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xen-blkfront: Provide for 'feature-flush-cache' the BLKIF_OP_WRITE_FLUSH_CACHE operation. 

The operation BLKIF_OP_WRITE_FLUSH_CACHE has existed in the Xen
tree header file for years but it was never present in the Linux tree
because the frontend (nor the backend) supported this interface.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
Konrad Rzeszutek Wilk 2011-05-05 12:41:03 -04:00
parent a19be5f0f0
commit 73d842af27
1 changed files with 13 additions and 0 deletions
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13
include/xen/interface/io/blkif.h
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@ -44,6 +44,19 @@ typedef uint64_t blkif_sector_t;
*/ */
#define BLKIF_OP_WRITE_BARRIER 2 #define BLKIF_OP_WRITE_BARRIER 2
/*
* Recognised if "feature-flush-cache" is present in backend xenbus
* info. A flush will ask the underlying storage hardware to flush its
* non-volatile caches as appropriate. The "feature-flush-cache" node
* contains a boolean indicating whether flush requests are likely to
* succeed or fail. Either way, a flush request may fail at any time
* with BLKIF_RSP_EOPNOTSUPP if it is unsupported by the underlying
* block-device hardware. The boolean simply indicates whether or not it
* is worthwhile for the frontend to attempt flushes. If a backend does
* not recognise BLKIF_OP_WRITE_FLUSH_CACHE, it should *not* create the
* "feature-flush-cache" node!
*/
#define BLKIF_OP_FLUSH_DISKCACHE 3
/* /*
* Maximum scatter/gather segments per request. * Maximum scatter/gather segments per request.
* This is carefully chosen so that sizeof(struct blkif_ring) <= PAGE_SIZE. * This is carefully chosen so that sizeof(struct blkif_ring) <= PAGE_SIZE.