/*
 * Copyright (c) 2008 The DragonFly Project.  All rights reserved.
 *
 * This code is derived from software contributed to The DragonFly Project
 * by Matthew Dillon <dillon@backplane.com>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name of The DragonFly Project nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific, prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $DragonFly: src/sys/vfs/hammer/hammer_prune.c,v 1.19 2008/09/23 21:03:52 dillon Exp $
 */

#include "hammer.h"

/*
 * Iterate through the specified range of object ids and remove any
 * deleted records that fall entirely within a prune modulo.
 *
 * A reverse iteration is used to prevent overlapping records from being
 * created during the iteration due to alignments.  This also allows us
 * to adjust alignments without blowing up the B-Tree.
 */
static int prune_should_delete(struct hammer_ioc_prune *prune,
                               hammer_btree_leaf_elm_t elm);
static void prune_check_nlinks(hammer_cursor_t cursor,
                               hammer_btree_leaf_elm_t elm);

int
hammer_ioc_prune(hammer_transaction_t trans, hammer_inode_t ip,
                 struct hammer_ioc_prune *prune)
{
        struct hammer_cursor cursor;
        hammer_btree_leaf_elm_t elm;
        struct hammer_ioc_prune_elm *copy_elms;
        struct hammer_ioc_prune_elm *user_elms;
        int error;
        int isdir;
        int elm_array_size;
        int seq;
        int64_t bytes;
        uint32_t key_beg_localization;

        if (prune->nelms < 0 || prune->nelms > HAMMER_MAX_PRUNE_ELMS)
                return(EINVAL);
        if ((prune->key_beg.localization | prune->key_end.localization) &
            HAMMER_LOCALIZE_PSEUDOFS_MASK) {
                return(EINVAL);
        }
        if (prune->key_beg.localization > prune->key_end.localization)
                return(EINVAL);
        if (prune->key_beg.localization == prune->key_end.localization) {
                if (prune->key_beg.obj_id > prune->key_end.obj_id)
                        return(EINVAL);
                /* key-space limitations - no check needed */
        }
        if ((prune->head.flags & HAMMER_IOC_PRUNE_ALL) && prune->nelms)
                return(EINVAL);

        /*
         * Ioctl caller has only set localization type to prune.
         * Initialize cursor key localization with ip localization.
         */
        key_beg_localization = prune->key_beg.localization;
        key_beg_localization &= HAMMER_LOCALIZE_MASK;
        key_beg_localization |= ip->obj_localization;

        prune->key_cur.localization = prune->key_end.localization;
        prune->key_cur.localization &= HAMMER_LOCALIZE_MASK;
        prune->key_cur.localization |= ip->obj_localization;

        prune->key_cur.obj_id = prune->key_end.obj_id;
        prune->key_cur.key = HAMMER_MAX_KEY;

        /*
         * Copy element array from userland
         */
        elm_array_size = sizeof(*copy_elms) * prune->nelms;
        user_elms = prune->elms;
        copy_elms = kmalloc(elm_array_size, M_TEMP, M_WAITOK);
        if ((error = copyin(user_elms, copy_elms, elm_array_size)) != 0)
                goto failed;
        prune->elms = copy_elms;

        seq = trans->hmp->flusher.done;

        /*
         * Scan backwards.  Retries typically occur if a deadlock is detected.
         */
retry:
        error = hammer_init_cursor(trans, &cursor, NULL, NULL);
        if (error) {
                hammer_done_cursor(&cursor);
                goto failed;
        }
        cursor.key_beg.localization = key_beg_localization;
        cursor.key_beg.obj_id = prune->key_beg.obj_id;
        cursor.key_beg.key = HAMMER_MIN_KEY;
        cursor.key_beg.create_tid = 1;
        cursor.key_beg.delete_tid = 0;
        cursor.key_beg.rec_type = HAMMER_MIN_RECTYPE;
        cursor.key_beg.obj_type = 0;

        cursor.key_end.localization = prune->key_cur.localization;
        cursor.key_end.obj_id = prune->key_cur.obj_id;
        cursor.key_end.key = prune->key_cur.key;
        cursor.key_end.create_tid = HAMMER_MAX_TID - 1;
        cursor.key_end.delete_tid = 0;
        cursor.key_end.rec_type = HAMMER_MAX_RECTYPE;
        cursor.key_end.obj_type = 0;

        cursor.flags |= HAMMER_CURSOR_END_INCLUSIVE;
        cursor.flags |= HAMMER_CURSOR_BACKEND;

        /*
         * This flag allows the B-Tree code to clean up loose ends.  At
         * the moment (XXX) it also means we have to hold the sync lock
         * through the iteration.
         */
        cursor.flags |= HAMMER_CURSOR_PRUNING;

        hammer_sync_lock_sh(trans);
        error = hammer_btree_last(&cursor);
        hammer_sync_unlock(trans);

        while (error == 0) {
                /*
                 * Check for work
                 */
                elm = &cursor.node->ondisk->elms[cursor.index].leaf;
                prune->key_cur = elm->base;

                /*
                 * Filesystem went read-only during rebalancing
                 */
                if (trans->hmp->ronly) {
                        error = EROFS;
                        break;
                }

                /*
                 * Yield to more important tasks
                 */
                if ((error = hammer_signal_check(trans->hmp)) != 0)
                        break;

                if (prune->stat_oldest_tid > elm->base.create_tid)
                        prune->stat_oldest_tid = elm->base.create_tid;

                if (hammer_debug_general & 0x0200) {
                        hdkprintf("check %016jx %016jx cre=%016jx del=%016jx\n",
                                        (intmax_t)elm->base.obj_id,
                                        (intmax_t)elm->base.key,
                                        (intmax_t)elm->base.create_tid,
                                        (intmax_t)elm->base.delete_tid);
                }

                if (prune_should_delete(prune, elm)) {
                        if (hammer_debug_general & 0x0200) {
                                hdkprintf("check %016jx %016jx: DELETE\n",
                                        (intmax_t)elm->base.obj_id,
                                        (intmax_t)elm->base.key);
                        }

