inode-map.c

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/*
 * Copyright (C) 2007 Oracle.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 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., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#include <linux/delay.h>
#include <linux/kthread.h>
#include <linux/pagemap.h>

#include "ctree.h"
#include "disk-io.h"
#include "free-space-cache.h"
#include "inode-map.h"
#include "transaction.h"

static int caching_kthread(void *data)
{
    struct btrfs_root *root = data;
    struct btrfs_fs_info *fs_info = root->fs_info;
    struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;
    struct btrfs_key key;
    struct btrfs_path *path;
    struct extent_buffer *leaf;
    u64 last = (u64)-1;
    int slot;
    int ret;

    if (!btrfs_test_opt(root, INODE_MAP_CACHE))
        return 0;

    path = btrfs_alloc_path();
    if (!path)
        return -ENOMEM;

    /* Since the commit root is read-only, we can safely skip locking. */
    path->skip_locking = 1;
    path->search_commit_root = 1;
    path->reada = 2;

    key.objectid = BTRFS_FIRST_FREE_OBJECTID;
    key.offset = 0;
    key.type = BTRFS_INODE_ITEM_KEY;
again:
    /* need to make sure the commit_root doesn't disappear */
    mutex_lock(&root->fs_commit_mutex);

    ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
    if (ret < 0)
        goto out;

    while (1) {
        if (btrfs_fs_closing(fs_info))
            goto out;

        leaf = path->nodes[0];
        slot = path->slots[0];
        if (slot >= btrfs_header_nritems(leaf)) {
            ret = btrfs_next_leaf(root, path);
            if (ret < 0)
                goto out;
            else if (ret > 0)
                break;

            if (need_resched() ||
                btrfs_transaction_in_commit(fs_info)) {
                leaf = path->nodes[0];

                if (btrfs_header_nritems(leaf) == 0) {
                    WARN_ON(1);
                    break;
                }

                /*
                 * Save the key so we can advances forward
                 * in the next search.
                 */
                btrfs_item_key_to_cpu(leaf, &key, 0);
                btrfs_release_path(path);
                root->cache_progress = last;
                mutex_unlock(&root->fs_commit_mutex);
                schedule_timeout(1);
                goto again;
            } else
                continue;
        }

        btrfs_item_key_to_cpu(leaf, &key, slot);

        if (key.type != BTRFS_INODE_ITEM_KEY)
            goto next;

        if (key.objectid >= root->highest_objectid)
            break;

        if (last != (u64)-1 && last + 1 != key.objectid) {
            __btrfs_add_free_space(ctl, last + 1,
                           key.objectid - last - 1);
            wake_up(&root->cache_wait);
        }

        last = key.objectid;
next:
        path->slots[0]++;
    }

    if (last < root->highest_objectid - 1) {
        __btrfs_add_free_space(ctl, last + 1,
                       root->highest_objectid - last - 1);
    }

    spin_lock(&root->cache_lock);
    root->cached = BTRFS_CACHE_FINISHED;
    spin_unlock(&root->cache_lock);

    root->cache_progress = (u64)-1;
    btrfs_unpin_free_ino(root);
out:
    wake_up(&root->cache_wait);
    mutex_unlock(&root->fs_commit_mutex);

    btrfs_free_path(path);

    return ret;
}

static void start_caching(struct btrfs_root *root)
{
    struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;
    struct task_struct *tsk;
    int ret;
    u64 objectid;

    if (!btrfs_test_opt(root, INODE_MAP_CACHE))
        return;

    spin_lock(&root->cache_lock);
    if (root->cached != BTRFS_CACHE_NO) {
        spin_unlock(&root->cache_lock);
        return;
    }

    root->cached = BTRFS_CACHE_STARTED;
    spin_unlock(&root->cache_lock);

    ret = load_free_ino_cache(root->fs_info, root);
    if (ret == 1) {
        spin_lock(&root->cache_lock);
        root->cached = BTRFS_CACHE_FINISHED;
        spin_unlock(&root->cache_lock);
        return;
    }

