/*
 * JFFS2 -- Journalling Flash File System, Version 2.
 *
 * Copyright © 2001-2007 Red Hat, Inc.
 *
 * 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/sched.h>
#include <linux/slab.h>
#include <linux/mtd/mtd.h>
#include <linux/pagemap.h>
#include <linux/crc32.h>
#include <linux/compiler.h>
#include "nodelist.h"
#include "summary.h"
#include "debug.h"

#define DEFAULT_EMPTY_SCAN_SIZE 256

#define noisy_printk(noise, fmt, ...)                                   \
do {                                                                    \
        if (*(noise)) {                                                 \
                pr_notice(fmt, ##__VA_ARGS__);                          \
                (*(noise))--;                                           \
                if (!(*(noise)))                                        \
                        pr_notice("Further such events for this erase block will not be printed\n"); \
        }                                                               \
} while (0)

static uint32_t pseudo_random;

static int jffs2_scan_eraseblock (struct jffs2_sb_info *c, struct jffs2_eraseblock *jeb,
                                  unsigned char *buf, uint32_t buf_size, struct jffs2_summary *s);

/* These helper functions _must_ increase ofs and also do the dirty/used space accounting.
 * Returning an error will abort the mount - bad checksums etc. should just mark the space
 * as dirty.
 */
static int jffs2_scan_inode_node(struct jffs2_sb_info *c, struct jffs2_eraseblock *jeb,
                                 struct jffs2_raw_inode *ri, uint32_t ofs, struct jffs2_summary *s);
static int jffs2_scan_dirent_node(struct jffs2_sb_info *c, struct jffs2_eraseblock *jeb,
                                 struct jffs2_raw_dirent *rd, uint32_t ofs, struct jffs2_summary *s);

static inline int min_free(struct jffs2_sb_info *c)
{
        uint32_t min = 2 * sizeof(struct jffs2_raw_inode);
#ifdef CONFIG_JFFS2_FS_WRITEBUFFER
        if (!jffs2_can_mark_obsolete(c) && min < c->wbuf_pagesize)
                return c->wbuf_pagesize;
#endif
        return min;

}

static inline uint32_t EMPTY_SCAN_SIZE(uint32_t sector_size) {
        if (sector_size < DEFAULT_EMPTY_SCAN_SIZE)
                return sector_size;
        else
                return DEFAULT_EMPTY_SCAN_SIZE;
}

static int file_dirty(struct jffs2_sb_info *c, struct jffs2_eraseblock *jeb)
{
        int ret;

        if ((ret = jffs2_prealloc_raw_node_refs(c, jeb, 1)))
                return ret;
        if ((ret = jffs2_scan_dirty_space(c, jeb, jeb->free_size)))
                return ret;
        /* Turned wasted size into dirty, since we apparently 
           think it's recoverable now. */
        jeb->dirty_size += jeb->wasted_size;
        c->dirty_size += jeb->wasted_size;
        c->wasted_size -= jeb->wasted_size;
        jeb->wasted_size = 0;
        if (VERYDIRTY(c, jeb->dirty_size)) {
                list_add(&jeb->list, &c->very_dirty_list);
        } else {
                list_add(&jeb->list, &c->dirty_list);
        }
        return 0;
}

int jffs2_scan_medium(struct jffs2_sb_info *c)
{
        int i, ret;
        uint32_t empty_blocks = 0, bad_blocks = 0;
        unsigned char *flashbuf = NULL;
        uint32_t buf_size = 0;
        struct jffs2_summary *s = NULL; /* summary info collected by the scan process */
#ifndef __ECOS
        size_t pointlen, try_size;

        ret = mtd_point(c->mtd, 0, c->mtd->size, &pointlen,
                        (void **)&flashbuf, NULL);
        if (!ret && pointlen < c->mtd->size) {
                /* Don't muck about if it won't let us point to the whole flash */
                jffs2_dbg(1, "MTD point returned len too short: 0x%zx\n",
                          pointlen);
                mtd_unpoint(c->mtd, 0, pointlen);
                flashbuf = NULL;
        }
        if (ret && ret != -EOPNOTSUPP)
                jffs2_dbg(1, "MTD point failed %d\n", ret);
#endif
        if (!flashbuf) {
                /* For NAND it's quicker to read a whole eraseblock at a time,
                   apparently */
                if (jffs2_cleanmarker_oob(c))
                        try_size = c->sector_size;
                else
                        try_size = PAGE_SIZE;

                jffs2_dbg(1, "Trying to allocate readbuf of %zu "
                          "bytes\n", try_size);

                flashbuf = mtd_kmalloc_up_to(c->mtd, &try_size);
                if (!flashbuf)
                        return -ENOMEM;

                jffs2_dbg(1, "Allocated readbuf of %zu bytes\n",
                          try_size);

                buf_size = (uint32_t)try_size;
        }

        if (jffs2_sum_active()) {
                s = kzalloc(sizeof(struct jffs2_summary), GFP_KERNEL);
                if (!s) {
                        JFFS2_WARNING("Can't allocate memory for summary\n");
                        ret = -ENOMEM;
                        goto out;
                }
        }

        for (i=0; i<c->nr_blocks; i++) {
                struct jffs2_eraseblock *jeb = &c->blocks[i];

                cond_resched();

                /* reset summary info for next eraseblock scan */
                jffs2_sum_reset_collected(s);

                ret = jffs2_scan_eraseblock(c, jeb, buf_size?flashbuf:(flashbuf+jeb->offset),
                                                buf_size, s);

                if (ret < 0)
                        goto out;

                jffs2_dbg_acct_paranoia_check_nolock(c, jeb);

