commit.c

Go to the documentation of this file.

/*
 * This file is part of UBIFS.
 *
 * Copyright (C) 2006-2008 Nokia Corporation.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 51
 * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 *
 * Authors: Adrian Hunter
 *          Artem Bityutskiy (Битюцкий Артём)
 */

/*
 * This file implements functions that manage the running of the commit process.
 * Each affected module has its own functions to accomplish their part in the
 * commit and those functions are called here.
 *
 * The commit is the process whereby all updates to the index and LEB properties
 * are written out together and the journal becomes empty. This keeps the
 * file system consistent - at all times the state can be recreated by reading
 * the index and LEB properties and then replaying the journal.
 *
 * The commit is split into two parts named "commit start" and "commit end".
 * During commit start, the commit process has exclusive access to the journal
 * by holding the commit semaphore down for writing. As few I/O operations as
 * possible are performed during commit start, instead the nodes that are to be
 * written are merely identified. During commit end, the commit semaphore is no
 * longer held and the journal is again in operation, allowing users to continue
 * to use the file system while the bulk of the commit I/O is performed. The
 * purpose of this two-step approach is to prevent the commit from causing any
 * latency blips. Note that in any case, the commit does not prevent lookups
 * (as permitted by the TNC mutex), or access to VFS data structures e.g. page
 * cache.
 */

#include <linux/freezer.h>
#include <linux/kthread.h>
#include <linux/slab.h>
#include "ubifs.h"

/*
 * nothing_to_commit - check if there is nothing to commit.
 * @c: UBIFS file-system description object
 *
 * This is a helper function which checks if there is anything to commit. It is
 * used as an optimization to avoid starting the commit if it is not really
 * necessary. Indeed, the commit operation always assumes flash I/O (e.g.,
 * writing the commit start node to the log), and it is better to avoid doing
 * this unnecessarily. E.g., 'ubifs_sync_fs()' runs the commit, but if there is
 * nothing to commit, it is more optimal to avoid any flash I/O.
 *
 * This function has to be called with @c->commit_sem locked for writing -
 * this function does not take LPT/TNC locks because the @c->commit_sem
 * guarantees that we have exclusive access to the TNC and LPT data structures.
 *
 * This function returns %1 if there is nothing to commit and %0 otherwise.
 */
static int nothing_to_commit(struct ubifs_info *c)
{
    /*
     * During mounting or remounting from R/O mode to R/W mode we may
     * commit for various recovery-related reasons.
     */
    if (c->mounting || c->remounting_rw)
        return 0;

    /*
     * If the root TNC node is dirty, we definitely have something to
     * commit.
     */
    if (c->zroot.znode && ubifs_zn_dirty(c->zroot.znode))
        return 0;

    /*
     * Even though the TNC is clean, the LPT tree may have dirty nodes. For
     * example, this may happen if the budgeting subsystem invoked GC to
     * make some free space, and the GC found an LEB with only dirty and
     * free space. In this case GC would just change the lprops of this
     * LEB (by turning all space into free space) and unmap it.
     */
    if (c->nroot && test_bit(DIRTY_CNODE, &c->nroot->flags))
        return 0;

    ubifs_assert(atomic_long_read(&c->dirty_zn_cnt) == 0);
    ubifs_assert(c->dirty_pn_cnt == 0);
    ubifs_assert(c->dirty_nn_cnt == 0);

    return 1;
}

static int do_commit(struct ubifs_info *c)
{
    int err, new_ltail_lnum, old_ltail_lnum, i;
    struct ubifs_zbranch zroot;
    struct ubifs_lp_stats lst;

    dbg_cmt("start");
    ubifs_assert(!c->ro_media && !c->ro_mount);

    if (c->ro_error) {
        err = -EROFS;
        goto out_up;
    }

    if (nothing_to_commit(c)) {
        up_write(&c->commit_sem);
        err = 0;
        goto out_cancel;
    }

