ext4: fix LOGFLUSH shutdown ordering to allow ordered-mode data writeback

In EXT4_GOING_FLAGS_LOGFLUSH mode, the EXT4_FLAGS_SHUTDOWN flag was set
before calling ext4_force_commit().  This caused ordered-mode data
writeback (triggered by journal commit) to fail with -EIO, since
ext4_do_writepages() checks for the shutdown flag.  The journal would
then be aborted prematurely before the commit could succeed.

Fix this by calling ext4_force_commit() first, then setting the
shutdown flag, so that pending data can be written back correctly.

Note that moving ext4_force_commit() before setting the shutdown flag
creates a small window in which new writes may occur and generate new
journal transactions.  When the journal is subsequently aborted, the
new transactions will not be able to write to disk.  This is intentional
because LOGFLUSH's semantics are to flush pre-existing journal entries
before shutdown, not to guarantee atomicity for writes that race with
the ioctl.

Fixes: 783d94854499 ("ext4: add EXT4_IOC_GOINGDOWN ioctl")
Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Baokun Li <libaokun@linux.alibaba.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20260424104201.1930823-1-yi.zhang@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index 1d0c3d4bdf472715a7070b184fdc7d9bf5885950..110e3fb194ec6bb6ef4c0038e0eb5750f7427d52 100644 (file)
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -830,11 +830,17 @@ int ext4_force_shutdown(struct super_block *sb, u32 flags)
                bdev_thaw(sb->s_bdev);
                break;
        case EXT4_GOING_FLAGS_LOGFLUSH:
+               /*
+                * Call ext4_force_commit() before setting EXT4_FLAGS_SHUTDOWN.
+                * This is because in data=ordered mode, journal commit
+                * triggers data writeback which fails if shutdown is already
+                * set, causing the journal to be aborted prematurely before
+                * the commit succeeds.
+                */
+               (void) ext4_force_commit(sb);
                set_bit(EXT4_FLAGS_SHUTDOWN, &sbi->s_ext4_flags);
-               if (sbi->s_journal && !is_journal_aborted(sbi->s_journal)) {
-                       (void) ext4_force_commit(sb);
+               if (sbi->s_journal && !is_journal_aborted(sbi->s_journal))
                        jbd2_journal_abort(sbi->s_journal, -ESHUTDOWN);
-               }
                break;
        case EXT4_GOING_FLAGS_NOLOGFLUSH:
                set_bit(EXT4_FLAGS_SHUTDOWN, &sbi->s_ext4_flags);