Commit f1167009 authored by Niu Yawei's avatar Niu Yawei Committed by Theodore Ts'o
Browse files

ext4: fix race in ext4_mb_add_n_trim() 



In ext4_mb_add_n_trim(), lg_prealloc_lock should be taken when
changing the lg_prealloc_list.

Signed-off-by: default avatarNiu Yawei <yawei.niu@intel.com>
Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org
parent 87e69873

fs/ext4/mballoc.c

+3 −3
Original line number Diff line number Diff line
@@ -4136,7 +4136,7 @@ static void ext4_mb_add_n_trim(struct ext4_allocation_context *ac) 
		/* The max size of hash table is PREALLOC_TB_SIZE */

		order = PREALLOC_TB_SIZE - 1;

	/* Add the prealloc space to lg */

	rcu_read_lock();

	spin_lock(&lg->lg_prealloc_lock);

	list_for_each_entry_rcu(tmp_pa, &lg->lg_prealloc_list[order],

						pa_inode_list) {

		spin_lock(&tmp_pa->pa_lock);
@@ -4160,7 +4160,7 @@ static void ext4_mb_add_n_trim(struct ext4_allocation_context *ac) 
	if (!added)

		list_add_tail_rcu(&pa->pa_inode_list,

					&lg->lg_prealloc_list[order]);

	rcu_read_unlock();

	spin_unlock(&lg->lg_prealloc_lock);



	/* Now trim the list to be not more than 8 elements */

	if (lg_prealloc_count > 8) {