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]
[v2: Use 'reserved' uint8_t instead of adding a new value]
[v3: Check for nseg when mapping instead of operation]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index d7104abc8b7238548721fd632ba79a7afd7635c3..9d2261b02f2483b82848ff7f213932e7921b9664 100644 (file)
--- 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_DISCARD_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;
@@ -643,8 +646,11 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
                break;
        }
 
-       /* Check that the number of segments is sane. */
-       nseg = req->u.rw.nr_segments;
+       if (unlikely(operation == REQ_DISCARD))
+               nseg = 0;
+       else
+               /* Check that the number of segments is sane. */
+               nseg = req->u.rw.nr_segments;
 
        if (unlikely(nseg == 0 && operation != WRITE_FLUSH &&
                                operation != REQ_DISCARD) ||
@@ -708,7 +714,7 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
         * the hypercall to unmap the grants - that is all done in
         * xen_blkbk_unmap.
         */
-       if (operation != REQ_DISCARD && xen_blkbk_map(req, pending_req, seg))
+       if (nseg && xen_blkbk_map(req, pending_req, seg))
                goto fail_flush;
 
        /*

diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
index dbfe7b3b07376b97860a39ac80e295a307aa940b..d0ee7edc9be8ad1819a91a491eb907f18d545fbf 100644 (file)
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -69,7 +69,7 @@ struct blkif_x86_32_request_rw {
 } __attribute__((__packed__));
 
 struct blkif_x86_32_request_discard {
-       uint8_t        nr_segments;  /* number of segments                   */
+       uint8_t        flag;         /* BLKIF_DISCARD_SECURE or zero         */
        blkif_vdev_t   _pad1;        /* was "handle" for read/write requests */
        uint64_t       id;           /* private guest value, echoed in resp  */
        blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
@@ -104,7 +104,7 @@ struct blkif_x86_64_request_rw {
 } __attribute__((__packed__));
 
 struct blkif_x86_64_request_discard {
-       uint8_t        nr_segments;  /* number of segments                   */
+       uint8_t        flag;         /* BLKIF_DISCARD_SECURE or zero         */
        blkif_vdev_t   _pad1;        /* was "handle" for read/write requests */
         uint32_t       _pad2;        /* offsetof(blkif_..,u.discard.id)==8   */
        uint64_t       id;
@@ -164,6 +164,7 @@ struct xen_vbd {
        /* Cached size parameter. */
        sector_t                size;
        bool                    flush_support;
+       bool                    discard_secure;
 };
 
 struct backend_info;
@@ -261,6 +262,7 @@ static inline void blkif_get_x86_32_req(struct blkif_request *dst,
                        dst->u.rw.seg[i] = src->u.rw.seg[i];
                break;
        case BLKIF_OP_DISCARD:
+               dst->u.discard.flag = src->u.discard.flag;
                dst->u.discard.sector_number = src->u.discard.sector_number;
                dst->u.discard.nr_sectors = src->u.discard.nr_sectors;
                break;
@@ -290,6 +292,7 @@ static inline void blkif_get_x86_64_req(struct blkif_request *dst,
                        dst->u.rw.seg[i] = src->u.rw.seg[i];
                break;
        case BLKIF_OP_DISCARD:
+               dst->u.discard.flag = src->u.discard.flag;
                dst->u.discard.sector_number = src->u.discard.sector_number;
                dst->u.discard.nr_sectors = src->u.discard.nr_sectors;
                break;

diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index f759ad4584c306acb8937c52d80c1f7b567ae986..187fd2c1a15d077cd8cf1c8f88877b3307f8a661 100644 (file)
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -338,6 +338,9 @@ 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;
@@ -420,6 +423,15 @@ 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 2c2c4be7d9d6a96d4aee171a441f631bb30c6154..351ddeffd430bf094c2dc57e56020ca38476097b 100644 (file)
--- 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 +306,14 @@ 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->u.discard.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_DISCARD_SECURE;
+               else
+                       ring_req->u.discard.flag = 0;
        } else {
                ring_req->u.rw.nr_segments = blk_rq_map_sg(req->q, req,
                                                           info->sg);
@@ -426,6 +430,8 @@ 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. */
@@ -707,6 +713,8 @@ static void blkif_free(struct blkfront_info *info, int suspend)
 static void blkif_completion(struct blk_shadow *s)
 {
        int i;
+       /* Do not let BLKIF_OP_DISCARD as nr_segment is in the same place
+        * flag. */
        for (i = 0; i < s->req.u.rw.nr_segments; i++)
                gnttab_end_foreign_access(s->req.u.rw.seg[i].gref, 0, 0UL);
 }
@@ -738,7 +746,8 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
                id   = bret->id;
                req  = info->shadow[id].request;
 
