[PATCH 1/2] btrfs: make fs_devices to be a local variable

[PATCH 1/2] btrfs: make fs_devices to be a local variable

[Gu Jinxiang]

Since output parameter fs_devices of btrfs_parse_early_options is
not used in the caller, make it be a local variable.

Signed-off-by: Gu Jinxiang <gujx@cn.fujitsu.com>
---
 fs/btrfs/super.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index bf546d6c286c..4ee082e96d51 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -886,11 +886,12 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
  * only when we need to allocate a new super block.
  */
 static int btrfs_parse_early_options(const char *options, fmode_t flags,
-		void *holder, struct btrfs_fs_devices **fs_devices)
+		void *holder)
 {
 	substring_t args[MAX_OPT_ARGS];
 	char *device_name, *opts, *orig, *p;
 	int error = 0;
+	struct btrfs_fs_devices *fs_devices = NULL;
 
 	if (!options)
 		return 0;
@@ -918,7 +919,7 @@ static int btrfs_parse_early_options(const char *options, fmode_t flags,
 				goto out;
 			}
 			error = btrfs_scan_one_device(device_name,
-					flags, holder, fs_devices);
+					flags, holder, &fs_devices);
 			kfree(device_name);
 			if (error)
 				goto out;
@@ -1526,8 +1527,7 @@ static struct dentry *btrfs_mount_root(struct file_system_type *fs_type,
 	if (!(flags & SB_RDONLY))
 		mode |= FMODE_WRITE;
 
-	error = btrfs_parse_early_options(data, mode, fs_type,
-					  &fs_devices);
+	error = btrfs_parse_early_options(data, mode, fs_type);
 	if (error) {
 		return ERR_PTR(error);
 	}
-- 
2.17.1

[PATCH 2/2] btrfs: get fs_devices pointer form btrfs_scan_one_device

[Gu Jinxiang]

Instead of pointer to btrfs_fs_devices as an arg in
btrfs_scan_one_device, better to make it as a return value.

Signed-off-by: Gu Jinxiang <gujx@cn.fujitsu.com>
---
 fs/btrfs/super.c   | 29 ++++++++++++++++++-----------
 fs/btrfs/volumes.c | 14 +++++++-------
 fs/btrfs/volumes.h |  4 ++--
 3 files changed, 27 insertions(+), 20 deletions(-)

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 4ee082e96d51..a5ddeb6836e3 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -918,11 +918,13 @@ static int btrfs_parse_early_options(const char *options, fmode_t flags,
 				error = -ENOMEM;
 				goto out;
 			}
-			error = btrfs_scan_one_device(device_name,
-					flags, holder, &fs_devices);
+			fs_devices = btrfs_scan_one_device(device_name,
+					flags, holder);
 			kfree(device_name);
-			if (error)
+			if (IS_ERR(fs_devices)) {
+				error = PTR_ERR(fs_devices);
 				goto out;
+			}
 		}
 	}
 
@@ -1539,9 +1541,11 @@ static struct dentry *btrfs_mount_root(struct file_system_type *fs_type,
 			return ERR_PTR(error);
 	}
 
-	error = btrfs_scan_one_device(device_name, mode, fs_type, &fs_devices);
-	if (error)
+	fs_devices = btrfs_scan_one_device(device_name, mode, fs_type);
+	if (IS_ERR(fs_devices)) {
+		error = PTR_ERR(fs_devices);
 		goto error_sec_opts;
+	}
 