    /* Sync all write buffers (necessary for recovery) */
    for (i = 0; i < c->jhead_cnt; i++) {
        err = ubifs_wbuf_sync(&c->jheads[i].wbuf);
        if (err)
            goto out_up;
    }

    c->cmt_no += 1;
    err = ubifs_gc_start_commit(c);
    if (err)
        goto out_up;
    err = dbg_check_lprops(c);
    if (err)
        goto out_up;
    err = ubifs_log_start_commit(c, &new_ltail_lnum);
    if (err)
        goto out_up;
    err = ubifs_tnc_start_commit(c, &zroot);
    if (err)
        goto out_up;
    err = ubifs_lpt_start_commit(c);
    if (err)
        goto out_up;
    err = ubifs_orphan_start_commit(c);
    if (err)
        goto out_up;

    ubifs_get_lp_stats(c, &lst);

    up_write(&c->commit_sem);

    err = ubifs_tnc_end_commit(c);
    if (err)
        goto out;
    err = ubifs_lpt_end_commit(c);
    if (err)
        goto out;
    err = ubifs_orphan_end_commit(c);
    if (err)
        goto out;
    old_ltail_lnum = c->ltail_lnum;
    err = ubifs_log_end_commit(c, new_ltail_lnum);
    if (err)
        goto out;
    err = dbg_check_old_index(c, &zroot);
    if (err)
        goto out;

    mutex_lock(&c->mst_mutex);
    c->mst_node->cmt_no      = cpu_to_le64(c->cmt_no);
    c->mst_node->log_lnum    = cpu_to_le32(new_ltail_lnum);
    c->mst_node->root_lnum   = cpu_to_le32(zroot.lnum);
    c->mst_node->root_offs   = cpu_to_le32(zroot.offs);
    c->mst_node->root_len    = cpu_to_le32(zroot.len);
    c->mst_node->ihead_lnum  = cpu_to_le32(c->ihead_lnum);
    c->mst_node->ihead_offs  = cpu_to_le32(c->ihead_offs);
    c->mst_node->index_size  = cpu_to_le64(c->bi.old_idx_sz);
    c->mst_node->lpt_lnum    = cpu_to_le32(c->lpt_lnum);
    c->mst_node->lpt_offs    = cpu_to_le32(c->lpt_offs);
    c->mst_node->nhead_lnum  = cpu_to_le32(c->nhead_lnum);
    c->mst_node->nhead_offs  = cpu_to_le32(c->nhead_offs);
    c->mst_node->ltab_lnum   = cpu_to_le32(c->ltab_lnum);
    c->mst_node->ltab_offs   = cpu_to_le32(c->ltab_offs);
    c->mst_node->lsave_lnum  = cpu_to_le32(c->lsave_lnum);
    c->mst_node->lsave_offs  = cpu_to_le32(c->lsave_offs);
    c->mst_node->lscan_lnum  = cpu_to_le32(c->lscan_lnum);
    c->mst_node->empty_lebs  = cpu_to_le32(lst.empty_lebs);
    c->mst_node->idx_lebs    = cpu_to_le32(lst.idx_lebs);
    c->mst_node->total_free  = cpu_to_le64(lst.total_free);
    c->mst_node->total_dirty = cpu_to_le64(lst.total_dirty);
    c->mst_node->total_used  = cpu_to_le64(lst.total_used);
    c->mst_node->total_dead  = cpu_to_le64(lst.total_dead);
    c->mst_node->total_dark  = cpu_to_le64(lst.total_dark);
    if (c->no_orphs)
        c->mst_node->flags |= cpu_to_le32(UBIFS_MST_NO_ORPHS);
    else
        c->mst_node->flags &= ~cpu_to_le32(UBIFS_MST_NO_ORPHS);
    err = ubifs_write_master(c);
    mutex_unlock(&c->mst_mutex);
    if (err)
        goto out;

    err = ubifs_log_post_commit(c, old_ltail_lnum);
    if (err)
        goto out;
    err = ubifs_gc_end_commit(c);
    if (err)
        goto out;
    err = ubifs_lpt_post_commit(c);
    if (err)
        goto out;

out_cancel:
    spin_lock(&c->cs_lock);
    c->cmt_state = COMMIT_RESTING;
    wake_up(&c->cmt_wq);
    dbg_cmt("commit end");
    spin_unlock(&c->cs_lock);
    return 0;

out_up:
    up_write(&c->commit_sem);
out:
    ubifs_err("commit failed, error %d", err);
    spin_lock(&c->cs_lock);
    c->cmt_state = COMMIT_BROKEN;
    wake_up(&c->cmt_wq);
    spin_unlock(&c->cs_lock);
    ubifs_ro_mode(c, err);
    return err;
}