                /* Now decide which list to put it on */
                switch(ret) {
                case BLK_STATE_ALLFF:
                        /*
                         * Empty block.   Since we can't be sure it
                         * was entirely erased, we just queue it for erase
                         * again.  It will be marked as such when the erase
                         * is complete.  Meanwhile we still count it as empty
                         * for later checks.
                         */
                        empty_blocks++;
                        list_add(&jeb->list, &c->erase_pending_list);
                        c->nr_erasing_blocks++;
                        break;

                case BLK_STATE_CLEANMARKER:
                        /* Only a CLEANMARKER node is valid */
                        if (!jeb->dirty_size) {
                                /* It's actually free */
                                list_add(&jeb->list, &c->free_list);
                                c->nr_free_blocks++;
                        } else {
                                /* Dirt */
                                jffs2_dbg(1, "Adding all-dirty block at 0x%08x to erase_pending_list\n",
                                          jeb->offset);
                                list_add(&jeb->list, &c->erase_pending_list);
                                c->nr_erasing_blocks++;
                        }
                        break;

                case BLK_STATE_CLEAN:
                        /* Full (or almost full) of clean data. Clean list */
                        list_add(&jeb->list, &c->clean_list);
                        break;

                case BLK_STATE_PARTDIRTY:
                        /* Some data, but not full. Dirty list. */
                        /* We want to remember the block with most free space
                        and stick it in the 'nextblock' position to start writing to it. */
                        if (jeb->free_size > min_free(c) &&
                                        (!c->nextblock || c->nextblock->free_size < jeb->free_size)) {
                                /* Better candidate for the next writes to go to */
                                if (c->nextblock) {
                                        ret = file_dirty(c, c->nextblock);
                                        if (ret)
                                                goto out;
                                        /* deleting summary information of the old nextblock */
                                        jffs2_sum_reset_collected(c->summary);
                                }
                                /* update collected summary information for the current nextblock */
                                jffs2_sum_move_collected(c, s);
                                jffs2_dbg(1, "%s(): new nextblock = 0x%08x\n",
                                          __func__, jeb->offset);
                                c->nextblock = jeb;
                        } else {
                                ret = file_dirty(c, jeb);
                                if (ret)
                                        goto out;
                        }
                        break;

                case BLK_STATE_ALLDIRTY:
                        /* Nothing valid - not even a clean marker. Needs erasing. */
                        /* For now we just put it on the erasing list. We'll start the erases later */
                        jffs2_dbg(1, "Erase block at 0x%08x is not formatted. It will be erased\n",
                                  jeb->offset);
                        list_add(&jeb->list, &c->erase_pending_list);
                        c->nr_erasing_blocks++;
                        break;

                case BLK_STATE_BADBLOCK:
                        jffs2_dbg(1, "Block at 0x%08x is bad\n", jeb->offset);
                        list_add(&jeb->list, &c->bad_list);
                        c->bad_size += c->sector_size;
                        c->free_size -= c->sector_size;
                        bad_blocks++;
                        break;
                default:
                        pr_warn("%s(): unknown block state\n", __func__);
                        BUG();
                }
        }

        /* Nextblock dirty is always seen as wasted, because we cannot recycle it now */
        if (c->nextblock && (c->nextblock->dirty_size)) {
                c->nextblock->wasted_size += c->nextblock->dirty_size;
                c->wasted_size += c->nextblock->dirty_size;
                c->dirty_size -= c->nextblock->dirty_size;
                c->nextblock->dirty_size = 0;
        }
#ifdef CONFIG_JFFS2_FS_WRITEBUFFER
        if (!jffs2_can_mark_obsolete(c) && c->wbuf_pagesize && c->nextblock && (c->nextblock->free_size % c->wbuf_pagesize)) {
                /* If we're going to start writing into a block which already
                   contains data, and the end of the data isn't page-aligned,
                   skip a little and align it. */

                uint32_t skip = c->nextblock->free_size % c->wbuf_pagesize;

                jffs2_dbg(1, "%s(): Skipping %d bytes in nextblock to ensure page alignment\n",
                          __func__, skip);
                jffs2_prealloc_raw_node_refs(c, c->nextblock, 1);
                jffs2_scan_dirty_space(c, c->nextblock, skip);
        }
#endif
        if (c->nr_erasing_blocks) {
                if (!c->used_size && !c->unchecked_size &&
                        ((c->nr_free_blocks+empty_blocks+bad_blocks) != c->nr_blocks || bad_blocks == c->nr_blocks)) {
                        pr_notice("Cowardly refusing to erase blocks on filesystem with no valid JFFS2 nodes\n");
                        pr_notice("empty_blocks %d, bad_blocks %d, c->nr_blocks %d\n",
                                  empty_blocks, bad_blocks, c->nr_blocks);
                        ret = -EIO;
                        goto out;
                }
                spin_lock(&c->erase_completion_lock);
                jffs2_garbage_collect_trigger(c);
                spin_unlock(&c->erase_completion_lock);
        }
        ret = 0;
 out:
        if (buf_size)
                kfree(flashbuf);
#ifndef __ECOS
        else
                mtd_unpoint(c->mtd, 0, c->mtd->size);
#endif
        kfree(s);
        return ret;
}

static int jffs2_fill_scan_buf(struct jffs2_sb_info *c, void *buf,
                               uint32_t ofs, uint32_t len)
{
        int ret;
        size_t retlen;

        ret = jffs2_flash_read(c, ofs, len, &retlen, buf);
        if (ret) {
                jffs2_dbg(1, "mtd->read(0x%x bytes from 0x%x) returned %d\n",
                          len, ofs, ret);
                return ret;
        }
        if (retlen < len) {
                jffs2_dbg(1, "Read at 0x%x gave only 0x%zx bytes\n",
                          ofs, retlen);
                return -EIO;
        }
        return 0;
}

int jffs2_scan_classify_jeb(struct jffs2_sb_info *c, struct jffs2_eraseblock *jeb)
{
        if ((jeb->used_size + jeb->unchecked_size) == PAD(c->cleanmarker_size) && !jeb->dirty_size
            && (!jeb->first_node || !ref_next(jeb->first_node)) )
                return BLK_STATE_CLEANMARKER;

        /* move blocks with max 4 byte dirty space to cleanlist */
        else if (!ISDIRTY(c->sector_size - (jeb->used_size + jeb->unchecked_size))) {
                c->dirty_size -= jeb->dirty_size;
                c->wasted_size += jeb->dirty_size;
                jeb->wasted_size += jeb->dirty_size;
                jeb->dirty_size = 0;
                return BLK_STATE_CLEAN;
        } else if (jeb->used_size || jeb->unchecked_size)
                return BLK_STATE_PARTDIRTY;
        else
                return BLK_STATE_ALLDIRTY;
}