 	/*
 	 * Setup a dummy root and fs_info for test/set super.  This is because
@@ -2222,7 +2226,7 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
 				unsigned long arg)
 {
 	struct btrfs_ioctl_vol_args *vol;
-	struct btrfs_fs_devices *fs_devices;
+	struct btrfs_fs_devices *fs_devices = NULL;
 	int ret = -ENOTTY;
 
 	if (!capable(CAP_SYS_ADMIN))
@@ -2234,14 +2238,17 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
 
 	switch (cmd) {
 	case BTRFS_IOC_SCAN_DEV:
-		ret = btrfs_scan_one_device(vol->name, FMODE_READ,
-					    &btrfs_root_fs_type, &fs_devices);
+		fs_devices = btrfs_scan_one_device(vol->name, FMODE_READ,
+					    &btrfs_root_fs_type);
+		ret = IS_ERR(fs_devices) ? PTR_ERR(fs_devices) : 0;
 		break;
 	case BTRFS_IOC_DEVICES_READY:
-		ret = btrfs_scan_one_device(vol->name, FMODE_READ,
-					    &btrfs_root_fs_type, &fs_devices);
-		if (ret)
+		fs_devices = btrfs_scan_one_device(vol->name, FMODE_READ,
+					    &btrfs_root_fs_type);
+		if (IS_ERR(fs_devices)) {
+			ret = PTR_ERR(fs_devices);
 			break;
+		}
 		ret = !(fs_devices->num_devices == fs_devices->total_devices);
 		break;
 	case BTRFS_IOC_GET_SUPPORTED_FEATURES:
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index b33bf29130b6..922c4ad6d421 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1215,14 +1215,14 @@ static int btrfs_read_disk_super(struct block_device *bdev, u64 bytenr,
  * and we are not allowed to call set_blocksize during the scan. The superblock
  * is read via pagecache
  */
-int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
-			  struct btrfs_fs_devices **fs_devices_ret)
+struct btrfs_fs_devices *btrfs_scan_one_device(const char *path, fmode_t flags,
+		void *holder)
 {
 	struct btrfs_super_block *disk_super;
 	struct btrfs_device *device;
 	struct block_device *bdev;
 	struct page *page;
-	int ret = 0;
+	struct btrfs_fs_devices *ret = NULL;
 	u64 bytenr;
 
 	/*
@@ -1236,19 +1236,19 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
 
 	bdev = blkdev_get_by_path(path, flags, holder);
 	if (IS_ERR(bdev))
-		return PTR_ERR(bdev);
+		return (struct btrfs_fs_devices *)bdev;
 
 	if (btrfs_read_disk_super(bdev, bytenr, &page, &disk_super)) {
-		ret = -EINVAL;
+		ret = ERR_PTR(-EINVAL);
 		goto error_bdev_put;
 	}
 
 	mutex_lock(&uuid_mutex);
 	device = device_list_add(path, disk_super);
 	if (IS_ERR(device))
-		ret = PTR_ERR(device);
+		ret = (struct btrfs_fs_devices *)device;
 	else
-		*fs_devices_ret = device->fs_devices;
+		ret = device->fs_devices;
 	mutex_unlock(&uuid_mutex);
 
 	btrfs_release_disk_super(page);
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 77e6004b6cb9..f867f07be963 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -406,8 +406,8 @@ blk_status_t btrfs_map_bio(struct btrfs_fs_info *fs_info, struct bio *bio,
 			   int mirror_num, int async_submit);
 int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
 		       fmode_t flags, void *holder);
-int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
-			  struct btrfs_fs_devices **fs_devices_ret);
+struct btrfs_fs_devices *btrfs_scan_one_device(const char *path, fmode_t flags,
+		void *holder);
 int btrfs_close_devices(struct btrfs_fs_devices *fs_devices);
 void btrfs_free_extra_devids(struct btrfs_fs_devices *fs_devices, int step);
 void btrfs_assign_next_active_device(struct btrfs_fs_info *fs_info,
-- 
2.17.1

Re: [PATCH 1/2] btrfs: make fs_devices to be a local variable

[Nikolay Borisov]

On 10.07.2018 09:33, Gu Jinxiang wrote:
> Since output parameter fs_devices of btrfs_parse_early_options is
> not used in the caller, make it be a local variable.

The changelog is a bit misleading, because 'fs_devices' is in fact used
in the caller, however it's always passed to btrfs_scan_one_device which
overrides it. Finally it is assigned to fs_info->fs_devices. So the
patch is correct however put more detail in the changelog explaining
it's overriden by btrfs_scan_one_device.

