linux-kernel - [PATCH RFC v3 for-6.8/block 16/17] ext4: remove block_device

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Message-Id: <20231221085907.1772856-1-yukuai1@huaweicloud.com>
Date: Thu, 21 Dec 2023 16:59:07 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
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Subject: [PATCH RFC v3 for-6.8/block 16/17] ext4: remove block_device_ejected()

From: Yu Kuai <yukuai3@...wei.com>

block_device_ejected() is added by commit bdfe0cbd746a ("Revert
"ext4: remove block_device_ejected"") in 2015. At that time 'bdi->wb'
is destroyed synchronized from del_gendisk(), hence if ext4 is still
mounted, and then mark_buffer_dirty() will reference destroyed 'wb'.
However, such problem doesn't exist anymore:

- commit d03f6cdc1fc4 ("block: Dynamically allocate and refcount
backing_dev_info") switch bdi to use refcounting;
- commit 13eec2363ef0 ("fs: Get proper reference for s_bdi"), will grab
additional reference of bdi while mounting, so that 'bdi->wb' will not
be destroyed until generic_shutdown_super().

Hence remove this dead function block_device_ejected().

Signed-off-by: Yu Kuai <yukuai3@...wei.com>
Reviewed-by: Jan Kara <jack@...e.cz>
Reviewed-by: Christoph Hellwig <hch@....de>
---
 fs/ext4/super.c | 18 ------------------
 1 file changed, 18 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 3f07eaa33332..a7935edbd7b1 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -467,22 +467,6 @@ static void ext4_maybe_update_superblock(struct super_block *sb)
 		schedule_work(&EXT4_SB(sb)->s_sb_upd_work);
 }
 
-/*
- * The del_gendisk() function uninitializes the disk-specific data
- * structures, including the bdi structure, without telling anyone
- * else.  Once this happens, any attempt to call mark_buffer_dirty()
- * (for example, by ext4_commit_super), will cause a kernel OOPS.
- * This is a kludge to prevent these oops until we can put in a proper
- * hook in del_gendisk() to inform the VFS and file system layers.
- */
-static int block_device_ejected(struct super_block *sb)
-{
-	struct inode *bd_inode = sb->s_bdev->bd_inode;
-	struct backing_dev_info *bdi = inode_to_bdi(bd_inode);
-
-	return bdi->dev == NULL;
-}
-
 static void ext4_journal_commit_callback(journal_t *journal, transaction_t *txn)
 {
 	struct super_block		*sb = journal->j_private;
@@ -6162,8 +6146,6 @@ static int ext4_commit_super(struct super_block *sb)
 
 	if (!sbh)
 		return -EINVAL;
-	if (block_device_ejected(sb))
-		return -ENODEV;
 
 	ext4_update_super(sb);
 
-- 
2.39.2