/*
 * 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/sched.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/mtd/mtd.h>
#include <linux/mm.h> /* kvfree() */
#include "nodelist.h"

static void jffs2_build_remove_unlinked_inode(struct jffs2_sb_info *,
                struct jffs2_inode_cache *, struct jffs2_full_dirent **);

static inline struct jffs2_inode_cache *
first_inode_chain(int *i, struct jffs2_sb_info *c)
{
        for (; *i < c->inocache_hashsize; (*i)++) {
                if (c->inocache_list[*i])
                        return c->inocache_list[*i];
        }
        return NULL;
}

static inline struct jffs2_inode_cache *
next_inode(int *i, struct jffs2_inode_cache *ic, struct jffs2_sb_info *c)
{
        /* More in this chain? */
        if (ic->next)
                return ic->next;
        (*i)++;
        return first_inode_chain(i, c);
}

#define for_each_inode(i, c, ic)                        \
        for (i = 0, ic = first_inode_chain(&i, (c));    \
             ic;                                        \
             ic = next_inode(&i, ic, (c)))


static void jffs2_build_inode_pass1(struct jffs2_sb_info *c,
                                    struct jffs2_inode_cache *ic,
                                    int *dir_hardlinks)
{
        struct jffs2_full_dirent *fd;

        dbg_fsbuild("building directory inode #%u\n", ic->ino);

        /* For each child, increase nlink */
        for(fd = ic->scan_dents; fd; fd = fd->next) {
                struct jffs2_inode_cache *child_ic;
                if (!fd->ino)
                        continue;

                /* we can get high latency here with huge directories */

                child_ic = jffs2_get_ino_cache(c, fd->ino);
                if (!child_ic) {
                        dbg_fsbuild("child \"%s\" (ino #%u) of dir ino #%u doesn't exist!\n",
                                  fd->name, fd->ino, ic->ino);
                        jffs2_mark_node_obsolete(c, fd->raw);
                        /* Clear the ic/raw union so it doesn't cause problems later. */
                        fd->ic = NULL;
                        continue;
                }

                /* From this point, fd->raw is no longer used so we can set fd->ic */
                fd->ic = child_ic;
                child_ic->pino_nlink++;
                /* If we appear (at this stage) to have hard-linked directories,
                 * set a flag to trigger a scan later */
                if (fd->type == DT_DIR) {
                        child_ic->flags |= INO_FLAGS_IS_DIR;
                        if (child_ic->pino_nlink > 1)
                                *dir_hardlinks = 1;
                }

                dbg_fsbuild("increased nlink for child \"%s\" (ino #%u)\n", fd->name, fd->ino);
                /* Can't free scan_dents so far. We might need them in pass 2 */
        }
}

/* Scan plan:
 - Scan physical nodes. Build map of inodes/dirents. Allocate inocaches as we go
 - Scan directory tree from top down, setting nlink in inocaches
 - Scan inocaches for inodes with nlink==0
*/
static int jffs2_build_filesystem(struct jffs2_sb_info *c)
{
        int ret, i, dir_hardlinks = 0;
        struct jffs2_inode_cache *ic;
        struct jffs2_full_dirent *fd;
        struct jffs2_full_dirent *dead_fds = NULL;

        dbg_fsbuild("build FS data structures\n");

        /* First, scan the medium and build all the inode caches with
           lists of physical nodes */

        c->flags |= JFFS2_SB_FLAG_SCANNING;
        ret = jffs2_scan_medium(c);
        c->flags &= ~JFFS2_SB_FLAG_SCANNING;
        if (ret)
                goto exit;

        dbg_fsbuild("scanned flash completely\n");
        jffs2_dbg_dump_block_lists_nolock(c);

        dbg_fsbuild("pass 1 starting\n");
        c->flags |= JFFS2_SB_FLAG_BUILDING;
        /* Now scan the directory tree, increasing nlink according to every dirent found. */
        for_each_inode(i, c, ic) {
                if (ic->scan_dents) {
                        jffs2_build_inode_pass1(c, ic, &dir_hardlinks);
                        cond_resched();
                }
        }

        dbg_fsbuild("pass 1 complete\n");

