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Subject[PATCH 1/4] xen/blk[front|back]: Squash blkif_request_rw and blkif_request_discard together
Date
In a union type structure to deal with the overlapping
attributes in a easier manner.

Suggested-by: Ian Campbell <Ian.Campbell@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
drivers/block/xen-blkback/blkback.c | 13 ++++---
drivers/block/xen-blkback/common.h | 64 +++++++++++++++++++---------------
drivers/block/xen-blkfront.c | 44 ++++++++++++-----------
include/xen/interface/io/blkif.h | 24 +++++++++----
4 files changed, 83 insertions(+), 62 deletions(-)
diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index 15ec4db..d7104ab 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -362,7 +362,7 @@ static int xen_blkbk_map(struct blkif_request *req,
{
struct gnttab_map_grant_ref map[BLKIF_MAX_SEGMENTS_PER_REQUEST];
int i;
- int nseg = req->nr_segments;
+ int nseg = req->u.rw.nr_segments;
int ret = 0;

/*
@@ -449,7 +449,7 @@ static void xen_blk_discard(struct xen_blkif *blkif, struct blkif_request *req)
} else if (err)
status = BLKIF_RSP_ERROR;

- make_response(blkif, req->id, req->operation, status);
+ make_response(blkif, req->u.discard.id, req->operation, status);
}

static void xen_blk_drain_io(struct xen_blkif *blkif)
@@ -644,7 +644,8 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
}

/* Check that the number of segments is sane. */
- nseg = req->nr_segments;
+ nseg = req->u.rw.nr_segments;
+
if (unlikely(nseg == 0 && operation != WRITE_FLUSH &&
operation != REQ_DISCARD) ||
unlikely(nseg > BLKIF_MAX_SEGMENTS_PER_REQUEST)) {
@@ -654,12 +655,12 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
goto fail_response;
}

- preq.dev = req->handle;
+ preq.dev = req->u.rw.handle;
preq.sector_number = req->u.rw.sector_number;
preq.nr_sects = 0;

pending_req->blkif = blkif;
- pending_req->id = req->id;
+ pending_req->id = req->u.rw.id;
pending_req->operation = req->operation;
pending_req->status = BLKIF_RSP_OKAY;
pending_req->nr_pages = nseg;
@@ -784,7 +785,7 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
xen_blkbk_unmap(pending_req);
fail_response:
/* Haven't submitted any bio's yet. */
- make_response(blkif, req->id, req->operation, BLKIF_RSP_ERROR);
+ make_response(blkif, req->u.rw.id, req->operation, BLKIF_RSP_ERROR);
free_req(pending_req);
msleep(1); /* back off a bit */
return -EIO;
diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
index dfb1b3a..dbfe7b3 100644
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -60,58 +60,66 @@ struct blkif_common_response {
char dummy;
};

-/* i386 protocol version */
-#pragma pack(push, 4)
-
struct blkif_x86_32_request_rw {
+ uint8_t nr_segments; /* number of segments */
+ blkif_vdev_t handle; /* only 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) */
struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
-};
+} __attribute__((__packed__));

struct blkif_x86_32_request_discard {
+ uint8_t nr_segments; /* number of segments */
+ 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) */
- uint64_t nr_sectors;
-};
+ uint64_t nr_sectors;
+} __attribute__((__packed__));

struct blkif_x86_32_request {
uint8_t operation; /* BLKIF_OP_??? */
- uint8_t nr_segments; /* number of segments */
- blkif_vdev_t handle; /* only for read/write requests */
- uint64_t id; /* private guest value, echoed in resp */
union {
struct blkif_x86_32_request_rw rw;
struct blkif_x86_32_request_discard discard;
} u;
-};
+} __attribute__((__packed__));
+
+/* i386 protocol version */
+#pragma pack(push, 4)
struct blkif_x86_32_response {
uint64_t id; /* copied from request */
uint8_t operation; /* copied from request */
int16_t status; /* BLKIF_RSP_??? */
};
#pragma pack(pop)
-
/* x86_64 protocol version */

struct blkif_x86_64_request_rw {
+ uint8_t nr_segments; /* number of segments */
+ blkif_vdev_t handle; /* only for read/write requests */
+ uint32_t _pad1; /* offsetof(blkif_reqest..,u.rw.id)==8 */
+ uint64_t id;
blkif_sector_t sector_number;/* start sector idx on disk (r/w only) */
struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
-};
+} __attribute__((__packed__));

struct blkif_x86_64_request_discard {
+ uint8_t nr_segments; /* number of segments */
+ blkif_vdev_t _pad1; /* was "handle" for read/write requests */
+ uint32_t _pad2; /* offsetof(blkif_..,u.discard.id)==8 */
+ uint64_t id;
blkif_sector_t sector_number;/* start sector idx on disk (r/w only) */
- uint64_t nr_sectors;
-};
+ uint64_t nr_sectors;
+} __attribute__((__packed__));

