// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2000-2006 Silicon Graphics, Inc.
 * All Rights Reserved.
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_shared.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_bit.h"
#include "xfs_mount.h"
#include "xfs_trans.h"
#include "xfs_buf_item.h"
#include "xfs_trans_priv.h"
#include "xfs_trace.h"
#include "xfs_log.h"
#include "xfs_log_priv.h"
#include "xfs_log_recover.h"
#include "xfs_error.h"
#include "xfs_inode.h"
#include "xfs_dir2.h"
#include "xfs_quota.h"

/*
 * This structure is used during recovery to record the buf log items which
 * have been canceled and should not be replayed.
 */
struct xfs_buf_cancel {
        xfs_daddr_t             bc_blkno;
        uint                    bc_len;
        int                     bc_refcount;
        struct list_head        bc_list;
};

static struct xfs_buf_cancel *
xlog_find_buffer_cancelled(
        struct xlog             *log,
        xfs_daddr_t             blkno,
        uint                    len)
{
        struct list_head        *bucket;
        struct xfs_buf_cancel   *bcp;

        if (!log->l_buf_cancel_table)
                return NULL;

        bucket = XLOG_BUF_CANCEL_BUCKET(log, blkno);
        list_for_each_entry(bcp, bucket, bc_list) {
                if (bcp->bc_blkno == blkno && bcp->bc_len == len)
                        return bcp;
        }

        return NULL;
}

static bool
xlog_add_buffer_cancelled(
        struct xlog             *log,
        xfs_daddr_t             blkno,
        uint                    len)
{
        struct xfs_buf_cancel   *bcp;

        /*
         * If we find an existing cancel record, this indicates that the buffer
         * was cancelled multiple times.  To ensure that during pass 2 we keep
         * the record in the table until we reach its last occurrence in the
         * log, a reference count is kept to tell how many times we expect to
         * see this record during the second pass.
         */
        bcp = xlog_find_buffer_cancelled(log, blkno, len);
        if (bcp) {
                bcp->bc_refcount++;
                return false;
        }

        bcp = kmem_alloc(sizeof(struct xfs_buf_cancel), 0);
        bcp->bc_blkno = blkno;
        bcp->bc_len = len;
        bcp->bc_refcount = 1;
        list_add_tail(&bcp->bc_list, XLOG_BUF_CANCEL_BUCKET(log, blkno));
        return true;
}

/*
 * Check if there is and entry for blkno, len in the buffer cancel record table.
 */
bool
xlog_is_buffer_cancelled(
        struct xlog             *log,
        xfs_daddr_t             blkno,
        uint                    len)
{
        return xlog_find_buffer_cancelled(log, blkno, len) != NULL;
}

/*
 * Check if there is and entry for blkno, len in the buffer cancel record table,
 * and decremented the reference count on it if there is one.
 *
 * Remove the cancel record once the refcount hits zero, so that if the same
 * buffer is re-used again after its last cancellation we actually replay the
 * changes made at that point.
 */
static bool
xlog_put_buffer_cancelled(
        struct xlog             *log,
        xfs_daddr_t             blkno,
        uint                    len)
{
        struct xfs_buf_cancel   *bcp;

        bcp = xlog_find_buffer_cancelled(log, blkno, len);
        if (!bcp) {
                ASSERT(0);
                return false;
        }

        if (--bcp->bc_refcount == 0) {
                list_del(&bcp->bc_list);
                kmem_free(bcp);
        }
        return true;
}

/* log buffer item recovery */

/*
 * Sort buffer items for log recovery.  Most buffer items should end up on the
 * buffer list and are recovered first, with the following exceptions:
 *
 * 1. XFS_BLF_CANCEL buffers must be processed last because some log items
 *    might depend on the incor ecancellation record, and replaying a cancelled
 *    buffer item can remove the incore record.
 *
 * 2. XFS_BLF_INODE_BUF buffers are handled after most regular items so that
 *    we replay di_next_unlinked only after flushing the inode 'free' state
 *    to the inode buffer.
 *
 * See xlog_recover_reorder_trans for more details.
 */
STATIC enum xlog_recover_reorder
xlog_recover_buf_reorder(
        struct xlog_recover_item        *item)
{
        struct xfs_buf_log_format       *buf_f = item->ri_buf[0].i_addr;

        if (buf_f->blf_flags & XFS_BLF_CANCEL)
                return XLOG_REORDER_CANCEL_LIST;
        if (buf_f->blf_flags & XFS_BLF_INODE_BUF)
                return XLOG_REORDER_INODE_BUFFER_LIST;
        return XLOG_REORDER_BUFFER_LIST;
}