static int run_bg_commit(struct ubifs_info *c)
{
    spin_lock(&c->cs_lock);
    /*
     * Run background commit only if background commit was requested or if
     * commit is required.
     */
    if (c->cmt_state != COMMIT_BACKGROUND &&
        c->cmt_state != COMMIT_REQUIRED)
        goto out;
    spin_unlock(&c->cs_lock);

    down_write(&c->commit_sem);
    spin_lock(&c->cs_lock);
    if (c->cmt_state == COMMIT_REQUIRED)
        c->cmt_state = COMMIT_RUNNING_REQUIRED;
    else if (c->cmt_state == COMMIT_BACKGROUND)
        c->cmt_state = COMMIT_RUNNING_BACKGROUND;
    else
        goto out_cmt_unlock;
    spin_unlock(&c->cs_lock);

    return do_commit(c);

out_cmt_unlock:
    up_write(&c->commit_sem);
out:
    spin_unlock(&c->cs_lock);
    return 0;
}

int ubifs_bg_thread(void *info)
{
    int err;
    struct ubifs_info *c = info;

    ubifs_msg("background thread \"%s\" started, PID %d",
          c->bgt_name, current->pid);
    set_freezable();

    while (1) {
        if (kthread_should_stop())
            break;

        if (try_to_freeze())
            continue;

        set_current_state(TASK_INTERRUPTIBLE);
        /* Check if there is something to do */
        if (!c->need_bgt) {
            /*
             * Nothing prevents us from going sleep now and
             * be never woken up and block the task which
             * could wait in 'kthread_stop()' forever.
             */
            if (kthread_should_stop())
                break;
            schedule();
            continue;
        } else
            __set_current_state(TASK_RUNNING);

        c->need_bgt = 0;
        err = ubifs_bg_wbufs_sync(c);
        if (err)
            ubifs_ro_mode(c, err);

        run_bg_commit(c);
        cond_resched();
    }

    ubifs_msg("background thread \"%s\" stops", c->bgt_name);
    return 0;
}

void ubifs_commit_required(struct ubifs_info *c)
{
    spin_lock(&c->cs_lock);
    switch (c->cmt_state) {
    case COMMIT_RESTING:
    case COMMIT_BACKGROUND:
        dbg_cmt("old: %s, new: %s", dbg_cstate(c->cmt_state),
            dbg_cstate(COMMIT_REQUIRED));
        c->cmt_state = COMMIT_REQUIRED;
        break;
    case COMMIT_RUNNING_BACKGROUND:
        dbg_cmt("old: %s, new: %s", dbg_cstate(c->cmt_state),
            dbg_cstate(COMMIT_RUNNING_REQUIRED));
        c->cmt_state = COMMIT_RUNNING_REQUIRED;
        break;
    case COMMIT_REQUIRED:
    case COMMIT_RUNNING_REQUIRED:
    case COMMIT_BROKEN:
        break;
    }
    spin_unlock(&c->cs_lock);
}

void ubifs_request_bg_commit(struct ubifs_info *c)
{
    spin_lock(&c->cs_lock);
    if (c->cmt_state == COMMIT_RESTING) {
        dbg_cmt("old: %s, new: %s", dbg_cstate(c->cmt_state),
            dbg_cstate(COMMIT_BACKGROUND));
        c->cmt_state = COMMIT_BACKGROUND;
        spin_unlock(&c->cs_lock);
        ubifs_wake_up_bgt(c);
    } else
        spin_unlock(&c->cs_lock);
}

static int wait_for_commit(struct ubifs_info *c)
{
    dbg_cmt("pid %d goes sleep", current->pid);

    /*
     * The following sleeps if the condition is false, and will be woken
     * when the commit ends. It is possible, although very unlikely, that we
     * will wake up and see the subsequent commit running, rather than the
     * one we were waiting for, and go back to sleep.  However, we will be
     * woken again, so there is no danger of sleeping forever.
     */
    wait_event(c->cmt_wq, c->cmt_state != COMMIT_RUNNING_BACKGROUND &&
                  c->cmt_state != COMMIT_RUNNING_REQUIRED);
    dbg_cmt("commit finished, pid %d woke up", current->pid);
    return 0;
}

int ubifs_run_commit(struct ubifs_info *c)
{
    int err = 0;

    spin_lock(&c->cs_lock);
    if (c->cmt_state == COMMIT_BROKEN) {
        err = -EROFS;
        goto out;
    }

    if (c->cmt_state == COMMIT_RUNNING_BACKGROUND)
        /*
         * We set the commit state to 'running required' to indicate
         * that we want it to complete as quickly as possible.
         */
        c->cmt_state = COMMIT_RUNNING_REQUIRED;

    if (c->cmt_state == COMMIT_RUNNING_REQUIRED) {
        spin_unlock(&c->cs_lock);
        return wait_for_commit(c);
    }
    spin_unlock(&c->cs_lock);

