On 08/02/2018 08:21 PM, David Sterba wrote:
On Thu, Aug 02, 2018 at 01:11:40PM +0300, Nikolay Borisov wrote:
On 2.08.2018 13:09, Anand Jain wrote:
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.jain@xxxxxxxxxx>
---
v2->v3: update changelog with not so obvious balance and repalce
co-existance secnario
v1->v2: add comments
fs/btrfs/volumes.c | 32 ++++++++++++++++++--------------
1 file changed, 18 insertions(+), 14 deletions(-)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index fe74fefc75f7..8844904f9009 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1854,6 +1854,21 @@ 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 excluding replace device if any */
+static inline u64 btrfs_num_devices(struct btrfs_fs_info *fs_info)
This does not need to be static inline, it's not in a header.
ok will fix.
+{
+ 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)) {
+ 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 +1880,7 @@ 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);
How about lifting the BUG_ON from btrfs_num_devices into a check in this
function, so if num_devices < 1 then we just exit with -EINVAL or some
such. We should be aiming at eliminating BUG_ONs.
Right, in both cases it's possible to return with an error instead of
the BUG_ON.
Actually we should just remove it as its a logical bug if num_devices <
1, so long we didn't hit this bug which means its stable OR keep BUG_ON
it until we add RAID-N. ?
Thanks, Anand
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