ext4: fix possible tid_t sequence overflows

In the fast commit code there are a few places where tid_t variables are
being compared without taking into account the fact that these sequence
numbers may wrap.  Fix this issue by using the helper functions tid_gt()
and tid_geq().

Signed-off-by: Luis Henriques (SUSE) <luis.henriques@linux.dev>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Harshad Shirwadkar <harshadshirwadkar@gmail.com>
Link: https://patch.msgid.link/20240529092030.9557-3-luis.henriques@linux.dev
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/ext4/fast_commit.c b/fs/ext4/fast_commit.c
index 87c009e0c59a5d7f352a1f6a437b59c496145fb2..f53a02bc0c3323f52ea623c50c505d88420cb3d1 100644 (file)
--- a/fs/ext4/fast_commit.c
+++ b/fs/ext4/fast_commit.c
@@ -353,7 +353,7 @@ void ext4_fc_mark_ineligible(struct super_block *sb, int reason, handle_t *handl
                read_unlock(&sbi->s_journal->j_state_lock);
        }
        spin_lock(&sbi->s_fc_lock);
-       if (sbi->s_fc_ineligible_tid < tid)
+       if (tid_gt(tid, sbi->s_fc_ineligible_tid))
                sbi->s_fc_ineligible_tid = tid;
        spin_unlock(&sbi->s_fc_lock);
        WARN_ON(reason >= EXT4_FC_REASON_MAX);
@@ -1207,7 +1207,7 @@ restart_fc:
        if (ret == -EALREADY) {
                /* There was an ongoing commit, check if we need to restart */
                if (atomic_read(&sbi->s_fc_subtid) <= subtid &&
-                       commit_tid > journal->j_commit_sequence)
+                   tid_gt(commit_tid, journal->j_commit_sequence))
                        goto restart_fc;
                ext4_fc_update_stats(sb, EXT4_FC_STATUS_SKIPPED, 0, 0,
                                commit_tid);
@@ -1282,7 +1282,7 @@ static void ext4_fc_cleanup(journal_t *journal, int full, tid_t tid)
                list_del_init(&iter->i_fc_list);
                ext4_clear_inode_state(&iter->vfs_inode,
                                       EXT4_STATE_FC_COMMITTING);
-               if (iter->i_sync_tid <= tid)
+               if (tid_geq(tid, iter->i_sync_tid))
                        ext4_fc_reset_inode(&iter->vfs_inode);
                /* Make sure EXT4_STATE_FC_COMMITTING bit is clear */
                smp_mb();
@@ -1313,7 +1313,7 @@ static void ext4_fc_cleanup(journal_t *journal, int full, tid_t tid)
        list_splice_init(&sbi->s_fc_q[FC_Q_STAGING],
                                &sbi->s_fc_q[FC_Q_MAIN]);
 
-       if (tid >= sbi->s_fc_ineligible_tid) {
+       if (tid_geq(tid, sbi->s_fc_ineligible_tid)) {
                sbi->s_fc_ineligible_tid = 0;
                ext4_clear_mount_flag(sb, EXT4_MF_FC_INELIGIBLE);
        }