When the replace is running the fs_devices::num_devices also includes
the replace device, however in some operations like device delete and
balance it needs the actual num_devices without the repalce devices, so
now the function btrfs_num_devices() just provides that.
And here is a scenario how balance and repalce items could co-exist.
Consider balance is started and paused, now start the replace
followed by a power-recycle of the system. During following mount,
the open_ctree() first restarts the balance so it must check for the
replace device otherwise our num_devices calculation will be wrong.
Signed-off-by: Anand Jain <anand.j...@oracle.com>
---
v3->v4: add comment and drop the inline (sorry missed it before)
v2->v3: update changelog with not so obvious balance and repalce
co-existance secnario
v1->v2: add comments
fs/btrfs/volumes.c | 38 ++++++++++++++++++++++++--------------
1 file changed, 24 insertions(+), 14 deletions(-)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 6dad9257d4ba..7359596ac8eb 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1854,6 +1854,27 @@ void btrfs_assign_next_active_device(struct btrfs_device
*device,
fs_info->fs_devices->latest_bdev = next_device->bdev;
}
+/* Returns btrfs_fs_devices::num_devices minus replace device if any */
+static u64 btrfs_num_devices(struct btrfs_fs_info *fs_info)
+{
+ u64 num_devices = fs_info->fs_devices->num_devices;
+
+ /*
+ * balance and replace co-exists in a scenario as below..
+ * start balance and pause, start replace and reboot.
+ * now open_ctree() restarts the balance first and checks for the
+ * num_devices which should exclude the replace target.
+ */
+ btrfs_dev_replace_read_lock(&fs_info->dev_replace);
+ if (btrfs_dev_replace_is_ongoing(&fs_info->dev_replace)) {
+ BUG_ON(num_devices < 1);
+ num_devices--;
+ }
+ btrfs_dev_replace_read_unlock(&fs_info->dev_replace);
+
+ return num_devices;
+}
+
int btrfs_rm_device(struct btrfs_fs_info *fs_info, const char *device_path,
u64 devid)
{
@@ -1865,13 +1886,7 @@ int btrfs_rm_device(struct btrfs_fs_info *fs_info, const
char *device_path,
mutex_lock(&uuid_mutex);
- num_devices = fs_devices->num_devices;
- btrfs_dev_replace_read_lock(&fs_info->dev_replace);
- if (btrfs_dev_replace_is_ongoing(&fs_info->dev_replace)) {
- BUG_ON(num_devices < 1);
- num_devices--;
- }
- btrfs_dev_replace_read_unlock(&fs_info->dev_replace);
+ num_devices = btrfs_num_devices(fs_info);
ret = btrfs_check_raid_min_devices(fs_info, num_devices - 1);
if (ret)
@@ -3740,13 +3755,8 @@ int btrfs_balance(struct btrfs_fs_info *fs_info,
}
}
- num_devices = fs_info->fs_devices->num_devices;
- btrfs_dev_replace_read_lock(&fs_info->dev_replace);
- if (btrfs_dev_replace_is_ongoing(&fs_info->dev_replace)) {
- BUG_ON(num_devices < 1);
- num_devices--;
- }
- btrfs_dev_replace_read_unlock(&fs_info->dev_replace);
+ num_devices = btrfs_num_devices(fs_info);
+
allowed = BTRFS_AVAIL_ALLOC_BIT_SINGLE | BTRFS_BLOCK_GROUP_DUP;
if (num_devices > 1)
allowed |= (BTRFS_BLOCK_GROUP_RAID0 | BTRFS_BLOCK_GROUP_RAID1);
--
2.7.0
--
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