#ifdef CONFIG_JFFS2_FS_XATTR
static int jffs2_scan_xattr_node(struct jffs2_sb_info *c, struct jffs2_eraseblock *jeb,
                                 struct jffs2_raw_xattr *rx, uint32_t ofs,
                                 struct jffs2_summary *s)
{
        struct jffs2_xattr_datum *xd;
        uint32_t xid, version, totlen, crc;
        int err;

        crc = crc32(0, rx, sizeof(struct jffs2_raw_xattr) - 4);
        if (crc != je32_to_cpu(rx->node_crc)) {
                JFFS2_WARNING("node CRC failed at %#08x, read=%#08x, calc=%#08x\n",
                              ofs, je32_to_cpu(rx->node_crc), crc);
                if ((err = jffs2_scan_dirty_space(c, jeb, je32_to_cpu(rx->totlen))))
                        return err;
                return 0;
        }

        xid = je32_to_cpu(rx->xid);
        version = je32_to_cpu(rx->version);

        totlen = PAD(sizeof(struct jffs2_raw_xattr)
                        + rx->name_len + 1 + je16_to_cpu(rx->value_len));
        if (totlen != je32_to_cpu(rx->totlen)) {
                JFFS2_WARNING("node length mismatch at %#08x, read=%u, calc=%u\n",
                              ofs, je32_to_cpu(rx->totlen), totlen);
                if ((err = jffs2_scan_dirty_space(c, jeb, je32_to_cpu(rx->totlen))))
                        return err;
                return 0;
        }

        xd = jffs2_setup_xattr_datum(c, xid, version);
        if (IS_ERR(xd))
                return PTR_ERR(xd);

        if (xd->version > version) {
                struct jffs2_raw_node_ref *raw
                        = jffs2_link_node_ref(c, jeb, ofs | REF_PRISTINE, totlen, NULL);
                raw->next_in_ino = xd->node->next_in_ino;
                xd->node->next_in_ino = raw;
        } else {
                xd->version = version;
                xd->xprefix = rx->xprefix;
                xd->name_len = rx->name_len;
                xd->value_len = je16_to_cpu(rx->value_len);
                xd->data_crc = je32_to_cpu(rx->data_crc);

                jffs2_link_node_ref(c, jeb, ofs | REF_PRISTINE, totlen, (void *)xd);
        }

        if (jffs2_sum_active())
                jffs2_sum_add_xattr_mem(s, rx, ofs - jeb->offset);
        dbg_xattr("scanning xdatum at %#08x (xid=%u, version=%u)\n",
                  ofs, xd->xid, xd->version);
        return 0;
}

static int jffs2_scan_xref_node(struct jffs2_sb_info *c, struct jffs2_eraseblock *jeb,
                                struct jffs2_raw_xref *rr, uint32_t ofs,
                                struct jffs2_summary *s)
{
        struct jffs2_xattr_ref *ref;
        uint32_t crc;
        int err;

        crc = crc32(0, rr, sizeof(*rr) - 4);
        if (crc != je32_to_cpu(rr->node_crc)) {
                JFFS2_WARNING("node CRC failed at %#08x, read=%#08x, calc=%#08x\n",
                              ofs, je32_to_cpu(rr->node_crc), crc);
                if ((err = jffs2_scan_dirty_space(c, jeb, PAD(je32_to_cpu(rr->totlen)))))
                        return err;
                return 0;
        }

        if (PAD(sizeof(struct jffs2_raw_xref)) != je32_to_cpu(rr->totlen)) {
                JFFS2_WARNING("node length mismatch at %#08x, read=%u, calc=%zd\n",
                              ofs, je32_to_cpu(rr->totlen),
                              PAD(sizeof(struct jffs2_raw_xref)));
                if ((err = jffs2_scan_dirty_space(c, jeb, je32_to_cpu(rr->totlen))))
                        return err;
                return 0;
        }

        ref = jffs2_alloc_xattr_ref();
        if (!ref)
                return -ENOMEM;

        /* BEFORE jffs2_build_xattr_subsystem() called, 
         * and AFTER xattr_ref is marked as a dead xref,
         * ref->xid is used to store 32bit xid, xd is not used
         * ref->ino is used to store 32bit inode-number, ic is not used
         * Thoes variables are declared as union, thus using those
         * are exclusive. In a similar way, ref->next is temporarily
         * used to chain all xattr_ref object. It's re-chained to
         * jffs2_inode_cache in jffs2_build_xattr_subsystem() correctly.
         */
        ref->ino = je32_to_cpu(rr->ino);
        ref->xid = je32_to_cpu(rr->xid);
        ref->xseqno = je32_to_cpu(rr->xseqno);
        if (ref->xseqno > c->highest_xseqno)
                c->highest_xseqno = (ref->xseqno & ~XREF_DELETE_MARKER);
        ref->next = c->xref_temp;
        c->xref_temp = ref;

        jffs2_link_node_ref(c, jeb, ofs | REF_PRISTINE, PAD(je32_to_cpu(rr->totlen)), (void *)ref);

        if (jffs2_sum_active())
                jffs2_sum_add_xref_mem(s, rr, ofs - jeb->offset);
        dbg_xattr("scan xref at %#08x (xid=%u, ino=%u)\n",
                  ofs, ref->xid, ref->ino);
        return 0;
}
#endif

/* Called with 'buf_size == 0' if buf is in fact a pointer _directly_ into
   the flash, XIP-style */
static int jffs2_scan_eraseblock (struct jffs2_sb_info *c, struct jffs2_eraseblock *jeb,
                                  unsigned char *buf, uint32_t buf_size, struct jffs2_summary *s) {
        struct jffs2_unknown_node *node;
        struct jffs2_unknown_node crcnode;
        uint32_t ofs, prevofs, max_ofs;
        uint32_t hdr_crc, buf_ofs, buf_len;
        int err;
        int noise = 0;


#ifdef CONFIG_JFFS2_FS_WRITEBUFFER
        int cleanmarkerfound = 0;
#endif

        ofs = jeb->offset;
        prevofs = jeb->offset - 1;

        jffs2_dbg(1, "%s(): Scanning block at 0x%x\n", __func__, ofs);

