The problem is:
Task0(device scan task) Task1(device replace task)
scan_one_device()
mutex_lock(&uuid_mutex)
device = find_device()
mutex_lock(&device_list_mutex)
lock_chunk()
rm_and_free_source_device
unlock_chunk()
mutex_unlock(&device_list_mutex)
check device
Destroying the target device if device replace fails also has the same problem.
We fix this problem by locking uuid_mutex during destroying source device or
target device, just like the device remove operation.
It is a temporary solution, we can fix this problem and make the code more
clear by atomic counter in the future.
Signed-off-by: Miao Xie <mi...@cn.fujitsu.com>
---
fs/btrfs/dev-replace.c | 3 +++
fs/btrfs/volumes.c | 4 +++-
fs/btrfs/volumes.h | 2 ++
3 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
index aa4c828..e9cbbdb 100644
--- a/fs/btrfs/dev-replace.c
+++ b/fs/btrfs/dev-replace.c
@@ -509,6 +509,7 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info
*fs_info,
ret = btrfs_commit_transaction(trans, root);
WARN_ON(ret);
+ mutex_lock(&uuid_mutex);
/* keep away write_all_supers() during the finishing procedure */
mutex_lock(&root->fs_info->fs_devices->device_list_mutex);
mutex_lock(&root->fs_info->chunk_mutex);
@@ -536,6 +537,7 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info
*fs_info,
btrfs_dev_replace_unlock(dev_replace);
mutex_unlock(&root->fs_info->chunk_mutex);
mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
+ mutex_unlock(&uuid_mutex);
if (tgt_device)
btrfs_destroy_dev_replace_tgtdev(fs_info, tgt_device);
mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
@@ -591,6 +593,7 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info
*fs_info,
*/
mutex_unlock(&root->fs_info->chunk_mutex);
mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
+ mutex_unlock(&uuid_mutex);
/* write back the superblocks */
trans = btrfs_start_transaction(root, 0);
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index f0173b1..24d7001 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -50,7 +50,7 @@ static void __btrfs_reset_dev_stats(struct btrfs_device *dev);
static void btrfs_dev_stat_print_on_error(struct btrfs_device *dev);
static void btrfs_dev_stat_print_on_load(struct btrfs_device *device);
-static DEFINE_MUTEX(uuid_mutex);
+DEFINE_MUTEX(uuid_mutex);
static LIST_HEAD(fs_uuids);
static void lock_chunks(struct btrfs_root *root)
@@ -1867,6 +1867,7 @@ void btrfs_destroy_dev_replace_tgtdev(struct
btrfs_fs_info *fs_info,
{
struct btrfs_device *next_device;
+ mutex_lock(&uuid_mutex);
WARN_ON(!tgtdev);
mutex_lock(&fs_info->fs_devices->device_list_mutex);
if (tgtdev->bdev) {
@@ -1886,6 +1887,7 @@ void btrfs_destroy_dev_replace_tgtdev(struct
btrfs_fs_info *fs_info,
call_rcu(&tgtdev->rcu, free_device);
mutex_unlock(&fs_info->fs_devices->device_list_mutex);
+ mutex_unlock(&uuid_mutex);
}
static int btrfs_find_device_by_path(struct btrfs_root *root, char
*device_path,
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 76600a3..2b37da3 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -24,6 +24,8 @@
#include <linux/btrfs.h>
#include "async-thread.h"
+extern struct mutex uuid_mutex;
+
#define BTRFS_STRIPE_LEN (64 * 1024)
struct buffer_head;
--
1.9.3
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