[Xen-devel] [PATCH 2/2 v2] Add trim operation to xen block devices

[Owen Smith <owen.smith@xxxxxxxxxx>]

Add Trim command interface

This patch adds the trim operation to the blkback ring protocol.

Trim commands are passed with sector_number as the sector index to 
begin trim operations at and nr_sectors as the number of sectors to 
be trimmed. The specified sectors should be trimmed if the underlying 
block device supports trim operations, or a BLKIF_RSP_EOPNOTSUPP should 
be returned. More information about trim operations:
http://t13.org/Documents/UploadedDocuments/docs2008/
       e07154r6-Data_Set_Management_Proposal_for_ATA-ACS2.doc

Signed-of-by: Owen Smith <owen.smith@xxxxxxxxxx>

# HG changeset patch
# User Owen Smith <owen.smith@xxxxxxxxxx>
# Date 1292938216 0
# Node ID 6be1a23977b82e44eba80feeca3fb77acf6bb2bb
# Parent  7015d7407eae8694ce1cc92e792b2087f109f6cb
imported patch add-trim

diff -r 7015d7407eae -r 6be1a23977b8 xen/include/public/io/blkif.h
--- a/xen/include/public/io/blkif.h     Tue Dec 21 13:28:48 2010 +0000
+++ b/xen/include/public/io/blkif.h     Tue Dec 21 13:30:16 2010 +0000
@@ -76,6 +76,17 @@
  * "feature-flush-cache" node!
  */
 #define BLKIF_OP_FLUSH_DISKCACHE   3
+/*
+ * Recognised only if "feature-trim" is present in backend xenbus info.
+ * The "feature-trim" node contains a boolean indicating whether trim
+ * requests are likely to succeed or fail. Either way, a trim 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 trim requests.
+ * If a backend does not recognise BLKIF_OP_TRIM, it should *not*
+ * create the "feature-trim" node!
+ */
+#define BLKIF_OP_TRIM              5
 
 /*
  * Maximum scatter/gather segments per request.
@@ -103,6 +114,11 @@
     struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 };
 
+struct blkif_request_trim {
+    blkif_sector_t sector_number;/* start sector idx on disk   */
+    uint64_t nr_sectors;
+};
+
 struct blkif_request {
     uint8_t        operation;    /* BLKIF_OP_???                         */
     uint8_t        nr_segments;  /* number of segments                   */
@@ -110,6 +126,7 @@
     uint64_t       id;           /* private guest value, echoed in resp  */
     union {
        struct blkif_request_rw rw;
+       struct blkif_request_trim trim;
     } u;
 };
 typedef struct blkif_request blkif_request_t;

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