    /* Ok, the commit is indeed needed */

    down_write(&c->commit_sem);
    spin_lock(&c->cs_lock);
    /*
     * Since we unlocked 'c->cs_lock', the state may have changed, so
     * re-check it.
     */
    if (c->cmt_state == COMMIT_BROKEN) {
        err = -EROFS;
        goto out_cmt_unlock;
    }

    if (c->cmt_state == COMMIT_RUNNING_BACKGROUND)
        c->cmt_state = COMMIT_RUNNING_REQUIRED;

    if (c->cmt_state == COMMIT_RUNNING_REQUIRED) {
        up_write(&c->commit_sem);
        spin_unlock(&c->cs_lock);
        return wait_for_commit(c);
    }
    c->cmt_state = COMMIT_RUNNING_REQUIRED;
    spin_unlock(&c->cs_lock);

    err = do_commit(c);
    return err;

out_cmt_unlock:
    up_write(&c->commit_sem);
out:
    spin_unlock(&c->cs_lock);
    return err;
}

int ubifs_gc_should_commit(struct ubifs_info *c)
{
    int ret = 0;

    spin_lock(&c->cs_lock);
    if (c->cmt_state == COMMIT_BACKGROUND) {
        dbg_cmt("commit required now");
        c->cmt_state = COMMIT_REQUIRED;
    } else
        dbg_cmt("commit not requested");
    if (c->cmt_state == COMMIT_REQUIRED)
        ret = 1;
    spin_unlock(&c->cs_lock);
    return ret;
}

/*
 * Everything below is related to debugging.
 */

struct idx_node {
    struct list_head list;
    int iip;
    union ubifs_key upper_key;
    struct ubifs_idx_node idx __aligned(8);
};

int dbg_old_index_check_init(struct ubifs_info *c, struct ubifs_zbranch *zroot)
{
    struct ubifs_idx_node *idx;
    int lnum, offs, len, err = 0;
    struct ubifs_debug_info *d = c->dbg;

    d->old_zroot = *zroot;
    lnum = d->old_zroot.lnum;
    offs = d->old_zroot.offs;
    len = d->old_zroot.len;

    idx = kmalloc(c->max_idx_node_sz, GFP_NOFS);
    if (!idx)
        return -ENOMEM;

    err = ubifs_read_node(c, idx, UBIFS_IDX_NODE, len, lnum, offs);
    if (err)
        goto out;

    d->old_zroot_level = le16_to_cpu(idx->level);
    d->old_zroot_sqnum = le64_to_cpu(idx->ch.sqnum);
out:
    kfree(idx);
    return err;
}

int dbg_check_old_index(struct ubifs_info *c, struct ubifs_zbranch *zroot)
{
    int lnum, offs, len, err = 0, uninitialized_var(last_level), child_cnt;
    int first = 1, iip;
    struct ubifs_debug_info *d = c->dbg;
    union ubifs_key uninitialized_var(lower_key), upper_key, l_key, u_key;
    unsigned long long uninitialized_var(last_sqnum);
    struct ubifs_idx_node *idx;
    struct list_head list;
    struct idx_node *i;
    size_t sz;

    if (!dbg_is_chk_index(c))
        return 0;

    INIT_LIST_HEAD(&list);

    sz = sizeof(struct idx_node) + ubifs_idx_node_sz(c, c->fanout) -
         UBIFS_IDX_NODE_SZ;

    /* Start at the old zroot */
    lnum = d->old_zroot.lnum;
    offs = d->old_zroot.offs;
    len = d->old_zroot.len;
    iip = 0;

    /*
     * Traverse the index tree preorder depth-first i.e. do a node and then
     * its subtrees from left to right.
     */
    while (1) {
        struct ubifs_branch *br;

