On 04/20/2018 12:33 AM, David Sterba wrote:
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.
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
---
fs/btrfs/ctree.h | 6 +++++-
fs/btrfs/disk-io.c | 1 -
fs/btrfs/ioctl.c | 6 +++---
fs/btrfs/volumes.c | 18 ++++++++++--------
4 files changed, 18 insertions(+), 13 deletions(-)
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 011cb9a8a967..fda94a264eb7 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -726,6 +726,11 @@ struct btrfs_delayed_root;
* (device replace, resize, device add/delete, balance)
*/
#define BTRFS_FS_EXCL_OP 16
+/*
+ * 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 17
Change looks good to me as such and its a good idea to drop
fs_info::balance_running;
However instead of making BTRFS_FS_BALANCE_RUNNING part of
btrfs_fs_info::flags
pls make it part of
btrfs_balance_control::flags
Because:
We already have BTRFS_BALANCE_RESUME there.
And at fs_info level BTRFS_FS_EXCL_OP tells someone excl is running.
And if its a balance (either in running or implicit-paused state)
then btrfs_fs_info::balance_ctl is not NULL.
Thanks, Anand
struct btrfs_fs_info {
u8 fsid[BTRFS_FSID_SIZE];
@@ -991,7 +996,6 @@ 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;
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index c0482ecea11f..b62559dfb053 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2168,7 +2168,6 @@ 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;
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 7c99f74c200e..3dfd5ab2807b 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -4506,7 +4506,7 @@ 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;
@@ -4558,7 +4558,7 @@ static long btrfs_ioctl_balance(struct file *file, void __user *arg)
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,
@@ -4567,7 +4567,7 @@ static long btrfs_ioctl_balance(struct file *file, void __user *arg)
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;
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index e95cc2f09fdd..a766d2f988c1 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -3886,13 +3886,14 @@ 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));
@@ -4031,16 +4032,16 @@ 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;
@@ -4066,10 +4067,10 @@ 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);
@@ -4085,7 +4086,8 @@ 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;
--
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