[PATCH v2] btrfs: Make btrfs_read_disk_super return struct btrfs_disk_super

[PATCH v2] btrfs: Make btrfs_read_disk_super return struct btrfs_disk_super

[Nikolay Borisov]

Instead of returning both the page and the super block structure, make
btrfs_read_disk_super just return a pointer to struct btrfs_disk_super.
As a result the function signature is simplified.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
---

V2:
 * Make btrfs_scan_one_device forward the error it got from btrfs_read_disk_super
 to its callers.
 * Return EINVAL in case sb byte offset or magic value don't match in btrfs_read_disk_super
 * Removed explicit mention that read_cache_page_gfp can't return a NULL value.

 fs/btrfs/volumes.c | 48 +++++++++++++++++++++++-----------------------
 1 file changed, 24 insertions(+), 24 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index c1909e5f4506..58a2c23ab91e 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1251,49 +1251,49 @@ void btrfs_release_disk_super(struct btrfs_super_block *super)
 	put_page(page);
 }

-static int btrfs_read_disk_super(struct block_device *bdev, u64 bytenr,
-				 struct page **page,
-				 struct btrfs_super_block **disk_super)
+static struct btrfs_super_block *btrfs_read_disk_super(struct block_device *bdev,
+						       u64 bytenr)
 {
+	struct btrfs_super_block *disk_super;
+	struct page *page;
 	void *p;
 	pgoff_t index;

 	/* make sure our super fits in the device */
 	if (bytenr + PAGE_SIZE >= i_size_read(bdev->bd_inode))
-		return 1;
+		return ERR_PTR(-EINVAL);

 	/* make sure our super fits in the page */
-	if (sizeof(**disk_super) > PAGE_SIZE)
-		return 1;
+	if (sizeof(*disk_super) > PAGE_SIZE)
+		return ERR_PTR(-EINVAL);

 	/* make sure our super doesn't straddle pages on disk */
 	index = bytenr >> PAGE_SHIFT;
-	if ((bytenr + sizeof(**disk_super) - 1) >> PAGE_SHIFT != index)
-		return 1;
+	if ((bytenr + sizeof(*disk_super) - 1) >> PAGE_SHIFT != index)
+		return ERR_PTR(-EINVAL);

 	/* pull in the page with our super */
-	*page = read_cache_page_gfp(bdev->bd_inode->i_mapping,
-				   index, GFP_KERNEL);
+	page = read_cache_page_gfp(bdev->bd_inode->i_mapping, index,
+				   GFP_KERNEL);

-	if (IS_ERR(*page))
-		return 1;
+	if (IS_ERR(page))
+		return ERR_CAST(page);

-	p = page_address(*page);
+	p = page_address(page);

 	/* align our pointer to the offset of the super block */
-	*disk_super = p + offset_in_page(bytenr);
+	disk_super = p + offset_in_page(bytenr);

-	if (btrfs_super_bytenr(*disk_super) != bytenr ||
-	    btrfs_super_magic(*disk_super) != BTRFS_MAGIC) {
+	if (btrfs_super_bytenr(disk_super) != bytenr ||
+	    btrfs_super_magic(disk_super) != BTRFS_MAGIC) {
 		btrfs_release_disk_super(p);
-		return 1;
+		return ERR_PTR(-EINVAL);
 	}

-	if ((*disk_super)->label[0] &&
-		(*disk_super)->label[BTRFS_LABEL_SIZE - 1])
-		(*disk_super)->label[BTRFS_LABEL_SIZE - 1] = '\0';
+	if (disk_super->label[0] && disk_super->label[BTRFS_LABEL_SIZE - 1])
+		disk_super->label[BTRFS_LABEL_SIZE - 1] = '\0';

-	return 0;
+	return disk_super;
 }

 int btrfs_forget_devices(const char *path)
@@ -1319,7 +1319,6 @@ struct btrfs_device *btrfs_scan_one_device(const char *path, fmode_t flags,
 	bool new_device_added = false;
 	struct btrfs_device *device = NULL;
 	struct block_device *bdev;
-	struct page *page;
 	u64 bytenr;

 	lockdep_assert_held(&uuid_mutex);
@@ -1337,8 +1336,9 @@ struct btrfs_device *btrfs_scan_one_device(const char *path, fmode_t flags,
 	if (IS_ERR(bdev))
 		return ERR_CAST(bdev);

-	if (btrfs_read_disk_super(bdev, bytenr, &page, &disk_super)) {
-		device = ERR_PTR(-EINVAL);
+	disk_super = btrfs_read_disk_super(bdev, bytenr);
+	if (IS_ERR(disk_super)) {
+		device = disk_super;
 		goto error_bdev_put;
 	}

--
2.17.1

Re: [PATCH v2] btrfs: Make btrfs_read_disk_super return struct btrfs_disk_super

[Johannes Thumshirn]

On 16/04/2020 13:26, Nikolay Borisov wrote:
> Instead of returning both the page and the super block structure, make
> btrfs_read_disk_super just return a pointer to struct btrfs_disk_super.
> As a result the function signature is simplified.

