Commit 85d9abcd authored by Juergen Gross's avatar Juergen Gross Committed by Jens Axboe
Browse files

xen/blkfront: speed up purge_persistent_grants() 



purge_persistent_grants() is scanning the grants list for persistent
grants being no longer in use by the backend. When having found such a
grant, it will be set to "invalid" and pushed to the tail of the list.

Instead of pushing it directly to the end of the list, add it first to
a temporary list, avoiding to scan those entries again in the main
list traversal. After having finished the scan, append the temporary
list to the grant list.

Suggested-by: default avatarJan Beulich <jbeulich@suse.com>
Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
Reviewed-by: default avatarRoger Pau Monné <roger.pau@citrix.com>
Reviewed-by: default avatarJan Beulich <jbeulich@suse.com>
Link: https://lore.kernel.org/r/20220311103527.12931-1-jgross@suse.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 67b56134

drivers/block/xen-blkfront.c

+4 −1
Original line number Original line Diff line number Diff line
@@ -2521,6 +2521,7 @@ static void purge_persistent_grants(struct blkfront_info *info) 




	for_each_rinfo(info, rinfo, i) {

	for_each_rinfo(info, rinfo, i) {

		struct grant *gnt_list_entry, *tmp;

		struct grant *gnt_list_entry, *tmp;

		LIST_HEAD(grants);





		spin_lock_irqsave(&rinfo->ring_lock, flags);

		spin_lock_irqsave(&rinfo->ring_lock, flags);
@@ -2539,9 +2540,11 @@ static void purge_persistent_grants(struct blkfront_info *info) 
			gnttab_end_foreign_access(gnt_list_entry->gref, 0, 0UL);

			gnttab_end_foreign_access(gnt_list_entry->gref, 0, 0UL);

			rinfo->persistent_gnts_c--;

			rinfo->persistent_gnts_c--;

			gnt_list_entry->gref = GRANT_INVALID_REF;

			gnt_list_entry->gref = GRANT_INVALID_REF;

			list_add_tail(&gnt_list_entry->node, &rinfo->grants);

			list_add_tail(&gnt_list_entry->node, &grants);

		}

		}





		list_splice_tail(&grants, &rinfo->grants);



		spin_unlock_irqrestore(&rinfo->ring_lock, flags);

		spin_unlock_irqrestore(&rinfo->ring_lock, flags);

	}

	}

}

}