/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (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 2004 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#include <sys/systm.h>
#include <sys/types.h>
#include <sys/vnode.h>
#include <sys/file.h>
#include <sys/buf.h>
#include <sys/ddi.h>
#include <sys/errno.h>
#include <sys/cmn_err.h>
#include <sys/fs/ufs_inode.h>
#include <sys/fs/ufs_filio.h>
#include <sys/fs/ufs_snap.h>
#include <sys/fssnap_if.h>
#include <sys/sysmacros.h>
#include <sys/modctl.h>
#include <sys/fs/ufs_bio.h>
#include <sys/debug.h>
#include <sys/kmem.h>
#include <sys/inttypes.h>
#include <sys/vfs.h>
#include <sys/disp.h>
#include <sys/atomic.h>
#include <sys/conf.h>
#include <sys/param.h>
#include <sys/policy.h>

static int ufs_snap_init_backfile(int  *, int, vnode_t ***, struct ufsvfs *);
static void release_backing_vnodes(vnode_t ***, int);
static int ufs_snap_find_candidates(void *, struct ufsvfs *, int);

/*
 * Create a snapshot on a file system
 */
int
ufs_snap_create(struct vnode *vp, struct fiosnapcreate_multi *fiosnapp,
    cred_t *cr)
{
        int             error = 0;
        struct ufsvfs   *ufsvfsp = VTOI(vp)->i_ufsvfs;
        struct fs       *fs = ufsvfsp->vfs_fs;
        vnode_t         **bfvpp = NULL;
        struct lockfs   lf;
        void            *snapid = NULL;

        u_offset_t      nchunks;
        uint_t          chunksize, fragsperchunk;

        /*
         * Only privilege processes can create a snapshot for now.  This
         * would be better if it was based on the permissions of the device
         * file.
         */
        if (secpolicy_fs_config(cr, ufsvfsp->vfs_vfs) != 0)
                return (EPERM);

        /*
         * There is no reason to make a snapshot of a read-only file system
         */
        if (fs->fs_ronly) {
                fiosnapp->error = FIOCOW_EREADONLY;
                return (EROFS);
        }

        /*
         * Initialize the backing files to store old data.  This assumes any
         * preallocation and setup has been done already.
         * ufs_snap_init_backfile() allocates and returns a pointer to
         * a null-terminated array of vnodes in bfvpp.
         */
        error = ufs_snap_init_backfile(fiosnapp->backfiledesc,
            fiosnapp->backfilecount, &bfvpp, ufsvfsp);
        if (error) {
                fiosnapp->error = FIOCOW_EBACKFILE;
                return (error);
        }

        /*
         * File system must be write locked to prevent updates while
         * the snapshot is being established.
         */
        if ((error = ufs_fiolfss(vp, &lf)) != 0) {
                release_backing_vnodes(&bfvpp, fiosnapp->backfilecount);
                return (error);
        }

        if (!LOCKFS_IS_ULOCK(&lf)) {
                release_backing_vnodes(&bfvpp, fiosnapp->backfilecount);
                fiosnapp->error = FIOCOW_EULOCK;
                return (EINVAL);
        }

        lf.lf_lock = LOCKFS_WLOCK;
        lf.lf_flags = 0;
        lf.lf_comment = NULL;
        if ((error = ufs_fiolfs(vp, &lf, 1)) != 0) {
                release_backing_vnodes(&bfvpp, fiosnapp->backfilecount);
                fiosnapp->error = FIOCOW_EWLOCK;
                return (EINVAL);
        }

        /*
         * File system must be fairly consistent to enable snapshots
         */
        if (fs->fs_clean != FSACTIVE &&
            fs->fs_clean != FSSTABLE &&
            fs->fs_clean != FSCLEAN &&
            fs->fs_clean != FSLOG) {
                fiosnapp->error = FIOCOW_ECLEAN;
                error = EINVAL;
                goto unlockout;
        }

        /*
         * Only one snapshot is allowed per file system, so error if
         * a snapshot is already enabled.
         */
        if (ufsvfsp->vfs_snapshot) {
                fiosnapp->error = FIOCOW_EBUSY;
                error = EBUSY;
                goto unlockout;
        }

