Commit 6aa7640f authored Sep 11, 2013 by Bob Peterson Committed by Steven Whitehouse Sep 17, 2013

GFS2: optimize rbm_from_block wrt bi_start

In function gfs2_rbm_from_block, it starts by checking if the block
falls within the first bitmap. It does so by checking if the rbm's
offset is less than (rbm->bi->bi_start + rbm->bi->bi_len) * GFS2_NBBY.
However, the first bitmap will always have bi_start==0. Therefore
this is an unnecessary calculation in a function that gets called
billions of times. This patch removes the reference to bi_start.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

parent 0d0d1107

fs/gfs2/rgrp.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -262,7 +262,7 @@ static int gfs2_rbm_from_block(struct gfs2_rbm *rbm, u64 block)
		rbm->bi = rbm->rgd->rd_bits;
		rbm->offset = (u32)(rblock);
		/* Check if the block is within the first block */
		if (rbm->offset < (rbm->bi->bi_start + rbm->bi->bi_len) * GFS2_NBBY)
		if (rbm->offset < rbm->bi->bi_len * GFS2_NBBY)
		return 0;

		/* Adjust for the size diff between gfs2_meta_header and gfs2_rgrp */

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