STATIC void
xlog_recover_buf_ra_pass2(
        struct xlog                     *log,
        struct xlog_recover_item        *item)
{
        struct xfs_buf_log_format       *buf_f = item->ri_buf[0].i_addr;

        xlog_buf_readahead(log, buf_f->blf_blkno, buf_f->blf_len, NULL);
}

/*
 * Build up the table of buf cancel records so that we don't replay cancelled
 * data in the second pass.
 */
static int
xlog_recover_buf_commit_pass1(
        struct xlog                     *log,
        struct xlog_recover_item        *item)
{
        struct xfs_buf_log_format       *bf = item->ri_buf[0].i_addr;

        if (!xfs_buf_log_check_iovec(&item->ri_buf[0])) {
                xfs_err(log->l_mp, "bad buffer log item size (%d)",
                                item->ri_buf[0].i_len);
                return -EFSCORRUPTED;
        }

        if (!(bf->blf_flags & XFS_BLF_CANCEL))
                trace_xfs_log_recover_buf_not_cancel(log, bf);
        else if (xlog_add_buffer_cancelled(log, bf->blf_blkno, bf->blf_len))
                trace_xfs_log_recover_buf_cancel_add(log, bf);
        else
                trace_xfs_log_recover_buf_cancel_ref_inc(log, bf);
        return 0;
}

/*
 * Validate the recovered buffer is of the correct type and attach the
 * appropriate buffer operations to them for writeback. Magic numbers are in a
 * few places:
 *      the first 16 bits of the buffer (inode buffer, dquot buffer),
 *      the first 32 bits of the buffer (most blocks),
 *      inside a struct xfs_da_blkinfo at the start of the buffer.
 */
static void
xlog_recover_validate_buf_type(
        struct xfs_mount                *mp,
        struct xfs_buf                  *bp,
        struct xfs_buf_log_format       *buf_f,
        xfs_lsn_t                       current_lsn)
{
        struct xfs_da_blkinfo           *info = bp->b_addr;
        uint32_t                        magic32;
        uint16_t                        magic16;
        uint16_t                        magicda;
        char                            *warnmsg = NULL;

        /*
         * We can only do post recovery validation on items on CRC enabled
         * fielsystems as we need to know when the buffer was written to be able
         * to determine if we should have replayed the item. If we replay old
         * metadata over a newer buffer, then it will enter a temporarily
         * inconsistent state resulting in verification failures. Hence for now
         * just avoid the verification stage for non-crc filesystems
         */
        if (!xfs_has_crc(mp))
                return;

