在 2023/9/12 0:18, Jan Kara 写道:
Hello!
On Sat 09-09-23 11:41:11, Zhang Yi wrote:
On 2023/9/8 20:43, Zhihao Cheng wrote:
JBD2 makes sure journal data is fallen on fs device by sync_blockdev(),
however, other process could intercept the EIO information from bdev's
mapping, which leads journal recovering successful even EIO occurs during
data written back to fs device.
We found this problem in our product, iscsi + multipath is chosen for block
device of ext4. Unstable network may trigger kpartx to rescan partitions in
device mapper layer. Detailed process is shown as following:
mount kpartx irq
jbd2_journal_recover
do_one_pass
memcpy(nbh->b_data, obh->b_data) // copy data to fs dev from journal
mark_buffer_dirty // mark bh dirty
vfs_read
generic_file_read_iter // dio
filemap_write_and_wait_range
__filemap_fdatawrite_range
do_writepages
block_write_full_folio
submit_bh_wbc
>> EIO occurs in disk <<
end_buffer_async_write
mark_buffer_write_io_error
mapping_set_error
set_bit(AS_EIO, &mapping->flags) // set!
filemap_check_errors
test_and_clear_bit(AS_EIO, &mapping->flags) // clear!
err2 = sync_blockdev
filemap_write_and_wait
filemap_check_errors
test_and_clear_bit(AS_EIO, &mapping->flags) // false
err2 = 0
Filesystem is mounted successfully even data from journal is failed written
into disk, and ext4 could become corrupted.
Fix it by comparing 'sbi->s_bdev_wb_err' before loading journal and after
loading journal.
Fetch a reproducer in [Link].
Link: https://bugzilla.kernel.org/show_bug.cgi?id=217888
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Zhihao Cheng <chengzhihao1@xxxxxxxxxx>
Signed-off-by: Zhang Yi <yi.zhang@xxxxxxxxxx>
---
v1->v2: Checks wb_err from block device only in ext4.
fs/ext4/super.c | 22 +++++++++++++++-------
1 file changed, 15 insertions(+), 7 deletions(-)
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 38217422f938..4dcaad2403be 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -4907,6 +4907,14 @@ static int ext4_load_and_init_journal(struct super_block *sb,
if (err)
return err;
+ err = errseq_check_and_advance(&sb->s_bdev->bd_inode->i_mapping->wb_err,
+ &sbi->s_bdev_wb_err);
+ if (err) {
+ ext4_msg(sb, KERN_ERR, "Background error %d when loading journal",
+ err);
+ goto out;
+ }
+
This solution cannot solve the problem, because the journal tail is
still updated in journal_reset() even if we detect the writeback error
and refuse to mount the ext4 filesystem here. So I suppose we have to
check the I/O error by jbd2 module itself like v1 does.
Hum, that's a good point because next time we will try to mount the fs we
will not try to replay the journal anymore. So let's return to v1 and I'm
sorry for misguiding you Zhihao.
But when we are doing background IO error detection in jbd2 during journal
replay, I'm wondering whether we shouldn't be doing something similar in
checkpointing code - like when we are about to remove a transaction from
the journal. And as I'm checking we already do that using
JBD2_CHECKPOINT_IO_ERROR bit handling - maybe we could replace that with a
more standard errseq mechanism that is available these days as a cleanup?
> And the ext4 handling in ext4_check_bdev_write_error() is useful only in
nojournal mode as otherwise jbd2 is taking care of all writeback errors
including the background ones. So maybe we can guard the
ext4_check_bdev_write_error() by a !ext4_handle_valid(handle) check to make
that obvious (and comment about that). >
What do you think?
Honza
Ok, I will try it. Thanks for suggestions.
