This is a note to let you know that I've just added the patch titled
xen-blkfront: revoke foreign access for grants not mapped by the backend
to the 3.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
xen-blkfront-revoke-foreign-access-for-grants-not-mapped-by-the-backend.patch
and it can be found in the queue-3.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From fbe363c476afe8ec992d3baf682670a4bd1b6ce6 Mon Sep 17 00:00:00 2001
From: Roger Pau Monne <[email protected]>
Date: Mon, 12 Aug 2013 12:53:44 +0200
Subject: xen-blkfront: revoke foreign access for grants not mapped by the
backend
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From: Roger Pau Monne <[email protected]>
commit fbe363c476afe8ec992d3baf682670a4bd1b6ce6 upstream.
There's no need to keep the foreign access in a grant if it is not
persistently mapped by the backend. This allows us to free grants that
are not mapped by the backend, thus preventing blkfront from hoarding
all grants.
The main effect of this is that blkfront will only persistently map
the same grants as the backend, and it will always try to use grants
that are already mapped by the backend. Also the number of persistent
grants in blkfront is the same as in blkback (and is controlled by the
value in blkback).
Signed-off-by: Roger Pau Monné <[email protected]>
Reviewed-by: David Vrabel <[email protected]>
Acked-by: Matt Wilson <[email protected]>
Cc: Konrad Rzeszutek Wilk <[email protected]>
Cc: David Vrabel <[email protected]>
Signed-off-by: Konrad Rzeszutek Wilk <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
drivers/block/xen-blkfront.c | 24 +++++++++++++++++++++---
1 file changed, 21 insertions(+), 3 deletions(-)
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -894,9 +894,27 @@ static void blkif_completion(struct blk_
}
}
/* Add the persistent grant into the list of free grants */
- for (i = 0; i < s->req.u.rw.nr_segments; i++) {
- list_add(&s->grants_used[i]->node, &info->persistent_gnts);
- info->persistent_gnts_c++;
+ for (i = 0; i < nseg; i++) {
+ if (gnttab_query_foreign_access(s->grants_used[i]->gref)) {
+ /*
+ * If the grant is still mapped by the backend (the
+ * backend has chosen to make this grant persistent)
+ * we add it at the head of the list, so it will be
+ * reused first.
+ */
+ list_add(&s->grants_used[i]->node,
&info->persistent_gnts);
+ info->persistent_gnts_c++;
+ } else {
+ /*
+ * If the grant is not mapped by the backend we end the
+ * foreign access and add it to the tail of the list,
+ * so it will not be picked again unless we run out of
+ * persistent grants.
+ */
+ gnttab_end_foreign_access(s->grants_used[i]->gref, 0,
0UL);
+ s->grants_used[i]->gref = GRANT_INVALID_REF;
+ list_add_tail(&s->grants_used[i]->node,
&info->persistent_gnts);
+ }
}
}
Patches currently in stable-queue which might be from [email protected] are
queue-3.10/xen-blkfront-revoke-foreign-access-for-grants-not-mapped-by-the-backend.patch
queue-3.10/xen-blkfront-restore-the-non-persistent-data-path.patch
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