        magic32 = be32_to_cpu(*(__be32 *)bp->b_addr);
        magic16 = be16_to_cpu(*(__be16*)bp->b_addr);
        magicda = be16_to_cpu(info->magic);
        switch (xfs_blft_from_flags(buf_f)) {
        case XFS_BLFT_BTREE_BUF:
                switch (magic32) {
                case XFS_ABTB_CRC_MAGIC:
                case XFS_ABTB_MAGIC:
                        bp->b_ops = &xfs_bnobt_buf_ops;
                        break;
                case XFS_ABTC_CRC_MAGIC:
                case XFS_ABTC_MAGIC:
                        bp->b_ops = &xfs_cntbt_buf_ops;
                        break;
                case XFS_IBT_CRC_MAGIC:
                case XFS_IBT_MAGIC:
                        bp->b_ops = &xfs_inobt_buf_ops;
                        break;
                case XFS_FIBT_CRC_MAGIC:
                case XFS_FIBT_MAGIC:
                        bp->b_ops = &xfs_finobt_buf_ops;
                        break;
                case XFS_BMAP_CRC_MAGIC:
                case XFS_BMAP_MAGIC:
                        bp->b_ops = &xfs_bmbt_buf_ops;
                        break;
                case XFS_RMAP_CRC_MAGIC:
                        bp->b_ops = &xfs_rmapbt_buf_ops;
                        break;
                case XFS_REFC_CRC_MAGIC:
                        bp->b_ops = &xfs_refcountbt_buf_ops;
                        break;
                default:
                        warnmsg = "Bad btree block magic!";
                        break;
                }
                break;
        case XFS_BLFT_AGF_BUF:
                if (magic32 != XFS_AGF_MAGIC) {
                        warnmsg = "Bad AGF block magic!";
                        break;
                }
                bp->b_ops = &xfs_agf_buf_ops;
                break;
        case XFS_BLFT_AGFL_BUF:
                if (magic32 != XFS_AGFL_MAGIC) {
                        warnmsg = "Bad AGFL block magic!";
                        break;
                }
                bp->b_ops = &xfs_agfl_buf_ops;
                break;
        case XFS_BLFT_AGI_BUF:
                if (magic32 != XFS_AGI_MAGIC) {
                        warnmsg = "Bad AGI block magic!";
                        break;
                }
                bp->b_ops = &xfs_agi_buf_ops;
                break;
        case XFS_BLFT_UDQUOT_BUF:
        case XFS_BLFT_PDQUOT_BUF:
        case XFS_BLFT_GDQUOT_BUF:
#ifdef CONFIG_XFS_QUOTA
                if (magic16 != XFS_DQUOT_MAGIC) {
                        warnmsg = "Bad DQUOT block magic!";
                        break;
                }
                bp->b_ops = &xfs_dquot_buf_ops;
#else
                xfs_alert(mp,
        "Trying to recover dquots without QUOTA support built in!");
                ASSERT(0);
#endif
                break;
        case XFS_BLFT_DINO_BUF:
                if (magic16 != XFS_DINODE_MAGIC) {
                        warnmsg = "Bad INODE block magic!";
                        break;
                }
                bp->b_ops = &xfs_inode_buf_ops;
                break;
        case XFS_BLFT_SYMLINK_BUF:
                if (magic32 != XFS_SYMLINK_MAGIC) {
                        warnmsg = "Bad symlink block magic!";
                        break;
                }
                bp->b_ops = &xfs_symlink_buf_ops;
                break;
        case XFS_BLFT_DIR_BLOCK_BUF:
                if (magic32 != XFS_DIR2_BLOCK_MAGIC &&
                    magic32 != XFS_DIR3_BLOCK_MAGIC) {
                        warnmsg = "Bad dir block magic!";
                        break;
                }
                bp->b_ops = &xfs_dir3_block_buf_ops;
                break;
        case XFS_BLFT_DIR_DATA_BUF:
                if (magic32 != XFS_DIR2_DATA_MAGIC &&
                    magic32 != XFS_DIR3_DATA_MAGIC) {
                        warnmsg = "Bad dir data magic!";
                        break;
                }
                bp->b_ops = &xfs_dir3_data_buf_ops;
                break;
        case XFS_BLFT_DIR_FREE_BUF:
                if (magic32 != XFS_DIR2_FREE_MAGIC &&
                    magic32 != XFS_DIR3_FREE_MAGIC) {
                        warnmsg = "Bad dir3 free magic!";
                        break;
                }
                bp->b_ops = &xfs_dir3_free_buf_ops;
                break;
        case XFS_BLFT_DIR_LEAF1_BUF:
                if (magicda != XFS_DIR2_LEAF1_MAGIC &&
                    magicda != XFS_DIR3_LEAF1_MAGIC) {
                        warnmsg = "Bad dir leaf1 magic!";
                        break;
                }
                bp->b_ops = &xfs_dir3_leaf1_buf_ops;
                break;
        case XFS_BLFT_DIR_LEAFN_BUF:
                if (magicda != XFS_DIR2_LEAFN_MAGIC &&
                    magicda != XFS_DIR3_LEAFN_MAGIC) {
                        warnmsg = "Bad dir leafn magic!";
                        break;
                }
                bp->b_ops = &xfs_dir3_leafn_buf_ops;
                break;
        case XFS_BLFT_DA_NODE_BUF:
                if (magicda != XFS_DA_NODE_MAGIC &&
                    magicda != XFS_DA3_NODE_MAGIC) {
                        warnmsg = "Bad da node magic!";
                        break;
                }
                bp->b_ops = &xfs_da3_node_buf_ops;
                break;
        case XFS_BLFT_ATTR_LEAF_BUF:
                if (magicda != XFS_ATTR_LEAF_MAGIC &&
                    magicda != XFS_ATTR3_LEAF_MAGIC) {
                        warnmsg = "Bad attr leaf magic!";
                        break;
                }
                bp->b_ops = &xfs_attr3_leaf_buf_ops;
                break;
        case XFS_BLFT_ATTR_RMT_BUF:
                if (magic32 != XFS_ATTR3_RMT_MAGIC) {
                        warnmsg = "Bad attr remote magic!";
                        break;
                }
                bp->b_ops = &xfs_attr3_rmt_buf_ops;
                break;
        case XFS_BLFT_SB_BUF:
                if (magic32 != XFS_SB_MAGIC) {
                        warnmsg = "Bad SB block magic!";
                        break;
                }
                bp->b_ops = &xfs_sb_buf_ops;
                break;
#ifdef CONFIG_XFS_RT
        case XFS_BLFT_RTBITMAP_BUF:
        case XFS_BLFT_RTSUMMARY_BUF:
                /* no magic numbers for verification of RT buffers */
                bp->b_ops = &xfs_rtbuf_ops;
                break;
#endif /* CONFIG_XFS_RT */
        default:
                xfs_warn(mp, "Unknown buffer type %d!",
                         xfs_blft_from_flags(buf_f));
                break;
        }

