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From:   Sarthak Kukreti <sarthakkukreti@chromium.org>
To:     dm-devel@redhat.com, linux-block@vger.kernel.org,
        linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org,
        virtualization@lists.linux-foundation.org
Cc:     Jens Axboe <axboe@kernel.dk>,
        "Michael S . Tsirkin" <mst@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Stefan Hajnoczi <stefanha@redhat.com>,
        Alasdair Kergon <agk@redhat.com>,
        Mike Snitzer <snitzer@kernel.org>,
        Theodore Ts'o <tytso@mit.edu>,
        Andreas Dilger <adilger.kernel@dilger.ca>,
        Bart Van Assche <bvanassche@google.com>,
        Daniil Lunev <dlunev@google.com>,
        Evan Green <evgreen@google.com>,
        Gwendal Grignou <gwendal@google.com>,
        Sarthak Kukreti <sarthakkukreti@chromium.org>
Subject: [PATCH RFC 5/8] loop: Add support for provision requests
Date:   Thu, 15 Sep 2022 09:48:23 -0700
Message-Id: <20220915164826.1396245-6-sarthakkukreti@google.com>
In-Reply-To: <20220915164826.1396245-1-sarthakkukreti@google.com>
References: <20220915164826.1396245-1-sarthakkukreti@google.com>
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From: Sarthak Kukreti <sarthakkukreti@chromium.org>

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.

Signed-off-by: Sarthak Kukreti <sarthakkukreti@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 ad92192c7d61..83f486b9bceb 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, FALLOC_FL_PROVISION, 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, WRITE);
@@ -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);
@@ -1815,6 +1856,7 @@ 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:
-- 
2.31.0