ext4: protect ext4_release_dquot against freezing

Protect ext4_release_dquot against freezing so that we
don't try to start a transaction when FS is frozen, leading
to warnings.

Further, avoid taking the freeze protection if a transaction
is already running so that we don't need end up in a deadlock
as described in

  46e294efc355 ext4: fix deadlock with fs freezing and EA inodes

Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Reviewed-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20241121123855.645335-3-ojaswin@linux.ibm.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index a963ffda692a74939309be721eebac1f62955570..7ba5ef80d502e6760311fa5bb34ec165345bdd7a 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -6920,12 +6920,25 @@ static int ext4_release_dquot(struct dquot *dquot)
 {
        int ret, err;
        handle_t *handle;
+       bool freeze_protected = false;
+
+       /*
+        * Trying to sb_start_intwrite() in a running transaction
+        * can result in a deadlock. Further, running transactions
+        * are already protected from freezing.
+        */
+       if (!ext4_journal_current_handle()) {
+               sb_start_intwrite(dquot->dq_sb);
+               freeze_protected = true;
+       }
 
        handle = ext4_journal_start(dquot_to_inode(dquot), EXT4_HT_QUOTA,
                                    EXT4_QUOTA_DEL_BLOCKS(dquot->dq_sb));
        if (IS_ERR(handle)) {
                /* Release dquot anyway to avoid endless cycle in dqput() */
                dquot_release(dquot);
+               if (freeze_protected)
+                       sb_end_intwrite(dquot->dq_sb);
                return PTR_ERR(handle);
        }
        ret = dquot_release(dquot);
@@ -6936,6 +6949,10 @@ static int ext4_release_dquot(struct dquot *dquot)
        err = ext4_journal_stop(handle);
        if (!ret)
                ret = err;
+
+       if (freeze_protected)
+               sb_end_intwrite(dquot->dq_sb);
+
        return ret;
 }