Frank Mayhar wrote: > On Wed, 2009-07-22 at 22:05 -0500, Eric Sandeen wrote: >> Frank Mayhar wrote: >>> On Tue, 2009-07-21 at 15:54 -0600, Andreas Dilger wrote: >> ... >> >>>> That said, we might need to have some kind of flag in the on-disk >>>> inode to indicate that it was preallocated beyond EOF. Otherwise, >>>> e2fsck will try and extend the file size to match the block count, >>>> which isn't correct. We could also use this flag to determine if >>>> truncate needs to be run on the inode even if the new size is the >>>> same. >>> After chatting with Curt about this today, it sounds like this needs two >>> things. One is your flag in the on-disk inode, set in fallocate() to >>> indicate that it has an allocation past EOF. E2fsck would use this to >>> avoid "fixing" the file size to match the block count. Truncate would >>> use this to notice that there are blocks allocated past i_size and get >>> rid of them. It would be cleared by truncate or by ext4_get_blocks when >>> using the last block of such an allocation. >>> >>> Does this make sense? Have I missed anything? >> I guess I'm not totally sold on the new on-disk flag; we can work out >> blocks past EOF w/o needing a new flag can't we? > > It's on-disk because e2fsck needs it to know when not to extend i_size > to the actual allocated length of the file. Were it not for that we > could easily solve the fallocate/trucate problem with an in-memory flag > only. Sorry I skimmed to fast, skipped over the fsck part. But: # mkfs.ext4 /dev/sdb3 mke2fs 1.41.5 (23-Apr-2009) ... # mount /dev/sdb3 /mnt/test # touch /mnt/test/testfile # /root/fallocate -n -l 16m /mnt/test/testfile # ls -l /mnt/test/testfile -rw-r--r-- 1 root root 0 Jul 23 12:13 /mnt/test/testfile # du -h /mnt/test/testfile 16M /mnt/test/testfile # umount /mnt/test # e2fsck -f /dev/sdb3 e2fsck 1.41.5 (23-Apr-2009) Pass 1: Checking inodes, blocks, and sizes Pass 2: Checking directory structure Pass 3: Checking directory connectivity Pass 4: Checking reference counts Pass 5: Checking group summary information /dev/sdb3: 12/244800 files (0.0% non-contiguous), 37766/977956 blocks there doesn't seem to be a problem in fsck w/ block past EOF, or am I missing something else? -Eric -- 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
