linux-kernel - [PATCH v6 RESEND 2/2] buffer: record blockdev write errors in super

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Date:   Tue, 28 Apr 2020 09:51:55 -0400
From:   Jeff Layton <jlayton@...nel.org>
To:     viro@...iv.linux.org.uk, akpm@...ux-foundation.org
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-api@...r.kernel.org, andres@...razel.de, willy@...radead.org,
        dhowells@...hat.com, hch@...radead.org, jack@...e.cz,
        david@...morbit.com
Subject: [PATCH v6 RESEND 2/2] buffer: record blockdev write errors in super_block that it backs

From: Jeff Layton <jlayton@...hat.com>

When syncing out a block device (a'la __sync_blockdev), any error
encountered will only be recorded in the bd_inode's mapping. When the
blockdev contains a filesystem however, we'd like to also record the
error in the super_block that's stored there.

Make mark_buffer_write_io_error also record the error in the
corresponding super_block when a writeback error occurs and the block
device contains a mounted superblock.

Since superblocks are RCU freed, hold the rcu_read_lock to ensure
that the superblock doesn't go away while we're marking it.

Reviewed-by: Jan Kara <jack@...e.cz>
Signed-off-by: Jeff Layton <jlayton@...nel.org>
---
 fs/buffer.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/buffer.c b/fs/buffer.c
index f73276d746bb..71be7e6cabca 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1154,12 +1154,19 @@ 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_page && bh->b_page->mapping)
 		mapping_set_error(bh->b_page->mapping, -EIO);
 	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();
 }
 EXPORT_SYMBOL(mark_buffer_write_io_error);
 
-- 
2.26.1