        /*
         * Nothing else to do in the case of a NULL current LSN as this means
         * the buffer is more recent than the change in the log and will be
         * skipped.
         */
        if (current_lsn == NULLCOMMITLSN)
                return;

        if (warnmsg) {
                xfs_warn(mp, warnmsg);
                ASSERT(0);
        }

        /*
         * We must update the metadata LSN of the buffer as it is written out to
         * ensure that older transactions never replay over this one and corrupt
         * the buffer. This can occur if log recovery is interrupted at some
         * point after the current transaction completes, at which point a
         * subsequent mount starts recovery from the beginning.
         *
         * Write verifiers update the metadata LSN from log items attached to
         * the buffer. Therefore, initialize a bli purely to carry the LSN to
         * the verifier.
         */
        if (bp->b_ops) {
                struct xfs_buf_log_item *bip;

                bp->b_flags |= _XBF_LOGRECOVERY;
                xfs_buf_item_init(bp, mp);
                bip = bp->b_log_item;
                bip->bli_item.li_lsn = current_lsn;
        }
}

/*
 * Perform a 'normal' buffer recovery.  Each logged region of the
 * buffer should be copied over the corresponding region in the
 * given buffer.  The bitmap in the buf log format structure indicates
 * where to place the logged data.
 */
STATIC void
xlog_recover_do_reg_buffer(
        struct xfs_mount                *mp,
        struct xlog_recover_item        *item,
        struct xfs_buf                  *bp,
        struct xfs_buf_log_format       *buf_f,
        xfs_lsn_t                       current_lsn)
{
        int                     i;
        int                     bit;
        int                     nbits;
        xfs_failaddr_t          fa;
        const size_t            size_disk_dquot = sizeof(struct xfs_disk_dquot);

        trace_xfs_log_recover_buf_reg_buf(mp->m_log, buf_f);

        bit = 0;
        i = 1;  /* 0 is the buf format structure */
        while (1) {
                bit = xfs_next_bit(buf_f->blf_data_map,
                                   buf_f->blf_map_size, bit);
                if (bit == -1)
                        break;
                nbits = xfs_contig_bits(buf_f->blf_data_map,
                                        buf_f->blf_map_size, bit);
                ASSERT(nbits > 0);
                ASSERT(item->ri_buf[i].i_addr != NULL);
                ASSERT(item->ri_buf[i].i_len % XFS_BLF_CHUNK == 0);
                ASSERT(BBTOB(bp->b_length) >=
                       ((uint)bit << XFS_BLF_SHIFT) + (nbits << XFS_BLF_SHIFT));

                /*
                 * The dirty regions logged in the buffer, even though
                 * contiguous, may span multiple chunks. This is because the
                 * dirty region may span a physical page boundary in a buffer
                 * and hence be split into two separate vectors for writing into
                 * the log. Hence we need to trim nbits back to the length of
                 * the current region being copied out of the log.
                 */
                if (item->ri_buf[i].i_len < (nbits << XFS_BLF_SHIFT))
                        nbits = item->ri_buf[i].i_len >> XFS_BLF_SHIFT;

                /*
                 * Do a sanity check if this is a dquot buffer. Just checking
                 * the first dquot in the buffer should do. XXXThis is
                 * probably a good thing to do for other buf types also.
                 */
                fa = NULL;
                if (buf_f->blf_flags &
                   (XFS_BLF_UDQUOT_BUF|XFS_BLF_PDQUOT_BUF|XFS_BLF_GDQUOT_BUF)) {
                        if (item->ri_buf[i].i_addr == NULL) {
                                xfs_alert(mp,
                                        "XFS: NULL dquot in %s.", __func__);
                                goto next;
                        }
                        if (item->ri_buf[i].i_len < size_disk_dquot) {
                                xfs_alert(mp,
                                        "XFS: dquot too small (%d) in %s.",
                                        item->ri_buf[i].i_len, __func__);
                                goto next;
                        }
                        fa = xfs_dquot_verify(mp, item->ri_buf[i].i_addr, -1);
                        if (fa) {
                                xfs_alert(mp,
        "dquot corrupt at %pS trying to replay into block 0x%llx",
                                        fa, xfs_buf_daddr(bp));
                                goto next;
                        }
                }

                memcpy(xfs_buf_offset(bp,
                        (uint)bit << XFS_BLF_SHIFT),    /* dest */
                        item->ri_buf[i].i_addr,         /* source */
                        nbits<<XFS_BLF_SHIFT);          /* length */
 next:
                i++;
                bit += nbits;
        }