    /*
     * It can be quite time-consuming to fill the cache by searching
     * through the extent tree, and this can keep ino allocation path
     * waiting. Therefore at start we quickly find out the highest
     * inode number and we know we can use inode numbers which fall in
     * [highest_ino + 1, BTRFS_LAST_FREE_OBJECTID].
     */
    ret = btrfs_find_free_objectid(root, &objectid);
    if (!ret && objectid <= BTRFS_LAST_FREE_OBJECTID) {
        __btrfs_add_free_space(ctl, objectid,
                       BTRFS_LAST_FREE_OBJECTID - objectid + 1);
    }

    tsk = kthread_run(caching_kthread, root, "btrfs-ino-cache-%llu\n",
              root->root_key.objectid);
    BUG_ON(IS_ERR(tsk)); /* -ENOMEM */
}

int btrfs_find_free_ino(struct btrfs_root *root, u64 *objectid)
{
    if (!btrfs_test_opt(root, INODE_MAP_CACHE))
        return btrfs_find_free_objectid(root, objectid);

again:
    *objectid = btrfs_find_ino_for_alloc(root);

    if (*objectid != 0)
        return 0;

    start_caching(root);

    wait_event(root->cache_wait,
           root->cached == BTRFS_CACHE_FINISHED ||
           root->free_ino_ctl->free_space > 0);

    if (root->cached == BTRFS_CACHE_FINISHED &&
        root->free_ino_ctl->free_space == 0)
        return -ENOSPC;
    else
        goto again;
}

void btrfs_return_ino(struct btrfs_root *root, u64 objectid)
{
    struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;
    struct btrfs_free_space_ctl *pinned = root->free_ino_pinned;

    if (!btrfs_test_opt(root, INODE_MAP_CACHE))
        return;

again:
    if (root->cached == BTRFS_CACHE_FINISHED) {
        __btrfs_add_free_space(ctl, objectid, 1);
    } else {
        /*
         * If we are in the process of caching free ino chunks,
         * to avoid adding the same inode number to the free_ino
         * tree twice due to cross transaction, we'll leave it
         * in the pinned tree until a transaction is committed
         * or the caching work is done.
         */

        mutex_lock(&root->fs_commit_mutex);
        spin_lock(&root->cache_lock);
        if (root->cached == BTRFS_CACHE_FINISHED) {
            spin_unlock(&root->cache_lock);
            mutex_unlock(&root->fs_commit_mutex);
            goto again;
        }
        spin_unlock(&root->cache_lock);

        start_caching(root);

        if (objectid <= root->cache_progress ||
            objectid > root->highest_objectid)
            __btrfs_add_free_space(ctl, objectid, 1);
        else
            __btrfs_add_free_space(pinned, objectid, 1);

        mutex_unlock(&root->fs_commit_mutex);
    }
}

/*
 * When a transaction is committed, we'll move those inode numbers which
 * are smaller than root->cache_progress from pinned tree to free_ino tree,
 * and others will just be dropped, because the commit root we were
 * searching has changed.
 *
 * Must be called with root->fs_commit_mutex held
 */
void btrfs_unpin_free_ino(struct btrfs_root *root)
{
    struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;
    struct rb_root *rbroot = &root->free_ino_pinned->free_space_offset;
    struct btrfs_free_space *info;
    struct rb_node *n;
    u64 count;

    if (!btrfs_test_opt(root, INODE_MAP_CACHE))
        return;

    while (1) {
        n = rb_first(rbroot);
        if (!n)
            break;

        info = rb_entry(n, struct btrfs_free_space, offset_index);
        BUG_ON(info->bitmap); /* Logic error */

        if (info->offset > root->cache_progress)
            goto free;
        else if (info->offset + info->bytes > root->cache_progress)
            count = root->cache_progress - info->offset + 1;
        else
            count = info->bytes;

        __btrfs_add_free_space(ctl, info->offset, count);
free:
        rb_erase(&info->offset_index, rbroot);
        kfree(info);
    }
}

#define INIT_THRESHOLD  (((1024 * 32) / 2) / sizeof(struct btrfs_free_space))
#define INODES_PER_BITMAP (PAGE_CACHE_SIZE * 8)

/*
 * The goal is to keep the memory used by the free_ino tree won't
 * exceed the memory if we use bitmaps only.
 */
static void recalculate_thresholds(struct btrfs_free_space_ctl *ctl)
{
    struct btrfs_free_space *info;
    struct rb_node *n;
    int max_ino;
    int max_bitmaps;

    n = rb_last(&ctl->free_space_offset);
    if (!n) {
        ctl->extents_thresh = INIT_THRESHOLD;
        return;
    }
    info = rb_entry(n, struct btrfs_free_space, offset_index);