-               blkif_completion(&info->shadow[id]);
+               if (bret->operation != BLKIF_OP_DISCARD)
+                       blkif_completion(&info->shadow[id]);
 
                add_id_to_freelist(info, id);
 
@@ -751,7 +760,9 @@ 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;
@@ -1039,13 +1050,15 @@ static int blkif_recover(struct blkfront_info *info)
                req->u.rw.id = get_id_from_freelist(info);
                memcpy(&info->shadow[req->u.rw.id], &copy[i], sizeof(copy[i]));
 
+               if (req->operation != BLKIF_OP_DISCARD) {
                /* Rewrite any grant references invalidated by susp/resume. */
-               for (j = 0; j < req->u.rw.nr_segments; j++)
-                       gnttab_grant_foreign_access_ref(
-                               req->u.rw.seg[j].gref,
-                               info->xbdev->otherend_id,
-                               pfn_to_mfn(info->shadow[req->u.rw.id].frame[j]),
-                               rq_data_dir(info->shadow[req->u.rw.id].request));
+                       for (j = 0; j < req->u.rw.nr_segments; j++)
+                               gnttab_grant_foreign_access_ref(
+                                       req->u.rw.seg[j].gref,
+                                       info->xbdev->otherend_id,
+                                       pfn_to_mfn(info->shadow[req->u.rw.id].frame[j]),
+                                       rq_data_dir(info->shadow[req->u.rw.id].request));
+               }
                info->shadow[req->u.rw.id].req = *req;
 
                info->ring.req_prod_pvt++;
@@ -1137,11 +1150,13 @@ 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,
@@ -1152,6 +1167,12 @@ 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 f88e28b6a27c67e65899cfda3ae6eb3882df6194..ee338bfde18b25d45bb0252ff41ea4160095d6e7 100644 (file)
--- a/include/xen/interface/io/blkif.h
+++ b/include/xen/interface/io/blkif.h
@@ -84,6 +84,21 @@ 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
+ * The backend can optionally provide three extra XenBus attributes to
+ * further optimize the discard functionality:
+ * 'discard-aligment' - Devices that support discard functionality may
+ * internally allocate space in units that are bigger than the exported
+ * logical block size. The discard-alignment parameter indicates how many bytes
+ * the beginning of the partition is offset from the internal allocation unit's
+ * natural alignment.
+ * 'discard-granularity'  - Devices that support discard functionality may
+ * internally allocate space using units that are bigger than the logical block
+ * size. The discard-granularity parameter indicates the size of the internal
+ * allocation unit in bytes if reported by the device. Otherwise the
+ * discard-granularity will be set to match the device's physical block size.
+ * 'discard-secure' - All copies of the discarded sectors (potentially created
+ * by garbage collection) must also be erased.  To use this feature, the flag
+ * BLKIF_DISCARD_SECURE must be set in the blkif_request_trim.
  */
 #define BLKIF_OP_DISCARD           5
 
@@ -111,7 +126,8 @@ struct blkif_request_rw {
 } __attribute__((__packed__));
 
 struct blkif_request_discard {
-       uint8_t        nr_segments;  /* number of segments                   */
+       uint8_t        flag;         /* BLKIF_DISCARD_SECURE or zero.        */
+#define BLKIF_DISCARD_SECURE (1<<0)  /* ignored if discard-secure=0          */
        blkif_vdev_t   _pad1;        /* only for read/write requests         */
 #ifdef CONFIG_X86_64
        uint32_t       _pad2;        /* offsetof(blkif_req..,u.discard.id)==8*/