#ifdef CONFIG_JFFS2_FS_WRITEBUFFER
        if (jffs2_cleanmarker_oob(c)) {
                int ret;

                if (mtd_block_isbad(c->mtd, jeb->offset))
                        return BLK_STATE_BADBLOCK;

                ret = jffs2_check_nand_cleanmarker(c, jeb);
                jffs2_dbg(2, "jffs_check_nand_cleanmarker returned %d\n", ret);

                /* Even if it's not found, we still scan to see
                   if the block is empty. We use this information
                   to decide whether to erase it or not. */
                switch (ret) {
                case 0:         cleanmarkerfound = 1; break;
                case 1:         break;
                default:        return ret;
                }
        }
#endif

        if (jffs2_sum_active()) {
                struct jffs2_sum_marker *sm;
                void *sumptr = NULL;
                uint32_t sumlen;
              
                if (!buf_size) {
                        /* XIP case. Just look, point at the summary if it's there */
                        sm = (void *)buf + c->sector_size - sizeof(*sm);
                        if (je32_to_cpu(sm->magic) == JFFS2_SUM_MAGIC) {
                                sumptr = buf + je32_to_cpu(sm->offset);
                                sumlen = c->sector_size - je32_to_cpu(sm->offset);
                        }
                } else {
                        /* If NAND flash, read a whole page of it. Else just the end */
                        if (c->wbuf_pagesize)
                                buf_len = c->wbuf_pagesize;
                        else
                                buf_len = sizeof(*sm);

                        /* Read as much as we want into the _end_ of the preallocated buffer */
                        err = jffs2_fill_scan_buf(c, buf + buf_size - buf_len, 
                                                  jeb->offset + c->sector_size - buf_len,
                                                  buf_len);                             
                        if (err)
                                return err;

                        sm = (void *)buf + buf_size - sizeof(*sm);
                        if (je32_to_cpu(sm->magic) == JFFS2_SUM_MAGIC) {
                                sumlen = c->sector_size - je32_to_cpu(sm->offset);
                                sumptr = buf + buf_size - sumlen;

                                /* sm->offset maybe wrong but MAGIC maybe right */
                                if (sumlen > c->sector_size)
                                        goto full_scan;

                                /* Now, make sure the summary itself is available */
                                if (sumlen > buf_size) {
                                        /* Need to kmalloc for this. */
                                        sumptr = kmalloc(sumlen, GFP_KERNEL);
                                        if (!sumptr)
                                                return -ENOMEM;
                                        memcpy(sumptr + sumlen - buf_len, buf + buf_size - buf_len, buf_len);
                                }
                                if (buf_len < sumlen) {
                                        /* Need to read more so that the entire summary node is present */
                                        err = jffs2_fill_scan_buf(c, sumptr, 
                                                                  jeb->offset + c->sector_size - sumlen,
                                                                  sumlen - buf_len);                            
                                        if (err) {
                                                if (sumlen > buf_size)
                                                        kfree(sumptr);
                                                return err;
                                        }
                                }
                        }

                }

                if (sumptr) {
                        err = jffs2_sum_scan_sumnode(c, jeb, sumptr, sumlen, &pseudo_random);

                        if (buf_size && sumlen > buf_size)
                                kfree(sumptr);
                        /* If it returns with a real error, bail. 
                           If it returns positive, that's a block classification
                           (i.e. BLK_STATE_xxx) so return that too.
                           If it returns zero, fall through to full scan. */
                        if (err)
                                return err;
                }
        }

full_scan:
        buf_ofs = jeb->offset;

        if (!buf_size) {
                /* This is the XIP case -- we're reading _directly_ from the flash chip */
                buf_len = c->sector_size;
        } else {
                buf_len = EMPTY_SCAN_SIZE(c->sector_size);
                err = jffs2_fill_scan_buf(c, buf, buf_ofs, buf_len);
                if (err)
                        return err;
        }

        /* We temporarily use 'ofs' as a pointer into the buffer/jeb */
        ofs = 0;
        max_ofs = EMPTY_SCAN_SIZE(c->sector_size);
        /* Scan only EMPTY_SCAN_SIZE of 0xFF before declaring it's empty */
        while(ofs < max_ofs && *(uint32_t *)(&buf[ofs]) == 0xFFFFFFFF)
                ofs += 4;

        if (ofs == max_ofs) {
#ifdef CONFIG_JFFS2_FS_WRITEBUFFER
                if (jffs2_cleanmarker_oob(c)) {
                        /* scan oob, take care of cleanmarker */
                        int ret = jffs2_check_oob_empty(c, jeb, cleanmarkerfound);
                        jffs2_dbg(2, "jffs2_check_oob_empty returned %d\n",
                                  ret);
                        switch (ret) {
                        case 0:         return cleanmarkerfound ? BLK_STATE_CLEANMARKER : BLK_STATE_ALLFF;
                        case 1:         return BLK_STATE_ALLDIRTY;
                        default:        return ret;
                        }
                }
#endif
                jffs2_dbg(1, "Block at 0x%08x is empty (erased)\n",
                          jeb->offset);
                if (c->cleanmarker_size == 0)
                        return BLK_STATE_CLEANMARKER;   /* don't bother with re-erase */
                else
                        return BLK_STATE_ALLFF; /* OK to erase if all blocks are like this */
        }
        if (ofs) {
                jffs2_dbg(1, "Free space at %08x ends at %08x\n", jeb->offset,
                          jeb->offset + ofs);
                if ((err = jffs2_prealloc_raw_node_refs(c, jeb, 1)))
                        return err;
                if ((err = jffs2_scan_dirty_space(c, jeb, ofs)))
                        return err;
        }

        /* Now ofs is a complete physical flash offset as it always was... */
        ofs += jeb->offset;

        noise = 10;

        dbg_summary("no summary found in jeb 0x%08x. Apply original scan.\n",jeb->offset);

scan_more:
        while(ofs < jeb->offset + c->sector_size) {

                jffs2_dbg_acct_paranoia_check_nolock(c, jeb);

