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rbd: initial discard bits from Guangliang Zhao
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This patch add the discard support for rbd driver.

There are three types operation in the driver:
1. The objects would be removed if they completely contained
   within the discard range.
2. The objects would be truncated if they partly contained within
   the discard range, and align with their boundary.
3. Others would be zeroed.

A discard request from blkdev_issue_discard() is defined which
REQ_WRITE and REQ_DISCARD both marked and no data, so we must
check the REQ_DISCARD first when getting the request type.

This resolve:
	http://tracker.ceph.com/issues/190

[ Ilya Dryomov: This is incomplete and somewhat buggy, see follow up
  commits by Josh Durgin for refinements and fixes which weren't
  folded in to preserve authorship. ]

Signed-off-by: Guangliang Zhao <[email protected]>
Reviewed-by: Josh Durgin <[email protected]>
Reviewed-by: Alex Elder <[email protected]>
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@glzhao @idryomov
glzhao authored and idryomov committed Oct 14, 2014
1 parent 6d2940c commit 90e98c5
Showing 1 changed file with 89 additions and 15 deletions.
104 changes: 89 additions & 15 deletions drivers/block/rbd.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -213,6 +213,7 @@ enum obj_request_type {
enum obj_operation_type {
OBJ_OP_WRITE,
OBJ_OP_READ,
OBJ_OP_DISCARD,
};

enum obj_req_flags {
Expand Down Expand Up @@ -281,6 +282,7 @@ enum img_req_flags {
IMG_REQ_WRITE, /* I/O direction: read = 0, write = 1 */
IMG_REQ_CHILD, /* initiator: block = 0, child image = 1 */
IMG_REQ_LAYERED, /* ENOENT handling: normal = 0, layered = 1 */
IMG_REQ_DISCARD, /* discard: normal = 0, discard request = 1 */
};

struct rbd_img_request {
Expand Down Expand Up @@ -797,6 +799,8 @@ static char* obj_op_name(enum obj_operation_type op_type)
return "read";
case OBJ_OP_WRITE:
return "write";
case OBJ_OP_DISCARD:
return "discard";
default:
return "???";
}
Expand Down Expand Up @@ -1617,6 +1621,21 @@ static bool img_request_write_test(struct rbd_img_request *img_request)
return test_bit(IMG_REQ_WRITE, &img_request->flags) != 0;
}

/*
* Set the discard flag when the img_request is an discard request
*/
static void img_request_discard_set(struct rbd_img_request *img_request)
{
set_bit(IMG_REQ_DISCARD, &img_request->flags);
smp_mb();
}

static bool img_request_discard_test(struct rbd_img_request *img_request)
{
smp_mb();
return test_bit(IMG_REQ_DISCARD, &img_request->flags) != 0;
}

static void img_request_child_set(struct rbd_img_request *img_request)
{
set_bit(IMG_REQ_CHILD, &img_request->flags);
Expand Down Expand Up @@ -1739,6 +1758,18 @@ static void rbd_osd_write_callback(struct rbd_obj_request *obj_request)
obj_request_done_set(obj_request);
}

static void rbd_osd_discard_callback(struct rbd_obj_request *obj_request)
{
dout("%s: obj %p result %d %llu\n", __func__, obj_request,
obj_request->result, obj_request->length);
/*
* There is no such thing as a successful short discard. Set
* it to our originally-requested length.
*/
obj_request->xferred = obj_request->length;
obj_request_done_set(obj_request);
}

/*
* For a simple stat call there's nothing to do. We'll do more if
* this is part of a write sequence for a layered image.
Expand Down Expand Up @@ -1790,6 +1821,11 @@ static void rbd_osd_req_callback(struct ceph_osd_request *osd_req,
case CEPH_OSD_OP_STAT:
rbd_osd_stat_callback(obj_request);
break;
case CEPH_OSD_OP_DELETE:
case CEPH_OSD_OP_TRUNCATE:
case CEPH_OSD_OP_ZERO:
rbd_osd_discard_callback(obj_request);
break;
case CEPH_OSD_OP_CALL:
case CEPH_OSD_OP_NOTIFY_ACK:
case CEPH_OSD_OP_WATCH:
Expand Down Expand Up @@ -1848,10 +1884,14 @@ static struct ceph_osd_request *rbd_osd_req_create(
struct ceph_osd_client *osdc;
struct ceph_osd_request *osd_req;

if (obj_request_img_data_test(obj_request) && op_type == OBJ_OP_WRITE) {
if (obj_request_img_data_test(obj_request) &&
(op_type == OBJ_OP_DISCARD || op_type == OBJ_OP_WRITE)) {
struct rbd_img_request *img_request = obj_request->img_request;

rbd_assert(img_request_write_test(img_request));
if (op_type == OBJ_OP_WRITE) {
rbd_assert(img_request_write_test(img_request));
} else {
rbd_assert(img_request_discard_test(img_request));
}
snapc = img_request->snapc;
}