Uh I was under the impression I had done this when removing the buffer 
heads.

Thanks for cleaning up behind me,
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>

Re: [PATCH v2] btrfs: Make btrfs_read_disk_super return struct btrfs_disk_super

[David Sterba]

On Thu, Apr 16, 2020 at 02:26:08PM +0300, Nikolay Borisov wrote:
> Instead of returning both the page and the super block structure, make
> btrfs_read_disk_super just return a pointer to struct btrfs_disk_super.
> As a result the function signature is simplified.
> 
> Signed-off-by: Nikolay Borisov <nborisov@suse.com>

Added to misc-next, thanks.

> @@ -1337,8 +1336,9 @@ struct btrfs_device *btrfs_scan_one_device(const char *path, fmode_t flags,
>  	if (IS_ERR(bdev))
>  		return ERR_CAST(bdev);
> 
> -	if (btrfs_read_disk_super(bdev, bytenr, &page, &disk_super)) {
> -		device = ERR_PTR(-EINVAL);
> +	disk_super = btrfs_read_disk_super(bdev, bytenr);
> +	if (IS_ERR(disk_super)) {
> +		device = disk_super;

With the ERR_CAST fixup.

>  		goto error_bdev_put;
>  	}
> 
> --
> 2.17.1

Re: [PATCH v2] btrfs: Make btrfs_read_disk_super return struct btrfs_disk_super

[kbuild test robot]

[-- Attachment #1: Type: text/plain, Size: 2978 bytes --]

Hi Nikolay,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on v5.7-rc1]
[also build test ERROR on next-20200416]
[cannot apply to btrfs/next]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Nikolay-Borisov/btrfs-Make-btrfs_read_disk_super-return-struct-btrfs_disk_super/20200416-230011
base:    8f3d9f354286745c751374f5f1fcafee6b3f3136
config: x86_64-randconfig-s1-20200416 (attached as .config)
compiler: gcc-7 (Ubuntu 7.5.0-6ubuntu2) 7.5.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kbuild test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   fs/btrfs/volumes.c: In function 'btrfs_scan_one_device':
>> fs/btrfs/volumes.c:1341:10: error: assignment from incompatible pointer type [-Werror=incompatible-pointer-types]
      device = disk_super;
             ^
   cc1: some warnings being treated as errors

vim +1341 fs/btrfs/volumes.c

  1309	
  1310	/*
  1311	 * Look for a btrfs signature on a device. This may be called out of the mount path
  1312	 * and we are not allowed to call set_blocksize during the scan. The superblock
  1313	 * is read via pagecache
  1314	 */
  1315	struct btrfs_device *btrfs_scan_one_device(const char *path, fmode_t flags,
  1316						   void *holder)
  1317	{
  1318		struct btrfs_super_block *disk_super;
  1319		bool new_device_added = false;
  1320		struct btrfs_device *device = NULL;
  1321		struct block_device *bdev;
  1322		u64 bytenr;
  1323	
  1324		lockdep_assert_held(&uuid_mutex);
  1325	
  1326		/*
  1327		 * we would like to check all the supers, but that would make
  1328		 * a btrfs mount succeed after a mkfs from a different FS.
  1329		 * So, we need to add a special mount option to scan for
  1330		 * later supers, using BTRFS_SUPER_MIRROR_MAX instead
  1331		 */
  1332		bytenr = btrfs_sb_offset(0);
  1333		flags |= FMODE_EXCL;
  1334	
  1335		bdev = blkdev_get_by_path(path, flags, holder);
  1336		if (IS_ERR(bdev))
  1337			return ERR_CAST(bdev);
  1338	
  1339		disk_super = btrfs_read_disk_super(bdev, bytenr);
  1340		if (IS_ERR(disk_super)) {
> 1341			device = disk_super;
  1342			goto error_bdev_put;
  1343		}
  1344	
  1345		device = device_list_add(path, disk_super, &new_device_added);
  1346		if (!IS_ERR(device)) {
  1347			if (new_device_added)
  1348				btrfs_free_stale_devices(path, device);
  1349		}
  1350	
  1351		btrfs_release_disk_super(disk_super);
  1352	
  1353	error_bdev_put:
  1354		blkdev_put(bdev, flags);
  1355	
  1356		return device;
  1357	}
  1358	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

