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btrfs: add helper to obtain number of devices with ongoing dev-replace

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When the replace is running the fs_devices::num_devices also includes
the replaced device, however in some operations like device delete and
balance it needs the actual num_devices without the repalced devices.
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 unmount or system power-cycle. During following mount, the
open_ctree() first restarts the balance so it must check for the device
replace otherwise our num_devices calculation will be wrong.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ update changelog ]
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Anand Jain 2018-08-10 13:53:21 +08:00 committed by David Sterba
parent 16220c467a
commit 1da739678e
1 changed files with 21 additions and 14 deletions
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35
fs/btrfs/volumes.c
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@ -1854,6 +1854,24 @@ void btrfs_assign_next_active_device(struct btrfs_device *device,
fs_info->fs_devices->latest_bdev = next_device->bdev;
}
/*
* Return btrfs_fs_devices::num_devices excluding the device that's being
* currently replaced.
*/
static u64 btrfs_num_devices(struct btrfs_fs_info *fs_info)
{
u64 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)) {
ASSERT(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 +1883,7 @@ 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)) {
ASSERT(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 +3752,8 @@ 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)) {
ASSERT(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);