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Commit a9bd24ac authored by Brian Foster's avatar Brian Foster Committed by Dave Chinner
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xfs: refactor delalloc indlen reservation split into helper 



The delayed allocation indirect reservation splitting code is not
sufficient in some cases where a delalloc extent is split in two. In
preparation for enhancements to this code, refactor the current indlen
distribution algorithm into a new helper function.

[dchinner: rename temp, temp2 variables]

Signed-off-by: default avatarBrian Foster <bfoster@redhat.com>
Reviewed-by: default avatarDave Chinner <dchinner@redhat.com>
Signed-off-by: default avatarDave Chinner <david@fromorbit.com>
parent b2706a05

fs/xfs/libxfs/xfs_bmap.c

+54 −19
Original line number Diff line number Diff line
@@ -4720,6 +4720,47 @@ xfs_bmapi_write( 
	return error;

}



/*

 * When a delalloc extent is split (e.g., due to a hole punch), the original

 * indlen reservation must be shared across the two new extents that are left

 * behind.

 *

 * Given the original reservation and the worst case indlen for the two new

 * extents (as calculated by xfs_bmap_worst_indlen()), split the original

 * reservation fairly across the two new extents.

 */

static void

xfs_bmap_split_indlen(

	xfs_filblks_t			ores,		/* original res. */

	xfs_filblks_t			*indlen1,	/* ext1 worst indlen */

	xfs_filblks_t			*indlen2)	/* ext2 worst indlen */

{

	xfs_filblks_t			len1 = *indlen1;

	xfs_filblks_t			len2 = *indlen2;

	xfs_filblks_t			nres = len1 + len2; /* new total res. */



	/*

	 * The only blocks available are those reserved for the original extent.

	 * Therefore, we have to skim blocks off each of the new reservations so

	 * long as the new total reservation is greater than the original.

	 */

	while (nres > ores) {

		if (len1) {

			len1--;

			nres--;

		}

		if (nres == ores)

			break;

		if (len2) {

			len2--;

			nres--;

		}

	}



	*indlen1 = len1;

	*indlen2 = len2;

}



/*

 * Called by xfs_bmapi to update file extent records and the btree

 * after removing space (or undoing a delayed allocation).
@@ -4985,27 +5026,21 @@ xfs_bmap_del_extent( 
				XFS_IFORK_NEXTENTS(ip, whichfork) + 1);

		} else {

			ASSERT(whichfork == XFS_DATA_FORK);

			temp = xfs_bmap_worst_indlen(ip, temp);



			/*

			 * Distribute the original indlen reservation across the

			 * two new extents.

			 */

			temp = xfs_bmap_worst_indlen(ip, got.br_blockcount);

			temp2 = xfs_bmap_worst_indlen(ip, new.br_blockcount);

			xfs_bmap_split_indlen(da_old, &temp, &temp2);

			da_new = temp + temp2;



			/*

			 * Set the reservation for each extent.

			 */

			xfs_bmbt_set_startblock(ep, nullstartblock((int)temp));

			temp2 = xfs_bmap_worst_indlen(ip, temp2);

			new.br_startblock = nullstartblock((int)temp2);

			da_new = temp + temp2;

			while (da_new > da_old) {

				if (temp) {

					temp--;

					da_new--;

					xfs_bmbt_set_startblock(ep,

						nullstartblock((int)temp));

				}

				if (da_new == da_old)

					break;

				if (temp2) {

					temp2--;

					da_new--;

					new.br_startblock =

						nullstartblock((int)temp2);

				}

			}

		}

		trace_xfs_bmap_post_update(ip, *idx, state, _THIS_IP_);

		xfs_iext_insert(ip, *idx + 1, 1, &new, state);