[Xen-devel] [PATCH] blkif: update persistent grants documentation

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

Update blkif protocol extensions documentation to reflect the new
behaviour in Linux persistent grants implementation.

Signed-off-by: Roger Pau Monnà <roger.pau@xxxxxxxxxx>
Cc: David Vrabel <david.vrabel@xxxxxxxxxx>
---
 xen/include/public/io/blkif.h |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/xen/include/public/io/blkif.h b/xen/include/public/io/blkif.h
index b9b9d98..27ae8b6 100644
--- a/xen/include/public/io/blkif.h
+++ b/xen/include/public/io/blkif.h
@@ -290,6 +290,12 @@
  *      the previous protocol, a frontend driver can choose to work in
  *      persistent mode even when the backend doesn't support it.
  *
+ *      When the backend driver needs to unmap a persistent grant it should
+ *      do so prior to completing a request that used that grant reference.
+ *      If a persistent grant is unmapped at any other time, the frontend
+ *      driver may not notice and may be unable to reclaim the grant
+ *      reference.
+ *
  *      It is recommended that the frontend driver stores the persistently
  *      mapped grants in a LIFO queue, so a subset of all persistently mapped
  *      grants gets used commonly. This is done in case the backend driver
-- 
1.7.7.5 (Apple Git-26)


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