From 85d9abcd7331566781b93ff46e4bccd4806ef2b2 Mon Sep 17 00:00:00 2001
From: Juergen Gross <jgross@suse.com>
Date: Fri, 11 Mar 2022 11:35:27 +0100
Subject: [PATCH] xen/blkfront: speed up purge_persistent_grants()
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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: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Link: https://lore.kernel.org/r/20220311103527.12931-1-jgross@suse.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
drivers/block/xen-blkfront.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index ccd0dd0c6b83c..5d04e480f36a7 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -2521,6 +2521,7 @@ static void purge_persistent_grants(struct blkfront_info *info)
for_each_rinfo(info, rinfo, i) {
struct grant *gnt_list_entry, *tmp;
+ LIST_HEAD(grants);
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);
rinfo->persistent_gnts_c--;
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);
}
}
--
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