        /* Get the next index node */
        i = kmalloc(sz, GFP_NOFS);
        if (!i) {
            err = -ENOMEM;
            goto out_free;
        }
        i->iip = iip;
        /* Keep the index nodes on our path in a linked list */
        list_add_tail(&i->list, &list);
        /* Read the index node */
        idx = &i->idx;
        err = ubifs_read_node(c, idx, UBIFS_IDX_NODE, len, lnum, offs);
        if (err)
            goto out_free;
        /* Validate index node */
        child_cnt = le16_to_cpu(idx->child_cnt);
        if (child_cnt < 1 || child_cnt > c->fanout) {
            err = 1;
            goto out_dump;
        }
        if (first) {
            first = 0;
            /* Check root level and sqnum */
            if (le16_to_cpu(idx->level) != d->old_zroot_level) {
                err = 2;
                goto out_dump;
            }
            if (le64_to_cpu(idx->ch.sqnum) != d->old_zroot_sqnum) {
                err = 3;
                goto out_dump;
            }
            /* Set last values as though root had a parent */
            last_level = le16_to_cpu(idx->level) + 1;
            last_sqnum = le64_to_cpu(idx->ch.sqnum) + 1;
            key_read(c, ubifs_idx_key(c, idx), &lower_key);
            highest_ino_key(c, &upper_key, INUM_WATERMARK);
        }
        key_copy(c, &upper_key, &i->upper_key);
        if (le16_to_cpu(idx->level) != last_level - 1) {
            err = 3;
            goto out_dump;
        }
        /*
         * The index is always written bottom up hence a child's sqnum
         * is always less than the parents.
         */
        if (le64_to_cpu(idx->ch.sqnum) >= last_sqnum) {
            err = 4;
            goto out_dump;
        }
        /* Check key range */
        key_read(c, ubifs_idx_key(c, idx), &l_key);
        br = ubifs_idx_branch(c, idx, child_cnt - 1);
        key_read(c, &br->key, &u_key);
        if (keys_cmp(c, &lower_key, &l_key) > 0) {
            err = 5;
            goto out_dump;
        }
        if (keys_cmp(c, &upper_key, &u_key) < 0) {
            err = 6;
            goto out_dump;
        }
        if (keys_cmp(c, &upper_key, &u_key) == 0)
            if (!is_hash_key(c, &u_key)) {
                err = 7;
                goto out_dump;
            }
        /* Go to next index node */
        if (le16_to_cpu(idx->level) == 0) {
            /* At the bottom, so go up until can go right */
            while (1) {
                /* Drop the bottom of the list */
                list_del(&i->list);
                kfree(i);
                /* No more list means we are done */
                if (list_empty(&list))
                    goto out;
                /* Look at the new bottom */
                i = list_entry(list.prev, struct idx_node,
                           list);
                idx = &i->idx;
                /* Can we go right */
                if (iip + 1 < le16_to_cpu(idx->child_cnt)) {
                    iip = iip + 1;
                    break;
                } else
                    /* Nope, so go up again */
                    iip = i->iip;
            }
        } else
            /* Go down left */
            iip = 0;
        /*
         * We have the parent in 'idx' and now we set up for reading the
         * child pointed to by slot 'iip'.
         */
        last_level = le16_to_cpu(idx->level);
        last_sqnum = le64_to_cpu(idx->ch.sqnum);
        br = ubifs_idx_branch(c, idx, iip);
        lnum = le32_to_cpu(br->lnum);
        offs = le32_to_cpu(br->offs);
        len = le32_to_cpu(br->len);
        key_read(c, &br->key, &lower_key);
        if (iip + 1 < le16_to_cpu(idx->child_cnt)) {
            br = ubifs_idx_branch(c, idx, iip + 1);
            key_read(c, &br->key, &upper_key);
        } else
            key_copy(c, &i->upper_key, &upper_key);
    }
out:
    err = dbg_old_index_check_init(c, zroot);
    if (err)
        goto out_free;

    return 0;

out_dump:
    ubifs_err("dumping index node (iip=%d)", i->iip);
    ubifs_dump_node(c, idx);
    list_del(&i->list);
    kfree(i);
    if (!list_empty(&list)) {
        i = list_entry(list.prev, struct idx_node, list);
        ubifs_err("dumping parent index node");
        ubifs_dump_node(c, &i->idx);
    }
out_free:
    while (!list_empty(&list)) {
        i = list_entry(list.next, struct idx_node, list);
        list_del(&i->list);
        kfree(i);
    }
    ubifs_err("failed, error %d", err);
    if (err > 0)
        err = -EINVAL;
    return err;
}