1 files changed, 58 insertions, 16 deletions

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 056474b..8553dfb 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -242,27 +242,44 @@ static void ext4_put_nojournal(handle_t *handle)
  * journal_end calls result in the superblock being marked dirty, so
  * that sync() will call the filesystem's write_super callback if
  * appropriate.
+ *
+ * To avoid j_barrier hold in userspace when a user calls freeze(),
+ * ext4 prevents a new handle from being started by s_frozen, which
+ * is in an upper layer.
  */
 handle_t *ext4_journal_start_sb(struct super_block *sb, int nblocks)
 {
 	journal_t *journal;
+	handle_t  *handle;
 
 	if (sb->s_flags & MS_RDONLY)
 		return ERR_PTR(-EROFS);
 
-	vfs_check_frozen(sb, SB_FREEZE_TRANS);
-	/* Special case here: if the journal has aborted behind our
-	 * backs (eg. EIO in the commit thread), then we still need to
-	 * take the FS itself readonly cleanly. */
 	journal = EXT4_SB(sb)->s_journal;
-	if (journal) {
-		if (is_journal_aborted(journal)) {
-			ext4_abort(sb, "Detected aborted journal");
-			return ERR_PTR(-EROFS);
-		}
-		return jbd2_journal_start(journal, nblocks);
+	handle = ext4_journal_current_handle();
+
+	/*
+	 * If a handle has been started, it should be allowed to
+	 * finish, otherwise deadlock could happen between freeze
+	 * and others(e.g. truncate) due to the restart of the
+	 * journal handle if the filesystem is forzen and active
+	 * handles are not stopped.
+	 */
+	if (!handle)
+		vfs_check_frozen(sb, SB_FREEZE_TRANS);
+
+	if (!journal)
+		return ext4_get_nojournal();
+	/*
+	 * Special case here: if the journal has aborted behind our
+	 * backs (eg. EIO in the commit thread), then we still need to
+	 * take the FS itself readonly cleanly.
+	 */
+	if (is_journal_aborted(journal)) {
+		ext4_abort(sb, "Detected aborted journal");
+		return ERR_PTR(-EROFS);
 	}
-	return ext4_get_nojournal();
+	return jbd2_journal_start(journal, nblocks);
 }
 
 /*
@@ -2975,6 +2992,12 @@ static int ext4_register_li_request(struct super_block *sb,
 	mutex_unlock(&ext4_li_info->li_list_mtx);
 
 	sbi->s_li_request = elr;
+	/*
+	 * set elr to NULL here since it has been inserted to
+	 * the request_list and the removal and free of it is
+	 * handled by ext4_clear_request_list from now on.
+	 */
+	elr = NULL;
 
 	if (!(ext4_li_info->li_state & EXT4_LAZYINIT_RUNNING)) {
 		ret = ext4_run_lazyinit_thread();
@@ -3385,6 +3408,10 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 	get_random_bytes(&sbi->s_next_generation, sizeof(u32));
 	spin_lock_init(&sbi->s_next_gen_lock);
 
+	init_timer(&sbi->s_err_report);
+	sbi->s_err_report.function = print_daily_error_info;
+	sbi->s_err_report.data = (unsigned long) sb;
+
 	err = percpu_counter_init(&sbi->s_freeblocks_counter,
 			ext4_count_free_blocks(sb));
 	if (!err) {
@@ -3646,9 +3673,6 @@ no_journal:
 		 "Opts: %s%s%s", descr, sbi->s_es->s_mount_opts,
 		 *sbi->s_es->s_mount_opts ? "; " : "", orig_data);
 
-	init_timer(&sbi->s_err_report);
-	sbi->s_err_report.function = print_daily_error_info;
-	sbi->s_err_report.data = (unsigned long) sb;
 	if (es->s_error_count)
 		mod_timer(&sbi->s_err_report, jiffies + 300*HZ); /* 5 minutes */
 
@@ -3672,6 +3696,7 @@ failed_mount_wq:
 		sbi->s_journal = NULL;
 	}
 failed_mount3:
+	del_timer(&sbi->s_err_report);
 	if (sbi->s_flex_groups) {
 		if (is_vmalloc_addr(sbi->s_flex_groups))
 			vfree(sbi->s_flex_groups);
@@ -4138,6 +4163,11 @@ static int ext4_sync_fs(struct super_block *sb, int wait)
 /*
  * LVM calls this function before a (read-only) snapshot is created.  This
  * gives us a chance to flush the journal completely and mark the fs clean.
+ *
+ * Note that only this function cannot bring a filesystem to be in a clean
+ * state independently, because ext4 prevents a new handle from being started
+ * by @sb->s_frozen, which stays in an upper layer.  It thus needs help from
+ * the upper layer.
  */
 static int ext4_freeze(struct super_block *sb)
 {
@@ -4614,11 +4644,24 @@ static int ext4_quota_on(struct super_block *sb, int type, int format_id,
 
 static int ext4_quota_off(struct super_block *sb, int type)
 {
+	struct inode *inode = sb_dqopt(sb)->files[type];
+	handle_t *handle;
+
 	/* Force all delayed allocation blocks to be allocated.
 	 * Caller already holds s_umount sem */
 	if (test_opt(sb, DELALLOC))
 		sync_filesystem(sb);
 
+	/* Update modification times of quota files when userspace can
+	 * start looking at them */
+	handle = ext4_journal_start(inode, 1);
+	if (IS_ERR(handle))
+		goto out;
+	inode->i_mtime = inode->i_ctime = CURRENT_TIME;
+	ext4_mark_inode_dirty(handle, inode);
+	ext4_journal_stop(handle);
+
+out:
 	return dquot_quota_off(sb, type);
 }
 
@@ -4714,9 +4757,8 @@ out:
 	if (inode->i_size < off + len) {
 		i_size_write(inode, off + len);
 		EXT4_I(inode)->i_disksize = inode->i_size;
+		ext4_mark_inode_dirty(handle, inode);
 	}
-	inode->i_mtime = inode->i_ctime = CURRENT_TIME;
-	ext4_mark_inode_dirty(handle, inode);
 	mutex_unlock(&inode->i_mutex);
 	return len;
 }