        /* Tell bio.c how to call our strategy routine.  XXX ugly hack */
        if (bio_snapshot_strategy == NULL)
                bio_snapshot_strategy =
                    (void (*) (void *, buf_t *))fssnap_strategy;

        /*
         * use chunk size that is passed in, or the file system
         * block size if it is zero.  For most cases, the file system
         * block size will be reasonably efficient.  A larger
         * chunksize uses less memory but may potentially induce more
         * I/O copying the larger chunks aside.
         */
        if (fiosnapp->chunksize != 0)
                chunksize = fiosnapp->chunksize;
        else
                chunksize = fs->fs_bsize * 4;


        /*
         * compute the number of chunks in this whole file system.  Since
         * the UFS allocation bitmaps are in units of fragments, we first
         * compute the number of fragments per chunk.  Things work out
         * nicer if the chunk size is a power-of-two multiple of the
         * fragment size.
         */
        if ((chunksize < fs->fs_fsize) || (chunksize % fs->fs_fsize != 0)) {
                fiosnapp->error = FIOCOW_ECHUNKSZ;
                error = EINVAL;
                goto unlockout;
        }
        fragsperchunk = chunksize >> fs->fs_fshift;
        nchunks = (fs->fs_size + fragsperchunk) / fragsperchunk;

        /*
         * Create and initialize snapshot state and allocate/initialize
         * translation table.  This does the real work of taking the snapshot.
         */
        snapid = fssnap_create(nchunks, chunksize, fiosnapp->maxsize, vp,
            fiosnapp->backfilecount, bfvpp, fiosnapp->backfilename,
            fiosnapp->backfilesize);
        if (snapid == NULL) {
                fiosnapp->error = FIOCOW_ECREATE;
                error = EINVAL;
                goto unlockout;
        }

        error = ufs_snap_find_candidates(snapid, ufsvfsp, chunksize);
        fiosnapp->snapshotnumber = fssnap_create_done(snapid);

        if (error) {
                cmn_err(CE_WARN, "ufs_snap_create: failed scanning bitmaps, "
                    "error = %d.", error);
                fiosnapp->error = FIOCOW_EBITMAP;
                goto unlockout;
        }

        ufsvfsp->vfs_snapshot = snapid;

unlockout:
        /*
         * Unlock the file system
         */
        lf.lf_lock = LOCKFS_ULOCK;
        lf.lf_flags = 0;
        if ((ufs_fiolfs(vp, &lf, 1) != 0) && !error) {
                fiosnapp->error = FIOCOW_ENOULOCK;
                error = EINVAL;
        } else {
                fiosnapp->error = 0;
        }

        /* clean up the snapshot if an error occurred. */
        if (error && snapid != NULL)
                (void) fssnap_delete(&snapid);
        else if (error && bfvpp != NULL)
                release_backing_vnodes(&bfvpp, fiosnapp->backfilecount);

        return (error);
}

static int
ufs_snap_init_backfile(int *filedesc, int count, vnode_t ***vppp,
    struct ufsvfs *ufsvfsp)
{
        file_t *fp;
        vnode_t **vpp;
        int i;

        vpp = (vnode_t **)kmem_zalloc((count  + 1) * sizeof (vnode_t *),
            KM_SLEEP);
        *vppp = vpp;
        for (i = 0; i < count; i++) {
                if ((fp = getf(*filedesc)) == NULL) {
                        release_backing_vnodes(vppp, count);
                        *vppp = NULL;
                        return (EBADF);
                }

                ASSERT(fp->f_vnode != NULL);
                VN_HOLD(fp->f_vnode);

                *vpp = fp->f_vnode;
                releasef(*filedesc);
                filedesc++;

