xfs: add helpers to dispose of old btree blocks after a repair
Now that we've plumbed in the ability to construct a list of dead btree blocks following a repair, add more helpers to dispose of them. This is done by examining the rmapbt -- if the btree was the only owner we can free the block, otherwise it's crosslinked and we can only remove the rmapbt record. Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Reviewed-by: Dave Chinner <dchinner@redhat.com>
This commit is contained in:
Darrick J. Wong
parent
64a39d876e
commit
12c6510e2f
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@ -585,3 +585,254 @@ out:
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}
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#undef LEFT_ALIGNED
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#undef RIGHT_ALIGNED
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/*
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* Disposal of Blocks from Old per-AG Btrees
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*
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* Now that we've constructed a new btree to replace the damaged one, we want
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* to dispose of the blocks that (we think) the old btree was using.
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* Previously, we used the rmapbt to collect the extents (exlist) with the
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* rmap owner corresponding to the tree we rebuilt, collected extents for any
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* blocks with the same rmap owner that are owned by another data structure
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* (sublist), and subtracted sublist from exlist. In theory the extents
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* remaining in exlist are the old btree's blocks.
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*
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* Unfortunately, it's possible that the btree was crosslinked with other
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* blocks on disk. The rmap data can tell us if there are multiple owners, so
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* if the rmapbt says there is an owner of this block other than @oinfo, then
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* the block is crosslinked. Remove the reverse mapping and continue.
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*
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* If there is one rmap record, we can free the block, which removes the
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* reverse mapping but doesn't add the block to the free space. Our repair
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* strategy is to hope the other metadata objects crosslinked on this block
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* will be rebuilt (atop different blocks), thereby removing all the cross
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* links.
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*
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* If there are no rmap records at all, we also free the block. If the btree
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* being rebuilt lives in the free space (bnobt/cntbt/rmapbt) then there isn't
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* supposed to be a rmap record and everything is ok. For other btrees there
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* had to have been an rmap entry for the block to have ended up on @exlist,
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* so if it's gone now there's something wrong and the fs will shut down.
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*
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* Note: If there are multiple rmap records with only the same rmap owner as
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* the btree we're trying to rebuild and the block is indeed owned by another
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* data structure with the same rmap owner, then the block will be in sublist
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* and therefore doesn't need disposal. If there are multiple rmap records
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* with only the same rmap owner but the block is not owned by something with
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* the same rmap owner, the block will be freed.
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*
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* The caller is responsible for locking the AG headers for the entire rebuild
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* operation so that nothing else can sneak in and change the AG state while
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* we're not looking. We also assume that the caller already invalidated any
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* buffers associated with @exlist.
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*/
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/*
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* Invalidate buffers for per-AG btree blocks we're dumping. This function
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* is not intended for use with file data repairs; we have bunmapi for that.
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*/
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int
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xfs_repair_invalidate_blocks(
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struct xfs_scrub_context *sc,
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struct xfs_repair_extent_list *exlist)
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{
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struct xfs_repair_extent *rex;
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struct xfs_repair_extent *n;
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struct xfs_buf *bp;
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xfs_fsblock_t fsbno;
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xfs_agblock_t i;
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/*
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* For each block in each extent, see if there's an incore buffer for
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* exactly that block; if so, invalidate it. The buffer cache only
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* lets us look for one buffer at a time, so we have to look one block
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* at a time. Avoid invalidating AG headers and post-EOFS blocks
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* because we never own those; and if we can't TRYLOCK the buffer we
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* assume it's owned by someone else.
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*/
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for_each_xfs_repair_extent_safe(rex, n, exlist) {
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for (fsbno = rex->fsbno, i = rex->len; i > 0; fsbno++, i--) {
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/* Skip AG headers and post-EOFS blocks */
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if (!xfs_verify_fsbno(sc->mp, fsbno))
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continue;
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bp = xfs_buf_incore(sc->mp->m_ddev_targp,
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XFS_FSB_TO_DADDR(sc->mp, fsbno),
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XFS_FSB_TO_BB(sc->mp, 1), XBF_TRYLOCK);
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if (bp) {
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xfs_trans_bjoin(sc->tp, bp);
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xfs_trans_binval(sc->tp, bp);
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}
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}
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}
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return 0;
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}
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/* Ensure the freelist is the correct size. */
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int
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xfs_repair_fix_freelist(
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struct xfs_scrub_context *sc,
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bool can_shrink)
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{
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struct xfs_alloc_arg args = {0};
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args.mp = sc->mp;
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args.tp = sc->tp;
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args.agno = sc->sa.agno;
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args.alignment = 1;
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args.pag = sc->sa.pag;
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return xfs_alloc_fix_freelist(&args,
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can_shrink ? 0 : XFS_ALLOC_FLAG_NOSHRINK);
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}
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/*
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* Put a block back on the AGFL.
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*/
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STATIC int
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xfs_repair_put_freelist(
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struct xfs_scrub_context *sc,
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xfs_agblock_t agbno)
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{
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struct xfs_owner_info oinfo;
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int error;
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/* Make sure there's space on the freelist. */
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error = xfs_repair_fix_freelist(sc, true);
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if (error)
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return error;
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/*
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* Since we're "freeing" a lost block onto the AGFL, we have to
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* create an rmap for the block prior to merging it or else other
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* parts will break.
