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For O_DIRECT writes to shared blocks, we have to CoW them just like we would with buffered writes. For writes that are not block-aligned, just bounce them to the page cache. For block-aligned writes, however, we can do better than that. Use the same mechanisms that we employ for buffered CoW to set up a delalloc reservation, allocate all the blocks at once, issue the writes against the new blocks and use the same ioend functions to remap the blocks after the write. This should be fairly performant. Christoph discovered that xfs_reflink_allocate_cow_range may stumble over invalid entries in the extent array given that it drops the ilock but still expects the index to be stable. Simple fixing it to a new lookup for every iteration still isn't correct given that xfs_bmapi_allocate will trigger a BUG_ON() if hitting a hole, and there is nothing preventing a xfs_bunmapi_cow call removing extents once we dropped the ilock either. This patch duplicates the inner loop of xfs_bmapi_allocate into a helper for xfs_reflink_allocate_cow_range so that it can be done under the same ilock critical section as our CoW fork delayed allocation. The directio CoW warts will be revisited in a later patch. Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Christoph Hellwig <hch@lst.de>
47 lines
2.0 KiB
C
47 lines
2.0 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_REFLINK_H
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#define __XFS_REFLINK_H 1
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extern int xfs_reflink_find_shared(struct xfs_mount *mp, xfs_agnumber_t agno,
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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_maximal);
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extern int xfs_reflink_trim_around_shared(struct xfs_inode *ip,
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struct xfs_bmbt_irec *irec, bool *shared, bool *trimmed);
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extern int xfs_reflink_reserve_cow_range(struct xfs_inode *ip,
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xfs_off_t offset, xfs_off_t count);
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extern int xfs_reflink_allocate_cow_range(struct xfs_inode *ip,
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xfs_off_t offset, xfs_off_t count);
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extern bool xfs_reflink_find_cow_mapping(struct xfs_inode *ip, xfs_off_t offset,
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struct xfs_bmbt_irec *imap, bool *need_alloc);
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extern int xfs_reflink_trim_irec_to_next_cow(struct xfs_inode *ip,
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xfs_fileoff_t offset_fsb, struct xfs_bmbt_irec *imap);
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extern int xfs_reflink_cancel_cow_blocks(struct xfs_inode *ip,
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struct xfs_trans **tpp, xfs_fileoff_t offset_fsb,
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xfs_fileoff_t end_fsb);
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extern int xfs_reflink_cancel_cow_range(struct xfs_inode *ip, xfs_off_t offset,
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xfs_off_t count);
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extern int xfs_reflink_end_cow(struct xfs_inode *ip, xfs_off_t offset,
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xfs_off_t count);
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#endif /* __XFS_REFLINK_H */
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