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Due to the way the CoW algorithm in XFS works, there's an interval during which blocks allocated to handle a CoW can be lost -- if the FS goes down after the blocks are allocated but before the block remapping takes place. This is exacerbated by the cowextsz hint -- allocated reservations can sit around for a while, waiting to get used. Since the refcount btree doesn't normally store records with refcount of 1, we can use it to record these in-progress extents. In-progress blocks cannot be shared because they're not user-visible, so there shouldn't be any conflicts with other programs. This is a better solution than holding EFIs during writeback because (a) EFIs can't be relogged currently, (b) even if they could, EFIs are bound by available log space, which puts an unnecessary upper bound on how much CoW we can have in flight, and (c) we already have a mechanism to track blocks. At mount time, read the refcount records and free anything we find with a refcount of 1 because those were in-progress when the FS went down. Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Reviewed-by: Christoph Hellwig <hch@lst.de>
70 lines
2.6 KiB
C
70 lines
2.6 KiB
C
/*
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* Copyright (C) 2016 Oracle. All Rights Reserved.
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*
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* Author: Darrick J. Wong <darrick.wong@oracle.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it would be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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#ifndef __XFS_REFCOUNT_H__
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#define __XFS_REFCOUNT_H__
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extern int xfs_refcount_lookup_le(struct xfs_btree_cur *cur,
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xfs_agblock_t bno, int *stat);
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extern int xfs_refcount_lookup_ge(struct xfs_btree_cur *cur,
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xfs_agblock_t bno, int *stat);
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extern int xfs_refcount_get_rec(struct xfs_btree_cur *cur,
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struct xfs_refcount_irec *irec, int *stat);
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enum xfs_refcount_intent_type {
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XFS_REFCOUNT_INCREASE = 1,
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XFS_REFCOUNT_DECREASE,
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XFS_REFCOUNT_ALLOC_COW,
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XFS_REFCOUNT_FREE_COW,
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};
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struct xfs_refcount_intent {
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struct list_head ri_list;
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enum xfs_refcount_intent_type ri_type;
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xfs_fsblock_t ri_startblock;
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xfs_extlen_t ri_blockcount;
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};
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extern int xfs_refcount_increase_extent(struct xfs_mount *mp,
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struct xfs_defer_ops *dfops, struct xfs_bmbt_irec *irec);
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extern int xfs_refcount_decrease_extent(struct xfs_mount *mp,
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struct xfs_defer_ops *dfops, struct xfs_bmbt_irec *irec);
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extern void xfs_refcount_finish_one_cleanup(struct xfs_trans *tp,
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struct xfs_btree_cur *rcur, int error);
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extern int xfs_refcount_finish_one(struct xfs_trans *tp,
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struct xfs_defer_ops *dfops, enum xfs_refcount_intent_type type,
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xfs_fsblock_t startblock, xfs_extlen_t blockcount,
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xfs_fsblock_t *new_fsb, xfs_extlen_t *new_len,
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struct xfs_btree_cur **pcur);
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extern int xfs_refcount_find_shared(struct xfs_btree_cur *cur,
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xfs_agblock_t agbno, xfs_extlen_t aglen, xfs_agblock_t *fbno,
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xfs_extlen_t *flen, bool find_end_of_shared);
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extern int xfs_refcount_alloc_cow_extent(struct xfs_mount *mp,
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struct xfs_defer_ops *dfops, xfs_fsblock_t fsb,
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xfs_extlen_t len);
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extern int xfs_refcount_free_cow_extent(struct xfs_mount *mp,
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struct xfs_defer_ops *dfops, xfs_fsblock_t fsb,
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xfs_extlen_t len);
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extern int xfs_refcount_recover_cow_leftovers(struct xfs_mount *mp,
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xfs_agnumber_t agno);
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#endif /* __XFS_REFCOUNT_H__ */
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