[PATCH 6/8] btrfs: extract out zone cache usage into it's own helper

[Josef Bacik <josef@toxicpanda.com>]

There's a special case for loading the device zone info if we have the
zone cache which is a fair bit of code.  Extract this out into it's own
helper to clean up the code a little bit, and as a side effect it fixes
an uninitialized error we get with -Wmaybe-uninitialized where it
thought zno may have been uninitialized.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/zoned.c | 73 +++++++++++++++++++++++++++++-------------------
 1 file changed, 45 insertions(+), 28 deletions(-)

diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
index a759668477bb..f3640ab95e5e 100644
--- a/fs/btrfs/zoned.c
+++ b/fs/btrfs/zoned.c
@@ -216,11 +216,46 @@ static int emulate_report_zones(struct btrfs_device *device, u64 pos,
 	return i;
 }
 
+static int load_zones_from_cache(struct btrfs_zoned_device_info *zinfo, u64 pos,
+				 struct blk_zone *zones, unsigned int *nr_zones)
+{
+	unsigned int i;
+	u32 zno;
+
+	if (!zinfo->zone_cache)
+		return -ENOENT;
+
+	ASSERT(IS_ALIGNED(pos, zinfo->zone_size));
+	zno = pos >> zinfo->zone_size_shift;
+
+	/*
+	 * We cannot report zones beyond the zone end. So, it is OK to
+	 * cap *nr_zones to at the end.
+	 */
+	*nr_zones = min_t(u32, *nr_zones, zinfo->nr_zones - zno);
+
+	for (i = 0; i < *nr_zones; i++) {
+		struct blk_zone *zone_info;
+
+		zone_info = &zinfo->zone_cache[zno + i];
+		if (!zone_info->len)
+			break;
+	}
+
+	if (i == *nr_zones) {
+		/* Cache hit on all the zones */
+		memcpy(zones, zinfo->zone_cache + zno,
+		       sizeof(*zinfo->zone_cache) * *nr_zones);
+		return 0;
+	}
+
+	return -ENOENT;
+}
+
 static int btrfs_get_dev_zones(struct btrfs_device *device, u64 pos,
 			       struct blk_zone *zones, unsigned int *nr_zones)
 {
 	struct btrfs_zoned_device_info *zinfo = device->zone_info;
-	u32 zno;
 	int ret;
 
 	if (!*nr_zones)
@@ -233,32 +268,8 @@ static int btrfs_get_dev_zones(struct btrfs_device *device, u64 pos,
 	}
 
 	/* Check cache */
-	if (zinfo->zone_cache) {
-		unsigned int i;
-
-		ASSERT(IS_ALIGNED(pos, zinfo->zone_size));
-		zno = pos >> zinfo->zone_size_shift;
-		/*
-		 * We cannot report zones beyond the zone end. So, it is OK to
-		 * cap *nr_zones to at the end.
-		 */
-		*nr_zones = min_t(u32, *nr_zones, zinfo->nr_zones - zno);
-
-		for (i = 0; i < *nr_zones; i++) {
-			struct blk_zone *zone_info;
-
-			zone_info = &zinfo->zone_cache[zno + i];
-			if (!zone_info->len)
-				break;
-		}
-
-		if (i == *nr_zones) {
-			/* Cache hit on all the zones */
-			memcpy(zones, zinfo->zone_cache + zno,
-			       sizeof(*zinfo->zone_cache) * *nr_zones);
-			return 0;
-		}
-	}
+	if (!load_zones_from_cache(zinfo, pos, zones, nr_zones))
+		return 0;
 
 	ret = blkdev_report_zones(device->bdev, pos >> SECTOR_SHIFT, *nr_zones,
 				  copy_zone_info_cb, zones);
@@ -274,9 +285,15 @@ static int btrfs_get_dev_zones(struct btrfs_device *device, u64 pos,
 		return -EIO;
 
 	/* Populate cache */
-	if (zinfo->zone_cache)
+	if (zinfo->zone_cache) {
+		u32 zno;
+
+		ASSERT(IS_ALIGNED(pos, zinfo->zone_size));
+		zno = pos >> zinfo->zone_size_shift;
+
 		memcpy(zinfo->zone_cache + zno, zones,
 		       sizeof(*zinfo->zone_cache) * *nr_zones);
+	}
 
 	return 0;
 }
-- 
2.26.3