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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>
This commit is contained in:
Juergen Gross 2022-03-11 11:35:27 +01:00 committed by Jens Axboe
parent 67b56134ce
commit 85d9abcd73
1 changed files with 4 additions and 1 deletions
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5
drivers/block/xen-blkfront.c
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@ -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);
}
}