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btrfs: track running balance in a simpler way 

Currently fs_info::balance_running is 0 or 1 and does not use the
semantics of atomics. The pause and cancel check for 0, that can happen
only after __btrfs_balance exits for whatever reason.

Parallel calls to balance ioctl may enter btrfs_ioctl_balance multiple
times but will block on the balance_mutex that protects the
fs_info::flags bit.

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
David Sterba 2018-03-21 01:31:04 +01:00
parent dccdb07bc9
commit 3009a62f3b
4 changed files with 19 additions and 13 deletions
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7
fs/btrfs/ctree.h
View File

@ -739,6 +739,12 @@ struct btrfs_delayed_root;
*/
#define BTRFS_FS_NEED_ASYNC_COMMIT 17
/*
* Indicate that balance has been set up from the ioctl and is in the main
* phase. The fs_info::balance_ctl is initialized.
*/
#define BTRFS_FS_BALANCE_RUNNING 18
struct btrfs_fs_info {
u8 fsid[BTRFS_FSID_SIZE];
u8 chunk_tree_uuid[BTRFS_UUID_SIZE];
@ -1003,7 +1009,6 @@ struct btrfs_fs_info {
/* restriper state */
spinlock_t balance_lock;
struct mutex balance_mutex;
atomic_t balance_running;
atomic_t balance_pause_req;
atomic_t balance_cancel_req;
struct btrfs_balance_control *balance_ctl;

1
fs/btrfs/disk-io.c
View File

@ -2164,7 +2164,6 @@ static void btrfs_init_balance(struct btrfs_fs_info *fs_info)
{
spin_lock_init(&fs_info->balance_lock);
mutex_init(&fs_info->balance_mutex);
atomic_set(&fs_info->balance_running, 0);
atomic_set(&fs_info->balance_pause_req, 0);
atomic_set(&fs_info->balance_cancel_req, 0);
fs_info->balance_ctl = NULL;

6
fs/btrfs/ioctl.c
View File

@ -4312,7 +4312,7 @@ void update_ioctl_balance_args(struct btrfs_fs_info *fs_info, int lock,
bargs->flags = bctl->flags;
if (atomic_read(&fs_info->balance_running))
if (test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags))
bargs->state |= BTRFS_BALANCE_STATE_RUNNING;
if (atomic_read(&fs_info->balance_pause_req))
bargs->state |= BTRFS_BALANCE_STATE_PAUSE_REQ;
@ -4364,7 +4364,7 @@ again:
mutex_lock(&fs_info->balance_mutex);
if (fs_info->balance_ctl) {
/* this is either (2) or (3) */
if (!atomic_read(&fs_info->balance_running)) {
if (!test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags)) {
mutex_unlock(&fs_info->balance_mutex);
/*
* Lock released to allow other waiters to continue,
@ -4373,7 +4373,7 @@ again:
mutex_lock(&fs_info->balance_mutex);
if (fs_info->balance_ctl &&
!atomic_read(&fs_info->balance_running)) {
!test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags)) {
/* this is (3) */
need_unlock = false;
goto locked;

18
fs/btrfs/volumes.c
View File

@ -3907,13 +3907,14 @@ int btrfs_balance(struct btrfs_balance_control *bctl,
spin_unlock(&fs_info->balance_lock);
}
atomic_inc(&fs_info->balance_running);
ASSERT(!test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags));
set_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags);
mutex_unlock(&fs_info->balance_mutex);
ret = __btrfs_balance(fs_info);
mutex_lock(&fs_info->balance_mutex);
atomic_dec(&fs_info->balance_running);
clear_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags);
if (bargs) {
memset(bargs, 0, sizeof(*bargs));
@ -4061,16 +4062,16 @@ int btrfs_pause_balance(struct btrfs_fs_info *fs_info)
return -ENOTCONN;
}
if (atomic_read(&fs_info->balance_running)) {
if (test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags)) {
atomic_inc(&fs_info->balance_pause_req);
mutex_unlock(&fs_info->balance_mutex);
wait_event(fs_info->balance_wait_q,
atomic_read(&fs_info->balance_running) == 0);
!test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags));
mutex_lock(&fs_info->balance_mutex);
/* we are good with balance_ctl ripped off from under us */
BUG_ON(atomic_read(&fs_info->balance_running));
BUG_ON(test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags));
atomic_dec(&fs_info->balance_pause_req);
} else {
ret = -ENOTCONN;
@ -4096,10 +4097,10 @@ int btrfs_cancel_balance(struct btrfs_fs_info *fs_info)
* if we are running just wait and return, balance item is
* deleted in btrfs_balance in this case
*/
if (atomic_read(&fs_info->balance_running)) {
if (test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags)) {
mutex_unlock(&fs_info->balance_mutex);
wait_event(fs_info->balance_wait_q,
atomic_read(&fs_info->balance_running) == 0);
!test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags));
mutex_lock(&fs_info->balance_mutex);
} else {
mutex_unlock(&fs_info->balance_mutex);
@ -4115,7 +4116,8 @@ int btrfs_cancel_balance(struct btrfs_fs_info *fs_info)
}
}
BUG_ON(fs_info->balance_ctl || atomic_read(&fs_info->balance_running));
BUG_ON(fs_info->balance_ctl ||
test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags));
atomic_dec(&fs_info->balance_cancel_req);
mutex_unlock(&fs_info->balance_mutex);
return 0;