                /* Make sure there are node refs available for use */
                err = jffs2_prealloc_raw_node_refs(c, jeb, 2);
                if (err)
                        return err;

                cond_resched();

                if (ofs & 3) {
                        pr_warn("Eep. ofs 0x%08x not word-aligned!\n", ofs);
                        ofs = PAD(ofs);
                        continue;
                }
                if (ofs == prevofs) {
                        pr_warn("ofs 0x%08x has already been seen. Skipping\n",
                                ofs);
                        if ((err = jffs2_scan_dirty_space(c, jeb, 4)))
                                return err;
                        ofs += 4;
                        continue;
                }
                prevofs = ofs;

                if (jeb->offset + c->sector_size < ofs + sizeof(*node)) {
                        jffs2_dbg(1, "Fewer than %zd bytes left to end of block. (%x+%x<%x+%zx) Not reading\n",
                                  sizeof(struct jffs2_unknown_node),
                                  jeb->offset, c->sector_size, ofs,
                                  sizeof(*node));
                        if ((err = jffs2_scan_dirty_space(c, jeb, (jeb->offset + c->sector_size)-ofs)))
                                return err;
                        break;
                }

                if (buf_ofs + buf_len < ofs + sizeof(*node)) {
                        buf_len = min_t(uint32_t, buf_size, jeb->offset + c->sector_size - ofs);
                        jffs2_dbg(1, "Fewer than %zd bytes (node header) left to end of buf. Reading 0x%x at 0x%08x\n",
                                  sizeof(struct jffs2_unknown_node),
                                  buf_len, ofs);
                        err = jffs2_fill_scan_buf(c, buf, ofs, buf_len);
                        if (err)
                                return err;
                        buf_ofs = ofs;
                }

                node = (struct jffs2_unknown_node *)&buf[ofs-buf_ofs];

                if (*(uint32_t *)(&buf[ofs-buf_ofs]) == 0xffffffff) {
                        uint32_t inbuf_ofs;
                        uint32_t empty_start, scan_end;

                        empty_start = ofs;
                        ofs += 4;
                        scan_end = min_t(uint32_t, EMPTY_SCAN_SIZE(c->sector_size)/8, buf_len);

                        jffs2_dbg(1, "Found empty flash at 0x%08x\n", ofs);
                more_empty:
                        inbuf_ofs = ofs - buf_ofs;
                        while (inbuf_ofs < scan_end) {
                                if (unlikely(*(uint32_t *)(&buf[inbuf_ofs]) != 0xffffffff)) {
                                        pr_warn("Empty flash at 0x%08x ends at 0x%08x\n",
                                                empty_start, ofs);
                                        if ((err = jffs2_scan_dirty_space(c, jeb, ofs-empty_start)))
                                                return err;
                                        goto scan_more;
                                }

                                inbuf_ofs+=4;
                                ofs += 4;
                        }
                        /* Ran off end. */
                        jffs2_dbg(1, "Empty flash to end of buffer at 0x%08x\n",
                                  ofs);

                        /* If we're only checking the beginning of a block with a cleanmarker,
                           bail now */
                        if (buf_ofs == jeb->offset && jeb->used_size == PAD(c->cleanmarker_size) &&
                            c->cleanmarker_size && !jeb->dirty_size && !ref_next(jeb->first_node)) {
                                jffs2_dbg(1, "%d bytes at start of block seems clean... assuming all clean\n",
                                          EMPTY_SCAN_SIZE(c->sector_size));
                                return BLK_STATE_CLEANMARKER;
                        }
                        if (!buf_size && (scan_end != buf_len)) {/* XIP/point case */
                                scan_end = buf_len;
                                goto more_empty;
                        }
                        
                        /* See how much more there is to read in this eraseblock... */
                        buf_len = min_t(uint32_t, buf_size, jeb->offset + c->sector_size - ofs);
                        if (!buf_len) {
                                /* No more to read. Break out of main loop without marking
                                   this range of empty space as dirty (because it's not) */
                                jffs2_dbg(1, "Empty flash at %08x runs to end of block. Treating as free_space\n",
                                          empty_start);
                                break;
                        }
                        /* point never reaches here */
                        scan_end = buf_len;
                        jffs2_dbg(1, "Reading another 0x%x at 0x%08x\n",
                                  buf_len, ofs);
                        err = jffs2_fill_scan_buf(c, buf, ofs, buf_len);
                        if (err)
                                return err;
                        buf_ofs = ofs;
                        goto more_empty;
                }

                if (ofs == jeb->offset && je16_to_cpu(node->magic) == KSAMTIB_CIGAM_2SFFJ) {
                        pr_warn("Magic bitmask is backwards at offset 0x%08x. Wrong endian filesystem?\n",
                                ofs);
                        if ((err = jffs2_scan_dirty_space(c, jeb, 4)))
                                return err;
                        ofs += 4;
                        continue;
                }
                if (je16_to_cpu(node->magic) == JFFS2_DIRTY_BITMASK) {
                        jffs2_dbg(1, "Dirty bitmask at 0x%08x\n", ofs);
                        if ((err = jffs2_scan_dirty_space(c, jeb, 4)))
                                return err;
                        ofs += 4;
                        continue;
                }
                if (je16_to_cpu(node->magic) == JFFS2_OLD_MAGIC_BITMASK) {
                        pr_warn("Old JFFS2 bitmask found at 0x%08x\n", ofs);
                        pr_warn("You cannot use older JFFS2 filesystems with newer kernels\n");
                        if ((err = jffs2_scan_dirty_space(c, jeb, 4)))
                                return err;
                        ofs += 4;
                        continue;
                }
                if (je16_to_cpu(node->magic) != JFFS2_MAGIC_BITMASK) {
                        /* OK. We're out of possibilities. Whinge and move on */
                        noisy_printk(&noise, "%s(): Magic bitmask 0x%04x not found at 0x%08x: 0x%04x instead\n",
                                     __func__,
                                     JFFS2_MAGIC_BITMASK, ofs,
                                     je16_to_cpu(node->magic));
                        if ((err = jffs2_scan_dirty_space(c, jeb, 4)))
                                return err;
                        ofs += 4;
                        continue;
                }
                /* We seem to have a node of sorts. Check the CRC */
                crcnode.magic = node->magic;
                crcnode.nodetype = cpu_to_je16( je16_to_cpu(node->nodetype) | JFFS2_NODE_ACCURATE);
                crcnode.totlen = node->totlen;
                hdr_crc = crc32(0, &crcnode, sizeof(crcnode)-4);