        /* Next, scan for inodes with nlink == 0 and remove them. If
           they were directories, then decrement the nlink of their
           children too, and repeat the scan. As that's going to be
           a fairly uncommon occurrence, it's not so evil to do it this
           way. Recursion bad. */
        dbg_fsbuild("pass 2 starting\n");

        for_each_inode(i, c, ic) {
                if (ic->pino_nlink)
                        continue;

                jffs2_build_remove_unlinked_inode(c, ic, &dead_fds);
                cond_resched();
        }

        dbg_fsbuild("pass 2a starting\n");

        while (dead_fds) {
                fd = dead_fds;
                dead_fds = fd->next;

                ic = jffs2_get_ino_cache(c, fd->ino);

                if (ic)
                        jffs2_build_remove_unlinked_inode(c, ic, &dead_fds);
                jffs2_free_full_dirent(fd);
        }

        dbg_fsbuild("pass 2a complete\n");

        if (dir_hardlinks) {
                /* If we detected directory hardlinks earlier, *hopefully*
                 * they are gone now because some of the links were from
                 * dead directories which still had some old dirents lying
                 * around and not yet garbage-collected, but which have
                 * been discarded above. So clear the pino_nlink field
                 * in each directory, so that the final scan below can
                 * print appropriate warnings. */
                for_each_inode(i, c, ic) {
                        if (ic->flags & INO_FLAGS_IS_DIR)
                                ic->pino_nlink = 0;
                }
        }
        dbg_fsbuild("freeing temporary data structures\n");

        /* Finally, we can scan again and free the dirent structs */
        for_each_inode(i, c, ic) {
                while(ic->scan_dents) {
                        fd = ic->scan_dents;
                        ic->scan_dents = fd->next;
                        /* We do use the pino_nlink field to count nlink of
                         * directories during fs build, so set it to the
                         * parent ino# now. Now that there's hopefully only
                         * one. */
                        if (fd->type == DT_DIR) {
                                if (!fd->ic) {
                                        /* We'll have complained about it and marked the coresponding
                                           raw node obsolete already. Just skip it. */
                                        continue;
                                }

                                /* We *have* to have set this in jffs2_build_inode_pass1() */
                                BUG_ON(!(fd->ic->flags & INO_FLAGS_IS_DIR));

                                /* We clear ic->pino_nlink ∀ directories' ic *only* if dir_hardlinks
                                 * is set. Otherwise, we know this should never trigger anyway, so
                                 * we don't do the check. And ic->pino_nlink still contains the nlink
                                 * value (which is 1). */
                                if (dir_hardlinks && fd->ic->pino_nlink) {
                                        JFFS2_ERROR("child dir \"%s\" (ino #%u) of dir ino #%u is also hard linked from dir ino #%u\n",
                                                    fd->name, fd->ino, ic->ino, fd->ic->pino_nlink);
                                        /* Should we unlink it from its previous parent? */
                                }

                                /* For directories, ic->pino_nlink holds that parent inode # */
                                fd->ic->pino_nlink = ic->ino;
                        }
                        jffs2_free_full_dirent(fd);
                }
                ic->scan_dents = NULL;
                cond_resched();
        }
        jffs2_build_xattr_subsystem(c);
        c->flags &= ~JFFS2_SB_FLAG_BUILDING;

        dbg_fsbuild("FS build complete\n");