struct blkif_x86_64_request {
uint8_t operation; /* BLKIF_OP_??? */
- uint8_t nr_segments; /* number of segments */
- blkif_vdev_t handle; /* only for read/write requests */
- uint64_t __attribute__((__aligned__(8))) id;
union {
struct blkif_x86_64_request_rw rw;
struct blkif_x86_64_request_discard discard;
} u;
-};
+} __attribute__((__packed__));
+
struct blkif_x86_64_response {
uint64_t __attribute__((__aligned__(8))) id;
uint8_t operation; /* copied from request */
@@ -237,18 +245,18 @@ static inline void blkif_get_x86_32_req(struct blkif_request *dst,
{
int i, n = BLKIF_MAX_SEGMENTS_PER_REQUEST;
dst->operation = src->operation;
- dst->nr_segments = src->nr_segments;
- dst->handle = src->handle;
- dst->id = src->id;
switch (src->operation) {
case BLKIF_OP_READ:
case BLKIF_OP_WRITE:
case BLKIF_OP_WRITE_BARRIER:
case BLKIF_OP_FLUSH_DISKCACHE:
+ dst->u.rw.nr_segments = src->u.rw.nr_segments;
+ dst->u.rw.handle = src->u.rw.handle;
+ dst->u.rw.id = src->u.rw.id;
dst->u.rw.sector_number = src->u.rw.sector_number;
barrier();
- if (n > dst->nr_segments)
- n = dst->nr_segments;
+ if (n > dst->u.rw.nr_segments)
+ n = dst->u.rw.nr_segments;
for (i = 0; i < n; i++)
dst->u.rw.seg[i] = src->u.rw.seg[i];
break;
@@ -266,18 +274,18 @@ static inline void blkif_get_x86_64_req(struct blkif_request *dst,
{
int i, n = BLKIF_MAX_SEGMENTS_PER_REQUEST;
dst->operation = src->operation;
- dst->nr_segments = src->nr_segments;
- dst->handle = src->handle;
- dst->id = src->id;
switch (src->operation) {
case BLKIF_OP_READ:
case BLKIF_OP_WRITE:
case BLKIF_OP_WRITE_BARRIER:
case BLKIF_OP_FLUSH_DISKCACHE:
+ dst->u.rw.nr_segments = src->u.rw.nr_segments;
+ dst->u.rw.handle = src->u.rw.handle;
+ dst->u.rw.id = src->u.rw.id;
dst->u.rw.sector_number = src->u.rw.sector_number;
barrier();
- if (n > dst->nr_segments)
- n = dst->nr_segments;
+ if (n > dst->u.rw.nr_segments)
+ n = dst->u.rw.nr_segments;
for (i = 0; i < n; i++)
dst->u.rw.seg[i] = src->u.rw.seg[i];
break;
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 7b2ec59..2c2c4be 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -135,15 +135,15 @@ static int get_id_from_freelist(struct blkfront_info *info)
{
unsigned long free = info->shadow_free;
BUG_ON(free >= BLK_RING_SIZE);
- info->shadow_free = info->shadow[free].req.id;
- info->shadow[free].req.id = 0x0fffffee; /* debug */
+ info->shadow_free = info->shadow[free].req.u.rw.id;
+ info->shadow[free].req.u.rw.id = 0x0fffffee; /* debug */
return free;
}

static void add_id_to_freelist(struct blkfront_info *info,
unsigned long id)
{
- info->shadow[id].req.id = info->shadow_free;
+ info->shadow[id].req.u.rw.id = info->shadow_free;
info->shadow[id].request = NULL;
info->shadow_free = id;
}
@@ -287,9 +287,9 @@ static int blkif_queue_request(struct request *req)
id = get_id_from_freelist(info);
info->shadow[id].request = req;

- ring_req->id = id;
+ ring_req->u.rw.id = id;
ring_req->u.rw.sector_number = (blkif_sector_t)blk_rq_pos(req);
- ring_req->handle = info->handle;
+ ring_req->u.rw.handle = info->handle;

ring_req->operation = rq_data_dir(req) ?
BLKIF_OP_WRITE : BLKIF_OP_READ;
@@ -308,13 +308,15 @@ static int blkif_queue_request(struct request *req)
if (unlikely(req->cmd_flags & REQ_DISCARD)) {
/* id, sector_number and handle are set above. */
ring_req->operation = BLKIF_OP_DISCARD;
- ring_req->nr_segments = 0;
+ ring_req->u.discard.nr_segments = 0;
ring_req->u.discard.nr_sectors = blk_rq_sectors(req);
} 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);
+ ring_req->u.rw.nr_segments = blk_rq_map_sg(req->q, req,
+ info->sg);
+ BUG_ON(ring_req->u.rw.nr_segments >
+ BLKIF_MAX_SEGMENTS_PER_REQUEST);

- for_each_sg(info->sg, sg, ring_req->nr_segments, i) {
+ for_each_sg(info->sg, sg, ring_req->u.rw.nr_segments, i) {
buffer_mfn = pfn_to_mfn(page_to_pfn(sg_page(sg)));
fsect = sg->offset >> 9;
lsect = fsect + (sg->length >> 9) - 1;
@@ -705,7 +707,7 @@ static void blkif_free(struct blkfront_info *info, int suspend)
static void blkif_completion(struct blk_shadow *s)
{
int i;
- for (i = 0; i < s->req.nr_segments; i++)
+ for (i = 0; i < s->req.u.rw.nr_segments; i++)
gnttab_end_foreign_access(s->req.u.rw.seg[i].gref, 0, 0UL);
}