Expand All @@ -1865,7 +1905,7 @@ static struct ceph_osd_request *rbd_osd_req_create(
if (!osd_req)
return NULL; /* ENOMEM */

if (op_type == OBJ_OP_WRITE)
if (op_type == OBJ_OP_WRITE || op_type == OBJ_OP_DISCARD)
osd_req->r_flags = CEPH_OSD_FLAG_WRITE | CEPH_OSD_FLAG_ONDISK;
else
osd_req->r_flags = CEPH_OSD_FLAG_READ;
Expand Down Expand Up @@ -2086,7 +2126,10 @@ static struct rbd_img_request *rbd_img_request_create(
img_request->offset = offset;
img_request->length = length;
img_request->flags = 0;
if (op_type == OBJ_OP_WRITE) {
if (op_type == OBJ_OP_DISCARD) {
img_request_discard_set(img_request);
img_request->snapc = snapc;
} else if (op_type == OBJ_OP_WRITE) {
img_request_write_set(img_request);
img_request->snapc = snapc;
} else {
Expand Down Expand Up @@ -2187,8 +2230,12 @@ static bool rbd_img_obj_end_request(struct rbd_obj_request *obj_request)
struct rbd_device *rbd_dev = img_request->rbd_dev;
enum obj_operation_type op_type;

op_type = img_request_write_test(img_request) ? OBJ_OP_WRITE :
OBJ_OP_READ;
if (img_request_discard_test(img_request))
op_type = OBJ_OP_DISCARD;
else if (img_request_write_test(img_request))
op_type = OBJ_OP_WRITE;
else
op_type = OBJ_OP_READ;

rbd_warn(rbd_dev, "%s %llx at %llx (%llx)",
obj_op_name(op_type), obj_request->length,
Expand Down Expand Up @@ -2275,23 +2322,25 @@ static int rbd_img_request_fill(struct rbd_img_request *img_request,
unsigned int bio_offset = 0;
struct page **pages = NULL;
enum obj_operation_type op_type;
u64 object_size = rbd_obj_bytes(&rbd_dev->header);
u64 img_offset;
u64 img_end;
u64 resid;
u16 opcode;

dout("%s: img %p type %d data_desc %p\n", __func__, img_request,
(int)type, data_desc);

img_offset = img_request->offset;
img_end = rbd_dev->header.image_size;
resid = img_request->length;
rbd_assert(resid > 0);

if (type == OBJ_REQUEST_BIO) {
bio_list = data_desc;
rbd_assert(img_offset ==
bio_list->bi_iter.bi_sector << SECTOR_SHIFT);
} else {
rbd_assert(type == OBJ_REQUEST_PAGES);
} else if (type == OBJ_REQUEST_PAGES) {
pages = data_desc;
}

Expand Down Expand Up @@ -2332,7 +2381,7 @@ static int rbd_img_request_fill(struct rbd_img_request *img_request,
GFP_ATOMIC);
if (!obj_request->bio_list)
goto out_unwind;
} else {
} else if (type == OBJ_REQUEST_PAGES) {
unsigned int page_count;

obj_request->pages = pages;
Expand All @@ -2343,7 +2392,19 @@ static int rbd_img_request_fill(struct rbd_img_request *img_request,
pages += page_count;
}

if (img_request_write_test(img_request)) {
if (img_request_discard_test(img_request)) {
op_type = OBJ_OP_DISCARD;
if (!offset && (length == object_size)
&& (!img_request_layered_test(img_request) ||
(rbd_dev->parent_overlap <=
obj_request->img_offset)))
opcode = CEPH_OSD_OP_DELETE;
else if ((offset + length == object_size) ||
(obj_request->img_offset + length == img_end))
opcode = CEPH_OSD_OP_TRUNCATE;
else
opcode = CEPH_OSD_OP_ZERO;
} else if (img_request_write_test(img_request)) {
op_type = OBJ_OP_WRITE;
opcode = CEPH_OSD_OP_WRITE;
} else {
Expand Down Expand Up @@ -2372,12 +2433,13 @@ static int rbd_img_request_fill(struct rbd_img_request *img_request,
if (type == OBJ_REQUEST_BIO)
osd_req_op_extent_osd_data_bio(osd_req, which,
obj_request->bio_list, length);
else
else if (type == OBJ_REQUEST_PAGES)
osd_req_op_extent_osd_data_pages(osd_req, which,
obj_request->pages, length,
offset & ~PAGE_MASK, false, false);

if (op_type == OBJ_OP_WRITE)
/* Discards are also writes */
if (op_type == OBJ_OP_WRITE || op_type == OBJ_OP_DISCARD)
rbd_osd_req_format_write(obj_request);
else
rbd_osd_req_format_read(obj_request);
Expand Down Expand Up @@ -3229,7 +3291,9 @@ static void rbd_handle_request(struct rbd_device *rbd_dev, struct request *rq)
u64 mapping_size;
int result;

if (rq->cmd_flags & REQ_WRITE)
if (rq->cmd_flags & REQ_DISCARD)
op_type = OBJ_OP_DISCARD;
else if (rq->cmd_flags & REQ_WRITE)
op_type = OBJ_OP_WRITE;
else
op_type = OBJ_OP_READ;
Expand Down Expand Up @@ -3295,7 +3359,12 @@ static void rbd_handle_request(struct rbd_device *rbd_dev, struct request *rq)
}
img_request->rq = rq;

result = rbd_img_request_fill(img_request, OBJ_REQUEST_BIO, rq->bio);
if (op_type == OBJ_OP_DISCARD)
result = rbd_img_request_fill(img_request, OBJ_REQUEST_NODATA,
NULL);
else
result = rbd_img_request_fill(img_request, OBJ_REQUEST_BIO,
rq->bio);
if (result)
goto err_img_request;

Expand Down Expand Up @@ -3667,6 +3736,11 @@ static int rbd_init_disk(struct rbd_device *rbd_dev)
blk_queue_io_min(q, segment_size);
blk_queue_io_opt(q, segment_size);

/* enable the discard support */
queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);
q->limits.discard_granularity = segment_size;
q->limits.discard_alignment = segment_size;

blk_queue_merge_bvec(q, rbd_merge_bvec);
disk->queue = q;

Expand Down

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