/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2012, 2015 by Delphix. All rights reserved.
 * Copyright (c) 2019, loli10K <ezomori.nozomu@gmail.com>. All rights reserved.
 */

#include <sys/dmu.h>
#include <sys/dmu_impl.h>
#include <sys/dmu_tx.h>
#include <sys/dbuf.h>
#include <sys/dnode.h>
#include <sys/zfs_context.h>
#include <sys/dmu_objset.h>
#include <sys/dmu_traverse.h>
#include <sys/dsl_dataset.h>
#include <sys/dsl_dir.h>
#include <sys/dsl_pool.h>
#include <sys/dsl_synctask.h>
#include <sys/zfs_ioctl.h>
#include <sys/zap.h>
#include <sys/zio_checksum.h>
#include <sys/zfs_znode.h>

struct diffarg {
        struct vnode *da_vp;            /* file to which we are reporting */
        offset_t *da_offp;
        int da_err;                     /* error that stopped diff search */
        dmu_diff_record_t da_ddr;
};

static int
write_record(struct diffarg *da)
{
        ssize_t resid; /* have to get resid to get detailed errno */

        if (da->da_ddr.ddr_type == DDR_NONE) {
                da->da_err = 0;
                return (0);
        }

        da->da_err = vn_rdwr(UIO_WRITE, da->da_vp, (caddr_t)&da->da_ddr,
            sizeof (da->da_ddr), 0, UIO_SYSSPACE, FAPPEND,
            RLIM64_INFINITY, CRED(), &resid);
        *da->da_offp += sizeof (da->da_ddr);
        return (da->da_err);
}

static int
report_free_dnode_range(struct diffarg *da, uint64_t first, uint64_t last)
{
        ASSERT(first <= last);
        if (da->da_ddr.ddr_type != DDR_FREE ||
            first != da->da_ddr.ddr_last + 1) {
                if (write_record(da) != 0)
                        return (da->da_err);
                da->da_ddr.ddr_type = DDR_FREE;
                da->da_ddr.ddr_first = first;
                da->da_ddr.ddr_last = last;
                return (0);
        }
        da->da_ddr.ddr_last = last;
        return (0);
}

static int
report_dnode(struct diffarg *da, uint64_t object, dnode_phys_t *dnp)
{
        ASSERT(dnp != NULL);
        if (dnp->dn_type == DMU_OT_NONE)
                return (report_free_dnode_range(da, object, object));

        if (da->da_ddr.ddr_type != DDR_INUSE ||
            object != da->da_ddr.ddr_last + 1) {
                if (write_record(da) != 0)
                        return (da->da_err);
                da->da_ddr.ddr_type = DDR_INUSE;
                da->da_ddr.ddr_first = da->da_ddr.ddr_last = object;
                return (0);
        }
        da->da_ddr.ddr_last = object;
        return (0);
}

#define DBP_SPAN(dnp, level)                              \
        (((uint64_t)dnp->dn_datablkszsec) << (SPA_MINBLOCKSHIFT + \
        (level) * (dnp->dn_indblkshift - SPA_BLKPTRSHIFT)))

/* ARGSUSED */
static int
diff_cb(spa_t *spa, zilog_t *zilog, const blkptr_t *bp,
    const zbookmark_phys_t *zb, const dnode_phys_t *dnp, void *arg)
{
        struct diffarg *da = arg;
        int err = 0;

        if (issig(JUSTLOOKING) && issig(FORREAL))
                return (SET_ERROR(EINTR));

        if (bp == NULL || zb->zb_object != DMU_META_DNODE_OBJECT)
                return (0);

        if (BP_IS_HOLE(bp)) {
                uint64_t span = DBP_SPAN(dnp, zb->zb_level);
                uint64_t dnobj = (zb->zb_blkid * span) >> DNODE_SHIFT;

