[dm-devel] [PATCH v5 5/5] loop: Add support for provision requests

[Sarthak Kukreti]

Add support for provision requests to loopback devices.
Loop devices will configure provision support based on
whether the underlying block device/file can support
the provision request and upon receiving a provision bio,
will map it to the backing device/storage. For loop devices
over files, a REQ_OP_PROVISION request will translate to
an fallocate mode 0 call on the backing file.

Signed-off-by: Sarthak Kukreti <sarthakkukr...@chromium.org>
---
 drivers/block/loop.c | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index bc31bb7072a2..13c4b4f8b9c1 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -327,6 +327,24 @@ static int lo_fallocate(struct loop_device *lo, struct 
request *rq, loff_t pos,
        return ret;
 }
 
+static int lo_req_provision(struct loop_device *lo, struct request *rq, loff_t 
pos)
+{
+       struct file *file = lo->lo_backing_file;
+       struct request_queue *q = lo->lo_queue;
+       int ret;
+
+       if (!q->limits.max_provision_sectors) {
+               ret = -EOPNOTSUPP;
+               goto out;
+       }
+
+       ret = file->f_op->fallocate(file, 0, pos, blk_rq_bytes(rq));
+       if (unlikely(ret && ret != -EINVAL && ret != -EOPNOTSUPP))
+               ret = -EIO;
+ out:
+       return ret;
+}
+
 static int lo_req_flush(struct loop_device *lo, struct request *rq)
 {
        int ret = vfs_fsync(lo->lo_backing_file, 0);
@@ -488,6 +506,8 @@ static int do_req_filebacked(struct loop_device *lo, struct 
request *rq)
                                FALLOC_FL_PUNCH_HOLE);
        case REQ_OP_DISCARD:
                return lo_fallocate(lo, rq, pos, FALLOC_FL_PUNCH_HOLE);
+       case REQ_OP_PROVISION:
+               return lo_req_provision(lo, rq, pos);
        case REQ_OP_WRITE:
                if (cmd->use_aio)
                        return lo_rw_aio(lo, cmd, pos, ITER_SOURCE);
@@ -754,6 +774,25 @@ static void loop_sysfs_exit(struct loop_device *lo)
                                   &loop_attribute_group);
 }
 
+static void loop_config_provision(struct loop_device *lo)
+{
+       struct file *file = lo->lo_backing_file;
+       struct inode *inode = file->f_mapping->host;
+
+       /*
+        * If the backing device is a block device, mirror its provisioning
+        * capability.
+        */
+       if (S_ISBLK(inode->i_mode)) {
+               blk_queue_max_provision_sectors(lo->lo_queue,
+                       bdev_max_provision_sectors(I_BDEV(inode)));
+       } else if (file->f_op->fallocate) {
+               blk_queue_max_provision_sectors(lo->lo_queue, UINT_MAX >> 9);
+       } else {
+               blk_queue_max_provision_sectors(lo->lo_queue, 0);
+       }
+}
+
 static void loop_config_discard(struct loop_device *lo)
 {
        struct file *file = lo->lo_backing_file;
@@ -1092,6 +1131,7 @@ static int loop_configure(struct loop_device *lo, fmode_t 
mode,
        blk_queue_io_min(lo->lo_queue, bsize);
 
        loop_config_discard(lo);
+       loop_config_provision(lo);
        loop_update_rotational(lo);
        loop_update_dio(lo);
        loop_sysfs_init(lo);
@@ -1304,6 +1344,7 @@ loop_set_status(struct loop_device *lo, const struct 
loop_info64 *info)
        }
 
        loop_config_discard(lo);
+       loop_config_provision(lo);
 
        /* update dio if lo_offset or transfer is changed */
        __loop_update_dio(lo, lo->use_dio);
@@ -1830,6 +1871,7 @@ static blk_status_t loop_queue_rq(struct blk_mq_hw_ctx 
*hctx,
        case REQ_OP_FLUSH:
        case REQ_OP_DISCARD:
        case REQ_OP_WRITE_ZEROES:
+       case REQ_OP_PROVISION:
                cmd->use_aio = false;
                break;
        default:
-- 
2.40.0.634.g4ca3ef3211-goog

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