                /* make sure the backing file is on a different file system */
                if ((*vpp)->v_vfsp == ufsvfsp->vfs_vfs) {
                        release_backing_vnodes(vppp, count);
                        *vppp = NULL;
                        return (EINVAL);
                }
                vpp++;
        }
        return (0);
}

static void
release_backing_vnodes(vnode_t ***bvppp, int count)
{
        vnode_t **vpp;

        vpp = *bvppp;
        while (*vpp) {
                VN_RELE(*vpp);
                *vpp++ = NULL;
        }
        kmem_free(*bvppp, (count + 1) * sizeof (vnode_t *));
        *bvppp = NULL;
}

static int
ufs_snap_find_candidates(void *snapid, struct ufsvfs *ufsvfsp, int chunksize)
{
        struct fs       *fs = ufsvfsp->vfs_fs;
        struct buf      *cgbp;  /* cylinder group buffer */
        struct cg       *cgp;   /* cylinder group data */
        ulong_t         cg;
        ulong_t         cgbase;
        ulong_t         chunk;
        uchar_t         *blksfree;

        ulong_t         curfrag;
        int             error = 0;

        /*
         * read through each ufs cylinder group and fetch the fragment
         * allocation bitmap.  UFS indicates a fragment is allocated by
         * a zero bit (not a one bit) in the fragment offset.
         */
        cgbase = 0LL;
        for (cg = 0; cg < fs->fs_ncg; cg++) {
                /* read the cylinder group in */
                cgbp = BREAD(ufsvfsp->vfs_dev,
                    (daddr_t)fsbtodb(fs, cgtod(fs, cg)), (int)fs->fs_cgsize);
                if ((error = geterror(cgbp)) != 0) {
                        brelse(cgbp);
                        goto errout;
                }
                cgp = cgbp->b_un.b_cg;

                /* check the magic number */
                if (cgp->cg_magic != CG_MAGIC) {
                        cmn_err(CE_WARN, "ufs_snap_find_candidates: cg %lu "
                            "magic number (0x%x) does not match expected "
                            "magic number (0x%x)", cg, cgp->cg_magic, CG_MAGIC);
                        error = EIO;
                        goto errout;
                }

                blksfree = cg_blksfree(cgp);

                /*
                 * go through the allocation bitmap and set the
                 * corresponding bit in the candidate map.
                 */
                for (curfrag = 0; curfrag < cgp->cg_ndblk; curfrag++) {
                        if (isclr(blksfree, curfrag)) {
                                /*
                                 * this assumes chunksize is a multiple of
                                 * the fragment size
                                 */
                                chunk = (ulong_t)((cgbase + curfrag) /
                                    (chunksize >> fs->fs_fshift));

                                fssnap_set_candidate(snapid, chunk);
                                /*
                                 * no need to scan the rest of this chunk since
                                 * it is already marked, so skip to the next
                                 */
                                curfrag += ((chunksize >> fs->fs_fshift) -
                                    ((cgbase + curfrag) %
                                    (chunksize >> fs->fs_fshift))) - 1;
                        }
                }

                cgbase += cgp->cg_ndblk;
                ASSERT(cgbase <= fs->fs_size);
                brelse(cgbp);
        } /* cylinder group loop */

        ASSERT(cgbase == fs->fs_size);

errout:
        return (error);
}


int
ufs_snap_delete(struct vnode *vp, struct fiosnapdelete *fiosnapp, cred_t *cr)
{
        struct ufsvfs   *ufsvfsp = VTOI(vp)->i_ufsvfs;
        struct fs       *fs = ufsvfsp->vfs_fs;

        /*
         * Initialize fields in the user's buffer
         */
        fiosnapp->error = 0;

        /*
         * No snapshot exists, we're done.
         */
        if (ufsvfsp->vfs_snapshot == NULL)
                return (ENOENT);

        /*
         * must have sufficient privileges.
         */
        if (secpolicy_fs_config(cr, ufsvfsp->vfs_vfs) != 0)
                return (EPERM);

        /*
         * Readonly file system
         */
        if (fs->fs_ronly) {
                fiosnapp->error = FIOCOW_EREADONLY;
                return (EROFS);
        }

        /* free the data structures and clear the vfs_snapshot field. */
        fiosnapp->snapshotnumber = fssnap_delete(&ufsvfsp->vfs_snapshot);

        if (fiosnapp->snapshotnumber == -1)
                return (EINVAL);

        return (0);
}