[PATCH v6 2/2] buffer: record blockdev write errors in super_block that it backs

From: Jeff Layton
Date: Thu Apr 16 2020 - 07:35:39 EST


From: Jeff Layton <jlayton@xxxxxxxxxx>

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.

Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
---
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);

--
2.25.2