> 
> Signed-off-by: Gu Jinxiang <gujx@cn.fujitsu.com>
> ---
>  fs/btrfs/super.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> index bf546d6c286c..4ee082e96d51 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -886,11 +886,12 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
>   * only when we need to allocate a new super block.
>   */
>  static int btrfs_parse_early_options(const char *options, fmode_t flags,
> -		void *holder, struct btrfs_fs_devices **fs_devices)
> +		void *holder)
>  {
>  	substring_t args[MAX_OPT_ARGS];
>  	char *device_name, *opts, *orig, *p;
>  	int error = 0;
> +	struct btrfs_fs_devices *fs_devices = NULL;
>  
>  	if (!options)
>  		return 0;
> @@ -918,7 +919,7 @@ static int btrfs_parse_early_options(const char *options, fmode_t flags,
>  				goto out;
>  			}
>  			error = btrfs_scan_one_device(device_name,
> -					flags, holder, fs_devices);
> +					flags, holder, &fs_devices);
>  			kfree(device_name);
>  			if (error)
>  				goto out;
> @@ -1526,8 +1527,7 @@ static struct dentry *btrfs_mount_root(struct file_system_type *fs_type,
>  	if (!(flags & SB_RDONLY))
>  		mode |= FMODE_WRITE;
>  
> -	error = btrfs_parse_early_options(data, mode, fs_type,
> -					  &fs_devices);
> +	error = btrfs_parse_early_options(data, mode, fs_type);
>  	if (error) {
>  		return ERR_PTR(error);
>  	}
> 

Re: [PATCH 2/2] btrfs: get fs_devices pointer form btrfs_scan_one_device

[Nikolay Borisov]

On 10.07.2018 09:33, Gu Jinxiang wrote:
> Instead of pointer to btrfs_fs_devices as an arg in
> btrfs_scan_one_device, better to make it as a return value.
> 
> Signed-off-by: Gu Jinxiang <gujx@cn.fujitsu.com>
> ---
>  fs/btrfs/super.c   | 29 ++++++++++++++++++-----------
>  fs/btrfs/volumes.c | 14 +++++++-------
>  fs/btrfs/volumes.h |  4 ++--
>  3 files changed, 27 insertions(+), 20 deletions(-)
> 
> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> index 4ee082e96d51..a5ddeb6836e3 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -918,11 +918,13 @@ static int btrfs_parse_early_options(const char *options, fmode_t flags,
>  				error = -ENOMEM;
>  				goto out;
>  			}
> -			error = btrfs_scan_one_device(device_name,
> -					flags, holder, &fs_devices);
> +			fs_devices = btrfs_scan_one_device(device_name,
> +					flags, holder);
>  			kfree(device_name);
> -			if (error)
> +			if (IS_ERR(fs_devices)) {
> +				error = PTR_ERR(fs_devices);
>  				goto out;
> +			}
>  		}
>  	}
>  
> @@ -1539,9 +1541,11 @@ static struct dentry *btrfs_mount_root(struct file_system_type *fs_type,
>  			return ERR_PTR(error);
>  	}
>  
> -	error = btrfs_scan_one_device(device_name, mode, fs_type, &fs_devices);
> -	if (error)
> +	fs_devices = btrfs_scan_one_device(device_name, mode, fs_type);
> +	if (IS_ERR(fs_devices)) {
> +		error = PTR_ERR(fs_devices);
>  		goto error_sec_opts;
> +	}
>  
>  	/*
>  	 * Setup a dummy root and fs_info for test/set super.  This is because
> @@ -2222,7 +2226,7 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
>  				unsigned long arg)
>  {
>  	struct btrfs_ioctl_vol_args *vol;
> -	struct btrfs_fs_devices *fs_devices;
> +	struct btrfs_fs_devices *fs_devices = NULL;
>  	int ret = -ENOTTY;
>  
>  	if (!capable(CAP_SYS_ADMIN))
> @@ -2234,14 +2238,17 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
>  
>  	switch (cmd) {
>  	case BTRFS_IOC_SCAN_DEV:
> -		ret = btrfs_scan_one_device(vol->name, FMODE_READ,
> -					    &btrfs_root_fs_type, &fs_devices);
> +		fs_devices = btrfs_scan_one_device(vol->name, FMODE_READ,
> +					    &btrfs_root_fs_type);
> +		ret = IS_ERR(fs_devices) ? PTR_ERR(fs_devices) : 0;
>  		break;
>  	case BTRFS_IOC_DEVICES_READY:
> -		ret = btrfs_scan_one_device(vol->name, FMODE_READ,
> -					    &btrfs_root_fs_type, &fs_devices);
> -		if (ret)
> +		fs_devices = btrfs_scan_one_device(vol->name, FMODE_READ,
> +					    &btrfs_root_fs_type);
> +		if (IS_ERR(fs_devices)) {
> +			ret = PTR_ERR(fs_devices);
>  			break;
> +		}
>  		ret = !(fs_devices->num_devices == fs_devices->total_devices);
>  		break;
>  	case BTRFS_IOC_GET_SUPPORTED_FEATURES:
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index b33bf29130b6..922c4ad6d421 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -1215,14 +1215,14 @@ static int btrfs_read_disk_super(struct block_device *bdev, u64 bytenr,
>   * and we are not allowed to call set_blocksize during the scan. The superblock
>   * is read via pagecache
>   */
> -int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
> -			  struct btrfs_fs_devices **fs_devices_ret)
> +struct btrfs_fs_devices *btrfs_scan_one_device(const char *path, fmode_t flags,
> +		void *holder)
>  {
>  	struct btrfs_super_block *disk_super;
>  	struct btrfs_device *device;
>  	struct block_device *bdev;
>  	struct page *page;
> -	int ret = 0;
> +	struct btrfs_fs_devices *ret = NULL;
>  	u64 bytenr;
>  
>  	/*
> @@ -1236,19 +1236,19 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
>  
>  	bdev = blkdev_get_by_path(path, flags, holder);
>  	if (IS_ERR(bdev))
> -		return PTR_ERR(bdev);
> +		return (struct btrfs_fs_devices *)bdev;

