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Subject[PATCH v7 6/6] loop: Add support for REQ_ALLOCATE
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Date
Support for new modifier of REQ_OP_WRITE_ZEROES command.
This results in allocation extents in backing file instead
of actual blocks zeroing.

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Reviewed-by: Bob Liu <bob.liu@oracle.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
---
drivers/block/loop.c | 20 +++++++++++++-------
1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 739b372a5112..0704167a5aaa 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -581,6 +581,16 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
return 0;
}

+/* Convert REQ_OP_WRITE_ZEROES modifiers into fallocate mode */
+static unsigned int write_zeroes_to_fallocate_mode(unsigned int flags)
+{
+ if (flags & REQ_ALLOCATE)
+ return 0;
+ if (flags & REQ_NOUNMAP)
+ return FALLOC_FL_ZERO_RANGE;
+ return FALLOC_FL_PUNCH_HOLE;
+}
+
static int do_req_filebacked(struct loop_device *lo, struct request *rq)
{
struct loop_cmd *cmd = blk_mq_rq_to_pdu(rq);
@@ -599,14 +609,8 @@ static int do_req_filebacked(struct loop_device *lo, struct request *rq)
case REQ_OP_FLUSH:
return lo_req_flush(lo, rq);
case REQ_OP_WRITE_ZEROES:
- /*
- * If the caller doesn't want deallocation, call zeroout to
- * write zeroes the range. Otherwise, punch them out.
- */
return lo_fallocate(lo, rq, pos,
- (rq->cmd_flags & REQ_NOUNMAP) ?
- FALLOC_FL_ZERO_RANGE :
- FALLOC_FL_PUNCH_HOLE);
+ write_zeroes_to_fallocate_mode(rq->cmd_flags));
case REQ_OP_DISCARD:
return lo_fallocate(lo, rq, pos, FALLOC_FL_PUNCH_HOLE);
case REQ_OP_WRITE:
@@ -877,6 +881,7 @@ static void loop_config_discard(struct loop_device *lo)
q->limits.discard_alignment = 0;
blk_queue_max_discard_sectors(q, 0);
blk_queue_max_write_zeroes_sectors(q, 0);
+ blk_queue_max_allocate_sectors(q, 0);
blk_queue_flag_clear(QUEUE_FLAG_DISCARD, q);
return;
}
@@ -886,6 +891,7 @@ static void loop_config_discard(struct loop_device *lo)

blk_queue_max_discard_sectors(q, UINT_MAX >> 9);
blk_queue_max_write_zeroes_sectors(q, UINT_MAX >> 9);
+ blk_queue_max_allocate_sectors(q, UINT_MAX >> 9);
blk_queue_flag_set(QUEUE_FLAG_DISCARD, q);
}


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