@@ -763,7 +765,7 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
error = -EOPNOTSUPP;
}
if (unlikely(bret->status == BLKIF_RSP_ERROR &&
- info->shadow[id].req.nr_segments == 0)) {
+ info->shadow[id].req.u.rw.nr_segments == 0)) {
printk(KERN_WARNING "blkfront: %s: empty write %s op failed\n",
info->flush_op == BLKIF_OP_WRITE_BARRIER ?
"barrier" : "flush disk cache",
@@ -984,8 +986,8 @@ static int blkfront_probe(struct xenbus_device *dev,
INIT_WORK(&info->work, blkif_restart_queue);

for (i = 0; i < BLK_RING_SIZE; i++)
- info->shadow[i].req.id = i+1;
- info->shadow[BLK_RING_SIZE-1].req.id = 0x0fffffff;
+ info->shadow[i].req.u.rw.id = i+1;
+ info->shadow[BLK_RING_SIZE-1].req.u.rw.id = 0x0fffffff;

/* Front end dir is a number, which is used as the id. */
info->handle = simple_strtoul(strrchr(dev->nodename, '/')+1, NULL, 0);
@@ -1019,9 +1021,9 @@ static int blkif_recover(struct blkfront_info *info)
/* Stage 2: Set up free list. */
memset(&info->shadow, 0, sizeof(info->shadow));
for (i = 0; i < BLK_RING_SIZE; i++)
- info->shadow[i].req.id = i+1;
+ info->shadow[i].req.u.rw.id = i+1;
info->shadow_free = info->ring.req_prod_pvt;
- info->shadow[BLK_RING_SIZE-1].req.id = 0x0fffffff;
+ info->shadow[BLK_RING_SIZE-1].req.u.rw.id = 0x0fffffff;

/* Stage 3: Find pending requests and requeue them. */
for (i = 0; i < BLK_RING_SIZE; i++) {
@@ -1034,17 +1036,17 @@ static int blkif_recover(struct blkfront_info *info)
*req = copy[i].req;

/* We get a new request id, and must reset the shadow state. */
- req->id = get_id_from_freelist(info);
- memcpy(&info->shadow[req->id], &copy[i], sizeof(copy[i]));
+ req->u.rw.id = get_id_from_freelist(info);
+ memcpy(&info->shadow[req->u.rw.id], &copy[i], sizeof(copy[i]));

/* Rewrite any grant references invalidated by susp/resume. */
- for (j = 0; j < req->nr_segments; j++)
+ 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->id].frame[j]),
- rq_data_dir(info->shadow[req->id].request));
- info->shadow[req->id].req = *req;
+ 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++;
}
diff --git a/include/xen/interface/io/blkif.h b/include/xen/interface/io/blkif.h
index 9324488..f88e28b 100644
--- a/include/xen/interface/io/blkif.h
+++ b/include/xen/interface/io/blkif.h
@@ -95,6 +95,12 @@ typedef uint64_t blkif_sector_t;
#define BLKIF_MAX_SEGMENTS_PER_REQUEST 11

struct blkif_request_rw {
+ uint8_t nr_segments; /* number of segments */
+ blkif_vdev_t handle; /* only for read/write requests */
+#ifdef CONFIG_X86_64
+ uint32_t _pad1; /* offsetof(blkif_request,u.rw.id) == 8 */
+#endif
+ uint64_t id; /* private guest value, echoed in resp */
blkif_sector_t sector_number;/* start sector idx on disk (r/w only) */
struct blkif_request_segment {
grant_ref_t gref; /* reference to I/O buffer frame */
@@ -102,23 +108,27 @@ struct blkif_request_rw {
/* @last_sect: last sector in frame to transfer (inclusive). */
uint8_t first_sect, last_sect;
} seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
-};
+} __attribute__((__packed__));

struct blkif_request_discard {
+ uint8_t nr_segments; /* number of segments */
+ blkif_vdev_t _pad1; /* only for read/write requests */
+#ifdef CONFIG_X86_64
+ uint32_t _pad2; /* offsetof(blkif_req..,u.discard.id)==8*/
+#endif
+ uint64_t id; /* private guest value, echoed in resp */
blkif_sector_t sector_number;
- uint64_t nr_sectors;
-};
+ uint64_t nr_sectors;
+ uint8_t _pad3;
+} __attribute__((__packed__));

struct blkif_request {
uint8_t operation; /* BLKIF_OP_??? */
- uint8_t nr_segments; /* number of segments */
- blkif_vdev_t handle; /* only for read/write requests */
- uint64_t id; /* private guest value, echoed in resp */
union {
struct blkif_request_rw rw;
struct blkif_request_discard discard;
} u;
-};
+} __attribute__((__packed__));

struct blkif_response {
uint64_t id; /* copied from request */
--
1.7.7.3


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