        /* Shouldn't be any more regions */
        ASSERT(i == item->ri_total);

        xlog_recover_validate_buf_type(mp, bp, buf_f, current_lsn);
}

/*
 * Perform a dquot buffer recovery.
 * Simple algorithm: if we have found a QUOTAOFF log item of the same type
 * (ie. USR or GRP), then just toss this buffer away; don't recover it.
 * Else, treat it as a regular buffer and do recovery.
 *
 * Return false if the buffer was tossed and true if we recovered the buffer to
 * indicate to the caller if the buffer needs writing.
 */
STATIC bool
xlog_recover_do_dquot_buffer(
        struct xfs_mount                *mp,
        struct xlog                     *log,
        struct xlog_recover_item        *item,
        struct xfs_buf                  *bp,
        struct xfs_buf_log_format       *buf_f)
{
        uint                    type;

        trace_xfs_log_recover_buf_dquot_buf(log, buf_f);

        /*
         * Filesystems are required to send in quota flags at mount time.
         */
        if (!mp->m_qflags)
                return false;

        type = 0;
        if (buf_f->blf_flags & XFS_BLF_UDQUOT_BUF)
                type |= XFS_DQTYPE_USER;
        if (buf_f->blf_flags & XFS_BLF_PDQUOT_BUF)
                type |= XFS_DQTYPE_PROJ;
        if (buf_f->blf_flags & XFS_BLF_GDQUOT_BUF)
                type |= XFS_DQTYPE_GROUP;
        /*
         * This type of quotas was turned off, so ignore this buffer
         */
        if (log->l_quotaoffs_flag & type)
                return false;

        xlog_recover_do_reg_buffer(mp, item, bp, buf_f, NULLCOMMITLSN);
        return true;
}

/*
 * Perform recovery for a buffer full of inodes.  In these buffers, the only
 * data which should be recovered is that which corresponds to the
 * di_next_unlinked pointers in the on disk inode structures.  The rest of the
 * data for the inodes is always logged through the inodes themselves rather
 * than the inode buffer and is recovered in xlog_recover_inode_pass2().
 *
 * The only time when buffers full of inodes are fully recovered is when the
 * buffer is full of newly allocated inodes.  In this case the buffer will
 * not be marked as an inode buffer and so will be sent to
 * xlog_recover_do_reg_buffer() below during recovery.
 */
STATIC int
xlog_recover_do_inode_buffer(
        struct xfs_mount                *mp,
        struct xlog_recover_item        *item,
        struct xfs_buf                  *bp,
        struct xfs_buf_log_format       *buf_f)
{
        int                             i;
        int                             item_index = 0;
        int                             bit = 0;
        int                             nbits = 0;
        int                             reg_buf_offset = 0;
        int                             reg_buf_bytes = 0;
        int                             next_unlinked_offset;
        int                             inodes_per_buf;
        xfs_agino_t                     *logged_nextp;
        xfs_agino_t                     *buffer_nextp;

        trace_xfs_log_recover_buf_inode_buf(mp->m_log, buf_f);

        /*
         * Post recovery validation only works properly on CRC enabled
         * filesystems.
         */
        if (xfs_has_crc(mp))
                bp->b_ops = &xfs_inode_buf_ops;

        inodes_per_buf = BBTOB(bp->b_length) >> mp->m_sb.sb_inodelog;
        for (i = 0; i < inodes_per_buf; i++) {
                next_unlinked_offset = (i * mp->m_sb.sb_inodesize) +
                        offsetof(xfs_dinode_t, di_next_unlinked);

                while (next_unlinked_offset >=
                       (reg_buf_offset + reg_buf_bytes)) {
                        /*
                         * The next di_next_unlinked field is beyond
                         * the current logged region.  Find the next
                         * logged region that contains or is beyond
                         * the current di_next_unlinked field.
                         */
                        bit += nbits;
                        bit = xfs_next_bit(buf_f->blf_data_map,
                                           buf_f->blf_map_size, bit);

                        /*
                         * If there are no more logged regions in the
                         * buffer, then we're done.
                         */
                        if (bit == -1)
                                return 0;

                        nbits = xfs_contig_bits(buf_f->blf_data_map,
                                                buf_f->blf_map_size, bit);
                        ASSERT(nbits > 0);
                        reg_buf_offset = bit << XFS_BLF_SHIFT;
                        reg_buf_bytes = nbits << XFS_BLF_SHIFT;
                        item_index++;
                }

                /*
                 * If the current logged region starts after the current
                 * di_next_unlinked field, then move on to the next
                 * di_next_unlinked field.
                 */
                if (next_unlinked_offset < reg_buf_offset)
                        continue;

                ASSERT(item->ri_buf[item_index].i_addr != NULL);
                ASSERT((item->ri_buf[item_index].i_len % XFS_BLF_CHUNK) == 0);
                ASSERT((reg_buf_offset + reg_buf_bytes) <= BBTOB(bp->b_length));