[-- Attachment #2: .config.gz --]
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Re: [PATCH v2] btrfs: Make btrfs_read_disk_super return struct btrfs_disk_super

[kbuild test robot]

[-- Attachment #1: Type: text/plain, Size: 3066 bytes --]

Hi Nikolay,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on v5.7-rc1]
[also build test ERROR on next-20200416]
[cannot apply to btrfs/next]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Nikolay-Borisov/btrfs-Make-btrfs_read_disk_super-return-struct-btrfs_disk_super/20200416-230011
base:    8f3d9f354286745c751374f5f1fcafee6b3f3136
config: x86_64-randconfig-s1-20200416 (attached as .config)
compiler: gcc-7 (Ubuntu 7.5.0-6ubuntu2) 7.5.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kbuild test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   fs/btrfs/volumes.c: In function 'btrfs_scan_one_device':
>> fs/btrfs/volumes.c:1341:10: error: assignment from incompatible pointer type [-Werror=incompatible-pointer-types]
      device = disk_super;
             ^
   cc1: some warnings being treated as errors

vim +1341 fs/btrfs/volumes.c

  1309	
  1310	/*
  1311	 * Look for a btrfs signature on a device. This may be called out of the mount path
  1312	 * and we are not allowed to call set_blocksize during the scan. The superblock
  1313	 * is read via pagecache
  1314	 */
  1315	struct btrfs_device *btrfs_scan_one_device(const char *path, fmode_t flags,
  1316						   void *holder)
  1317	{
  1318		struct btrfs_super_block *disk_super;
  1319		bool new_device_added = false;
  1320		struct btrfs_device *device = NULL;
  1321		struct block_device *bdev;
  1322		u64 bytenr;
  1323	
  1324		lockdep_assert_held(&uuid_mutex);
  1325	
  1326		/*
  1327		 * we would like to check all the supers, but that would make
  1328		 * a btrfs mount succeed after a mkfs from a different FS.
  1329		 * So, we need to add a special mount option to scan for
  1330		 * later supers, using BTRFS_SUPER_MIRROR_MAX instead
  1331		 */
  1332		bytenr = btrfs_sb_offset(0);
  1333		flags |= FMODE_EXCL;
  1334	
  1335		bdev = blkdev_get_by_path(path, flags, holder);
  1336		if (IS_ERR(bdev))
  1337			return ERR_CAST(bdev);
  1338	
  1339		disk_super = btrfs_read_disk_super(bdev, bytenr);
  1340		if (IS_ERR(disk_super)) {
> 1341			device = disk_super;
  1342			goto error_bdev_put;
  1343		}
  1344	
  1345		device = device_list_add(path, disk_super, &new_device_added);
  1346		if (!IS_ERR(device)) {
  1347			if (new_device_added)
  1348				btrfs_free_stale_devices(path, device);
  1349		}
  1350	
  1351		btrfs_release_disk_super(disk_super);
  1352	
  1353	error_bdev_put:
  1354		blkdev_put(bdev, flags);
  1355	
  1356		return device;
  1357	}
  1358	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org

[-- Attachment #2: config.gz --]
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Re: [PATCH v2] btrfs: Make btrfs_read_disk_super return struct btrfs_disk_super

[kbuild test robot]

[-- Attachment #1: Type: text/plain, Size: 3217 bytes --]

Hi Nikolay,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on v5.7-rc1]
[also build test ERROR on next-20200416]
[cannot apply to btrfs/next]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Nikolay-Borisov/btrfs-Make-btrfs_read_disk_super-return-struct-btrfs_disk_super/20200416-230011
base:    8f3d9f354286745c751374f5f1fcafee6b3f3136
config: sh-allmodconfig (attached as .config)
compiler: sh4-linux-gcc (GCC) 9.3.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day GCC_VERSION=9.3.0 make.cross ARCH=sh 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kbuild test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   fs/btrfs/volumes.c: In function 'btrfs_scan_one_device':
>> fs/btrfs/volumes.c:1341:10: error: assignment to 'struct btrfs_device *' from incompatible pointer type 'struct btrfs_super_block *' [-Werror=incompatible-pointer-types]
    1341 |   device = disk_super;
         |          ^
   cc1: some warnings being treated as errors