    /*
     * Find the maximum inode number in the filesystem. Note we
     * ignore the fact that this can be a bitmap, because we are
     * not doing precise calculation.
     */
    max_ino = info->bytes - 1;

    max_bitmaps = ALIGN(max_ino, INODES_PER_BITMAP) / INODES_PER_BITMAP;
    if (max_bitmaps <= ctl->total_bitmaps) {
        ctl->extents_thresh = 0;
        return;
    }

    ctl->extents_thresh = (max_bitmaps - ctl->total_bitmaps) *
                PAGE_CACHE_SIZE / sizeof(*info);
}

/*
 * We don't fall back to bitmap, if we are below the extents threshold
 * or this chunk of inode numbers is a big one.
 */
static bool use_bitmap(struct btrfs_free_space_ctl *ctl,
               struct btrfs_free_space *info)
{
    if (ctl->free_extents < ctl->extents_thresh ||
        info->bytes > INODES_PER_BITMAP / 10)
        return false;

    return true;
}

static struct btrfs_free_space_op free_ino_op = {
    .recalc_thresholds  = recalculate_thresholds,
    .use_bitmap     = use_bitmap,
};

static void pinned_recalc_thresholds(struct btrfs_free_space_ctl *ctl)
{
}

static bool pinned_use_bitmap(struct btrfs_free_space_ctl *ctl,
                  struct btrfs_free_space *info)
{
    /*
     * We always use extents for two reasons:
     *
     * - The pinned tree is only used during the process of caching
     *   work.
     * - Make code simpler. See btrfs_unpin_free_ino().
     */
    return false;
}

static struct btrfs_free_space_op pinned_free_ino_op = {
    .recalc_thresholds  = pinned_recalc_thresholds,
    .use_bitmap     = pinned_use_bitmap,
};

void btrfs_init_free_ino_ctl(struct btrfs_root *root)
{
    struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;
    struct btrfs_free_space_ctl *pinned = root->free_ino_pinned;

    spin_lock_init(&ctl->tree_lock);
    ctl->unit = 1;
    ctl->start = 0;
    ctl->private = NULL;
    ctl->op = &free_ino_op;

    /*
     * Initially we allow to use 16K of ram to cache chunks of
     * inode numbers before we resort to bitmaps. This is somewhat
     * arbitrary, but it will be adjusted in runtime.
     */
    ctl->extents_thresh = INIT_THRESHOLD;

    spin_lock_init(&pinned->tree_lock);
    pinned->unit = 1;
    pinned->start = 0;
    pinned->private = NULL;
    pinned->extents_thresh = 0;
    pinned->op = &pinned_free_ino_op;
}

int btrfs_save_ino_cache(struct btrfs_root *root,
             struct btrfs_trans_handle *trans)
{
    struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;
    struct btrfs_path *path;
    struct inode *inode;
    struct btrfs_block_rsv *rsv;
    u64 num_bytes;
    u64 alloc_hint = 0;
    int ret;
    int prealloc;
    bool retry = false;

    /* only fs tree and subvol/snap needs ino cache */
    if (root->root_key.objectid != BTRFS_FS_TREE_OBJECTID &&
        (root->root_key.objectid < BTRFS_FIRST_FREE_OBJECTID ||
         root->root_key.objectid > BTRFS_LAST_FREE_OBJECTID))
        return 0;

    /* Don't save inode cache if we are deleting this root */
    if (btrfs_root_refs(&root->root_item) == 0 &&
        root != root->fs_info->tree_root)
        return 0;

    if (!btrfs_test_opt(root, INODE_MAP_CACHE))
        return 0;

    path = btrfs_alloc_path();
    if (!path)
        return -ENOMEM;

    rsv = trans->block_rsv;
    trans->block_rsv = &root->fs_info->trans_block_rsv;

    num_bytes = trans->bytes_reserved;
    /*
     * 1 item for inode item insertion if need
     * 3 items for inode item update (in the worst case)
     * 1 item for free space object
     * 3 items for pre-allocation
     */
    trans->bytes_reserved = btrfs_calc_trans_metadata_size(root, 8);
    ret = btrfs_block_rsv_add_noflush(root, trans->block_rsv,
                      trans->bytes_reserved);
    if (ret)
        goto out;
    trace_btrfs_space_reservation(root->fs_info, "ino_cache",
                      trans->transid, trans->bytes_reserved, 1);
again:
    inode = lookup_free_ino_inode(root, path);
    if (IS_ERR(inode) && (PTR_ERR(inode) != -ENOENT || retry)) {
        ret = PTR_ERR(inode);
        goto out_release;
    }

    if (IS_ERR(inode)) {
        BUG_ON(retry); /* Logic error */
        retry = true;

        ret = create_free_ino_inode(root, trans, path);
        if (ret)
            goto out_release;
        goto again;
    }

