When a device is deleted the btrfs_super_block::number_devices is
reduced by 1, but since we are do that after the last commit transaction
for the device delete transaction, the update to
btrfs_super_block::number_devices waits for the next commit/fsync
transaction to make it to the disk.
This can be easily demonstrated using the following test case where I
use the btrfs device ready cli to read the and report, as it reads the
device directly (which is unnecessary for the mounted device) and checks
for the fs_devices::total_devices.
mkfs.btrfs -fq -dsingle -msingle $dev1 $dev2
mount $dev1 /btrfs
btrfs dev del $dev2 /btrfs
btrfs dev ready $dev1; echo RESULT=$? <-- 1
Without this patch RESULT returns 1, indicating not ready!
Same thing using seed device:
mkfs.btrfs -fq $dev1
btrfstune -S1 $dev1
mount $dev1 /btrfs
btrfs dev add -f $dev2 /btrfs
umount /btrfs
mount $dev2 /btrfs
btrfs dev del $dev1 /btrfs
btrfs dev ready $dev2; echo RESULT=$?
Signed-off-by: Anand Jain <anand.j...@oracle.com>
---
The seed device test case needs to fix the bug as in the patch,
[PATCH 1/2] btrfs: fix parent in memory total_devices after seed delete
As there is a bug in the btrfs_device_rm() code,
fs/btrfs/volumes.c | 38 ++++++++++++++++++--------------------
1 file changed, 18 insertions(+), 20 deletions(-)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 5296f26be2f6..4138f17d4e58 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1843,46 +1843,32 @@ static void update_dev_time(const char *path_name)
}
static int btrfs_rm_dev_item(struct btrfs_fs_info *fs_info,
- struct btrfs_device *device)
+ struct btrfs_device *device,
+ struct btrfs_trans_handle *trans)
{
struct btrfs_root *root = fs_info->chunk_root;
int ret;
struct btrfs_path *path;
struct btrfs_key key;
- struct btrfs_trans_handle *trans;
path = btrfs_alloc_path();
if (!path)
return -ENOMEM;
- trans = btrfs_start_transaction(root, 0);
- if (IS_ERR(trans)) {
- btrfs_free_path(path);
- return PTR_ERR(trans);
- }
key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
key.type = BTRFS_DEV_ITEM_KEY;
key.offset = device->devid;
ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
- if (ret) {
- if (ret > 0)
- ret = -ENOENT;
- btrfs_abort_transaction(trans, ret);
- btrfs_end_transaction(trans);
+ if (ret > 0) {
+ ret = -ENOENT;
goto out;
}
ret = btrfs_del_item(trans, root, path);
- if (ret) {
- btrfs_abort_transaction(trans, ret);
- btrfs_end_transaction(trans);
- }
out:
btrfs_free_path(path);
- if (!ret)
- ret = btrfs_commit_transaction(trans);
return ret;
}
@@ -1966,7 +1952,9 @@ int btrfs_rm_device(struct btrfs_fs_info *fs_info, const
char *device_path,
u64 devid)
{
struct btrfs_device *device;
+ struct btrfs_trans_handle *trans;
struct btrfs_fs_devices *cur_devices;
+ struct btrfs_root *root = fs_info->dev_root;
struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
u64 num_devices;
int ret = 0;
@@ -2014,14 +2002,23 @@ int btrfs_rm_device(struct btrfs_fs_info *fs_info,
const char *device_path,
if (ret)
goto error_undo;
+ trans = btrfs_start_transaction(root, 0);
+ if (IS_ERR(trans)) {
+ ret = PTR_ERR(trans);
+ goto error_undo;
+ }
+
/*
* TODO: the superblock still includes this device in its num_devices
* counter although write_all_supers() is not locked out. This
* could give a filesystem state which requires a degraded mount.
*/
- ret = btrfs_rm_dev_item(fs_info, device);
- if (ret)
+ ret = btrfs_rm_dev_item(fs_info, device, trans);
+ if (ret) {
+ btrfs_abort_transaction(trans, ret);
+ btrfs_end_transaction(trans);
goto error_undo;
+ }
clear_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
btrfs_scrub_cancel_dev(fs_info, device);
@@ -2090,6 +2087,7 @@ int btrfs_rm_device(struct btrfs_fs_info *fs_info, const
char *device_path,
free_fs_devices(cur_devices);
}
+ ret = btrfs_commit_transaction(trans);
out:
mutex_unlock(&uuid_mutex);
return ret;
--
2.7.0
--
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