Commit ed0fb78f authored by Ilya Dryomov's avatar Ilya Dryomov

Btrfs: bring back balance pause/resume logic

Balance pause/resume logic got broken by 5ac00add (went in into 3.8-rc1
as part of dev-replace merge).  Offending commit took a stab at making
mutually exclusive volume operations (add_dev, rm_dev, resize, balance,
replace_dev) not block behind volume_mutex if another such operation is
in progress and instead return an error right away.  Balancing front-end
relied on the blocking behaviour, so the fix is ugly, but short of a
complete rework, it's the best we can do.
Reported-by: default avatarLiu Bo <bo.li.liu@oracle.com>
Signed-off-by: default avatarIlya Dryomov <idryomov@gmail.com>
parent 3972f260
......@@ -3440,8 +3440,8 @@ static long btrfs_ioctl_balance(struct file *file, void __user *arg)
struct btrfs_fs_info *fs_info = root->fs_info;
struct btrfs_ioctl_balance_args *bargs;
struct btrfs_balance_control *bctl;
bool need_unlock; /* for mut. excl. ops lock */
int ret;
int need_to_clear_lock = 0;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
......@@ -3450,14 +3450,61 @@ static long btrfs_ioctl_balance(struct file *file, void __user *arg)
if (ret)
return ret;
mutex_lock(&fs_info->volume_mutex);
again:
if (!atomic_xchg(&fs_info->mutually_exclusive_operation_running, 1)) {
mutex_lock(&fs_info->volume_mutex);
mutex_lock(&fs_info->balance_mutex);
need_unlock = true;
goto locked;
}
/*
* mut. excl. ops lock is locked. Three possibilites:
* (1) some other op is running
* (2) balance is running
* (3) balance is paused -- special case (think resume)
*/
mutex_lock(&fs_info->balance_mutex);
if (fs_info->balance_ctl) {
/* this is either (2) or (3) */
if (!atomic_read(&fs_info->balance_running)) {
mutex_unlock(&fs_info->balance_mutex);
if (!mutex_trylock(&fs_info->volume_mutex))
goto again;
mutex_lock(&fs_info->balance_mutex);
if (fs_info->balance_ctl &&
!atomic_read(&fs_info->balance_running)) {
/* this is (3) */
need_unlock = false;
goto locked;
}
mutex_unlock(&fs_info->balance_mutex);
mutex_unlock(&fs_info->volume_mutex);
goto again;
} else {
/* this is (2) */
mutex_unlock(&fs_info->balance_mutex);
ret = -EINPROGRESS;
goto out;
}
} else {
/* this is (1) */
mutex_unlock(&fs_info->balance_mutex);
pr_info("btrfs: dev add/delete/balance/replace/resize operation in progress\n");
ret = -EINVAL;
goto out;
}
locked:
BUG_ON(!atomic_read(&fs_info->mutually_exclusive_operation_running));
if (arg) {
bargs = memdup_user(arg, sizeof(*bargs));
if (IS_ERR(bargs)) {
ret = PTR_ERR(bargs);
goto out;
goto out_unlock;
}
if (bargs->flags & BTRFS_BALANCE_RESUME) {
......@@ -3477,13 +3524,10 @@ static long btrfs_ioctl_balance(struct file *file, void __user *arg)
bargs = NULL;
}
if (atomic_xchg(&root->fs_info->mutually_exclusive_operation_running,
1)) {
pr_info("btrfs: dev add/delete/balance/replace/resize operation in progress\n");
if (fs_info->balance_ctl) {
ret = -EINPROGRESS;
goto out_bargs;
}
need_to_clear_lock = 1;
bctl = kzalloc(sizeof(*bctl), GFP_NOFS);
if (!bctl) {
......@@ -3504,11 +3548,17 @@ static long btrfs_ioctl_balance(struct file *file, void __user *arg)
}
do_balance:
ret = btrfs_balance(bctl, bargs);
/*
* bctl is freed in __cancel_balance or in free_fs_info if
* restriper was paused all the way until unmount
* Ownership of bctl and mutually_exclusive_operation_running
* goes to to btrfs_balance. bctl is freed in __cancel_balance,
* or, if restriper was paused all the way until unmount, in
* free_fs_info. mutually_exclusive_operation_running is
* cleared in __cancel_balance.
*/
need_unlock = false;
ret = btrfs_balance(bctl, bargs);
if (arg) {
if (copy_to_user(arg, bargs, sizeof(*bargs)))
ret = -EFAULT;
......@@ -3516,12 +3566,12 @@ static long btrfs_ioctl_balance(struct file *file, void __user *arg)
out_bargs:
kfree(bargs);
out:
if (need_to_clear_lock)
atomic_set(&root->fs_info->mutually_exclusive_operation_running,
0);
out_unlock:
mutex_unlock(&fs_info->balance_mutex);
mutex_unlock(&fs_info->volume_mutex);
if (need_unlock)
atomic_set(&fs_info->mutually_exclusive_operation_running, 0);
out:
mnt_drop_write_file(file);
return ret;
}
......
......@@ -2959,6 +2959,8 @@ static void __cancel_balance(struct btrfs_fs_info *fs_info)
unset_balance_control(fs_info);
ret = del_balance_item(fs_info->tree_root);
BUG_ON(ret);
atomic_set(&fs_info->mutually_exclusive_operation_running, 0);
}
void update_ioctl_balance_args(struct btrfs_fs_info *fs_info, int lock,
......@@ -3138,8 +3140,10 @@ int btrfs_balance(struct btrfs_balance_control *bctl,
out:
if (bctl->flags & BTRFS_BALANCE_RESUME)
__cancel_balance(fs_info);
else
else {
kfree(bctl);
atomic_set(&fs_info->mutually_exclusive_operation_running, 0);
}
return ret;
}
......@@ -3156,7 +3160,6 @@ static int balance_kthread(void *data)
ret = btrfs_balance(fs_info->balance_ctl, NULL);
}
atomic_set(&fs_info->mutually_exclusive_operation_running, 0);
mutex_unlock(&fs_info->balance_mutex);
mutex_unlock(&fs_info->volume_mutex);
......@@ -3179,7 +3182,6 @@ int btrfs_resume_balance_async(struct btrfs_fs_info *fs_info)
return 0;
}
WARN_ON(atomic_xchg(&fs_info->mutually_exclusive_operation_running, 1));
tsk = kthread_run(balance_kthread, fs_info, "btrfs-balance");
if (IS_ERR(tsk))
return PTR_ERR(tsk);
......@@ -3233,6 +3235,8 @@ int btrfs_recover_balance(struct btrfs_fs_info *fs_info)
btrfs_balance_sys(leaf, item, &disk_bargs);
btrfs_disk_balance_args_to_cpu(&bctl->sys, &disk_bargs);
WARN_ON(atomic_xchg(&fs_info->mutually_exclusive_operation_running, 1));
mutex_lock(&fs_info->volume_mutex);
mutex_lock(&fs_info->balance_mutex);
......
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