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SubjectRe: [Xen-devel] [PATCH 3/3] xen/blk[front|back]: Enhance discard support with secure erasing support.
> > I think an explicit flag variable is likely to be less trouble WRT
> > maintaining compatibility in the future than a bit-field. Also I think
> > you may as well align the struct size to something larger than a byte,
> > either 4 or 8 bytes would make sense.
>
> Ok. Will change it and make it an uint64_t secure_flag
> variable. Later on if there are any "other" flags we can chop it down.

New patch (it also looks like the patch I sent to xen-devel to update
the blkif.h was never merged) - so let me send right now.

BTW, it seems that the #pragma pack(push, 4) is used in the
drivers/block/xen-blkback/common.h to compact the structures already so
I don't think we need the aligment.


From f74cc58b77c2a1c1a93c0324a50b9d1b9a0cb159 Mon Sep 17 00:00:00 2001
From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Date: Mon, 10 Oct 2011 10:58:40 -0400
Subject: [PATCH] xen/blk[front|back]: Enhance discard support with secure
erasing support.

Part of the blkdev_issue_discard(xx) operation is that it can also
issue a secure discard operation that will permanantly remove the
sectors in question. We advertise that we can support that via the
'discard-secure' attribute and on the request, if the 'secure' bit
is set, we will attempt to pass in REQ_DISCARD | REQ_SECURE.

CC: Li Dongyang <lidongyang@novell.com>
[v1: Used 'flag' instead of 'secure:1' bit]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
drivers/block/xen-blkback/blkback.c | 9 ++++++---
drivers/block/xen-blkback/common.h | 5 +++++
drivers/block/xen-blkback/xenbus.c | 12 ++++++++++++
drivers/block/xen-blkfront.c | 19 +++++++++++++++++--
include/xen/interface/io/blkif.h | 6 ++++++
5 files changed, 46 insertions(+), 5 deletions(-)

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index ca23dff..5ccb648 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -422,13 +422,16 @@ static void xen_blk_discard(struct xen_blkif *blkif, struct blkif_request *req)
int status = BLKIF_RSP_OKAY;
struct block_device *bdev = blkif->vbd.bdev;

- if (blkif->blk_backend_type == BLKIF_BACKEND_PHY)
+ if (blkif->blk_backend_type == BLKIF_BACKEND_PHY) {
+ unsigned long secure = (blkif->vbd.discard_secure &&
+ (req->u.discard.flag & BLKIF_OP_DISCARD_FLAG_SECURE)) ?
+ BLKDEV_DISCARD_SECURE : 0;
/* just forward the discard request */
err = blkdev_issue_discard(bdev,
req->u.discard.sector_number,
req->u.discard.nr_sectors,
- GFP_KERNEL, 0);
- else if (blkif->blk_backend_type == BLKIF_BACKEND_FILE) {
+ GFP_KERNEL, secure);
+ } else if (blkif->blk_backend_type == BLKIF_BACKEND_FILE) {
/* punch a hole in the backing file */
struct loop_device *lo = bdev->bd_disk->private_data;
struct file *file = lo->lo_backing_file;
diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
index e638457..43b72a7 100644
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -72,6 +72,7 @@ struct blkif_x86_32_request_rw {
struct blkif_x86_32_request_discard {
blkif_sector_t sector_number;/* start sector idx on disk (r/w only) */
uint64_t nr_sectors;
+ uint32_t flag;
};

struct blkif_x86_32_request {
@@ -101,6 +102,7 @@ struct blkif_x86_64_request_rw {
struct blkif_x86_64_request_discard {
blkif_sector_t sector_number;/* start sector idx on disk (r/w only) */
uint64_t nr_sectors;
+ uint32_t flag;
};

struct blkif_x86_64_request {
@@ -157,6 +159,7 @@ struct xen_vbd {
/* Cached size parameter. */
sector_t size;
bool flush_support;
+ bool discard_secure;
};

struct backend_info;
@@ -259,6 +262,7 @@ static inline void blkif_get_x86_32_req(struct blkif_request *dst,
case BLKIF_OP_DISCARD:
dst->u.discard.sector_number = src->u.discard.sector_number;
dst->u.discard.nr_sectors = src->u.discard.nr_sectors;
+ dst->u.discard.flag = src->u.discard.flag;
break;
default:
break;
@@ -288,6 +292,7 @@ static inline void blkif_get_x86_64_req(struct blkif_request *dst,
case BLKIF_OP_DISCARD:
dst->u.discard.sector_number = src->u.discard.sector_number;
dst->u.discard.nr_sectors = src->u.discard.nr_sectors;
+ dst->u.discard.flag = src->u.discard.flag;
break;
default:
break;
diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index a6d4303..0c0ce39 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -378,6 +378,9 @@ static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle,
if (q && q->flush_flags)
vbd->flush_support = true;