                if (hdr_crc != je32_to_cpu(node->hdr_crc)) {
                        noisy_printk(&noise, "%s(): Node at 0x%08x {0x%04x, 0x%04x, 0x%08x) has invalid CRC 0x%08x (calculated 0x%08x)\n",
                                     __func__,
                                     ofs, je16_to_cpu(node->magic),
                                     je16_to_cpu(node->nodetype),
                                     je32_to_cpu(node->totlen),
                                     je32_to_cpu(node->hdr_crc),
                                     hdr_crc);
                        if ((err = jffs2_scan_dirty_space(c, jeb, 4)))
                                return err;
                        ofs += 4;
                        continue;
                }

                if (ofs + je32_to_cpu(node->totlen) > jeb->offset + c->sector_size) {
                        /* Eep. Node goes over the end of the erase block. */
                        pr_warn("Node at 0x%08x with length 0x%08x would run over the end of the erase block\n",
                                ofs, je32_to_cpu(node->totlen));
                        pr_warn("Perhaps the file system was created with the wrong erase size?\n");
                        if ((err = jffs2_scan_dirty_space(c, jeb, 4)))
                                return err;
                        ofs += 4;
                        continue;
                }

                if (!(je16_to_cpu(node->nodetype) & JFFS2_NODE_ACCURATE)) {
                        /* Wheee. This is an obsoleted node */
                        jffs2_dbg(2, "Node at 0x%08x is obsolete. Skipping\n",
                                  ofs);
                        if ((err = jffs2_scan_dirty_space(c, jeb, PAD(je32_to_cpu(node->totlen)))))
                                return err;
                        ofs += PAD(je32_to_cpu(node->totlen));
                        continue;
                }

                switch(je16_to_cpu(node->nodetype)) {
                case JFFS2_NODETYPE_INODE:
                        if (buf_ofs + buf_len < ofs + sizeof(struct jffs2_raw_inode)) {
                                buf_len = min_t(uint32_t, buf_size, jeb->offset + c->sector_size - ofs);
                                jffs2_dbg(1, "Fewer than %zd bytes (inode node) left to end of buf. Reading 0x%x at 0x%08x\n",
                                          sizeof(struct jffs2_raw_inode),
                                          buf_len, ofs);
                                err = jffs2_fill_scan_buf(c, buf, ofs, buf_len);
                                if (err)
                                        return err;
                                buf_ofs = ofs;
                                node = (void *)buf;
                        }
                        err = jffs2_scan_inode_node(c, jeb, (void *)node, ofs, s);
                        if (err) return err;
                        ofs += PAD(je32_to_cpu(node->totlen));
                        break;

                case JFFS2_NODETYPE_DIRENT:
                        if (buf_ofs + buf_len < ofs + je32_to_cpu(node->totlen)) {
                                buf_len = min_t(uint32_t, buf_size, jeb->offset + c->sector_size - ofs);
                                jffs2_dbg(1, "Fewer than %d bytes (dirent node) left to end of buf. Reading 0x%x at 0x%08x\n",
                                          je32_to_cpu(node->totlen), buf_len,
                                          ofs);
                                err = jffs2_fill_scan_buf(c, buf, ofs, buf_len);
                                if (err)
                                        return err;
                                buf_ofs = ofs;
                                node = (void *)buf;
                        }
                        err = jffs2_scan_dirent_node(c, jeb, (void *)node, ofs, s);
                        if (err) return err;
                        ofs += PAD(je32_to_cpu(node->totlen));
                        break;

#ifdef CONFIG_JFFS2_FS_XATTR
                case JFFS2_NODETYPE_XATTR:
                        if (buf_ofs + buf_len < ofs + je32_to_cpu(node->totlen)) {
                                buf_len = min_t(uint32_t, buf_size, jeb->offset + c->sector_size - ofs);
                                jffs2_dbg(1, "Fewer than %d bytes (xattr node) left to end of buf. Reading 0x%x at 0x%08x\n",
                                          je32_to_cpu(node->totlen), buf_len,
                                          ofs);
                                err = jffs2_fill_scan_buf(c, buf, ofs, buf_len);
                                if (err)
                                        return err;
                                buf_ofs = ofs;
                                node = (void *)buf;
                        }
                        err = jffs2_scan_xattr_node(c, jeb, (void *)node, ofs, s);
                        if (err)
                                return err;
                        ofs += PAD(je32_to_cpu(node->totlen));
                        break;
                case JFFS2_NODETYPE_XREF:
                        if (buf_ofs + buf_len < ofs + je32_to_cpu(node->totlen)) {
                                buf_len = min_t(uint32_t, buf_size, jeb->offset + c->sector_size - ofs);
                                jffs2_dbg(1, "Fewer than %d bytes (xref node) left to end of buf. Reading 0x%x at 0x%08x\n",
                                          je32_to_cpu(node->totlen), buf_len,
                                          ofs);
                                err = jffs2_fill_scan_buf(c, buf, ofs, buf_len);
                                if (err)
                                        return err;
                                buf_ofs = ofs;
                                node = (void *)buf;
                        }
                        err = jffs2_scan_xref_node(c, jeb, (void *)node, ofs, s);
                        if (err)
                                return err;
                        ofs += PAD(je32_to_cpu(node->totlen));
                        break;
#endif  /* CONFIG_JFFS2_FS_XATTR */

                case JFFS2_NODETYPE_CLEANMARKER:
                        jffs2_dbg(1, "CLEANMARKER node found at 0x%08x\n", ofs);
                        if (je32_to_cpu(node->totlen) != c->cleanmarker_size) {
                                pr_notice("CLEANMARKER node found at 0x%08x has totlen 0x%x != normal 0x%x\n",
                                          ofs, je32_to_cpu(node->totlen),
                                          c->cleanmarker_size);
                                if ((err = jffs2_scan_dirty_space(c, jeb, PAD(sizeof(struct jffs2_unknown_node)))))
                                        return err;
                                ofs += PAD(sizeof(struct jffs2_unknown_node));
                        } else if (jeb->first_node) {
                                pr_notice("CLEANMARKER node found at 0x%08x, not first node in block (0x%08x)\n",
                                          ofs, jeb->offset);
                                if ((err = jffs2_scan_dirty_space(c, jeb, PAD(sizeof(struct jffs2_unknown_node)))))
                                        return err;
                                ofs += PAD(sizeof(struct jffs2_unknown_node));
                        } else {
                                jffs2_link_node_ref(c, jeb, ofs | REF_NORMAL, c->cleanmarker_size, NULL);

