linux-ext4 - [PATCH 1/4] fs: stop using bdev->bd_super in mark_buffer_write_io

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Date:   Mon,  7 Aug 2023 12:26:22 +0100
From:   Christoph Hellwig <hch@....de>
To:     Al Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>
Cc:     "Theodore Ts'o" <tytso@....edu>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Mark Fasheh <mark@...heh.com>,
        Joel Becker <jlbec@...lplan.org>,
        Joseph Qi <joseph.qi@...ux.alibaba.com>,
        Jens Axboe <axboe@...nel.dk>, linux-fsdevel@...r.kernel.org,
        linux-ext4@...r.kernel.org, ocfs2-devel@...ts.linux.dev,
        linux-block@...r.kernel.org
Subject: [PATCH 1/4] fs: stop using bdev->bd_super in mark_buffer_write_io_error

bdev->bd_super is a somewhat awkward backpointer from a block device to
an owning file system with unclear rules.

For the buffer_head code we already have a good backpointer for the
inode that the buffer_head is associated with, even if it lives on the
block device mapping: b_assoc_map. It is used track dirty buffers
associated with an inode but living on the block device mapping like
directory buffers in ext4.

mark_buffer_write_io_error already uses it for the call to
mapping_set_error, and should be doing the same for the per-sb error
sequence.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 fs/buffer.c | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index bd091329026c0f..f36ef03c078af6 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1225,19 +1225,14 @@ EXPORT_SYMBOL(mark_buffer_dirty);
 
 void mark_buffer_write_io_error(struct buffer_head *bh)
 {
-	struct super_block *sb;
-
 	set_buffer_write_io_error(bh);
 	/* FIXME: do we need to set this in both places? */
 	if (bh->b_folio && bh->b_folio->mapping)
 		mapping_set_error(bh->b_folio->mapping, -EIO);
-	if (bh->b_assoc_map)
+	if (bh->b_assoc_map) {
 		mapping_set_error(bh->b_assoc_map, -EIO);
-	rcu_read_lock();
-	sb = READ_ONCE(bh->b_bdev->bd_super);
-	if (sb)
-		errseq_set(&sb->s_wb_err, -EIO);
-	rcu_read_unlock();
+		errseq_set(&bh->b_assoc_map->host->i_sb->s_wb_err, -EIO);
+	}
 }
 EXPORT_SYMBOL(mark_buffer_write_io_error);
 
-- 
2.39.2