+ if (q && blk_queue_secdiscard(q))
+ vbd->discard_secure = true;
+
DPRINTK("Successful creation of handle=%04x (dom=%u)\n",
handle, blkif->domid);
return 0;
@@ -460,6 +463,15 @@ int xen_blkbk_discard(struct xenbus_transaction xbt, struct backend_info *be)
state = 1;
blkif->blk_backend_type = BLKIF_BACKEND_PHY;
}
+ /* Optional. */
+ err = xenbus_printf(xbt, dev->nodename,
+ "discard-secure", "%d",
+ blkif->vbd.discard_secure);
+ if (err) {
+ xenbus_dev_fatal(dev, err,
+ "writting discard-secure");
+ goto kfree;
+ }
}
} else {
err = PTR_ERR(type);
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 7b2ec59..807b7b6 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -98,7 +98,8 @@ struct blkfront_info
unsigned long shadow_free;
unsigned int feature_flush;
unsigned int flush_op;
- unsigned int feature_discard;
+ unsigned int feature_discard:1;
+ unsigned int feature_secdiscard:1;
unsigned int discard_granularity;
unsigned int discard_alignment;
int is_ready;
@@ -305,11 +306,13 @@ static int blkif_queue_request(struct request *req)
ring_req->operation = info->flush_op;
}

- if (unlikely(req->cmd_flags & REQ_DISCARD)) {
+ if (unlikely(req->cmd_flags & (REQ_DISCARD | REQ_SECURE))) {
/* id, sector_number and handle are set above. */
ring_req->operation = BLKIF_OP_DISCARD;
ring_req->nr_segments = 0;
ring_req->u.discard.nr_sectors = blk_rq_sectors(req);
+ if ((req->cmd_flags & REQ_SECURE) && info->feature_secdiscard)
+ ring_req->u.discard.flag = BLKIF_OP_DISCARD_FLAG_SECURE;
} else {
ring_req->nr_segments = blk_rq_map_sg(req->q, req, info->sg);
BUG_ON(ring_req->nr_segments > BLKIF_MAX_SEGMENTS_PER_REQUEST);
@@ -424,6 +427,8 @@ static int xlvbd_init_blk_queue(struct gendisk *gd, u16 sector_size)
blk_queue_max_discard_sectors(rq, get_capacity(gd));
rq->limits.discard_granularity = info->discard_granularity;
rq->limits.discard_alignment = info->discard_alignment;
+ if (info->feature_secdiscard)
+ queue_flag_set_unlocked(QUEUE_FLAG_SECDISCARD, rq);
}

/* Hard sector size and max sectors impersonate the equiv. hardware. */
@@ -749,7 +754,9 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
info->gd->disk_name);
error = -EOPNOTSUPP;
info->feature_discard = 0;
+ info->feature_secdiscard = 0;
queue_flag_clear(QUEUE_FLAG_DISCARD, rq);
+ queue_flag_clear(QUEUE_FLAG_SECDISCARD, rq);
}
__blk_end_request_all(req, error);
break;
@@ -1135,11 +1142,13 @@ static void blkfront_setup_discard(struct blkfront_info *info)
char *type;
unsigned int discard_granularity;
unsigned int discard_alignment;
+ unsigned int discard_secure;

type = xenbus_read(XBT_NIL, info->xbdev->otherend, "type", NULL);
if (IS_ERR(type))
return;

+ info->feature_secdiscard = 0;
if (strncmp(type, "phy", 3) == 0) {
err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
"discard-granularity", "%u", &discard_granularity,
@@ -1150,6 +1159,12 @@ static void blkfront_setup_discard(struct blkfront_info *info)
info->discard_granularity = discard_granularity;
info->discard_alignment = discard_alignment;
}
+ err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
+ "discard-secure", "%d", &discard_secure,
+ NULL);
+ if (!err)
+ info->feature_secdiscard = discard_secure;
+
} else if (strncmp(type, "file", 4) == 0)
info->feature_discard = 1;

diff --git a/include/xen/interface/io/blkif.h b/include/xen/interface/io/blkif.h
index 9324488..13d040e 100644
--- a/include/xen/interface/io/blkif.h
+++ b/include/xen/interface/io/blkif.h
@@ -84,6 +84,10 @@ typedef uint64_t blkif_sector_t;
* e07154r6-Data_Set_Management_Proposal_for_ATA-ACS2.doc
* http://www.seagate.com/staticfiles/support/disc/manuals/
* Interface%20manuals/100293068c.pdf
+ * We also provide three extra XenBus options to the discard operation:
+ * 'discard-granularity' - Max amount of sectors that can be discarded.
+ * 'discard-alignment' - 4K, 128K, etc aligment on sectors to erased.
+ * 'discard-secure' - whether the discard can also securely erase data.
*/
#define BLKIF_OP_DISCARD 5

@@ -107,6 +111,8 @@ struct blkif_request_rw {
struct blkif_request_discard {
blkif_sector_t sector_number;
uint64_t nr_sectors;
+#define BLKIF_OP_DISCARD_FLAG_SECURE (1<<1) /* ignored if discard-secure=0 */
+ uint32_t flag;
};

struct blkif_request {
--
1.7.5.4


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