[v6,05/28] btrfs: disallow space_cache in HMZONED mode
diff mbox series

Message ID 20191213040915.3502922-6-naohiro.aota@wdc.com
State New
Headers show
Series
  • btrfs: zoned block device support
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Commit Message

Naohiro Aota Dec. 13, 2019, 4:08 a.m. UTC
As updates to the space cache v1 are in-place, the space cache cannot be
located over sequential zones and there is no guarantees that the device
will have enough conventional zones to store this cache. Resolve this
problem by disabling completely the space cache v1.  This does not
introduces any problems with sequential block groups: all the free space is
located after the allocation pointer and no free space before the pointer.
There is no need to have such cache.

Note: we can technically use free-space-tree (space cache v2) on HMZONED
mode. But, since HMZONED mode now always allocate extents in a block group
sequentially regardless of underlying device zone type, it's no use to
enable and maintain the tree.

Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
---
 fs/btrfs/hmzoned.c | 18 ++++++++++++++++++
 fs/btrfs/hmzoned.h |  5 +++++
 fs/btrfs/super.c   | 11 +++++++++--
 3 files changed, 32 insertions(+), 2 deletions(-)

Comments

Josef Bacik Dec. 13, 2019, 4:24 p.m. UTC | #1
On 12/12/19 11:08 PM, Naohiro Aota wrote:
> As updates to the space cache v1 are in-place, the space cache cannot be
> located over sequential zones and there is no guarantees that the device
> will have enough conventional zones to store this cache. Resolve this
> problem by disabling completely the space cache v1.  This does not
> introduces any problems with sequential block groups: all the free space is
> located after the allocation pointer and no free space before the pointer.
> There is no need to have such cache.
> 
> Note: we can technically use free-space-tree (space cache v2) on HMZONED
> mode. But, since HMZONED mode now always allocate extents in a block group
> sequentially regardless of underlying device zone type, it's no use to
> enable and maintain the tree.
> 
> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
> ---
>   fs/btrfs/hmzoned.c | 18 ++++++++++++++++++
>   fs/btrfs/hmzoned.h |  5 +++++
>   fs/btrfs/super.c   | 11 +++++++++--
>   3 files changed, 32 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/btrfs/hmzoned.c b/fs/btrfs/hmzoned.c
> index 1b24facd46b8..d62f11652973 100644
> --- a/fs/btrfs/hmzoned.c
> +++ b/fs/btrfs/hmzoned.c
> @@ -250,3 +250,21 @@ int btrfs_check_hmzoned_mode(struct btrfs_fs_info *fs_info)
>   out:
>   	return ret;
>   }
> +
> +int btrfs_check_mountopts_hmzoned(struct btrfs_fs_info *info)
> +{
> +	if (!btrfs_fs_incompat(info, HMZONED))
> +		return 0;
> +
> +	/*
> +	 * SPACE CACHE writing is not CoWed. Disable that to avoid write
> +	 * errors in sequential zones.
> +	 */
> +	if (btrfs_test_opt(info, SPACE_CACHE)) {
> +		btrfs_err(info,
> +			  "space cache v1 not supportted in HMZONED mode");
> +		return -EOPNOTSUPP;
> +	}
> +
> +	return 0;
> +}
> diff --git a/fs/btrfs/hmzoned.h b/fs/btrfs/hmzoned.h
> index 8e17f64ff986..d9ebe11afdf5 100644
> --- a/fs/btrfs/hmzoned.h
> +++ b/fs/btrfs/hmzoned.h
> @@ -29,6 +29,7 @@ int btrfs_get_dev_zone(struct btrfs_device *device, u64 pos,
>   int btrfs_get_dev_zone_info(struct btrfs_device *device);
>   void btrfs_destroy_dev_zone_info(struct btrfs_device *device);
>   int btrfs_check_hmzoned_mode(struct btrfs_fs_info *fs_info);
> +int btrfs_check_mountopts_hmzoned(struct btrfs_fs_info *info);
>   #else /* CONFIG_BLK_DEV_ZONED */
>   static inline int btrfs_get_dev_zone(struct btrfs_device *device, u64 pos,
>   				     struct blk_zone *zone)
> @@ -48,6 +49,10 @@ static inline int btrfs_check_hmzoned_mode(struct btrfs_fs_info *fs_info)
>   	btrfs_err(fs_info, "Zoned block devices support is not enabled");
>   	return -EOPNOTSUPP;
>   }
> +static inline int btrfs_check_mountopts_hmzoned(struct btrfs_fs_info *info)
> +{
> +	return 0;
> +}
>   #endif
>   
>   static inline bool btrfs_dev_is_sequential(struct btrfs_device *device, u64 pos)
> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> index 616f5abec267..1424c3c6e3cf 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -442,8 +442,13 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
>   	cache_gen = btrfs_super_cache_generation(info->super_copy);
>   	if (btrfs_fs_compat_ro(info, FREE_SPACE_TREE))
>   		btrfs_set_opt(info->mount_opt, FREE_SPACE_TREE);
> -	else if (cache_gen)
> -		btrfs_set_opt(info->mount_opt, SPACE_CACHE);
> +	else if (cache_gen) {
> +		if (btrfs_fs_incompat(info, HMZONED))
> +			btrfs_info(info,
> +			"ignoring existing space cache in HMZONED mode");

