ext4: fix race in ext4_mb_add_n_trim()
Niu Yawei [Sat, 2 Feb 2013 02:31:27 +0000 (21:31 -0500)]
commit f1167009711032b0d747ec89a632a626c901a1ad upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/ext4/mballoc.c

index e77c4fe..3122ece 100644 (file)
@@ -4126,7 +4126,7 @@ 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);
@@ -4150,12 +4150,12 @@ 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) {
                ext4_mb_discard_lg_preallocations(sb, lg,
-                                               order, lg_prealloc_count);
+                                                 order, lg_prealloc_count);
                return;
        }
        return ;