xfs: rework insert range into an atomic operation (dd87f87d) · Commits · 戴 / test

The insert range operation uses a unique transaction and ilock cycle for the extent split and each extent shift iteration of the overall operation. While this works, it is risks racing with other operations in subtle ways such as COW writeback modifying an extent tree in the middle of a shift operation. To avoid this problem, make insert range atomic with respect to ilock. Hold the ilock across the entire operation, replace the individual transactions with a single rolling transaction sequence and relog the inode to keep it moving in the log. This guarantees that nothing else can change the extent mapping of an inode while an insert range operation is in progress. Signed-off-by:

Brian Foster <bfoster@redhat.com> Reviewed-by:

Allison Collins <allison.henderson@oracle.com> Reviewed-by:

Christoph Hellwig <hch@lst.de> Reviewed-by:

Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by:

Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/xfs_bmap_util.c

+13 −19

Original line number	Diff line number	Diff line
		@@ -1146,47 +1146,41 @@ xfs_insert_file_space(
		if (error)
		return error;

		/*
		* The extent shifting code works on extent granularity. So, if stop_fsb
		* is not the starting block of extent, we need to split the extent at
		* stop_fsb.
		*/
		error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write,
		XFS_DIOSTRAT_SPACE_RES(mp, 0), 0, 0, &tp);
		if (error)
		return error;

		xfs_ilock(ip, XFS_ILOCK_EXCL);
		xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);
		xfs_trans_ijoin(tp, ip, 0);

		/*
		* The extent shifting code works on extent granularity. So, if stop_fsb
		* is not the starting block of extent, we need to split the extent at
		* stop_fsb.
		*/
		error = xfs_bmap_split_extent(tp, ip, stop_fsb);
		if (error)
		goto out_trans_cancel;

		error = xfs_trans_commit(tp);
		if (error)
		return error;

		while (!error && !done) {
		error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, 0, 0, 0,
		&tp);
		do {
		error = xfs_trans_roll_inode(&tp, ip);
		if (error)
		break;
		goto out_trans_cancel;

		xfs_ilock(ip, XFS_ILOCK_EXCL);
		xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);
		error = xfs_bmap_insert_extents(tp, ip, &next_fsb, shift_fsb,
		&done, stop_fsb);
		if (error)
		goto out_trans_cancel;
		} while (!done);

		error = xfs_trans_commit(tp);
		}

		xfs_iunlock(ip, XFS_ILOCK_EXCL);
		return error;

		out_trans_cancel:
		xfs_trans_cancel(tp);
		xfs_iunlock(ip, XFS_ILOCK_EXCL);
		return error;
		}

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