It would be good to clear the cache gen in this case.  I assume this can happen 
if we add a hmzoned device to an existing fs with space cache already?  I'd hate 
for weird corner cases to pop up if we removed it later and still had a valid 
cache gen in place.  Thanks,

Josef
Naohiro Aota Dec. 18, 2019, 4:28 a.m. UTC | #2
On Fri, Dec 13, 2019 at 11:24:10AM -0500, Josef Bacik wrote:
>On 12/12/19 11:08 PM, Naohiro Aota wrote:
>>As updates to the space cache v1 are in-place, the space cache cannot be
>>located over sequential zones and there is no guarantees that the device
>>will have enough conventional zones to store this cache. Resolve this
>>problem by disabling completely the space cache v1.  This does not
>>introduces any problems with sequential block groups: all the free space is
>>located after the allocation pointer and no free space before the pointer.
>>There is no need to have such cache.
>>
>>Note: we can technically use free-space-tree (space cache v2) on HMZONED
>>mode. But, since HMZONED mode now always allocate extents in a block group
>>sequentially regardless of underlying device zone type, it's no use to
>>enable and maintain the tree.
>>
>>Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
>>---
>>  fs/btrfs/hmzoned.c | 18 ++++++++++++++++++
>>  fs/btrfs/hmzoned.h |  5 +++++
>>  fs/btrfs/super.c   | 11 +++++++++--
>>  3 files changed, 32 insertions(+), 2 deletions(-)
>>
>>diff --git a/fs/btrfs/hmzoned.c b/fs/btrfs/hmzoned.c
>>index 1b24facd46b8..d62f11652973 100644
>>--- a/fs/btrfs/hmzoned.c
>>+++ b/fs/btrfs/hmzoned.c
>>@@ -250,3 +250,21 @@ int btrfs_check_hmzoned_mode(struct btrfs_fs_info *fs_info)
>>  out:
>>  	return ret;
>>  }
>>+
>>+int btrfs_check_mountopts_hmzoned(struct btrfs_fs_info *info)
>>+{
>>+	if (!btrfs_fs_incompat(info, HMZONED))
>>+		return 0;
>>+
>>+	/*
>>+	 * SPACE CACHE writing is not CoWed. Disable that to avoid write
>>+	 * errors in sequential zones.
>>+	 */
>>+	if (btrfs_test_opt(info, SPACE_CACHE)) {
>>+		btrfs_err(info,
>>+			  "space cache v1 not supportted in HMZONED mode");
>>+		return -EOPNOTSUPP;
>>+	}
>>+
>>+	return 0;
>>+}
>>diff --git a/fs/btrfs/hmzoned.h b/fs/btrfs/hmzoned.h
>>index 8e17f64ff986..d9ebe11afdf5 100644
>>--- a/fs/btrfs/hmzoned.h
>>+++ b/fs/btrfs/hmzoned.h
>>@@ -29,6 +29,7 @@ int btrfs_get_dev_zone(struct btrfs_device *device, u64 pos,
>>  int btrfs_get_dev_zone_info(struct btrfs_device *device);
>>  void btrfs_destroy_dev_zone_info(struct btrfs_device *device);
>>  int btrfs_check_hmzoned_mode(struct btrfs_fs_info *fs_info);
>>+int btrfs_check_mountopts_hmzoned(struct btrfs_fs_info *info);
>>  #else /* CONFIG_BLK_DEV_ZONED */
>>  static inline int btrfs_get_dev_zone(struct btrfs_device *device, u64 pos,
>>  				     struct blk_zone *zone)
>>@@ -48,6 +49,10 @@ static inline int btrfs_check_hmzoned_mode(struct btrfs_fs_info *fs_info)
>>  	btrfs_err(fs_info, "Zoned block devices support is not enabled");
>>  	return -EOPNOTSUPP;
>>  }
>>+static inline int btrfs_check_mountopts_hmzoned(struct btrfs_fs_info *info)
>>+{
>>+	return 0;
>>+}
>>  #endif
>>  static inline bool btrfs_dev_is_sequential(struct btrfs_device *device, u64 pos)
>>diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
>>index 616f5abec267..1424c3c6e3cf 100644
>>--- a/fs/btrfs/super.c
>>+++ b/fs/btrfs/super.c
>>@@ -442,8 +442,13 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
>>  	cache_gen = btrfs_super_cache_generation(info->super_copy);
>>  	if (btrfs_fs_compat_ro(info, FREE_SPACE_TREE))
>>  		btrfs_set_opt(info->mount_opt, FREE_SPACE_TREE);
>>-	else if (cache_gen)
>>-		btrfs_set_opt(info->mount_opt, SPACE_CACHE);
>>+	else if (cache_gen) {
>>+		if (btrfs_fs_incompat(info, HMZONED))
>>+			btrfs_info(info,
>>+			"ignoring existing space cache in HMZONED mode");
>
>It would be good to clear the cache gen in this case.  I assume this 
>can happen if we add a hmzoned device to an existing fs with space 
>cache already?  I'd hate for weird corner cases to pop up if we 
>removed it later and still had a valid cache gen in place.  Thanks,
>
>Josef