                                ofs += PAD(c->cleanmarker_size);
                        }
                        break;

                case JFFS2_NODETYPE_PADDING:
                        if (jffs2_sum_active())
                                jffs2_sum_add_padding_mem(s, je32_to_cpu(node->totlen));
                        if ((err = jffs2_scan_dirty_space(c, jeb, PAD(je32_to_cpu(node->totlen)))))
                                return err;
                        ofs += PAD(je32_to_cpu(node->totlen));
                        break;

                default:
                        switch (je16_to_cpu(node->nodetype) & JFFS2_COMPAT_MASK) {
                        case JFFS2_FEATURE_ROCOMPAT:
                                pr_notice("Read-only compatible feature node (0x%04x) found at offset 0x%08x\n",
                                          je16_to_cpu(node->nodetype), ofs);
                                c->flags |= JFFS2_SB_FLAG_RO;
                                if (!(jffs2_is_readonly(c)))
                                        return -EROFS;
                                if ((err = jffs2_scan_dirty_space(c, jeb, PAD(je32_to_cpu(node->totlen)))))
                                        return err;
                                ofs += PAD(je32_to_cpu(node->totlen));
                                break;

                        case JFFS2_FEATURE_INCOMPAT:
                                pr_notice("Incompatible feature node (0x%04x) found at offset 0x%08x\n",
                                          je16_to_cpu(node->nodetype), ofs);
                                return -EINVAL;

                        case JFFS2_FEATURE_RWCOMPAT_DELETE:
                                jffs2_dbg(1, "Unknown but compatible feature node (0x%04x) found at offset 0x%08x\n",
                                          je16_to_cpu(node->nodetype), ofs);
                                if ((err = jffs2_scan_dirty_space(c, jeb, PAD(je32_to_cpu(node->totlen)))))
                                        return err;
                                ofs += PAD(je32_to_cpu(node->totlen));
                                break;

                        case JFFS2_FEATURE_RWCOMPAT_COPY: {
                                jffs2_dbg(1, "Unknown but compatible feature node (0x%04x) found at offset 0x%08x\n",
                                          je16_to_cpu(node->nodetype), ofs);

                                jffs2_link_node_ref(c, jeb, ofs | REF_PRISTINE, PAD(je32_to_cpu(node->totlen)), NULL);

                                /* We can't summarise nodes we don't grok */
                                jffs2_sum_disable_collecting(s);
                                ofs += PAD(je32_to_cpu(node->totlen));
                                break;
                                }
                        }
                }
        }

        if (jffs2_sum_active()) {
                if (PAD(s->sum_size + JFFS2_SUMMARY_FRAME_SIZE) > jeb->free_size) {
                        dbg_summary("There is not enough space for "
                                "summary information, disabling for this jeb!\n");
                        jffs2_sum_disable_collecting(s);
                }
        }

        jffs2_dbg(1, "Block at 0x%08x: free 0x%08x, dirty 0x%08x, unchecked 0x%08x, used 0x%08x, wasted 0x%08x\n",
                  jeb->offset, jeb->free_size, jeb->dirty_size,
                  jeb->unchecked_size, jeb->used_size, jeb->wasted_size);
        
        /* mark_node_obsolete can add to wasted !! */
        if (jeb->wasted_size) {
                jeb->dirty_size += jeb->wasted_size;
                c->dirty_size += jeb->wasted_size;
                c->wasted_size -= jeb->wasted_size;
                jeb->wasted_size = 0;
        }

        return jffs2_scan_classify_jeb(c, jeb);
}

struct jffs2_inode_cache *jffs2_scan_make_ino_cache(struct jffs2_sb_info *c, uint32_t ino)
{
        struct jffs2_inode_cache *ic;

        ic = jffs2_get_ino_cache(c, ino);
        if (ic)
                return ic;

        if (ino > c->highest_ino)
                c->highest_ino = ino;

        ic = jffs2_alloc_inode_cache();
        if (!ic) {
                pr_notice("%s(): allocation of inode cache failed\n", __func__);
                return NULL;
        }
        memset(ic, 0, sizeof(*ic));

        ic->ino = ino;
        ic->nodes = (void *)ic;
        jffs2_add_ino_cache(c, ic);
        if (ino == 1)
                ic->pino_nlink = 1;
        return ic;
}

static int jffs2_scan_inode_node(struct jffs2_sb_info *c, struct jffs2_eraseblock *jeb,
                                 struct jffs2_raw_inode *ri, uint32_t ofs, struct jffs2_summary *s)
{
        struct jffs2_inode_cache *ic;
        uint32_t crc, ino = je32_to_cpu(ri->ino);

        jffs2_dbg(1, "%s(): Node at 0x%08x\n", __func__, ofs);

        /* We do very little here now. Just check the ino# to which we should attribute
           this node; we can do all the CRC checking etc. later. There's a tradeoff here --
           we used to scan the flash once only, reading everything we want from it into
           memory, then building all our in-core data structures and freeing the extra

           information. Now we allow the first part of the mount to complete a lot quicker,
           but we have to go _back_ to the flash in order to finish the CRC checking, etc.
           Which means that the _full_ amount of time to get to proper write mode with GC
           operational may actually be _longer_ than before. Sucks to be me. */

