[PATCH AUTOSEL 6.1 14/35] btrfs: factor out scratching of one regular super block

[PATCH AUTOSEL 6.1 14/35] btrfs: factor out scratching of one regular super block

[Sasha Levin]

From: Christoph Hellwig <hch@lst.de>

[ Upstream commit 0e0078f72be81bbb2a02b229fd2cec8ad63e4fb1 ]

btrfs_scratch_superblocks open codes scratching super block of a
non-zoned super block.  Split the code to read, zero and write the
superblock for regular devices into a separate helper.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
[ update changelog ]
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/btrfs/volumes.c | 51 +++++++++++++++++++++++-----------------------
 1 file changed, 26 insertions(+), 25 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index dba087ad40ea..8fd14dc7f667 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2017,42 +2017,43 @@ static u64 btrfs_num_devices(struct btrfs_fs_info *fs_info)
 	return num_devices;
 }
 
+static void btrfs_scratch_superblock(struct btrfs_fs_info *fs_info,
+				     struct block_device *bdev, int copy_num)
+{
+	struct btrfs_super_block *disk_super;
+	struct page *page;
+	int ret;
+
+	disk_super = btrfs_read_dev_one_super(bdev, copy_num, false);
+	if (IS_ERR(disk_super))
+		return;
+
+	memset(&disk_super->magic, 0, sizeof(disk_super->magic));
+	page = virt_to_page(disk_super);
+	set_page_dirty(page);
+	lock_page(page);
+	/* write_on_page() unlocks the page */
+	ret = write_one_page(page);
+	if (ret)
+		btrfs_warn(fs_info, "error clearing superblock number %d (%d)",
+			copy_num, ret);
+	btrfs_release_disk_super(disk_super);
+}
+
 void btrfs_scratch_superblocks(struct btrfs_fs_info *fs_info,
 			       struct block_device *bdev,
 			       const char *device_path)
 {
-	struct btrfs_super_block *disk_super;
 	int copy_num;
 
 	if (!bdev)
 		return;
 
 	for (copy_num = 0; copy_num < BTRFS_SUPER_MIRROR_MAX; copy_num++) {
-		struct page *page;
-		int ret;
-
-		disk_super = btrfs_read_dev_one_super(bdev, copy_num, false);
-		if (IS_ERR(disk_super))
-			continue;
-
-		if (bdev_is_zoned(bdev)) {
+		if (bdev_is_zoned(bdev))
 			btrfs_reset_sb_log_zones(bdev, copy_num);
-			continue;
-		}
-
-		memset(&disk_super->magic, 0, sizeof(disk_super->magic));
-
-		page = virt_to_page(disk_super);
-		set_page_dirty(page);
-		lock_page(page);
-		/* write_on_page() unlocks the page */
-		ret = write_one_page(page);
-		if (ret)
-			btrfs_warn(fs_info,
-				"error clearing superblock number %d (%d)",
-				copy_num, ret);
-		btrfs_release_disk_super(disk_super);
-
+		else
+			btrfs_scratch_superblock(fs_info, bdev, copy_num);
 	}
 
 	/* Notify udev that device has changed */
-- 
2.39.0

[PATCH AUTOSEL 6.1 15/35] btrfs: stop using write_one_page in btrfs_scratch_superblock

[Sasha Levin]

From: Christoph Hellwig <hch@lst.de>

[ Upstream commit 26ecf243e407be54807ad67210f7e83b9fad71ea ]

write_one_page is an awkward interface that expects the page locked and
->writepage to be implemented.  Replace that by zeroing the signature
bytes and synchronize the block device page using the proper bdev
helpers.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
[ update changelog ]
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/btrfs/volumes.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 8fd14dc7f667..36bb664a25a2 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2021,23 +2021,22 @@ static void btrfs_scratch_superblock(struct btrfs_fs_info *fs_info,
 				     struct block_device *bdev, int copy_num)
 {
 	struct btrfs_super_block *disk_super;
-	struct page *page;
+	const size_t len = sizeof(disk_super->magic);
+	const u64 bytenr = btrfs_sb_offset(copy_num);
 	int ret;
 
-	disk_super = btrfs_read_dev_one_super(bdev, copy_num, false);
+	disk_super = btrfs_read_disk_super(bdev, bytenr, bytenr);
 	if (IS_ERR(disk_super))
 		return;
 
-	memset(&disk_super->magic, 0, sizeof(disk_super->magic));
-	page = virt_to_page(disk_super);
-	set_page_dirty(page);
-	lock_page(page);
-	/* write_on_page() unlocks the page */
-	ret = write_one_page(page);
+	memset(&disk_super->magic, 0, len);
+	folio_mark_dirty(virt_to_folio(disk_super));
+	btrfs_release_disk_super(disk_super);
+
+	ret = sync_blockdev_range(bdev, bytenr, bytenr + len - 1);
 	if (ret)
 		btrfs_warn(fs_info, "error clearing superblock number %d (%d)",
 			copy_num, ret);
-	btrfs_release_disk_super(disk_super);
 }
 
 void btrfs_scratch_superblocks(struct btrfs_fs_info *fs_info,
-- 
2.39.0

Re: [PATCH AUTOSEL 6.1 15/35] btrfs: stop using write_one_page in btrfs_scratch_superblock

[David Sterba]

On Tue, Jan 24, 2023 at 08:41:11AM -0500, Sasha Levin wrote:
> From: Christoph Hellwig <hch@lst.de>
> 
> [ Upstream commit 26ecf243e407be54807ad67210f7e83b9fad71ea ]
> 
> write_one_page is an awkward interface that expects the page locked and
> ->writepage to be implemented.  Replace that by zeroing the signature
> bytes and synchronize the block device page using the proper bdev
> helpers.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> Reviewed-by: David Sterba <dsterba@suse.com>
> [ update changelog ]
> Signed-off-by: David Sterba <dsterba@suse.com>
> Signed-off-by: Sasha Levin <sashal@kernel.org>

Please drop this patch and "btrfs: factor out scratching of one regular
super block" from all stable queues. It's not a fix, only preparatory
work to allow removing write_one_page from MM code.

Commit ids: 0e0078f72be81bbb and 26ecf243e407be54

Re: [PATCH AUTOSEL 6.1 15/35] btrfs: stop using write_one_page in btrfs_scratch_superblock

[Sasha Levin]

On Tue, Jan 24, 2023 at 05:57:16PM +0100, David Sterba wrote:
>On Tue, Jan 24, 2023 at 08:41:11AM -0500, Sasha Levin wrote:
>> From: Christoph Hellwig <hch@lst.de>
>>
>> [ Upstream commit 26ecf243e407be54807ad67210f7e83b9fad71ea ]
>>
>> write_one_page is an awkward interface that expects the page locked and
>> ->writepage to be implemented.  Replace that by zeroing the signature
>> bytes and synchronize the block device page using the proper bdev
>> helpers.
>>
>> Signed-off-by: Christoph Hellwig <hch@lst.de>
>> Reviewed-by: David Sterba <dsterba@suse.com>
>> [ update changelog ]
>> Signed-off-by: David Sterba <dsterba@suse.com>
>> Signed-off-by: Sasha Levin <sashal@kernel.org>
>
>Please drop this patch and "btrfs: factor out scratching of one regular
>super block" from all stable queues. It's not a fix, only preparatory
>work to allow removing write_one_page from MM code.
>
>Commit ids: 0e0078f72be81bbb and 26ecf243e407be54

Ack, dropped.

-- 
Thanks,
Sasha