This makes my eyes bleed. There is already a construct which handles
this and it's called ERR_CAST so use it.

>  
>  	if (btrfs_read_disk_super(bdev, bytenr, &page, &disk_super)) {
> -		ret = -EINVAL;
> +		ret = ERR_PTR(-EINVAL);
>  		goto error_bdev_put;
>  	}
>  
>  	mutex_lock(&uuid_mutex);
>  	device = device_list_add(path, disk_super);
>  	if (IS_ERR(device))
> -		ret = PTR_ERR(device);
> +		ret = (struct btrfs_fs_devices *)device;
ERR_CAST

>  	else
> -		*fs_devices_ret = device->fs_devices;
> +		ret = device->fs_devices;
>  	mutex_unlock(&uuid_mutex);
>  
>  	btrfs_release_disk_super(page);
> diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
> index 77e6004b6cb9..f867f07be963 100644
> --- a/fs/btrfs/volumes.h
> +++ b/fs/btrfs/volumes.h
> @@ -406,8 +406,8 @@ blk_status_t btrfs_map_bio(struct btrfs_fs_info *fs_info, struct bio *bio,
>  			   int mirror_num, int async_submit);
>  int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
>  		       fmode_t flags, void *holder);
> -int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
> -			  struct btrfs_fs_devices **fs_devices_ret);
> +struct btrfs_fs_devices *btrfs_scan_one_device(const char *path, fmode_t flags,
> +		void *holder);
>  int btrfs_close_devices(struct btrfs_fs_devices *fs_devices);
>  void btrfs_free_extra_devids(struct btrfs_fs_devices *fs_devices, int step);
>  void btrfs_assign_next_active_device(struct btrfs_fs_info *fs_info,
> 

[PATCH 2/2] btrfs: get fs_devices pointer form btrfs_scan_one_device

[Gu Jinxiang]

Instead of pointer to btrfs_fs_devices as an arg in
btrfs_scan_one_device, better to make it as a return value.