                        /*
                         * NOTE: This can return EDEADLK
                         *
                         * Acquiring the sync lock guarantees that the
                         * operation will not cross a synchronization
                         * boundary (see the flusher).
                         *
                         * We dont need to track inodes or next_tid when
                         * we are destroying deleted records.
                         */
                        isdir = (elm->base.rec_type == HAMMER_RECTYPE_DIRENTRY);

                        hammer_sync_lock_sh(trans);
                        error = hammer_delete_at_cursor(&cursor,
                                                        HAMMER_DELETE_DESTROY,
                                                        cursor.trans->tid,
                                                        cursor.trans->time32,
                                                        0, &bytes);
                        hammer_sync_unlock(trans);
                        if (error)
                                break;

                        if (isdir)
                                ++prune->stat_dirrecords;
                        else
                                ++prune->stat_rawrecords;
                        prune->stat_bytes += bytes;

                        /*
                         * The current record might now be the one after
                         * the one we deleted, set ATEDISK to force us
                         * to skip it (since we are iterating backwards).
                         */
                        cursor.flags |= HAMMER_CURSOR_ATEDISK;
                } else {
                        /*
                         * Nothing to delete, but we may have to check other
                         * things.
                         */
                        prune_check_nlinks(&cursor, elm);
                        cursor.flags |= HAMMER_CURSOR_ATEDISK;
                        if (hammer_debug_general & 0x0100) {
                                hdkprintf("check %016jx %016jx: SKIP\n",
                                        (intmax_t)elm->base.obj_id,
                                        (intmax_t)elm->base.key);
                        }
                }
                ++prune->stat_scanrecords;

                /*
                 * WARNING: See warnings in hammer_unlock_cursor() function.
                 */
                while (hammer_flusher_meta_halflimit(trans->hmp) ||
                       hammer_flusher_undo_exhausted(trans, 2)) {
                        hammer_unlock_cursor(&cursor);
                        hammer_flusher_wait(trans->hmp, seq);
                        hammer_lock_cursor(&cursor);
                        seq = hammer_flusher_async_one(trans->hmp);
                }
                hammer_sync_lock_sh(trans);
                error = hammer_btree_iterate_reverse(&cursor);
                hammer_sync_unlock(trans);
        }
        if (error == ENOENT)
                error = 0;
        hammer_done_cursor(&cursor);
        if (error == EDEADLK)
                goto retry;
        if (error == EINTR) {
                prune->head.flags |= HAMMER_IOC_HEAD_INTR;
                error = 0;
        }
failed:
        prune->key_cur.localization &= HAMMER_LOCALIZE_MASK;
        prune->elms = user_elms;
        kfree(copy_elms, M_TEMP);
        return(error);
}

/*
 * Check pruning list.  The list must be sorted in descending order.
 *
 * Return non-zero if the record should be deleted.
 */
static int
prune_should_delete(struct hammer_ioc_prune *prune, hammer_btree_leaf_elm_t elm)
{
        struct hammer_ioc_prune_elm *scan;
        int i;

        /*
         * If pruning everything remove all records with a non-zero
         * delete_tid.
         */
        if (prune->head.flags & HAMMER_IOC_PRUNE_ALL) {
                if (elm->base.delete_tid != 0)
                        return(1);
                return(0);
        }

        for (i = 0; i < prune->nelms; ++i) {
                scan = &prune->elms[i];

                /*
                 * Check for loop termination.
                 */
                if (elm->base.create_tid >= scan->end_tid ||
                    elm->base.delete_tid > scan->end_tid) {
                        break;
                }

                /*
                 * Determine if we can delete the record.
                 */
                if (elm->base.delete_tid &&
                    elm->base.create_tid >= scan->beg_tid &&
                    elm->base.delete_tid <= scan->end_tid &&
                    (elm->base.create_tid - scan->beg_tid) / scan->mod_tid ==
                    (elm->base.delete_tid - scan->beg_tid) / scan->mod_tid) {
                        return(1);
                }
        }
        return(0);
}

/*
 * Dangling inodes can occur if processes are holding open descriptors on
 * deleted files as-of when a machine crashes.  When we find one simply
 * acquire the inode and release it.  The inode handling code will then
 * do the right thing.
 */
static
void
prune_check_nlinks(hammer_cursor_t cursor, hammer_btree_leaf_elm_t elm)
{
        hammer_inode_t ip;
        int error;

        if (elm->base.rec_type != HAMMER_RECTYPE_INODE)
                return;
        if (elm->base.delete_tid != 0)
                return;
        if (hammer_btree_extract_data(cursor))
                return;
        if (cursor->data->inode.nlinks)
                return;
        hammer_cursor_downgrade(cursor);
        ip = hammer_get_inode(cursor->trans, NULL, elm->base.obj_id,
                      HAMMER_MAX_TID,
                      elm->base.localization & HAMMER_LOCALIZE_PSEUDOFS_MASK,
                      0, &error);
        if (ip) {
                if (hammer_debug_general & 0x0001) {
                        hdkprintf("pruning disconnected inode %016jx\n",
                                (intmax_t)elm->base.obj_id);
                }
                hammer_rel_inode(ip, 0);
                hammer_inode_waitreclaims(cursor->trans);
        } else {
                hkprintf("unable to prune disconnected inode %016jx\n",
                        (intmax_t)elm->base.obj_id);
        }
}