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dm thin: unroll issue_discard() to create longer discard bio chains

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There is little benefit to doing this but it does structure DM thinp's
code to more cleanly use the __blkdev_issue_discard() interface --
particularly in passdown_double_checking_shared_status().

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Joe Thornber 2016-05-04 14:12:42 -04:00 committed by Mike Snitzer
parent 3dba53a958
commit 202bae5293
1 changed files with 71 additions and 37 deletions
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108
drivers/md/dm-thin.c
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@ -334,26 +334,55 @@ static sector_t block_to_sectors(struct pool *pool, dm_block_t b)
(b * pool->sectors_per_block);
}
static int issue_discard(struct thin_c *tc, dm_block_t data_b, dm_block_t data_e,
struct bio *parent_bio)
/*----------------------------------------------------------------*/
struct discard_op {
struct thin_c *tc;
struct blk_plug plug;
struct bio *parent_bio;
struct bio *bio;
};
static void begin_discard(struct discard_op *op, struct thin_c *tc, struct bio *parent)
{
int type = REQ_WRITE | REQ_DISCARD;
BUG_ON(!parent);
op->tc = tc;
blk_start_plug(&op->plug);
op->parent_bio = parent;
op->bio = NULL;
}
static int issue_discard(struct discard_op *op, dm_block_t data_b, dm_block_t data_e)
{
struct thin_c *tc = op->tc;
sector_t s = block_to_sectors(tc->pool, data_b);
sector_t len = block_to_sectors(tc->pool, data_e - data_b);
struct bio *bio = NULL;
struct blk_plug plug;
int ret;
blk_start_plug(&plug);
ret = __blkdev_issue_discard(tc->pool_dev->bdev, s, len,
GFP_NOWAIT, type, &bio);
if (!ret && bio) {
bio_chain(bio, parent_bio);
submit_bio(type, bio);
return __blkdev_issue_discard(tc->pool_dev->bdev, s, len,
GFP_NOWAIT, REQ_WRITE | REQ_DISCARD, &op->bio);
}
static void end_discard(struct discard_op *op, int r)
{
if (op->bio) {
/*
* Even if one of the calls to issue_discard failed, we
* need to wait for the chain to complete.
*/
bio_chain(op->bio, op->parent_bio);
submit_bio(REQ_WRITE | REQ_DISCARD, op->bio);
}
blk_finish_plug(&plug);
return ret;
blk_finish_plug(&op->plug);
/*
* Even if r is set, there could be sub discards in flight that we
* need to wait for.
*/
if (r && !op->parent_bio->bi_error)
op->parent_bio->bi_error = r;
bio_endio(op->parent_bio);
}
/*----------------------------------------------------------------*/
@ -968,24 +997,28 @@ static void process_prepared_discard_no_passdown(struct dm_thin_new_mapping *m)
mempool_free(m, tc->pool->mapping_pool);
}
static int passdown_double_checking_shared_status(struct dm_thin_new_mapping *m)
/*----------------------------------------------------------------*/
static void passdown_double_checking_shared_status(struct dm_thin_new_mapping *m)
{
/*
* We've already unmapped this range of blocks, but before we
* passdown we have to check that these blocks are now unused.
*/
int r;
int r = 0;
bool used = true;
struct thin_c *tc = m->tc;
struct pool *pool = tc->pool;
dm_block_t b = m->data_block, e, end = m->data_block + m->virt_end - m->virt_begin;
struct discard_op op;
begin_discard(&op, tc, m->bio);
while (b != end) {
/* find start of unmapped run */
for (; b < end; b++) {
r = dm_pool_block_is_used(pool->pmd, b, &used);
if (r)
return r;
goto out;
if (!used)
break;
@ -998,20 +1031,20 @@ static int passdown_double_checking_shared_status(struct dm_thin_new_mapping *m)
for (e = b + 1; e != end; e++) {
r = dm_pool_block_is_used(pool->pmd, e, &used);
if (r)
return r;
goto out;
if (used)
break;
}
r = issue_discard(tc, b, e, m->bio);
r = issue_discard(&op, b, e);
if (r)
return r;
goto out;
b = e;
}
return 0;
out:
end_discard(&op, r);
}
static void process_prepared_discard_passdown(struct dm_thin_new_mapping *m)
@ -1021,20 +1054,21 @@ static void process_prepared_discard_passdown(struct dm_thin_new_mapping *m)
struct pool *pool = tc->pool;
r = dm_thin_remove_range(tc->td, m->virt_begin, m->virt_end);
if (r)
if (r) {
metadata_operation_failed(pool, "dm_thin_remove_range", r);
bio_io_error(m->bio);
else if (m->maybe_shared)
r = passdown_double_checking_shared_status(m);
else
r = issue_discard(tc, m->data_block, m->data_block + (m->virt_end - m->virt_begin), m->bio);
} else if (m->maybe_shared) {
passdown_double_checking_shared_status(m);
} else {
struct discard_op op;
begin_discard(&op, tc, m->bio);
r = issue_discard(&op, m->data_block,
m->data_block + (m->virt_end - m->virt_begin));
end_discard(&op, r);
}
/*
* Even if r is set, there could be sub discards in flight that we
* need to wait for.
*/
m->bio->bi_error = r;
bio_endio(m->bio);
cell_defer_no_holder(tc, m->cell);
mempool_free(m, pool->mapping_pool);
}
@ -1505,11 +1539,11 @@ static void break_up_discard_bio(struct thin_c *tc, dm_block_t begin, dm_block_t
/*
* The parent bio must not complete before sub discard bios are
* chained to it (see issue_discard's bio_chain)!
* chained to it (see end_discard's bio_chain)!
*
* This per-mapping bi_remaining increment is paired with
* the implicit decrement that occurs via bio_endio() in
* process_prepared_discard_passdown().
* end_discard().
*/
bio_inc_remaining(bio);
if (!dm_deferred_set_add_work(pool->all_io_ds, &m->list))
@ -3850,7 +3884,7 @@ static struct target_type pool_target = {
.name = "thin-pool",
.features = DM_TARGET_SINGLETON | DM_TARGET_ALWAYS_WRITEABLE |
DM_TARGET_IMMUTABLE,
.version = {1, 18, 0},
.version = {1, 19, 0},
.module = THIS_MODULE,
.ctr = pool_ctr,
.dtr = pool_dtr,
@ -4224,7 +4258,7 @@ static void thin_io_hints(struct dm_target *ti, struct queue_limits *limits)
static struct target_type thin_target = {
.name = "thin",
.version = {1, 18, 0},
.version = {1, 19, 0},
.module = THIS_MODULE,
.ctr = thin_ctr,
.dtr = thin_dtr,