_readpage_unlock(void *data, struct page *pg)
{
        int ret = jffs2_do_readpage_nolock(data, pg);
        unlock_page(pg);
        return ret;
}


static int jffs2_readpage (struct file *filp, struct page *pg)
{
        struct jffs2_inode_info *f = JFFS2_INODE_INFO(pg->mapping->host);
        int ret;

        mutex_lock(&f->sem);
        ret = jffs2_do_readpage_unlock(pg->mapping->host, pg);
        mutex_unlock(&f->sem);
        return ret;
}

static int jffs2_write_begin(struct file *filp, struct address_space *mapping,
                        loff_t pos, unsigned len, unsigned flags,
                        struct page **pagep, void **fsdata)
{
        struct page *pg;
        struct inode *inode = mapping->host;
        struct jffs2_inode_info *f = JFFS2_INODE_INFO(inode);
        pgoff_t index = pos >> PAGE_SHIFT;
        uint32_t pageofs = index << PAGE_SHIFT;
        int ret = 0;

        pg = grab_cache_page_write_begin(mapping, index, flags);
        if (!pg)
                return -ENOMEM;
        *pagep = pg;

        jffs2_dbg(1, "%s()\n", __func__);

        if (pageofs > inode->i_size) {
                /* Make new hole frag from old EOF to new page */
                struct jffs2_sb_info *c = JFFS2_SB_INFO(inode->i_sb);
                struct jffs2_raw_inode ri;
                struct jffs2_full_dnode *fn;
                uint32_t alloc_len;

                jffs2_dbg(1, "Writing new hole frag 0x%x-0x%x between current EOF and new page\n",
                          (unsigned int)inode->i_size, pageofs);

                ret = jffs2_reserve_space(c, sizeof(ri), &alloc_len,
                                          ALLOC_NORMAL, JFFS2_SUMMARY_INODE_SIZE);
                if (ret)
                        goto out_page;

                mutex_lock(&f->sem);
                memset(&ri, 0, sizeof(ri));

                ri.magic = cpu_to_je16(JFFS2_MAGIC_BITMASK);
                ri.nodetype = cpu_to_je16(JFFS2_NODETYPE_INODE);
                ri.totlen = cpu_to_je32(sizeof(ri));
                ri.hdr_crc = cpu_to_je32(crc32(0, &ri, sizeof(struct jffs2_unknown_node)-4));

                ri.ino = cpu_to_je32(f->inocache->ino);
                ri.version = cpu_to_je32(++f->highest_version);
                ri.mode = cpu_to_jemode(inode->i_mode);
                ri.uid = cpu_to_je16(i_uid_read(inode));
                ri.gid = cpu_to_je16(i_gid_read(inode));
                ri.isize = cpu_to_je32(max((uint32_t)inode->i_size, pageofs));
                ri.atime = ri.ctime = ri.mtime = cpu_to_je32(JFFS2_NOW());
                ri.offset = cpu_to_je32(inode->i_size);
                ri.dsize = cpu_to_je32(pageofs - inode->i_size);
                ri.csize = cpu_to_je32(0);
                ri.compr = JFFS2_COMPR_ZERO;
                ri.node_crc = cpu_to_je32(crc32(0, &ri, sizeof(ri)-8));
                ri.data_crc = cpu_to_je32(0);

                fn = jffs2_write_dnode(c, f, &ri, NULL, 0, ALLOC_NORMAL);

                if (IS_ERR(fn)) {
                        ret = PTR_ERR(fn);
                        jffs2_complete_reservation(c);
                        mutex_unlock(&f->sem);
                        goto out_page;
                }
                ret = jffs2_add_full_dnode_to_inode(c, f, fn);
                if (f->metadata) {
                        jffs2_mark_node_obsolete(c, f->metadata->raw);
                        jffs2_free_full_dnode(f->metadata);
                        f->metadata = NULL;
                }
                if (ret) {
                        jffs2_dbg(1, "Eep. add_full_dnode_to_inode() failed in write_begin, returned %d\n",
                                  ret);
                        jffs2_mark_node_obsolete(c, fn->raw);
                        jffs2_free_full_dnode(fn);
                        jffs2_complete_reservation(c);
                        mutex_unlock(&f->sem);
                        goto out_page;
                }
                jffs2_complete_reservation(c);
                inode->i_size = pageofs;
                mutex_unlock(&f->sem);
        }

