[PATCH v3 1/2] btrfs: make fs_devices to be a local variable

[PATCH v3 1/2] btrfs: make fs_devices to be a local variable

[Gu Jinxiang]

fs_devices is always passed to btrfs_scan_one_device which
overrides it. And in the call stack below fs_devices is passed to
btrfs_scan_one_device from btrfs_mount_root.
And in btrfs_mount_root the output fs_devices of this call stack
is not used.
btrfs_mount_root
	-> btrfs_parse_early_options
		->btrfs_scan_one_device
So, there is no necessary to pass fs_devices from btrfs_mount_root,
use a local variable in btrfs_parse_early_options is enough.

Signed-off-by: Gu Jinxiang <gujx@cn.fujitsu.com>
---

Changelog:
v3: rebase to misc-next.
v2: deal with Nikolay's comment, make changelog more clair.

 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 e04bcf0b0ed4..78b5d51c7bc7 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -884,11 +884,12 @@ 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;
@@ -916,7 +917,7 @@ 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;
@@ -1524,8 +1525,7 @@ 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 v3 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>
---

Changelog:
v3: as comment by robot, use PTR_ERR_OR_ZERO, and rebase to misc-next.
v2: as comment by Nikolay, use ERR_CAST instead of cast type manually.

 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 78b5d51c7bc7..20e1ee338a95 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -916,11 +916,13 @@ 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;
+			}
 		}
 	}
 
@@ -1537,9 +1539,11 @@ 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
@@ -2220,7 +2224,7 @@ 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))
@@ -2232,14 +2236,17 @@ 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 = PTR_ERR_OR_ZERO(fs_devices);
 		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 af2704de9ff9..6a6321e41f1b 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1212,14 +1212,14 @@ 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;
 
 	/*
@@ -1233,19 +1233,19 @@ 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 275c31c730cf..d8f0b6f85e35 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -405,8 +405,8 @@ 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 v3 1/2] btrfs: make fs_devices to be a local variable

[Anand Jain]

On 07/11/2018 09:22 AM, Gu Jinxiang wrote:
> fs_devices is always passed to btrfs_scan_one_device which
> overrides it. And in the call stack below fs_devices is passed to
> btrfs_scan_one_device from btrfs_mount_root.
> And in btrfs_mount_root the output fs_devices of this call stack
> is not used.
> btrfs_mount_root
> 	-> btrfs_parse_early_options
> 		->btrfs_scan_one_device
> So, there is no necessary to pass fs_devices from btrfs_mount_root,
> use a local variable in btrfs_parse_early_options is enough.
> 
> Signed-off-by: Gu Jinxiang <gujx@cn.fujitsu.com>

Other than two nit below.

Reviewed-by: Anand Jain <Anand.Jain@oracle.com>

> ---
> 
> Changelog:
> v3: rebase to misc-next.
> v2: deal with Nikolay's comment, make changelog more clair.
> 
>   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 e04bcf0b0ed4..78b5d51c7bc7 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -884,11 +884,12 @@ 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)

  While here pls indent the 2nd line argument to be below the
  const char options.


>   {
>   	substring_t args[MAX_OPT_ARGS];
>   	char *device_name, *opts, *orig, *p;
>   	int error = 0;
> +	struct btrfs_fs_devices *fs_devices = NULL;

  Its a good idea to align the declarations to avoid space wastage,

    	char *device_name, *opts, *orig, *p;
  +	struct btrfs_fs_devices *fs_devices = NULL;
    	int error = 0;

Thanks, Anand

>   	if (!options)
>   		return 0;
> @@ -916,7 +917,7 @@ 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;
> @@ -1524,8 +1525,7 @@ 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 v3 2/2] btrfs: get fs_devices pointer form btrfs_scan_one_device

[Anand Jain]

On 07/11/2018 09:22 AM, 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.

Yep this was in the list to fix. However I didn't like the idea
to return the btrfs_fs_devices pointer, instead return the
btrfs_device pointer, so that we can still retrieve its fs_devices.

Thanks, Anand

> Signed-off-by: Gu Jinxiang <gujx@cn.fujitsu.com>
> ---
> 
> Changelog:
> v3: as comment by robot, use PTR_ERR_OR_ZERO, and rebase to misc-next.
> v2: as comment by Nikolay, use ERR_CAST instead of cast type manually.
> 
>   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 78b5d51c7bc7..20e1ee338a95 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -916,11 +916,13 @@ 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;
> +			}
>   		}
>   	}
>   
> @@ -1537,9 +1539,11 @@ 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
> @@ -2220,7 +2224,7 @@ 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))
> @@ -2232,14 +2236,17 @@ 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 = PTR_ERR_OR_ZERO(fs_devices);
>   		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 af2704de9ff9..6a6321e41f1b 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -1212,14 +1212,14 @@ 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;
>   
>   	/*
> @@ -1233,19 +1233,19 @@ 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 275c31c730cf..d8f0b6f85e35 100644
> --- a/fs/btrfs/volumes.h
> +++ b/fs/btrfs/volumes.h
> @@ -405,8 +405,8 @@ 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,
>