Commit 9e07f2cb authored by Steven Whitehouse's avatar Steven Whitehouse
Browse files

GFS2: Speed up starting point selection for block allocation 



When setting the starting point for block allocation, there were calls
to both gfs2_rbm_to_block() and gfs2_rbm_from_block() in the common case
of there being an active reservation. The gfs2_rbm_from_block() function
can be quite slow, and since the two conversions were effectively a
no-op, it makes sense to avoid them entirely in this case.

There is no functional change here, but the code should be a bit more
efficient after this patch.

Signed-off-by: default avatarSteven Whitehouse <swhiteho@redhat.com>
parent 7b9cff46

fs/gfs2/rgrp.c

+31 −10
Original line number Diff line number Diff line
@@ -2133,6 +2133,35 @@ out: 
	spin_unlock(&rgd->rd_rsspin);

}



/**

 * gfs2_set_alloc_start - Set starting point for block allocation

 * @rbm: The rbm which will be set to the required location

 * @ip: The gfs2 inode

 * @dinode: Flag to say if allocation includes a new inode

 *

 * This sets the starting point from the reservation if one is active

 * otherwise it falls back to guessing a start point based on the

 * inode's goal block or the last allocation point in the rgrp.

 */



static void gfs2_set_alloc_start(struct gfs2_rbm *rbm,

				 const struct gfs2_inode *ip, bool dinode)

{

	u64 goal;



	if (gfs2_rs_active(ip->i_res)) {

		*rbm = ip->i_res->rs_rbm;

		return;

	}



	if (!dinode && rgrp_contains_block(rbm->rgd, ip->i_goal))

		goal = ip->i_goal;

	else

		goal = rbm->rgd->rd_last_alloc + rbm->rgd->rd_data0;



	gfs2_rbm_from_block(rbm, goal);

}



/**

 * gfs2_alloc_blocks - Allocate one or more blocks of data and/or a dinode

 * @ip: the inode to allocate the block for
@@ -2151,22 +2180,14 @@ int gfs2_alloc_blocks(struct gfs2_inode *ip, u64 *bn, unsigned int *nblocks, 
	struct buffer_head *dibh;

	struct gfs2_rbm rbm = { .rgd = ip->i_rgd, };

	unsigned int ndata;

	u64 goal;

	u64 block; /* block, within the file system scope */

	int error;



	if (gfs2_rs_active(ip->i_res))

		goal = gfs2_rbm_to_block(&ip->i_res->rs_rbm);

	else if (!dinode && rgrp_contains_block(rbm.rgd, ip->i_goal))

		goal = ip->i_goal;

	else

		goal = rbm.rgd->rd_last_alloc + rbm.rgd->rd_data0;



	gfs2_rbm_from_block(&rbm, goal);

	gfs2_set_alloc_start(&rbm, ip, dinode);

	error = gfs2_rbm_find(&rbm, GFS2_BLKST_FREE, 0, ip, false);



	if (error == -ENOSPC) {

		gfs2_rbm_from_block(&rbm, goal);

		gfs2_set_alloc_start(&rbm, ip, dinode);

		error = gfs2_rbm_find(&rbm, GFS2_BLKST_FREE, 0, NULL, false);

	}

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