We at least currently prohibit to add a zoned device to an non-zoned
files system. So, that case of adding zoned device to an existing fs
with space cache, won't happen usually. This condintion deals with
device corruption or bug in userland tools. Anyway, I will clear the
cache in this case.

Patch
diff mbox series

diff --git a/fs/btrfs/hmzoned.c b/fs/btrfs/hmzoned.c
index 1b24facd46b8..d62f11652973 100644
--- a/fs/btrfs/hmzoned.c
+++ b/fs/btrfs/hmzoned.c
@@ -250,3 +250,21 @@  int btrfs_check_hmzoned_mode(struct btrfs_fs_info *fs_info)
 out:
 	return ret;
 }
+
+int btrfs_check_mountopts_hmzoned(struct btrfs_fs_info *info)
+{
+	if (!btrfs_fs_incompat(info, HMZONED))
+		return 0;
+
+	/*
+	 * SPACE CACHE writing is not CoWed. Disable that to avoid write
+	 * errors in sequential zones.
+	 */
+	if (btrfs_test_opt(info, SPACE_CACHE)) {
+		btrfs_err(info,
+			  "space cache v1 not supportted in HMZONED mode");
+		return -EOPNOTSUPP;
+	}
+
+	return 0;
+}
diff --git a/fs/btrfs/hmzoned.h b/fs/btrfs/hmzoned.h
index 8e17f64ff986..d9ebe11afdf5 100644
--- a/fs/btrfs/hmzoned.h
+++ b/fs/btrfs/hmzoned.h
@@ -29,6 +29,7 @@  int btrfs_get_dev_zone(struct btrfs_device *device, u64 pos,
 int btrfs_get_dev_zone_info(struct btrfs_device *device);
 void btrfs_destroy_dev_zone_info(struct btrfs_device *device);
 int btrfs_check_hmzoned_mode(struct btrfs_fs_info *fs_info);
+int btrfs_check_mountopts_hmzoned(struct btrfs_fs_info *info);
 #else /* CONFIG_BLK_DEV_ZONED */
 static inline int btrfs_get_dev_zone(struct btrfs_device *device, u64 pos,
 				     struct blk_zone *zone)
@@ -48,6 +49,10 @@  static inline int btrfs_check_hmzoned_mode(struct btrfs_fs_info *fs_info)
 	btrfs_err(fs_info, "Zoned block devices support is not enabled");
 	return -EOPNOTSUPP;
 }
+static inline int btrfs_check_mountopts_hmzoned(struct btrfs_fs_info *info)
+{
+	return 0;
+}
 #endif
 
 static inline bool btrfs_dev_is_sequential(struct btrfs_device *device, u64 pos)
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 616f5abec267..1424c3c6e3cf 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -442,8 +442,13 @@  int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
 	cache_gen = btrfs_super_cache_generation(info->super_copy);
 	if (btrfs_fs_compat_ro(info, FREE_SPACE_TREE))
 		btrfs_set_opt(info->mount_opt, FREE_SPACE_TREE);
-	else if (cache_gen)
-		btrfs_set_opt(info->mount_opt, SPACE_CACHE);
+	else if (cache_gen) {
+		if (btrfs_fs_incompat(info, HMZONED))
+			btrfs_info(info,
+			"ignoring existing space cache in HMZONED mode");
+		else
+			btrfs_set_opt(info->mount_opt, SPACE_CACHE);
+	}
 
 	/*
 	 * Even the options are empty, we still need to do extra check
@@ -879,6 +884,8 @@  int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
 		ret = -EINVAL;
 
 	}
+	if (!ret)
+		ret = btrfs_check_mountopts_hmzoned(info);
 	if (!ret && btrfs_test_opt(info, SPACE_CACHE))
 		btrfs_info(info, "disk space caching is enabled");
 	if (!ret && btrfs_test_opt(info, FREE_SPACE_TREE))