                /*
                 * The current logged region contains a copy of the
                 * current di_next_unlinked field.  Extract its value
                 * and copy it to the buffer copy.
                 */
                logged_nextp = item->ri_buf[item_index].i_addr +
                                next_unlinked_offset - reg_buf_offset;
                if (XFS_IS_CORRUPT(mp, *logged_nextp == 0)) {
                        xfs_alert(mp,
                "Bad inode buffer log record (ptr = "PTR_FMT", bp = "PTR_FMT"). "
                "Trying to replay bad (0) inode di_next_unlinked field.",
                                item, bp);
                        return -EFSCORRUPTED;
                }

                buffer_nextp = xfs_buf_offset(bp, next_unlinked_offset);
                *buffer_nextp = *logged_nextp;

                /*
                 * If necessary, recalculate the CRC in the on-disk inode. We
                 * have to leave the inode in a consistent state for whoever
                 * reads it next....
                 */
                xfs_dinode_calc_crc(mp,
                                xfs_buf_offset(bp, i * mp->m_sb.sb_inodesize));

        }

        return 0;
}

/*
 * V5 filesystems know the age of the buffer on disk being recovered. We can
 * have newer objects on disk than we are replaying, and so for these cases we
 * don't want to replay the current change as that will make the buffer contents
 * temporarily invalid on disk.
 *
 * The magic number might not match the buffer type we are going to recover
 * (e.g. reallocated blocks), so we ignore the xfs_buf_log_format flags.  Hence
 * extract the LSN of the existing object in the buffer based on it's current
 * magic number.  If we don't recognise the magic number in the buffer, then
 * return a LSN of -1 so that the caller knows it was an unrecognised block and
 * so can recover the buffer.
 *
 * Note: we cannot rely solely on magic number matches to determine that the
 * buffer has a valid LSN - we also need to verify that it belongs to this
 * filesystem, so we need to extract the object's LSN and compare it to that
 * which we read from the superblock. If the UUIDs don't match, then we've got a
 * stale metadata block from an old filesystem instance that we need to recover
 * over the top of.
 */
static xfs_lsn_t
xlog_recover_get_buf_lsn(
        struct xfs_mount        *mp,
        struct xfs_buf          *bp,
        struct xfs_buf_log_format *buf_f)
{
        uint32_t                magic32;
        uint16_t                magic16;
        uint16_t                magicda;
        void                    *blk = bp->b_addr;
        uuid_t                  *uuid;
        xfs_lsn_t               lsn = -1;
        uint16_t                blft;

        /* v4 filesystems always recover immediately */
        if (!xfs_has_crc(mp))
                goto recover_immediately;

        /*
         * realtime bitmap and summary file blocks do not have magic numbers or
         * UUIDs, so we must recover them immediately.
         */
        blft = xfs_blft_from_flags(buf_f);
        if (blft == XFS_BLFT_RTBITMAP_BUF || blft == XFS_BLFT_RTSUMMARY_BUF)
                goto recover_immediately;

        magic32 = be32_to_cpu(*(__be32 *)blk);
        switch (magic32) {
        case XFS_ABTB_CRC_MAGIC:
        case XFS_ABTC_CRC_MAGIC:
        case XFS_ABTB_MAGIC:
        case XFS_ABTC_MAGIC:
        case XFS_RMAP_CRC_MAGIC:
        case XFS_REFC_CRC_MAGIC:
        case XFS_FIBT_CRC_MAGIC:
        case XFS_FIBT_MAGIC:
        case XFS_IBT_CRC_MAGIC:
        case XFS_IBT_MAGIC: {
                struct xfs_btree_block *btb = blk;

                lsn = be64_to_cpu(btb->bb_u.s.bb_lsn);
                uuid = &btb->bb_u.s.bb_uuid;
                break;
        }
        case XFS_BMAP_CRC_MAGIC:
        case XFS_BMAP_MAGIC: {
                struct xfs_btree_block *btb = blk;

