linux-kernel - [PATCH 08/19] btrfs: make unmirroed BGs readonly only if we have at least one writable BG

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Message-Id: <20190607131025.31996-9-naohiro.aota@wdc.com>
Date:   Fri,  7 Jun 2019 22:10:14 +0900
From:   Naohiro Aota <naohiro.aota@....com>
To:     linux-btrfs@...r.kernel.org, David Sterba <dsterba@...e.com>
Cc:     Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>,
        Qu Wenruo <wqu@...e.com>, Nikolay Borisov <nborisov@...e.com>,
        linux-kernel@...r.kernel.org, Hannes Reinecke <hare@...e.com>,
        linux-fsdevel@...r.kernel.org,
        Damien Le Moal <damien.lemoal@....com>,
        Matias Bjørling <mb@...htnvm.io>,
        Johannes Thumshirn <jthumshirn@...e.de>,
        Bart Van Assche <bvanassche@....org>,
        Naohiro Aota <naohiro.aota@....com>
Subject: [PATCH 08/19] btrfs: make unmirroed BGs readonly only if we have at least one writable BG

If the btrfs volume has mirrored block groups, it unconditionally makes
un-mirrored block groups read only. When we have mirrored block groups, but
don't have writable block groups, this will drop all writable block groups.
So, check if we have at least one writable mirrored block group before
setting un-mirrored block groups read only.

Signed-off-by: Naohiro Aota <naohiro.aota@....com>
---
 fs/btrfs/extent-tree.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index ebd0d6eae038..3d41d840fe5c 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -10791,6 +10791,9 @@ int btrfs_read_block_groups(struct btrfs_fs_info *info)
 	}
 
 	list_for_each_entry_rcu(space_info, &info->space_info, list) {
+		bool has_rw = false;
+		int i;
+
 		if (!(get_alloc_profile(info, space_info->flags) &
 		      (BTRFS_BLOCK_GROUP_RAID10 |
 		       BTRFS_BLOCK_GROUP_RAID1 |
@@ -10798,6 +10801,25 @@ int btrfs_read_block_groups(struct btrfs_fs_info *info)
 		       BTRFS_BLOCK_GROUP_RAID6 |
 		       BTRFS_BLOCK_GROUP_DUP)))
 			continue;
+
+		/* check if we have at least one writable mirroed block group */
+		for (i = 0; i < BTRFS_NR_RAID_TYPES; i++) {
+			if (i == BTRFS_RAID_RAID0 || i == BTRFS_RAID_SINGLE)
+				continue;
+			list_for_each_entry(cache, &space_info->block_groups[i],
+					    list) {
+				if (!cache->ro) {
+					has_rw = true;
+					break;
+				}
+			}
+			if (has_rw)
+				break;
+		}
+
+		if (!has_rw)
+			continue;
+
 		/*
 		 * avoid allocating from un-mirrored block group if there are
 		 * mirrored block groups.
-- 
2.21.0