[06/10] Btrfs: Fix the problem that the dirty flag of dev stats is cleared
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Message ID 1406173035-29478-6-git-send-email-miaox@cn.fujitsu.com
State Superseded
Headers show

Commit Message

Miao Xie July 24, 2014, 3:37 a.m. UTC
The io error might happen during writing out the device stats, and the
device stats information and dirty flag would be update at that time,
but the current code didn't consider this case, just clear the dirty
flag, it would cause that we forgot to write out the new device stats
information. Fix it.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
---
 fs/btrfs/volumes.c |  7 +++++--
 fs/btrfs/volumes.h | 19 +++++++++++++++----
 2 files changed, 20 insertions(+), 6 deletions(-)

Comments

David Sterba July 24, 2014, 1:45 p.m. UTC | #1
On Thu, Jul 24, 2014 at 11:37:11AM +0800, Miao Xie wrote:
> The io error might happen during writing out the device stats, and the
> device stats information and dirty flag would be update at that time,
> but the current code didn't consider this case, just clear the dirty
> flag, it would cause that we forgot to write out the new device stats
> information. Fix it.
> 
> Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
> ---
>  fs/btrfs/volumes.c |  7 +++++--
>  fs/btrfs/volumes.h | 19 +++++++++++++++----
>  2 files changed, 20 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index 19188df..0d37746 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -159,6 +159,7 @@ static struct btrfs_device *__alloc_device(void)
>  
>  	spin_lock_init(&dev->reada_lock);
>  	atomic_set(&dev->reada_in_flight, 0);
> +	atomic_set(&dev->dev_stats_ccnt, 0);
>  	INIT_RADIX_TREE(&dev->reada_zones, GFP_NOFS & ~__GFP_WAIT);
>  	INIT_RADIX_TREE(&dev->reada_extents, GFP_NOFS & ~__GFP_WAIT);
>  
> @@ -6398,16 +6399,18 @@ int btrfs_run_dev_stats(struct btrfs_trans_handle *trans,
>  	struct btrfs_root *dev_root = fs_info->dev_root;
>  	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
>  	struct btrfs_device *device;
> +	int stats_cnt;
>  	int ret = 0;
>  
>  	mutex_lock(&fs_devices->device_list_mutex);
>  	list_for_each_entry(device, &fs_devices->devices, dev_list) {
> -		if (!device->dev_stats_valid || !device->dev_stats_dirty)
> +		if (!device->dev_stats_valid || !btrfs_dev_stats_dirty(device))

The helper btrfs_dev_stats_dirty is used only once and IMHO not
necessary.
>  			continue;
>  
> +		stats_cnt = atomic_read(&device->dev_stats_ccnt);

Here it is opencoded anyway.

>  		ret = update_dev_stat_item(trans, dev_root, device);
>  		if (!ret)
> -			device->dev_stats_dirty = 0;
> +			atomic_sub(stats_cnt, &device->dev_stats_ccnt);
>  	}
>  	mutex_unlock(&fs_devices->device_list_mutex);
>  
> diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
> index 6fcc8ea..0defd23 100644
> --- a/fs/btrfs/volumes.h
> +++ b/fs/btrfs/volumes.h
> @@ -110,7 +110,9 @@ struct btrfs_device {
>  	/* disk I/O failure stats. For detailed description refer to
>  	 * enum btrfs_dev_stat_values in ioctl.h */
>  	int dev_stats_valid;
> -	int dev_stats_dirty; /* counters need to be written to disk */
> +
> +	/* Counter to record the change of device stats */
> +	atomic_t dev_stats_ccnt;

dev_stats_dirty is more descriptive, please keep it. The counter
semantics can be documented here.

>  	atomic_t dev_stat_values[BTRFS_DEV_STAT_VALUES_MAX];
>  };
>  
> @@ -359,11 +361,18 @@ unsigned long btrfs_full_stripe_len(struct btrfs_root *root,
>  int btrfs_finish_chunk_alloc(struct btrfs_trans_handle *trans,
>  				struct btrfs_root *extent_root,
>  				u64 chunk_offset, u64 chunk_size);
> +
> +static inline int btrfs_dev_stats_dirty(struct btrfs_device *dev)
> +{
> +	return atomic_read(&dev->dev_stats_ccnt);

IMHO too trivial, not necessary.

> +}
> +
>  static inline void btrfs_dev_stat_inc(struct btrfs_device *dev,
>  				      int index)
>  {
>  	atomic_inc(dev->dev_stat_values + index);
> -	dev->dev_stats_dirty = 1;

> +	smp_mb__before_atomic();
> +	atomic_inc(&dev->dev_stats_ccnt);

Please put the two lines into a wrapper, 3 times repeating the same is
worth it.

