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: Liu Bo <bo.li....@oracle.com>
Signed-off-by: Ilya Dryomov <idryo...@gmail.com>
---
fs/btrfs/ioctl.c | 78 ++++++++++++++++++++++++++++++++++++++++++---------
fs/btrfs/volumes.c | 10 ++++--
2 files changed, 71 insertions(+), 17 deletions(-)
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 171786a..ab82636 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3441,8 +3441,8 @@ 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;
@@ -3451,14 +3451,61 @@ 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) {
@@ -3478,13 +3525,10 @@ 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) {
@@ -3505,11 +3549,17 @@ 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;
@@ -3517,12 +3567,12 @@ do_balance:
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;
}
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 86279c3..9c84dbe 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -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);
--
1.7.9.1
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