        /* Check the node CRC in any case. */
        crc = crc32(0, ri, sizeof(*ri)-8);
        if (crc != je32_to_cpu(ri->node_crc)) {
                pr_notice("%s(): CRC failed on node at 0x%08x: Read 0x%08x, calculated 0x%08x\n",
                          __func__, ofs, je32_to_cpu(ri->node_crc), crc);
                /*
                 * We believe totlen because the CRC on the node
                 * _header_ was OK, just the node itself failed.
                 */
                return jffs2_scan_dirty_space(c, jeb,
                                              PAD(je32_to_cpu(ri->totlen)));
        }

        ic = jffs2_get_ino_cache(c, ino);
        if (!ic) {
                ic = jffs2_scan_make_ino_cache(c, ino);
                if (!ic)
                        return -ENOMEM;
        }

        /* Wheee. It worked */
        jffs2_link_node_ref(c, jeb, ofs | REF_UNCHECKED, PAD(je32_to_cpu(ri->totlen)), ic);

        jffs2_dbg(1, "Node is ino #%u, version %d. Range 0x%x-0x%x\n",
                  je32_to_cpu(ri->ino), je32_to_cpu(ri->version),
                  je32_to_cpu(ri->offset),
                  je32_to_cpu(ri->offset)+je32_to_cpu(ri->dsize));

        pseudo_random += je32_to_cpu(ri->version);

        if (jffs2_sum_active()) {
                jffs2_sum_add_inode_mem(s, ri, ofs - jeb->offset);
        }

        return 0;
}

static int jffs2_scan_dirent_node(struct jffs2_sb_info *c, struct jffs2_eraseblock *jeb,
                                  struct jffs2_raw_dirent *rd, uint32_t ofs, struct jffs2_summary *s)
{
        struct jffs2_full_dirent *fd;
        struct jffs2_inode_cache *ic;
        uint32_t checkedlen;
        uint32_t crc;
        int err;

        jffs2_dbg(1, "%s(): Node at 0x%08x\n", __func__, ofs);

        /* We don't get here unless the node is still valid, so we don't have to
           mask in the ACCURATE bit any more. */
        crc = crc32(0, rd, sizeof(*rd)-8);

        if (crc != je32_to_cpu(rd->node_crc)) {
                pr_notice("%s(): Node CRC failed on node at 0x%08x: Read 0x%08x, calculated 0x%08x\n",
                          __func__, ofs, je32_to_cpu(rd->node_crc), crc);
                /* We believe totlen because the CRC on the node _header_ was OK, just the node itself failed. */
                if ((err = jffs2_scan_dirty_space(c, jeb, PAD(je32_to_cpu(rd->totlen)))))
                        return err;
                return 0;
        }

        pseudo_random += je32_to_cpu(rd->version);

        /* Should never happen. Did. (OLPC trac #4184)*/
        checkedlen = strnlen(rd->name, rd->nsize);
        if (checkedlen < rd->nsize) {
                pr_err("Dirent at %08x has zeroes in name. Truncating to %d chars\n",
                       ofs, checkedlen);
        }
        fd = jffs2_alloc_full_dirent(checkedlen+1);
        if (!fd) {
                return -ENOMEM;
        }
        memcpy(&fd->name, rd->name, checkedlen);
        fd->name[checkedlen] = 0;

        crc = crc32(0, fd->name, checkedlen);
        if (crc != je32_to_cpu(rd->name_crc)) {
                pr_notice("%s(): Name CRC failed on node at 0x%08x: Read 0x%08x, calculated 0x%08x\n",
                          __func__, ofs, je32_to_cpu(rd->name_crc), crc);
                jffs2_dbg(1, "Name for which CRC failed is (now) '%s', ino #%d\n",
                          fd->name, je32_to_cpu(rd->ino));
                jffs2_free_full_dirent(fd);
                /* FIXME: Why do we believe totlen? */
                /* We believe totlen because the CRC on the node _header_ was OK, just the name failed. */
                if ((err = jffs2_scan_dirty_space(c, jeb, PAD(je32_to_cpu(rd->totlen)))))
                        return err;
                return 0;
        }
        ic = jffs2_scan_make_ino_cache(c, je32_to_cpu(rd->pino));
        if (!ic) {
                jffs2_free_full_dirent(fd);
                return -ENOMEM;
        }

        fd->raw = jffs2_link_node_ref(c, jeb, ofs | dirent_node_state(rd),
                                      PAD(je32_to_cpu(rd->totlen)), ic);

        fd->next = NULL;
        fd->version = je32_to_cpu(rd->version);
        fd->ino = je32_to_cpu(rd->ino);
        fd->nhash = full_name_hash(NULL, fd->name, checkedlen);
        fd->type = rd->type;
        jffs2_add_fd_to_list(c, fd, &ic->scan_dents);

        if (jffs2_sum_active()) {
                jffs2_sum_add_dirent_mem(s, rd, ofs - jeb->offset);
        }

        return 0;
}

static int count_list(struct list_head *l)
{
        uint32_t count = 0;
        struct list_head *tmp;

        list_for_each(tmp, l) {
                count++;
        }
        return count;
}

/* Note: This breaks if list_empty(head). I don't care. You
   might, if you copy this code and use it elsewhere :) */
static void rotate_list(struct list_head *head, uint32_t count)
{
        struct list_head *n = head->next;

        list_del(head);
        while(count--) {
                n = n->next;
        }
        list_add(head, n);
}

void jffs2_rotate_lists(struct jffs2_sb_info *c)
{
        uint32_t x;
        uint32_t rotateby;

        x = count_list(&c->clean_list);
        if (x) {
                rotateby = pseudo_random % x;
                rotate_list((&c->clean_list), rotateby);
        }

        x = count_list(&c->very_dirty_list);
        if (x) {
                rotateby = pseudo_random % x;
                rotate_list((&c->very_dirty_list), rotateby);
        }

        x = count_list(&c->dirty_list);
        if (x) {
                rotateby = pseudo_random % x;
                rotate_list((&c->dirty_list), rotateby);
        }

        x = count_list(&c->erasable_list);
        if (x) {
                rotateby = pseudo_random % x;
                rotate_list((&c->erasable_list), rotateby);
        }

        if (c->nr_erasing_blocks) {
                rotateby = pseudo_random % c->nr_erasing_blocks;
                rotate_list((&c->erase_pending_list), rotateby);
        }

        if (c->nr_free_blocks) {
                rotateby = pseudo_random % c->nr_free_blocks;
                rotate_list((&c->free_list), rotateby);
        }
}