From 89b4336fd5ec78f51f9d3a1d100f3ffa3228e604 Mon Sep 17 00:00:00 2001 From: Li Chen Date: Thu, 11 Dec 2025 19:51:41 +0800 Subject: [PATCH] ext4: mark group add fast-commit ineligible Fast commits only log operations that have dedicated replay support. Online resize via EXT4_IOC_GROUP_ADD updates the superblock and group descriptor metadata without going through the fast commit tracking paths. In practice these operations are rare and usually followed by further updates, but mixing them into a fast commit makes the overall semantics harder to reason about and risks replay gaps if new call sites appear. Teach ext4 to mark the filesystem fast-commit ineligible when ext4_ioctl_group_add() adds new block groups. This forces those transactions to fall back to a full commit, ensuring that the filesystem geometry updates are captured by the normal journal rather than partially encoded in fast commit TLVs. This change should not affect common workloads but makes online resize via GROUP_ADD safer and easier to reason about under fast commit. Testing: 1. prepare: dd if=/dev/zero of=/root/fc_resize.img bs=1M count=0 seek=256 mkfs.ext4 -O fast_commit -F /root/fc_resize.img mkdir -p /mnt/fc_resize && mount -t ext4 -o loop /root/fc_resize.img /mnt/fc_resize 2. Ran a helper that issues EXT4_IOC_GROUP_ADD on the mounted filesystem and checked the resize ineligible reason: ./group_add_helper /mnt/fc_resize cat /proc/fs/ext4/loop0/fc_info shows "Resize": > 0. 3. Fsynced a file on the resized filesystem and verified that the fast commit stats report at least one ineligible commit: touch /mnt/fc_resize/file /root/fsync_file /mnt/fc_resize/file sync cat /proc/fs/ext4/loop0/fc_info shows fc stats ineligible > 0. Signed-off-by: Li Chen Link: https://patch.msgid.link/20251211115146.897420-5-me@linux.beauty Signed-off-by: Theodore Ts'o --- fs/ext4/ioctl.c | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c index 7ce0fc40aec2f..5109b005e0286 100644 --- a/fs/ext4/ioctl.c +++ b/fs/ext4/ioctl.c @@ -966,6 +966,7 @@ static long ext4_ioctl_group_add(struct file *file, err = ext4_group_add(sb, input); if (EXT4_SB(sb)->s_journal) { + ext4_fc_mark_ineligible(sb, EXT4_FC_REASON_RESIZE, NULL); jbd2_journal_lock_updates(EXT4_SB(sb)->s_journal); err2 = jbd2_journal_flush(EXT4_SB(sb)->s_journal, 0); jbd2_journal_unlock_updates(EXT4_SB(sb)->s_journal); -- 2.47.3