ext4: update 'state->fc_regions_size' after successful memory allocation

To avoid to 'state->fc_regions_size' mismatch with 'state->fc_regions'
when fail to reallocate 'fc_reqions',only update 'state->fc_regions_size'
after 'state->fc_regions' is allocated successfully.

Cc: stable@kernel.org
Signed-off-by: Ye Bin <yebin10@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20220921064040.3693255-4-yebin10@huawei.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/fast_commit.c

@@ -1681,14 +1681,15 @@ int ext4_fc_record_regions(struct super_block *sb, int ino,
 	if (state->fc_regions_used == state->fc_regions_size) {
 		struct ext4_fc_alloc_region *fc_regions;
 
-		state->fc_regions_size +=
-			EXT4_FC_REPLAY_REALLOC_INCREMENT;
 		fc_regions = krealloc(state->fc_regions,
-				      state->fc_regions_size *
-				      sizeof(struct ext4_fc_alloc_region),
+				      sizeof(struct ext4_fc_alloc_region) *
+				      (state->fc_regions_size +
+				       EXT4_FC_REPLAY_REALLOC_INCREMENT),
 				      GFP_KERNEL);
 		if (!fc_regions)
 			return -ENOMEM;
+		state->fc_regions_size +=
+			EXT4_FC_REPLAY_REALLOC_INCREMENT;
 		state->fc_regions = fc_regions;
 	}
 	region = &state->fc_regions[state->fc_regions_used++];