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Subject[PATCH AUTOSEL 5.12 38/43] ext4: fix WARN_ON_ONCE(!buffer_uptodate) after an error writing the superblock
Date
From: Ye Bin <yebin10@huawei.com>

[ Upstream commit 558d6450c7755aa005d89021204b6cdcae5e848f ]

If a writeback of the superblock fails with an I/O error, the buffer
is marked not uptodate. However, this can cause a WARN_ON to trigger
when we attempt to write superblock a second time. (Which might
succeed this time, for cerrtain types of block devices such as iSCSI
devices over a flaky network.)

Try to detect this case in flush_stashed_error_work(), and also change
__ext4_handle_dirty_metadata() so we always set the uptodate flag, not
just in the nojournal case.

Before this commit, this problem can be repliciated via:

1. dmsetup create dust1 --table '0 2097152 dust /dev/sdc 0 4096'
2. mount /dev/mapper/dust1 /home/test
3. dmsetup message dust1 0 addbadblock 0 10
4. cd /home/test
5. echo "XXXXXXX" > t

After a few seconds, we got following warning:

[ 80.654487] end_buffer_async_write: bh=0xffff88842f18bdd0
[ 80.656134] Buffer I/O error on dev dm-0, logical block 0, lost async page write
[ 85.774450] EXT4-fs error (device dm-0): ext4_check_bdev_write_error:193: comm kworker/u16:8: Error while async write back metadata
[ 91.415513] mark_buffer_dirty: bh=0xffff88842f18bdd0
[ 91.417038] ------------[ cut here ]------------
[ 91.418450] WARNING: CPU: 1 PID: 1944 at fs/buffer.c:1092 mark_buffer_dirty.cold+0x1c/0x5e
[ 91.440322] Call Trace:
[ 91.440652] __jbd2_journal_temp_unlink_buffer+0x135/0x220
[ 91.441354] __jbd2_journal_unfile_buffer+0x24/0x90
[ 91.441981] __jbd2_journal_refile_buffer+0x134/0x1d0
[ 91.442628] jbd2_journal_commit_transaction+0x249a/0x3240
[ 91.443336] ? put_prev_entity+0x2a/0x200
[ 91.443856] ? kjournald2+0x12e/0x510
[ 91.444324] kjournald2+0x12e/0x510
[ 91.444773] ? woken_wake_function+0x30/0x30
[ 91.445326] kthread+0x150/0x1b0
[ 91.445739] ? commit_timeout+0x20/0x20
[ 91.446258] ? kthread_flush_worker+0xb0/0xb0
[ 91.446818] ret_from_fork+0x1f/0x30
[ 91.447293] ---[ end trace 66f0b6bf3d1abade ]---

Signed-off-by: Ye Bin <yebin10@huawei.com>
Link: https://lore.kernel.org/r/20210615090537.3423231-1-yebin10@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/ext4/ext4_jbd2.c | 2 +-
fs/ext4/super.c | 12 ++++++++++--
2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/fs/ext4/ext4_jbd2.c b/fs/ext4/ext4_jbd2.c
index be799040a415..b96ecba91899 100644
--- a/fs/ext4/ext4_jbd2.c
+++ b/fs/ext4/ext4_jbd2.c
@@ -327,6 +327,7 @@ int __ext4_handle_dirty_metadata(const char *where, unsigned int line,

set_buffer_meta(bh);
set_buffer_prio(bh);
+ set_buffer_uptodate(bh);
if (ext4_handle_valid(handle)) {
err = jbd2_journal_dirty_metadata(handle, bh);
/* Errors can only happen due to aborted journal or a nasty bug */
@@ -355,7 +356,6 @@ int __ext4_handle_dirty_metadata(const char *where, unsigned int line,
err);
}
} else {
- set_buffer_uptodate(bh);
if (inode)
mark_buffer_dirty_inode(bh, inode);
else
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 0e3a847b5d27..67fb3cb34c6f 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -705,15 +705,23 @@ static void flush_stashed_error_work(struct work_struct *work)
* ext4 error handling code during handling of previous errors.
*/
if (!sb_rdonly(sbi->s_sb) && journal) {
+ struct buffer_head *sbh = sbi->s_sbh;
handle = jbd2_journal_start(journal, 1);
if (IS_ERR(handle))
goto write_directly;
- if (jbd2_journal_get_write_access(handle, sbi->s_sbh)) {
+ if (jbd2_journal_get_write_access(handle, sbh)) {
jbd2_journal_stop(handle);
goto write_directly;
}
ext4_update_super(sbi->s_sb);
- if (jbd2_journal_dirty_metadata(handle, sbi->s_sbh)) {
+ if (buffer_write_io_error(sbh) || !buffer_uptodate(sbh)) {
+ ext4_msg(sbi->s_sb, KERN_ERR, "previous I/O error to "
+ "superblock detected");
+ clear_buffer_write_io_error(sbh);
+ set_buffer_uptodate(sbh);
+ }
+
+ if (jbd2_journal_dirty_metadata(handle, sbh)) {
jbd2_journal_stop(handle);
goto write_directly;
}
--
2.30.2
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