                lsn = be64_to_cpu(btb->bb_u.l.bb_lsn);
                uuid = &btb->bb_u.l.bb_uuid;
                break;
        }
        case XFS_AGF_MAGIC:
                lsn = be64_to_cpu(((struct xfs_agf *)blk)->agf_lsn);
                uuid = &((struct xfs_agf *)blk)->agf_uuid;
                break;
        case XFS_AGFL_MAGIC:
                lsn = be64_to_cpu(((struct xfs_agfl *)blk)->agfl_lsn);
                uuid = &((struct xfs_agfl *)blk)->agfl_uuid;
                break;
        case XFS_AGI_MAGIC:
                lsn = be64_to_cpu(((struct xfs_agi *)blk)->agi_lsn);
                uuid = &((struct xfs_agi *)blk)->agi_uuid;
                break;
        case XFS_SYMLINK_MAGIC:
                lsn = be64_to_cpu(((struct xfs_dsymlink_hdr *)blk)->sl_lsn);
                uuid = &((struct xfs_dsymlink_hdr *)blk)->sl_uuid;
                break;
        case XFS_DIR3_BLOCK_MAGIC:
        case XFS_DIR3_DATA_MAGIC:
        case XFS_DIR3_FREE_MAGIC:
                lsn = be64_to_cpu(((struct xfs_dir3_blk_hdr *)blk)->lsn);
                uuid = &((struct xfs_dir3_blk_hdr *)blk)->uuid;
                break;
        case XFS_ATTR3_RMT_MAGIC:
                /*
                 * Remote attr blocks are written synchronously, rather than
                 * being logged. That means they do not contain a valid LSN
                 * (i.e. transactionally ordered) in them, and hence any time we
                 * see a buffer to replay over the top of a remote attribute
                 * block we should simply do so.
                 */
                goto recover_immediately;
        case XFS_SB_MAGIC:
                /*
                 * superblock uuids are magic. We may or may not have a
                 * sb_meta_uuid on disk, but it will be set in the in-core
                 * superblock. We set the uuid pointer for verification
                 * according to the superblock feature mask to ensure we check
                 * the relevant UUID in the superblock.
                 */
                lsn = be64_to_cpu(((struct xfs_dsb *)blk)->sb_lsn);
                if (xfs_has_metauuid(mp))
                        uuid = &((struct xfs_dsb *)blk)->sb_meta_uuid;
                else
                        uuid = &((struct xfs_dsb *)blk)->sb_uuid;
                break;
        default:
                break;
        }

        if (lsn != (xfs_lsn_t)-1) {
                if (!uuid_equal(&mp->m_sb.sb_meta_uuid, uuid))
                        goto recover_immediately;
                return lsn;
        }

        magicda = be16_to_cpu(((struct xfs_da_blkinfo *)blk)->magic);
        switch (magicda) {
        case XFS_DIR3_LEAF1_MAGIC:
        case XFS_DIR3_LEAFN_MAGIC:
        case XFS_ATTR3_LEAF_MAGIC:
        case XFS_DA3_NODE_MAGIC:
                lsn = be64_to_cpu(((struct xfs_da3_blkinfo *)blk)->lsn);
                uuid = &((struct xfs_da3_blkinfo *)blk)->uuid;
                break;
        default:
                break;
        }

        if (lsn != (xfs_lsn_t)-1) {
                if (!uuid_equal(&mp->m_sb.sb_uuid, uuid))
                        goto recover_immediately;
                return lsn;
        }

        /*
         * We do individual object checks on dquot and inode buffers as they
         * have their own individual LSN records. Also, we could have a stale
         * buffer here, so we have to at least recognise these buffer types.
         *
         * A notd complexity here is inode unlinked list processing - it logs
         * the inode directly in the buffer, but we don't know which inodes have
         * been modified, and there is no global buffer LSN. Hence we need to
         * recover all inode buffer types immediately. This problem will be
         * fixed by logical logging of the unlinked list modifications.
         */
        magic16 = be16_to_cpu(*(__be16 *)blk);
        switch (magic16) {
        case XFS_DQUOT_MAGIC:
        case XFS_DINODE_MAGIC:
                goto recover_immediately;
        default:
                break;
        }

        /* unknown buffer contents, recover immediately */

recover_immediately:
        return (xfs_lsn_t)-1;

}

/*
 * This routine replays a modification made to a buffer at runtime.
 * There are actually two types of buffer, regular and inode, which
 * are handled differently.  Inode buffers are handled differently
 * in that we only recover a specific set of data from them, namely
 * the inode di_next_unlinked fields.  This is because all other inode
 * data is actually logged via inode records and any data we replay
 * here which overlaps that may be stale.
 *
 * When meta-data buffers are freed at run time we log a buffer item
 * with the XFS_BLF_CANCEL bit set to indicate that previous copies
 * of the buffer in the log should not be replayed at recovery time.
 * This is so that if the blocks covered by the buffer are reused for
 * file data before we crash we don't end up replaying old, freed
 * meta-data into a user's file.
 *
 * To handle the cancellation of buffer log items, we make two passes
 * over the log during recovery.  During the first we build a table of
 * those buffers which have been cancelled, and during the second we
 * only replay those buffers which do not have corresponding cancel
 * records in the table.  See xlog_recover_buf_pass[1,2] above
 * for more details on the implementation of the table of cancel records.
 */
STATIC int
xlog_recover_buf_commit_pass2(
        struct xlog                     *log,
        struct list_head                *buffer_list,
        struct xlog_recover_item        *item,
        xfs_lsn_t                       current_lsn)
{
        struct xfs_buf_log_format       *buf_f = item->ri_buf[0].i_addr;
        struct xfs_mount                *mp = log->l_mp;
        struct xfs_buf                  *bp;
        int                             error;
        uint                            buf_flags;
        xfs_lsn_t                       lsn;