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*/
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xfs_rmap_ag_owner(&oinfo, XFS_RMAP_OWN_AG);
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error = xfs_rmap_alloc(sc->tp, sc->sa.agf_bp, sc->sa.agno, agbno, 1,
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&oinfo);
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if (error)
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return error;
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/* Put the block on the AGFL. */
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error = xfs_alloc_put_freelist(sc->tp, sc->sa.agf_bp, sc->sa.agfl_bp,
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agbno, 0);
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if (error)
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return error;
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xfs_extent_busy_insert(sc->tp, sc->sa.agno, agbno, 1,
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XFS_EXTENT_BUSY_SKIP_DISCARD);
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return 0;
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}
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/* Dispose of a single metadata block. */
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STATIC int
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xfs_repair_dispose_btree_block(
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struct xfs_scrub_context *sc,
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xfs_fsblock_t fsbno,
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struct xfs_owner_info *oinfo,
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enum xfs_ag_resv_type resv)
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{
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struct xfs_btree_cur *cur;
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struct xfs_buf *agf_bp = NULL;
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xfs_agnumber_t agno;
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xfs_agblock_t agbno;
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bool has_other_rmap;
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int error;
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agno = XFS_FSB_TO_AGNO(sc->mp, fsbno);
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agbno = XFS_FSB_TO_AGBNO(sc->mp, fsbno);
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/*
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* If we are repairing per-inode metadata, we need to read in the AGF
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* buffer. Otherwise, we're repairing a per-AG structure, so reuse
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* the AGF buffer that the setup functions already grabbed.
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*/
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if (sc->ip) {
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error = xfs_alloc_read_agf(sc->mp, sc->tp, agno, 0, &agf_bp);
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if (error)
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return error;
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if (!agf_bp)
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return -ENOMEM;
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} else {
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agf_bp = sc->sa.agf_bp;
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}
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cur = xfs_rmapbt_init_cursor(sc->mp, sc->tp, agf_bp, agno);
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/* Can we find any other rmappings? */
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error = xfs_rmap_has_other_keys(cur, agbno, 1, oinfo, &has_other_rmap);
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if (error)
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goto out_cur;
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xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
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/*
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* If there are other rmappings, this block is cross linked and must
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* not be freed. Remove the reverse mapping and move on. Otherwise,
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* we were the only owner of the block, so free the extent, which will
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* also remove the rmap.
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*
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* XXX: XFS doesn't support detecting the case where a single block
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* metadata structure is crosslinked with a multi-block structure
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* because the buffer cache doesn't detect aliasing problems, so we
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* can't fix 100% of crosslinking problems (yet). The verifiers will
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* blow on writeout, the filesystem will shut down, and the admin gets
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* to run xfs_repair.
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*/
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if (has_other_rmap)
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error = xfs_rmap_free(sc->tp, agf_bp, agno, agbno, 1, oinfo);
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else if (resv == XFS_AG_RESV_AGFL)
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error = xfs_repair_put_freelist(sc, agbno);
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else
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error = xfs_free_extent(sc->tp, fsbno, 1, oinfo, resv);
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if (agf_bp != sc->sa.agf_bp)
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xfs_trans_brelse(sc->tp, agf_bp);
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if (error)
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return error;
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if (sc->ip)
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return xfs_trans_roll_inode(&sc->tp, sc->ip);
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return xfs_repair_roll_ag_trans(sc);
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out_cur:
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xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
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if (agf_bp != sc->sa.agf_bp)
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xfs_trans_brelse(sc->tp, agf_bp);
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return error;
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}
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/* Dispose of btree blocks from an old per-AG btree. */
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int
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xfs_repair_reap_btree_extents(
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struct xfs_scrub_context *sc,
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struct xfs_repair_extent_list *exlist,
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struct xfs_owner_info *oinfo,
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enum xfs_ag_resv_type type)
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{
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struct xfs_repair_extent *rex;
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struct xfs_repair_extent *n;
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int error = 0;
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ASSERT(xfs_sb_version_hasrmapbt(&sc->mp->m_sb));
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/* Dispose of every block from the old btree. */
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for_each_xfs_repair_extent_safe(rex, n, exlist) {
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ASSERT(sc->ip != NULL ||
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XFS_FSB_TO_AGNO(sc->mp, rex->fsbno) == sc->sa.agno);
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trace_xfs_repair_dispose_btree_extent(sc->mp,
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XFS_FSB_TO_AGNO(sc->mp, rex->fsbno),
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XFS_FSB_TO_AGBNO(sc->mp, rex->fsbno), rex->len);
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for (; rex->len > 0; rex->len--, rex->fsbno++) {
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error = xfs_repair_dispose_btree_block(sc, rex->fsbno,
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oinfo, type);
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if (error)
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goto out;
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}
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list_del(&rex->list);
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kmem_free(rex);
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}
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out:
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xfs_repair_cancel_btree_extents(sc, exlist);
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return error;
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}
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@ -70,6 +70,12 @@ void xfs_repair_cancel_btree_extents(struct xfs_scrub_context *sc,
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int xfs_repair_subtract_extents(struct xfs_scrub_context *sc,
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struct xfs_repair_extent_list *exlist,
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struct xfs_repair_extent_list *sublist);
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int xfs_repair_fix_freelist(struct xfs_scrub_context *sc, bool can_shrink);
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int xfs_repair_invalidate_blocks(struct xfs_scrub_context *sc,
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struct xfs_repair_extent_list *btlist);
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int xfs_repair_reap_btree_extents(struct xfs_scrub_context *sc,
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struct xfs_repair_extent_list *exlist,
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struct xfs_owner_info *oinfo, enum xfs_ag_resv_type type);
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/* Metadata repairers */
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