        /* Rotate the lists by some number to ensure wear levelling */
        jffs2_rotate_lists(c);

        ret = 0;

exit:
        if (ret) {
                for_each_inode(i, c, ic) {
                        while(ic->scan_dents) {
                                fd = ic->scan_dents;
                                ic->scan_dents = fd->next;
                                jffs2_free_full_dirent(fd);
                        }
                }
                jffs2_clear_xattr_subsystem(c);
        }

        return ret;
}

static void jffs2_build_remove_unlinked_inode(struct jffs2_sb_info *c,
                                        struct jffs2_inode_cache *ic,
                                        struct jffs2_full_dirent **dead_fds)
{
        struct jffs2_raw_node_ref *raw;
        struct jffs2_full_dirent *fd;

        dbg_fsbuild("removing ino #%u with nlink == zero.\n", ic->ino);

        raw = ic->nodes;
        while (raw != (void *)ic) {
                struct jffs2_raw_node_ref *next = raw->next_in_ino;
                dbg_fsbuild("obsoleting node at 0x%08x\n", ref_offset(raw));
                jffs2_mark_node_obsolete(c, raw);
                raw = next;
        }

        if (ic->scan_dents) {
                int whinged = 0;
                dbg_fsbuild("inode #%u was a directory which may have children...\n", ic->ino);

                while(ic->scan_dents) {
                        struct jffs2_inode_cache *child_ic;

                        fd = ic->scan_dents;
                        ic->scan_dents = fd->next;

                        if (!fd->ino) {
                                /* It's a deletion dirent. Ignore it */
                                dbg_fsbuild("child \"%s\" is a deletion dirent, skipping...\n", fd->name);
                                jffs2_free_full_dirent(fd);
                                continue;
                        }
                        if (!whinged)
                                whinged = 1;

                        dbg_fsbuild("removing child \"%s\", ino #%u\n", fd->name, fd->ino);

                        child_ic = jffs2_get_ino_cache(c, fd->ino);
                        if (!child_ic) {
                                dbg_fsbuild("cannot remove child \"%s\", ino #%u, because it doesn't exist\n",
                                                fd->name, fd->ino);
                                jffs2_free_full_dirent(fd);
                                continue;
                        }

                        /* Reduce nlink of the child. If it's now zero, stick it on the
                           dead_fds list to be cleaned up later. Else just free the fd */
                        child_ic->pino_nlink--;

                        if (!child_ic->pino_nlink) {
                                dbg_fsbuild("inode #%u (\"%s\") now has no links; adding to dead_fds list.\n",
                                          fd->ino, fd->name);
                                fd->next = *dead_fds;
                                *dead_fds = fd;
                        } else {
                                dbg_fsbuild("inode #%u (\"%s\") has now got nlink %d. Ignoring.\n",
                                          fd->ino, fd->name, child_ic->pino_nlink);
                                jffs2_free_full_dirent(fd);
                        }
                }
        }

        /*
           We don't delete the inocache from the hash list and free it yet.
           The erase code will do that, when all the nodes are completely gone.
        */
}

static void jffs2_calc_trigger_levels(struct jffs2_sb_info *c)
{
        uint32_t size;

        /* Deletion should almost _always_ be allowed. We're fairly
           buggered once we stop allowing people to delete stuff
           because there's not enough free space... */
        c->resv_blocks_deletion = 2;

        /* Be conservative about how much space we need before we allow writes.
           On top of that which is required for deletia, require an extra 2%
           of the medium to be available, for overhead caused by nodes being
           split across blocks, etc. */

        size = c->flash_size / 50; /* 2% of flash size */
        size += c->nr_blocks * 100; /* And 100 bytes per eraseblock */
        size += c->sector_size - 1; /* ... and round up */

        c->resv_blocks_write = c->resv_blocks_deletion + (size / c->sector_size);

        /* When do we let the GC thread run in the background */

        c->resv_blocks_gctrigger = c->resv_blocks_write + 1;

        /* When do we allow garbage collection to merge nodes to make
           long-term progress at the expense of short-term space exhaustion? */
        c->resv_blocks_gcmerge = c->resv_blocks_deletion + 1;

        /* When do we allow garbage collection to eat from bad blocks rather
           than actually making progress? */
        c->resv_blocks_gcbad = 0;//c->resv_blocks_deletion + 2;

