build.c

Go to the documentation of this file.

/*
 * JFFS2 -- Journalling Flash File System, Version 2.
 *
 * Copyright © 2001-2007 Red Hat, Inc.
 * Copyright © 2004-2010 David Woodhouse <[email protected]>
 *
 * Created by David Woodhouse <[email protected]>
 *
 * 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 "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)
{
    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);
            continue;
        }

        if (fd->type == DT_DIR) {
            if (child_ic->pino_nlink) {
                JFFS2_ERROR("child dir \"%s\" (ino #%u) of dir ino #%u appears to be a hard link\n",
                        fd->name, fd->ino, ic->ino);
                /* TODO: What do we do about it? */
            } else {
                child_ic->pino_nlink = ic->ino;
            }
        } else
            child_ic->pino_nlink++;

        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;
    int i;
    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);
            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");
    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;
            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 */

            if (fd->type == DT_DIR)
                child_ic->pino_nlink = 0;
            else
                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:
#ifndef __ECOS
    if (jffs2_blocks_use_vmalloc(c))
        vfree(c->blocks);
    else
#endif
        kfree(c->blocks);

    return ret;
}