1103 /*
1104 * bd_mutex locking:
1105 *
1106 * mutex_lock(part->bd_mutex)
1107 * mutex_lock_nested(whole->bd_mutex, 1)
1108 */
1109
1110 static int do_open(struct block_device *bdev, struct file *file, int for_part)
1111 {
1112 struct module *owner = NULL;
1113 struct gendisk *disk;
1114 int ret = -ENXIO;
1115 int part;
1116
1117 file->f_mapping = bdev->bd_inode->i_mapping;
1118 lock_kernel();
1119 disk = get_gendisk(bdev->bd_dev, &part);
1120 if (!disk) {
1121 unlock_kernel();
1122 bdput(bdev);
1123 return ret;
1124 }
1125 owner = disk->fops->owner;
1126
1127 mutex_lock_nested(&bdev->bd_mutex, for_part);
1128 if (!bdev->bd_openers) {
1129 bdev->bd_disk = disk;
1130 bdev->bd_contains = bdev;
1131 if (!part) {
1132 struct backing_dev_info *bdi;
1133 if (disk->fops->open) {
1134 ret = disk->fops->open(bdev->bd_inode, file);
1135 if (ret)
1136 goto out_first;
1137 }
1138 if (!bdev->bd_openers) {
1139 bd_set_size(bdev,(loff_t)get_capacity(disk)<<9);
1140 bdi = blk_get_backing_dev_info(bdev);
1141 if (bdi == NULL)
1142 bdi = &default_backing_dev_info;
1143 bdev->bd_inode->i_data.backing_dev_info = bdi;
1144 }
1145 if (bdev->bd_invalidated)
1146 rescan_partitions(disk, bdev);
1147 } else {
1148 struct hd_struct *p;
1149 struct block_device *whole;
1150 whole = bdget_disk(disk, 0);
1151 ret = -ENOMEM;
1152 if (!whole)
1153 goto out_first;
1154 BUG_ON(for_part);
1155 ret = __blkdev_get(whole, file->f_mode, file->f_flags, 1);
1156 if (ret)
1157 goto out_first;
1158 bdev->bd_contains = whole;
1159 p = disk->part[part – 1];
1160 bdev->bd_inode->i_data.backing_dev_info =
1161 whole->bd_inode->i_data.backing_dev_info;
1162 if (!(disk->flags & GENHD_FL_UP) || !p || !p->nr_sects) {
1163 ret = -ENXIO;
1164 goto out_first;
1165 }
1166 kobject_get(&p->kobj);
1167 bdev->bd_part = p;
1168 bd_set_size(bdev, (loff_t) p->nr_sects << 9);
1169 }
1170 } else {
1171 put_disk(disk);
1172 module_put(owner);
1173 if (bdev->bd_contains == bdev) {
1174 if (bdev->bd_disk->fops->open) {
1175 ret = bdev->bd_disk->fops->open(bdev->bd_inode, file);
1176 if (ret)
1177 goto out;
1178 }
1179 if (bdev->bd_invalidated)
1180 rescan_partitions(bdev->bd_disk, bdev);
1181 }
1182 }
1183 bdev->bd_openers++;
1184 if (for_part)
1185 bdev->bd_part_count++;
1186 mutex_unlock(&bdev->bd_mutex);
1187 unlock_kernel();
1188 return 0;
1189
1190 out_first:
1191 bdev->bd_disk = NULL;
1192 bdev->bd_inode->i_data.backing_dev_info = &default_backing_dev_info;
1193 if (bdev != bdev->bd_contains)
1194 __blkdev_put(bdev->bd_contains, 1);
1195 bdev->bd_contains = NULL;
1196 put_disk(disk);
1197 module_put(owner);
1198 out:
1199 mutex_unlock(&bdev->bd_mutex);
1200 unlock_kernel();
1201 if (ret)
1202 bdput(bdev);
1203 return ret;
1204 }
爬上那座山，听最圣洁的经。