        /* What number of 'very dirty' eraseblocks do we allow before we
           trigger the GC thread even if we don't _need_ the space. When we
           can't mark nodes obsolete on the medium, the old dirty nodes cause
           performance problems because we have to inspect and discard them. */
        c->vdirty_blocks_gctrigger = c->resv_blocks_gctrigger;
        if (jffs2_can_mark_obsolete(c))
                c->vdirty_blocks_gctrigger *= 10;

        /* If there's less than this amount of dirty space, don't bother
           trying to GC to make more space. It'll be a fruitless task */
        c->nospc_dirty_size = c->sector_size + (c->flash_size / 100);

        dbg_fsbuild("trigger levels (size %d KiB, block size %d KiB, %d blocks)\n",
                    c->flash_size / 1024, c->sector_size / 1024, c->nr_blocks);
        dbg_fsbuild("Blocks required to allow deletion:    %d (%d KiB)\n",
                  c->resv_blocks_deletion, c->resv_blocks_deletion*c->sector_size/1024);
        dbg_fsbuild("Blocks required to allow writes:      %d (%d KiB)\n",
                  c->resv_blocks_write, c->resv_blocks_write*c->sector_size/1024);
        dbg_fsbuild("Blocks required to quiesce GC thread: %d (%d KiB)\n",
                  c->resv_blocks_gctrigger, c->resv_blocks_gctrigger*c->sector_size/1024);
        dbg_fsbuild("Blocks required to allow GC merges:   %d (%d KiB)\n",
                  c->resv_blocks_gcmerge, c->resv_blocks_gcmerge*c->sector_size/1024);
        dbg_fsbuild("Blocks required to GC bad blocks:     %d (%d KiB)\n",
                  c->resv_blocks_gcbad, c->resv_blocks_gcbad*c->sector_size/1024);
        dbg_fsbuild("Amount of dirty space required to GC: %d bytes\n",
                  c->nospc_dirty_size);
        dbg_fsbuild("Very dirty blocks before GC triggered: %d\n",
                  c->vdirty_blocks_gctrigger);
}

int jffs2_do_mount_fs(struct jffs2_sb_info *c)
{
        int ret;
        int i;
        int size;

        c->free_size = c->flash_size;
        c->nr_blocks = c->flash_size / c->sector_size;
        size = sizeof(struct jffs2_eraseblock) * c->nr_blocks;
#ifndef __ECOS
        if (jffs2_blocks_use_vmalloc(c))
                c->blocks = vzalloc(size);
        else
#endif
                c->blocks = kzalloc(size, GFP_KERNEL);
        if (!c->blocks)
                return -ENOMEM;

        for (i=0; i<c->nr_blocks; i++) {
                INIT_LIST_HEAD(&c->blocks[i].list);
                c->blocks[i].offset = i * c->sector_size;
                c->blocks[i].free_size = c->sector_size;
        }

        INIT_LIST_HEAD(&c->clean_list);
        INIT_LIST_HEAD(&c->very_dirty_list);
        INIT_LIST_HEAD(&c->dirty_list);
        INIT_LIST_HEAD(&c->erasable_list);
        INIT_LIST_HEAD(&c->erasing_list);
        INIT_LIST_HEAD(&c->erase_checking_list);
        INIT_LIST_HEAD(&c->erase_pending_list);
        INIT_LIST_HEAD(&c->erasable_pending_wbuf_list);
        INIT_LIST_HEAD(&c->erase_complete_list);
        INIT_LIST_HEAD(&c->free_list);
        INIT_LIST_HEAD(&c->bad_list);
        INIT_LIST_HEAD(&c->bad_used_list);
        c->highest_ino = 1;
        c->summary = NULL;

        ret = jffs2_sum_init(c);
        if (ret)
                goto out_free;

        if (jffs2_build_filesystem(c)) {
                dbg_fsbuild("build_fs failed\n");
                jffs2_free_ino_caches(c);
                jffs2_free_raw_node_refs(c);
                ret = -EIO;
                goto out_free;
        }

        jffs2_calc_trigger_levels(c);

        return 0;

 out_free:
        kvfree(c->blocks);

        return ret;
}