On Wed, Mar 05, 2014 at 12:33:32PM +0000, Zhang, Hongchao wrote: > > in ext4_fill_super, the variables related to statfs should be > initialized after journal recovery is completed. otherwise, if a > large number of blocks were being allocated before the filesystem > crashed, then the blocks and inode counters may become negative > during use and report incorrect values to statfs call. The ext4_statfs() doesn't use the free blocks and inodes count from the superblock. For scalability reasons, we no longer update the journal values in the superblock while they are in use, but rather compute them from the sum of the values from the blockgroup descriptors, and then track them via percpu counters. Hence, the problem you described isn't an issue in practice. What we are doing does mean that values in the superblock are not accurate while the file system is mounted and if the system crashes before an file system can be cleanly unmounted --- we do update these values when the file system is unmounted. However, using tools such as dumpe2fs to determine the free blocks/inodes available while the file system is mounted or after an unclean shutdown was not considered an important use case, especially compared to the scalability concerns of supporting high cpu core count systems. Cheers, - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