vim +1341 fs/btrfs/volumes.c

  1309	
  1310	/*
  1311	 * Look for a btrfs signature on a device. This may be called out of the mount path
  1312	 * and we are not allowed to call set_blocksize during the scan. The superblock
  1313	 * is read via pagecache
  1314	 */
  1315	struct btrfs_device *btrfs_scan_one_device(const char *path, fmode_t flags,
  1316						   void *holder)
  1317	{
  1318		struct btrfs_super_block *disk_super;
  1319		bool new_device_added = false;
  1320		struct btrfs_device *device = NULL;
  1321		struct block_device *bdev;
  1322		u64 bytenr;
  1323	
  1324		lockdep_assert_held(&uuid_mutex);
  1325	
  1326		/*
  1327		 * we would like to check all the supers, but that would make
  1328		 * a btrfs mount succeed after a mkfs from a different FS.
  1329		 * So, we need to add a special mount option to scan for
  1330		 * later supers, using BTRFS_SUPER_MIRROR_MAX instead
  1331		 */
  1332		bytenr = btrfs_sb_offset(0);
  1333		flags |= FMODE_EXCL;
  1334	
  1335		bdev = blkdev_get_by_path(path, flags, holder);
  1336		if (IS_ERR(bdev))
  1337			return ERR_CAST(bdev);
  1338	
  1339		disk_super = btrfs_read_disk_super(bdev, bytenr);
  1340		if (IS_ERR(disk_super)) {
> 1341			device = disk_super;
  1342			goto error_bdev_put;
  1343		}
  1344	
  1345		device = device_list_add(path, disk_super, &new_device_added);
  1346		if (!IS_ERR(device)) {
  1347			if (new_device_added)
  1348				btrfs_free_stale_devices(path, device);
  1349		}
  1350	
  1351		btrfs_release_disk_super(disk_super);
  1352	
  1353	error_bdev_put:
  1354		blkdev_put(bdev, flags);
  1355	
  1356		return device;
  1357	}
  1358	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 54657 bytes --]

Re: [PATCH v2] btrfs: Make btrfs_read_disk_super return struct btrfs_disk_super

[kbuild test robot]

[-- Attachment #1: Type: text/plain, Size: 3307 bytes --]

Hi Nikolay,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on v5.7-rc1]
[also build test ERROR on next-20200416]
[cannot apply to btrfs/next]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Nikolay-Borisov/btrfs-Make-btrfs_read_disk_super-return-struct-btrfs_disk_super/20200416-230011
base:    8f3d9f354286745c751374f5f1fcafee6b3f3136
config: sh-allmodconfig (attached as .config)
compiler: sh4-linux-gcc (GCC) 9.3.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day GCC_VERSION=9.3.0 make.cross ARCH=sh 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kbuild test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   fs/btrfs/volumes.c: In function 'btrfs_scan_one_device':
>> fs/btrfs/volumes.c:1341:10: error: assignment to 'struct btrfs_device *' from incompatible pointer type 'struct btrfs_super_block *' [-Werror=incompatible-pointer-types]
    1341 |   device = disk_super;
         |          ^
   cc1: some warnings being treated as errors

vim +1341 fs/btrfs/volumes.c

  1309	
  1310	/*
  1311	 * Look for a btrfs signature on a device. This may be called out of the mount path
  1312	 * and we are not allowed to call set_blocksize during the scan. The superblock
  1313	 * is read via pagecache
  1314	 */
  1315	struct btrfs_device *btrfs_scan_one_device(const char *path, fmode_t flags,
  1316						   void *holder)
  1317	{
  1318		struct btrfs_super_block *disk_super;
  1319		bool new_device_added = false;
  1320		struct btrfs_device *device = NULL;
  1321		struct block_device *bdev;
  1322		u64 bytenr;
  1323	
  1324		lockdep_assert_held(&uuid_mutex);
  1325	
  1326		/*
  1327		 * we would like to check all the supers, but that would make
  1328		 * a btrfs mount succeed after a mkfs from a different FS.
  1329		 * So, we need to add a special mount option to scan for
  1330		 * later supers, using BTRFS_SUPER_MIRROR_MAX instead
  1331		 */
  1332		bytenr = btrfs_sb_offset(0);
  1333		flags |= FMODE_EXCL;
  1334	
  1335		bdev = blkdev_get_by_path(path, flags, holder);
  1336		if (IS_ERR(bdev))
  1337			return ERR_CAST(bdev);
  1338	
  1339		disk_super = btrfs_read_disk_super(bdev, bytenr);
  1340		if (IS_ERR(disk_super)) {
> 1341			device = disk_super;
  1342			goto error_bdev_put;
  1343		}
  1344	
  1345		device = device_list_add(path, disk_super, &new_device_added);
  1346		if (!IS_ERR(device)) {
  1347			if (new_device_added)
  1348				btrfs_free_stale_devices(path, device);
  1349		}
  1350	
  1351		btrfs_release_disk_super(disk_super);
  1352	
  1353	error_bdev_put:
  1354		blkdev_put(bdev, flags);
  1355	
  1356		return device;
  1357	}
  1358	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org

[-- Attachment #2: config.gz --]
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