        /*
         * In this pass we only want to recover all the buffers which have
         * not been cancelled and are not cancellation buffers themselves.
         */
        if (buf_f->blf_flags & XFS_BLF_CANCEL) {
                if (xlog_put_buffer_cancelled(log, buf_f->blf_blkno,
                                buf_f->blf_len))
                        goto cancelled;
        } else {

                if (xlog_is_buffer_cancelled(log, buf_f->blf_blkno,
                                buf_f->blf_len))
                        goto cancelled;
        }

        trace_xfs_log_recover_buf_recover(log, buf_f);

        buf_flags = 0;
        if (buf_f->blf_flags & XFS_BLF_INODE_BUF)
                buf_flags |= XBF_UNMAPPED;

        error = xfs_buf_read(mp->m_ddev_targp, buf_f->blf_blkno, buf_f->blf_len,
                          buf_flags, &bp, NULL);
        if (error)
                return error;

        /*
         * Recover the buffer only if we get an LSN from it and it's less than
         * the lsn of the transaction we are replaying.
         *
         * Note that we have to be extremely careful of readahead here.
         * Readahead does not attach verfiers to the buffers so if we don't
         * actually do any replay after readahead because of the LSN we found
         * in the buffer if more recent than that current transaction then we
         * need to attach the verifier directly. Failure to do so can lead to
         * future recovery actions (e.g. EFI and unlinked list recovery) can
         * operate on the buffers and they won't get the verifier attached. This
         * can lead to blocks on disk having the correct content but a stale
         * CRC.
         *
         * It is safe to assume these clean buffers are currently up to date.
         * If the buffer is dirtied by a later transaction being replayed, then
         * the verifier will be reset to match whatever recover turns that
         * buffer into.
         */
        lsn = xlog_recover_get_buf_lsn(mp, bp, buf_f);
        if (lsn && lsn != -1 && XFS_LSN_CMP(lsn, current_lsn) >= 0) {
                trace_xfs_log_recover_buf_skip(log, buf_f);
                xlog_recover_validate_buf_type(mp, bp, buf_f, NULLCOMMITLSN);
                goto out_release;
        }

        if (buf_f->blf_flags & XFS_BLF_INODE_BUF) {
                error = xlog_recover_do_inode_buffer(mp, item, bp, buf_f);
                if (error)
                        goto out_release;
        } else if (buf_f->blf_flags &
                  (XFS_BLF_UDQUOT_BUF|XFS_BLF_PDQUOT_BUF|XFS_BLF_GDQUOT_BUF)) {
                bool    dirty;

                dirty = xlog_recover_do_dquot_buffer(mp, log, item, bp, buf_f);
                if (!dirty)
                        goto out_release;
        } else {
                xlog_recover_do_reg_buffer(mp, item, bp, buf_f, current_lsn);
        }

        /*
         * Perform delayed write on the buffer.  Asynchronous writes will be
         * slower when taking into account all the buffers to be flushed.
         *
         * Also make sure that only inode buffers with good sizes stay in
         * the buffer cache.  The kernel moves inodes in buffers of 1 block
         * or inode_cluster_size bytes, whichever is bigger.  The inode
         * buffers in the log can be a different size if the log was generated
         * by an older kernel using unclustered inode buffers or a newer kernel
         * running with a different inode cluster size.  Regardless, if
         * the inode buffer size isn't max(blocksize, inode_cluster_size)
         * for *our* value of inode_cluster_size, then we need to keep
         * the buffer out of the buffer cache so that the buffer won't
         * overlap with future reads of those inodes.
         */
        if (XFS_DINODE_MAGIC ==
            be16_to_cpu(*((__be16 *)xfs_buf_offset(bp, 0))) &&
            (BBTOB(bp->b_length) != M_IGEO(log->l_mp)->inode_cluster_size)) {
                xfs_buf_stale(bp);
                error = xfs_bwrite(bp);
        } else {
                ASSERT(bp->b_mount == mp);
                bp->b_flags |= _XBF_LOGRECOVERY;
                xfs_buf_delwri_queue(bp, buffer_list);
        }

out_release:
        xfs_buf_relse(bp);
        return error;
cancelled:
        trace_xfs_log_recover_buf_cancel(log, buf_f);
        return 0;
}

const struct xlog_recover_item_ops xlog_buf_item_ops = {
        .item_type              = XFS_LI_BUF,
        .reorder                = xlog_recover_buf_reorder,
        .ra_pass2               = xlog_recover_buf_ra_pass2,
        .commit_pass1           = xlog_recover_buf_commit_pass1,
        .commit_pass2           = xlog_recover_buf_commit_pass2,
};