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: Niu Yawei <yawei.niu@intel.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 1bf6fe7..061727a 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4136,7 +4136,7 @@
/* 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);
@@ -4160,12 +4160,12 @@
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) {
ext4_mb_discard_lg_preallocations(sb, lg,
- order, lg_prealloc_count);
+ order, lg_prealloc_count);
return;
}
return ;