Signed-off-by: Gu Jinxiang <gujx@cn.fujitsu.com>
---
 fs/btrfs/super.c   | 29 ++++++++++++++++++-----------
 fs/btrfs/volumes.c | 14 +++++++-------
 fs/btrfs/volumes.h |  4 ++--
 3 files changed, 27 insertions(+), 20 deletions(-)

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 4ee082e96d51..a5ddeb6836e3 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -918,11 +918,13 @@ static int btrfs_parse_early_options(const char *options, fmode_t flags,
 				error = -ENOMEM;
 				goto out;
 			}
-			error = btrfs_scan_one_device(device_name,
-					flags, holder, &fs_devices);
+			fs_devices = btrfs_scan_one_device(device_name,
+					flags, holder);
 			kfree(device_name);
-			if (error)
+			if (IS_ERR(fs_devices)) {
+				error = PTR_ERR(fs_devices);
 				goto out;
+			}
 		}
 	}
 
@@ -1539,9 +1541,11 @@ static struct dentry *btrfs_mount_root(struct file_system_type *fs_type,
 			return ERR_PTR(error);
 	}
 
-	error = btrfs_scan_one_device(device_name, mode, fs_type, &fs_devices);
-	if (error)
+	fs_devices = btrfs_scan_one_device(device_name, mode, fs_type);
+	if (IS_ERR(fs_devices)) {
+		error = PTR_ERR(fs_devices);
 		goto error_sec_opts;
+	}
 
 	/*
 	 * Setup a dummy root and fs_info for test/set super.  This is because
@@ -2222,7 +2226,7 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
 				unsigned long arg)
 {
 	struct btrfs_ioctl_vol_args *vol;
-	struct btrfs_fs_devices *fs_devices;
+	struct btrfs_fs_devices *fs_devices = NULL;
 	int ret = -ENOTTY;
 
 	if (!capable(CAP_SYS_ADMIN))
@@ -2234,14 +2238,17 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
 
 	switch (cmd) {
 	case BTRFS_IOC_SCAN_DEV:
-		ret = btrfs_scan_one_device(vol->name, FMODE_READ,
-					    &btrfs_root_fs_type, &fs_devices);
+		fs_devices = btrfs_scan_one_device(vol->name, FMODE_READ,
+					    &btrfs_root_fs_type);
+		ret = IS_ERR(fs_devices) ? PTR_ERR(fs_devices) : 0;
 		break;
 	case BTRFS_IOC_DEVICES_READY:
-		ret = btrfs_scan_one_device(vol->name, FMODE_READ,
-					    &btrfs_root_fs_type, &fs_devices);
-		if (ret)
+		fs_devices = btrfs_scan_one_device(vol->name, FMODE_READ,
+					    &btrfs_root_fs_type);
+		if (IS_ERR(fs_devices)) {
+			ret = PTR_ERR(fs_devices);
 			break;
+		}
 		ret = !(fs_devices->num_devices == fs_devices->total_devices);
 		break;
 	case BTRFS_IOC_GET_SUPPORTED_FEATURES:
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index b33bf29130b6..ea1ca4da413d 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1215,14 +1215,14 @@ static int btrfs_read_disk_super(struct block_device *bdev, u64 bytenr,
  * and we are not allowed to call set_blocksize during the scan. The superblock
  * is read via pagecache
  */
-int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
-			  struct btrfs_fs_devices **fs_devices_ret)
+struct btrfs_fs_devices *btrfs_scan_one_device(const char *path, fmode_t flags,
+		void *holder)
 {
 	struct btrfs_super_block *disk_super;
 	struct btrfs_device *device;
 	struct block_device *bdev;
 	struct page *page;
-	int ret = 0;
+	struct btrfs_fs_devices *ret = NULL;
 	u64 bytenr;
 