    BTRFS_I(inode)->generation = 0;
    ret = btrfs_update_inode(trans, root, inode);
    if (ret) {
        btrfs_abort_transaction(trans, root, ret);
        goto out_put;
    }

    if (i_size_read(inode) > 0) {
        ret = btrfs_truncate_free_space_cache(root, trans, path, inode);
        if (ret) {
            btrfs_abort_transaction(trans, root, ret);
            goto out_put;
        }
    }

    spin_lock(&root->cache_lock);
    if (root->cached != BTRFS_CACHE_FINISHED) {
        ret = -1;
        spin_unlock(&root->cache_lock);
        goto out_put;
    }
    spin_unlock(&root->cache_lock);

    spin_lock(&ctl->tree_lock);
    prealloc = sizeof(struct btrfs_free_space) * ctl->free_extents;
    prealloc = ALIGN(prealloc, PAGE_CACHE_SIZE);
    prealloc += ctl->total_bitmaps * PAGE_CACHE_SIZE;
    spin_unlock(&ctl->tree_lock);

    /* Just to make sure we have enough space */
    prealloc += 8 * PAGE_CACHE_SIZE;

    ret = btrfs_delalloc_reserve_space(inode, prealloc);
    if (ret)
        goto out_put;

    ret = btrfs_prealloc_file_range_trans(inode, trans, 0, 0, prealloc,
                          prealloc, prealloc, &alloc_hint);
    if (ret) {
        btrfs_delalloc_release_space(inode, prealloc);
        goto out_put;
    }
    btrfs_free_reserved_data_space(inode, prealloc);

    ret = btrfs_write_out_ino_cache(root, trans, path);
out_put:
    iput(inode);
out_release:
    trace_btrfs_space_reservation(root->fs_info, "ino_cache",
                      trans->transid, trans->bytes_reserved, 0);
    btrfs_block_rsv_release(root, trans->block_rsv, trans->bytes_reserved);
out:
    trans->block_rsv = rsv;
    trans->bytes_reserved = num_bytes;

    btrfs_free_path(path);
    return ret;
}

static int btrfs_find_highest_objectid(struct btrfs_root *root, u64 *objectid)
{
    struct btrfs_path *path;
    int ret;
    struct extent_buffer *l;
    struct btrfs_key search_key;
    struct btrfs_key found_key;
    int slot;

    path = btrfs_alloc_path();
    if (!path)
        return -ENOMEM;

    search_key.objectid = BTRFS_LAST_FREE_OBJECTID;
    search_key.type = -1;
    search_key.offset = (u64)-1;
    ret = btrfs_search_slot(NULL, root, &search_key, path, 0, 0);
    if (ret < 0)
        goto error;
    BUG_ON(ret == 0); /* Corruption */
    if (path->slots[0] > 0) {
        slot = path->slots[0] - 1;
        l = path->nodes[0];
        btrfs_item_key_to_cpu(l, &found_key, slot);
        *objectid = max_t(u64, found_key.objectid,
                  BTRFS_FIRST_FREE_OBJECTID - 1);
    } else {
        *objectid = BTRFS_FIRST_FREE_OBJECTID - 1;
    }
    ret = 0;
error:
    btrfs_free_path(path);
    return ret;
}

int btrfs_find_free_objectid(struct btrfs_root *root, u64 *objectid)
{
    int ret;
    mutex_lock(&root->objectid_mutex);

    if (unlikely(root->highest_objectid < BTRFS_FIRST_FREE_OBJECTID)) {
        ret = btrfs_find_highest_objectid(root,
                          &root->highest_objectid);
        if (ret)
            goto out;
    }

    if (unlikely(root->highest_objectid >= BTRFS_LAST_FREE_OBJECTID)) {
        ret = -ENOSPC;
        goto out;
    }

    *objectid = ++root->highest_objectid;
    ret = 0;
out:
    mutex_unlock(&root->objectid_mutex);
    return ret;
}