[Devel] [PATCH RH7 5/5] ploop: Allow to set discard_granuality for io_kaio

[Kirill Tkhai]

Here is a problem we call autoconfigure on PLOOP_IOC_START,
so it may rewrite user written data, which was made before.

Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
---
 drivers/block/ploop/io_kaio.c |   51 +++++++++-----------------
 drivers/block/ploop/sysfs.c   |   79 ++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 95 insertions(+), 35 deletions(-)

diff --git a/drivers/block/ploop/io_kaio.c b/drivers/block/ploop/io_kaio.c
index 2f6164cc16fd..6cfd9a63ab3f 100644
--- a/drivers/block/ploop/io_kaio.c
+++ b/drivers/block/ploop/io_kaio.c
@@ -1138,42 +1138,25 @@ static void kaio_queue_settings(struct ploop_io * io, struct request_queue * q)
 	struct inode *inode = file->f_mapping->host;
 
 	if (inode->i_sb->s_magic == EXT4_SUPER_MAGIC) {
-		blk_queue_stack_limits(q, bdev_get_queue(io->files.bdev));
-		/*
-		 * There is no a way to force block engine to split a request
-		 * to fit a single cluster, when discard granuality is 4K
-		 * (inherited from fs block size in blk_queue_stack_limits()).
-		 * So, ploop_make_request() splits them.
-		 */
-		io->plo->force_split_discard_reqs = true;
+		unsigned int max_discard_sectors = q->limits.max_discard_sectors;
+		unsigned int discard_granularity = q->limits.discard_granularity;
+
 		/*
-		 * Why not (1 << io->plo->cluster_log)?
-		 * Someone may want to clear indexes in case of a request
-		 * is big enough to fit the whole cluster.
-		 * In case of max_discard_sectors is 1 cluster, a request
-		 * for [cluster_start - 4K, cluster_start + cluster_size)
-		 * at block level will be splitted in two requests:
-		 *
-		 * [cluster_start - 4K, cluster_start + cluster_size - 4K)
-		 * [cluster_start + cluster_size - 4K, cluster_start + cluster_size)
-		 *
-		 * Then, ploop_make_request() splits the first of them in two
-		 * to fit a single cluster, so all three requests will be smaller
-		 * then 1 cluster, and no index will be cleared.
-		 *
-		 * Note, this does not solve a problem, when a request covers
-		 * 3 clusters: [cluster_start - 4K, cluster_start + 2 * cluster_size],
-		 * so the third cluster's index will remain. This will require
-		 * unlimited max_discard_sectors and splitting every request
-		 * in ploop_make_request(). We don't want that in that context.
-		 *
-		 * But even in current view, this makes indexes to be cleared
-		 * more frequently, and index-clearing code will be tested better.
-		 *
-		 * Anyway, in general this may be an excess functionality.
-		 * If it's so, it will be dropped later.
+		 * It would be better to call this function not only on start
+		 * like now (on every top delta update, e.g. before start).
+		 * But this is difficult with two engines and different holes
+		 * policy. This should be reworked after we switch to io_kaio
+		 * completely.
 		 */
-		q->limits.max_discard_sectors = (1 << io->plo->cluster_log) * 2 - 1;
+		blk_queue_stack_limits(q, bdev_get_queue(io->files.bdev));
+		if (discard_granularity) {
+			/* Restore user values set before PLOOP_IOC_START */
+			q->limits.max_discard_sectors = max_discard_sectors;
+			q->limits.discard_granularity = discard_granularity;
+		} else {
+			/* Set defaults */
+			ploop_set_discard_limits(io->plo);
+		}
 		return;
 	}
 
diff --git a/drivers/block/ploop/sysfs.c b/drivers/block/ploop/sysfs.c
index 3fadf404311b..9a1c01dba2b1 100644
--- a/drivers/block/ploop/sysfs.c
+++ b/drivers/block/ploop/sysfs.c
@@ -373,6 +373,83 @@ static u32 show_discard_granularity(struct ploop_device * plo)
 	return plo->queue->limits.discard_granularity;
 }
 
+static int store_discard_granularity(struct ploop_device *plo, u32 val)
+{
+	struct ploop_delta *delta;
+	struct request_queue *q;
+	struct inode *inode;
+	int ret = 0;
+
+	mutex_lock(&plo->ctl_mutex);
+	q = plo->queue;
+	if (val == q->limits.discard_granularity)
+		goto unlock;
+
+	delta = ploop_top_delta(plo);
+	if (!delta) {
+		ret = -ENODEV;
+		goto unlock;
+	}
+
+	inode = delta->io.files.inode;
+	if (inode->i_sb->s_magic != EXT4_SUPER_MAGIC) {
+		ret = -EINVAL;
+		goto unlock;
+	}
+
+	if (val == cluster_size_in_bytes(plo)) {
+		ploop_set_discard_limits(plo);
+		plo->force_split_discard_reqs = false;
+		goto unlock;
+	}
+
+	if (val != inode->i_sb->s_blocksize) {
+		ret = -EINVAL;
+		goto unlock;
+	}
+
+	q->limits.discard_granularity = val;
+	/*
+	 * There is no a way to force block engine to split a request
+	 * to fit a single cluster, when discard granuality is 4K
+	 * (inherited from fs block size in blk_queue_stack_limits()).
+	 * So, ploop_make_request() splits them.
+	 */
+	plo->force_split_discard_reqs = true;
+	/*
+	 * Why not (1 << io->plo->cluster_log)?
+	 * Someone may want to clear indexes in case of a request
+	 * is big enough to fit the whole cluster.
+	 * In case of max_discard_sectors is 1 cluster, a request
+	 * for [cluster_start - 4K, cluster_start + cluster_size)
+	 * at block level will be splitted in two requests:
+	 *
+	 * [cluster_start - 4K, cluster_start + cluster_size - 4K)
+	 * [cluster_start + cluster_size - 4K, cluster_start + cluster_size)
+	 *
+	 * Then, ploop_make_request() splits the first of them in two
+	 * to fit a single cluster, so all three requests will be smaller
+	 * then 1 cluster, and no index will be cleared.
+	 *
+	 * Note, this does not solve a problem, when a request covers
+	 * 3 clusters: [cluster_start - 4K, cluster_start + 2 * cluster_size],
+	 * so the third cluster's index will remain. This will require
+	 * unlimited max_discard_sectors and splitting every request
+	 * in ploop_make_request(). We don't want that in that context.
+	 *
+	 * But even in current view, this makes indexes to be cleared
+	 * more frequently, and index-clearing code will be tested better.
+	 *
+	 * Anyway, in general this may be an excess functionality.
+	 * If it's so, it will be dropped later.
+	 */
+	q->limits.max_discard_sectors = (1 << plo->cluster_log) * 2 - 1;
+
+unlock:
+	mutex_unlock(&plo->ctl_mutex);
+	return ret;
+}
+
 static u32 show_discard_alignment(struct ploop_device * plo)
 {
 	return plo->queue->limits.discard_alignment;
@@ -612,7 +689,7 @@ static struct attribute *tune_attributes[] = {
 	_A2(congestion_low_watermark),
 	_A2(max_active_requests),
 	_A2(push_backup_timeout),
-	_A(discard_granularity),
+	_A2(discard_granularity),
 	_A(discard_alignment),
 	_A2(discard_zeroes_data),
 	_A2(trusted),