 	/*
@@ -1236,19 +1236,19 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
 
 	bdev = blkdev_get_by_path(path, flags, holder);
 	if (IS_ERR(bdev))
-		return PTR_ERR(bdev);
+		return ERR_CAST(bdev);
 
 	if (btrfs_read_disk_super(bdev, bytenr, &page, &disk_super)) {
-		ret = -EINVAL;
+		ret = ERR_PTR(-EINVAL);
 		goto error_bdev_put;
 	}
 
 	mutex_lock(&uuid_mutex);
 	device = device_list_add(path, disk_super);
 	if (IS_ERR(device))
-		ret = PTR_ERR(device);
+		ret = ERR_CAST(device);
 	else
-		*fs_devices_ret = device->fs_devices;
+		ret = device->fs_devices;
 	mutex_unlock(&uuid_mutex);
 
 	btrfs_release_disk_super(page);
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 77e6004b6cb9..f867f07be963 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -406,8 +406,8 @@ blk_status_t btrfs_map_bio(struct btrfs_fs_info *fs_info, struct bio *bio,
 			   int mirror_num, int async_submit);
 int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
 		       fmode_t flags, void *holder);
-int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
-			  struct btrfs_fs_devices **fs_devices_ret);
+struct btrfs_fs_devices *btrfs_scan_one_device(const char *path, fmode_t flags,
+		void *holder);
 int btrfs_close_devices(struct btrfs_fs_devices *fs_devices);
 void btrfs_free_extra_devids(struct btrfs_fs_devices *fs_devices, int step);
 void btrfs_assign_next_active_device(struct btrfs_fs_info *fs_info,
-- 
2.17.1

RE: [PATCH 2/2] btrfs: get fs_devices pointer form btrfs_scan_one_device

[Gu, Jinxiang]

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Duplicate one, please ignore this.

