ext4: fix incorrect tid assumption in jbd2_journal_shrink_checkpoint_list()

Function jbd2_journal_shrink_checkpoint_list() assumes that '0' is not a
valid value for transaction IDs, which is incorrect.  Don't assume that and
use two extra boolean variables to control the loop iterations and keep
track of the first and last tid.

Signed-off-by: Luis Henriques (SUSE) <luis.henriques@linux.dev>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20240724161119.13448-4-luis.henriques@linux.dev
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org

diff --git a/fs/jbd2/checkpoint.c b/fs/jbd2/checkpoint.c
index bd34083d5fa2fe582d925777f4eefdb60a1055cf..b3971e91e8eb8059178b9994a27fc62d101f9efe 100644 (file)
--- a/fs/jbd2/checkpoint.c
+++ b/fs/jbd2/checkpoint.c
@@ -413,6 +413,7 @@ unsigned long jbd2_journal_shrink_checkpoint_list(journal_t *journal,
        tid_t tid = 0;
        unsigned long nr_freed = 0;
        unsigned long freed;
+       bool first_set = false;
 
 again:
        spin_lock(&journal->j_list_lock);
@@ -432,8 +433,10 @@ again:
        else
                transaction = journal->j_checkpoint_transactions;
 
-       if (!first_tid)
+       if (!first_set) {
                first_tid = transaction->t_tid;
+               first_set = true;
+       }
        last_transaction = journal->j_checkpoint_transactions->t_cpprev;
        next_transaction = transaction;
        last_tid = last_transaction->t_tid;
@@ -463,7 +466,7 @@ again:
        spin_unlock(&journal->j_list_lock);
        cond_resched();
 
-       if (*nr_to_scan && next_tid)
+       if (*nr_to_scan && journal->j_shrink_transaction)
                goto again;
 out:
        trace_jbd2_shrink_checkpoint_list(journal, first_tid, tid, last_tid,