                err = report_free_dnode_range(da, dnobj,
                    dnobj + (span >> DNODE_SHIFT) - 1);
                if (err)
                        return (err);
        } else if (zb->zb_level == 0) {
                dnode_phys_t *blk;
                arc_buf_t *abuf;
                arc_flags_t aflags = ARC_FLAG_WAIT;
                int epb = BP_GET_LSIZE(bp) >> DNODE_SHIFT;
                int zio_flags = ZIO_FLAG_CANFAIL;
                int i;

                if (BP_IS_PROTECTED(bp))
                        zio_flags |= ZIO_FLAG_RAW;

                if (arc_read(NULL, spa, bp, arc_getbuf_func, &abuf,
                    ZIO_PRIORITY_ASYNC_READ, zio_flags, &aflags, zb) != 0)
                        return (SET_ERROR(EIO));

                blk = abuf->b_data;
                for (i = 0; i < epb; i += blk[i].dn_extra_slots + 1) {
                        uint64_t dnobj = (zb->zb_blkid <<
                            (DNODE_BLOCK_SHIFT - DNODE_SHIFT)) + i;
                        err = report_dnode(da, dnobj, blk+i);
                        if (err)
                                break;
                }
                arc_buf_destroy(abuf, &abuf);
                if (err)
                        return (err);
                /* Don't care about the data blocks */
                return (TRAVERSE_VISIT_NO_CHILDREN);
        }
        return (0);
}

int
dmu_diff(const char *tosnap_name, const char *fromsnap_name,
    struct vnode *vp, offset_t *offp)
{
        struct diffarg da;
        dsl_dataset_t *fromsnap;
        dsl_dataset_t *tosnap;
        dsl_pool_t *dp;
        int error;
        uint64_t fromtxg;

        if (strchr(tosnap_name, '@') == NULL ||
            strchr(fromsnap_name, '@') == NULL)
                return (SET_ERROR(EINVAL));

        error = dsl_pool_hold(tosnap_name, FTAG, &dp);
        if (error != 0)
                return (error);

        error = dsl_dataset_hold(dp, tosnap_name, FTAG, &tosnap);
        if (error != 0) {
                dsl_pool_rele(dp, FTAG);
                return (error);
        }

        error = dsl_dataset_hold(dp, fromsnap_name, FTAG, &fromsnap);
        if (error != 0) {
                dsl_dataset_rele(tosnap, FTAG);
                dsl_pool_rele(dp, FTAG);
                return (error);
        }

        if (!dsl_dataset_is_before(tosnap, fromsnap, 0)) {
                dsl_dataset_rele(fromsnap, FTAG);
                dsl_dataset_rele(tosnap, FTAG);
                dsl_pool_rele(dp, FTAG);
                return (SET_ERROR(EXDEV));
        }

        fromtxg = dsl_dataset_phys(fromsnap)->ds_creation_txg;
        dsl_dataset_rele(fromsnap, FTAG);

        dsl_dataset_long_hold(tosnap, FTAG);
        dsl_pool_rele(dp, FTAG);

        da.da_vp = vp;
        da.da_offp = offp;
        da.da_ddr.ddr_type = DDR_NONE;
        da.da_ddr.ddr_first = da.da_ddr.ddr_last = 0;
        da.da_err = 0;

        /*
         * Since zfs diff only looks at dnodes which are stored in plaintext
         * (other than bonus buffers), we don't technically need to decrypt
         * the dataset to perform this operation. However, the command line
         * utility will still fail if the keys are not loaded because the
         * dataset isn't mounted and because it will fail when it attempts to
         * call the ZFS_IOC_OBJ_TO_STATS ioctl.
         */
        error = traverse_dataset(tosnap, fromtxg,
            TRAVERSE_PRE | TRAVERSE_PREFETCH_METADATA | TRAVERSE_NO_DECRYPT,
            diff_cb, &da);

        if (error != 0) {
                da.da_err = error;
        } else {
                /* we set the da.da_err we return as side-effect */
                (void) write_record(&da);
        }

        dsl_dataset_long_rele(tosnap, FTAG);
        dsl_dataset_rele(tosnap, FTAG);

        return (da.da_err);
}