> -----Original Message-----
> From: linux-btrfs-owner@vger.kernel.org [mailto:linux-btrfs-owner@vger.kernel.org] On Behalf Of Gu Jinxiang
> Sent: Tuesday, July 10, 2018 6:27 PM
> To: linux-btrfs@vger.kernel.org
> Cc: nborisov@suse.com
> Subject: [PATCH 2/2] btrfs: get fs_devices pointer form btrfs_scan_one_device
> 
> Instead of pointer to btrfs_fs_devices as an arg in
> btrfs_scan_one_device, better to make it as a return value.
> 
> Signed-off-by: Gu Jinxiang <gujx@cn.fujitsu.com>
> ---
>  fs/btrfs/super.c   | 29 ++++++++++++++++++-----------
>  fs/btrfs/volumes.c | 14 +++++++-------
>  fs/btrfs/volumes.h |  4 ++--
>  3 files changed, 27 insertions(+), 20 deletions(-)
> 
> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> index 4ee082e96d51..a5ddeb6836e3 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -918,11 +918,13 @@ static int btrfs_parse_early_options(const char *options, fmode_t flags,
>  				error = -ENOMEM;
>  				goto out;
>  			}
> -			error = btrfs_scan_one_device(device_name,
> -					flags, holder, &fs_devices);
> +			fs_devices = btrfs_scan_one_device(device_name,
> +					flags, holder);
>  			kfree(device_name);
> -			if (error)
> +			if (IS_ERR(fs_devices)) {
> +				error = PTR_ERR(fs_devices);
>  				goto out;
> +			}
>  		}
>  	}
> 
> @@ -1539,9 +1541,11 @@ static struct dentry *btrfs_mount_root(struct file_system_type *fs_type,
>  			return ERR_PTR(error);
>  	}
> 
> -	error = btrfs_scan_one_device(device_name, mode, fs_type, &fs_devices);
> -	if (error)
> +	fs_devices = btrfs_scan_one_device(device_name, mode, fs_type);
> +	if (IS_ERR(fs_devices)) {
> +		error = PTR_ERR(fs_devices);
>  		goto error_sec_opts;
> +	}
> 
>  	/*
>  	 * Setup a dummy root and fs_info for test/set super.  This is because
> @@ -2222,7 +2226,7 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
>  				unsigned long arg)
>  {
>  	struct btrfs_ioctl_vol_args *vol;
> -	struct btrfs_fs_devices *fs_devices;
> +	struct btrfs_fs_devices *fs_devices = NULL;
>  	int ret = -ENOTTY;
> 
>  	if (!capable(CAP_SYS_ADMIN))
> @@ -2234,14 +2238,17 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
> 
>  	switch (cmd) {
>  	case BTRFS_IOC_SCAN_DEV:
> -		ret = btrfs_scan_one_device(vol->name, FMODE_READ,
> -					    &btrfs_root_fs_type, &fs_devices);
> +		fs_devices = btrfs_scan_one_device(vol->name, FMODE_READ,
> +					    &btrfs_root_fs_type);
> +		ret = IS_ERR(fs_devices) ? PTR_ERR(fs_devices) : 0;
>  		break;
>  	case BTRFS_IOC_DEVICES_READY:
> -		ret = btrfs_scan_one_device(vol->name, FMODE_READ,
> -					    &btrfs_root_fs_type, &fs_devices);
> -		if (ret)
> +		fs_devices = btrfs_scan_one_device(vol->name, FMODE_READ,
> +					    &btrfs_root_fs_type);
> +		if (IS_ERR(fs_devices)) {
> +			ret = PTR_ERR(fs_devices);
>  			break;
> +		}
>  		ret = !(fs_devices->num_devices == fs_devices->total_devices);
>  		break;
>  	case BTRFS_IOC_GET_SUPPORTED_FEATURES:
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index b33bf29130b6..ea1ca4da413d 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -1215,14 +1215,14 @@ static int btrfs_read_disk_super(struct block_device *bdev, u64 bytenr,
>   * and we are not allowed to call set_blocksize during the scan. The superblock
>   * is read via pagecache
>   */
> -int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
> -			  struct btrfs_fs_devices **fs_devices_ret)
> +struct btrfs_fs_devices *btrfs_scan_one_device(const char *path, fmode_t flags,
> +		void *holder)
>  {
>  	struct btrfs_super_block *disk_super;
>  	struct btrfs_device *device;
>  	struct block_device *bdev;
>  	struct page *page;
> -	int ret = 0;
> +	struct btrfs_fs_devices *ret = NULL;
>  	u64 bytenr;
> 
>  	/*
> @@ -1236,19 +1236,19 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
> 
>  	bdev = blkdev_get_by_path(path, flags, holder);
>  	if (IS_ERR(bdev))
> -		return PTR_ERR(bdev);
> +		return ERR_CAST(bdev);
> 
>  	if (btrfs_read_disk_super(bdev, bytenr, &page, &disk_super)) {
> -		ret = -EINVAL;
> +		ret = ERR_PTR(-EINVAL);
>  		goto error_bdev_put;
>  	}
> 
>  	mutex_lock(&uuid_mutex);
>  	device = device_list_add(path, disk_super);
>  	if (IS_ERR(device))
> -		ret = PTR_ERR(device);
> +		ret = ERR_CAST(device);
>  	else
> -		*fs_devices_ret = device->fs_devices;
> +		ret = device->fs_devices;
>  	mutex_unlock(&uuid_mutex);
> 
>  	btrfs_release_disk_super(page);
> diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
> index 77e6004b6cb9..f867f07be963 100644
> --- a/fs/btrfs/volumes.h
> +++ b/fs/btrfs/volumes.h
> @@ -406,8 +406,8 @@ blk_status_t btrfs_map_bio(struct btrfs_fs_info *fs_info, struct bio *bio,
>  			   int mirror_num, int async_submit);
>  int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
>  		       fmode_t flags, void *holder);
> -int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
> -			  struct btrfs_fs_devices **fs_devices_ret);
> +struct btrfs_fs_devices *btrfs_scan_one_device(const char *path, fmode_t flags,
> +		void *holder);
>  int btrfs_close_devices(struct btrfs_fs_devices *fs_devices);
>  void btrfs_free_extra_devids(struct btrfs_fs_devices *fs_devices, int step);
>  void btrfs_assign_next_active_device(struct btrfs_fs_info *fs_info,
> --
> 2.17.1
> 
> 
> 
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