> @@ -378,7 +387,8 @@ static inline int btrfs_dev_stat_read_and_reset(struct btrfs_device *dev,
>  	int ret;
>  
>  	ret = atomic_xchg(dev->dev_stat_values + index, 0);
> -	dev->dev_stats_dirty = 1;
> +	smp_mb__before_atomic();
> +	atomic_inc(&dev->dev_stats_ccnt);

> @@ -386,7 +396,8 @@ static inline void btrfs_dev_stat_set(struct btrfs_device *dev,
>  				      int index, unsigned long val)
>  {
>  	atomic_set(dev->dev_stat_values + index, val);
> -	dev->dev_stats_dirty = 1;
> +	smp_mb__before_atomic();
> +	atomic_inc(&dev->dev_stats_ccnt);
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Patch
diff mbox

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 19188df..0d37746 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -159,6 +159,7 @@  static struct btrfs_device *__alloc_device(void)
 
 	spin_lock_init(&dev->reada_lock);
 	atomic_set(&dev->reada_in_flight, 0);
+	atomic_set(&dev->dev_stats_ccnt, 0);
 	INIT_RADIX_TREE(&dev->reada_zones, GFP_NOFS & ~__GFP_WAIT);
 	INIT_RADIX_TREE(&dev->reada_extents, GFP_NOFS & ~__GFP_WAIT);
 
@@ -6398,16 +6399,18 @@  int btrfs_run_dev_stats(struct btrfs_trans_handle *trans,
 	struct btrfs_root *dev_root = fs_info->dev_root;
 	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
 	struct btrfs_device *device;
+	int stats_cnt;
 	int ret = 0;
 
 	mutex_lock(&fs_devices->device_list_mutex);
 	list_for_each_entry(device, &fs_devices->devices, dev_list) {
-		if (!device->dev_stats_valid || !device->dev_stats_dirty)
+		if (!device->dev_stats_valid || !btrfs_dev_stats_dirty(device))
 			continue;
 
+		stats_cnt = atomic_read(&device->dev_stats_ccnt);
 		ret = update_dev_stat_item(trans, dev_root, device);
 		if (!ret)
-			device->dev_stats_dirty = 0;
+			atomic_sub(stats_cnt, &device->dev_stats_ccnt);
 	}
 	mutex_unlock(&fs_devices->device_list_mutex);
 
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 6fcc8ea..0defd23 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -110,7 +110,9 @@  struct btrfs_device {
 	/* disk I/O failure stats. For detailed description refer to
 	 * enum btrfs_dev_stat_values in ioctl.h */
 	int dev_stats_valid;
-	int dev_stats_dirty; /* counters need to be written to disk */
+
+	/* Counter to record the change of device stats */
+	atomic_t dev_stats_ccnt;
 	atomic_t dev_stat_values[BTRFS_DEV_STAT_VALUES_MAX];
 };
 
@@ -359,11 +361,18 @@  unsigned long btrfs_full_stripe_len(struct btrfs_root *root,
 int btrfs_finish_chunk_alloc(struct btrfs_trans_handle *trans,
 				struct btrfs_root *extent_root,
 				u64 chunk_offset, u64 chunk_size);
+
+static inline int btrfs_dev_stats_dirty(struct btrfs_device *dev)
+{
+	return atomic_read(&dev->dev_stats_ccnt);
+}
+
 static inline void btrfs_dev_stat_inc(struct btrfs_device *dev,
 				      int index)
 {
 	atomic_inc(dev->dev_stat_values + index);
-	dev->dev_stats_dirty = 1;
+	smp_mb__before_atomic();
+	atomic_inc(&dev->dev_stats_ccnt);
 }
 
 static inline int btrfs_dev_stat_read(struct btrfs_device *dev,
@@ -378,7 +387,8 @@  static inline int btrfs_dev_stat_read_and_reset(struct btrfs_device *dev,
 	int ret;
 
 	ret = atomic_xchg(dev->dev_stat_values + index, 0);
-	dev->dev_stats_dirty = 1;
+	smp_mb__before_atomic();
+	atomic_inc(&dev->dev_stats_ccnt);
 	return ret;
 }
 
@@ -386,7 +396,8 @@  static inline void btrfs_dev_stat_set(struct btrfs_device *dev,
 				      int index, unsigned long val)
 {
 	atomic_set(dev->dev_stat_values + index, val);
-	dev->dev_stats_dirty = 1;
+	smp_mb__before_atomic();
+	atomic_inc(&dev->dev_stats_ccnt);
 }
 
 static inline void btrfs_dev_stat_reset(struct btrfs_device *dev,