        /*
         * Read in the page if it wasn't already present. Cannot optimize away
         * the whole page write case until jffs2_write_end can handle the
         * case of a short-copy.
         */
        if (!PageUptodate(pg)) {
                mutex_lock(&f->sem);
                ret = jffs2_do_readpage_nolock(inode, pg);
                mutex_unlock(&f->sem);
                if (ret)
                        goto out_page;
        }
        jffs2_dbg(1, "end write_begin(). pg->flags %lx\n", pg->flags);
        return ret;

out_page:
        unlock_page(pg);
        put_page(pg);
        return ret;
}

static int jffs2_write_end(struct file *filp, struct address_space *mapping,
                        loff_t pos, unsigned len, unsigned copied,
                        struct page *pg, void *fsdata)
{
        /* Actually commit the write from the page cache page we're looking at.
         * For now, we write the full page out each time. It sucks, but it's simple
         */
        struct inode *inode = mapping->host;
        struct jffs2_inode_info *f = JFFS2_INODE_INFO(inode);
        struct jffs2_sb_info *c = JFFS2_SB_INFO(inode->i_sb);
        struct jffs2_raw_inode *ri;
        unsigned start = pos & (PAGE_SIZE - 1);
        unsigned end = start + copied;
        unsigned aligned_start = start & ~3;
        int ret = 0;
        uint32_t writtenlen = 0;

        jffs2_dbg(1, "%s(): ino #%lu, page at 0x%lx, range %d-%d, flags %lx\n",
                  __func__, inode->i_ino, pg->index << PAGE_SHIFT,
                  start, end, pg->flags);

        /* We need to avoid deadlock with page_cache_read() in
           jffs2_garbage_collect_pass(). So the page must be
           up to date to prevent page_cache_read() from trying
           to re-lock it. */
        BUG_ON(!PageUptodate(pg));

        if (end == PAGE_SIZE) {
                /* When writing out the end of a page, write out the
                   _whole_ page. This helps to reduce the number of
                   nodes in files which have many short writes, like
                   syslog files. */
                aligned_start = 0;
        }

        ri = jffs2_alloc_raw_inode();

        if (!ri) {
                jffs2_dbg(1, "%s(): Allocation of raw inode failed\n",
                          __func__);
                unlock_page(pg);
                put_page(pg);
                return -ENOMEM;
        }

        /* Set the fields that the generic jffs2_write_inode_range() code can't find */
        ri->ino = cpu_to_je32(inode->i_ino);
        ri->mode = cpu_to_jemode(inode->i_mode);
        ri->uid = cpu_to_je16(i_uid_read(inode));
        ri->gid = cpu_to_je16(i_gid_read(inode));
        ri->isize = cpu_to_je32((uint32_t)inode->i_size);
        ri->atime = ri->ctime = ri->mtime = cpu_to_je32(JFFS2_NOW());

        /* In 2.4, it was already kmapped by generic_file_write(). Doesn't
           hurt to do it again. The alternative is ifdefs, which are ugly. */
        kmap(pg);

        ret = jffs2_write_inode_range(c, f, ri, page_address(pg) + aligned_start,
                                      (pg->index << PAGE_SHIFT) + aligned_start,
                                      end - aligned_start, &writtenlen);

        kunmap(pg);

        if (ret) {
                /* There was an error writing. */
                SetPageError(pg);
        }

        /* Adjust writtenlen for the padding we did, so we don't confuse our caller */
        writtenlen -= min(writtenlen, (start - aligned_start));

        if (writtenlen) {
                if (inode->i_size < pos + writtenlen) {
                        inode->i_size = pos + writtenlen;
                        inode->i_blocks = (inode->i_size + 511) >> 9;

                        inode->i_ctime = inode->i_mtime = ITIME(je32_to_cpu(ri->ctime));
                }
        }

        jffs2_free_raw_inode(ri);

        if (start+writtenlen < end) {
                /* generic_file_write has written more to the page cache than we've
                   actually written to the medium. Mark the page !Uptodate so that
                   it gets reread */
                jffs2_dbg(1, "%s(): Not all bytes written. Marking page !uptodate\n",
                        __func__);
                SetPageError(pg);
                ClearPageUptodate(pg);
        }

        jffs2_dbg(1, "%s() returning %d\n",
                  __func__, writtenlen > 0 ? writtenlen : ret);
        unlock_page(pg);
        put_page(pg);
        return writtenlen > 0 ? writtenlen : ret;
}