Hi Ted, Thanks for your comments. > First of all, explicit comparisons against the current uid is bad. A > non-root user might have read/write access to the raw device where a > file sysem is located. It's bad to encode an assumption one way or > another into a userspace program. Secondly, whenever a userspace progam > is explicitly trying to encode permission checking, that's a red flag. I will fix it. > I'm not sure why checking to see if a file's st_uid matches the > current_uid has any validity at all. e4defrag tries to change the location of data blocks, so I assumed that non-root users should execute e4defrag only to their file. It would be better that users who have read/write permission can e4defrag to the file. > What really matters are the number of extents which are non-tail > extents, and smaller than some threshold (probably around 256 MB for > most HDD's), and not forced by skips in the logical block numbering > (i.e., caused by a file being sparse). The basic idea here is to go > back to why fragments are bad, which is that they slow down file access. > If every few hundred megabytes, you need to seek to another part of the > disk, it's really not the end of the world. What does 256MB mean? If "some threshold" means the maximum size of one extent, I think the size is 128MB. > There's a more general question which is I'm not sure how much the > functionality of e4dfrag -c really belongs in e4defrag. I'm thinking > perhaps that perhaps this functionality should instead go in filefrag, > and/or in e2fsck, which can do the job much more efficiently since it by > definition has direct access to the file system, so it can scan the > inode tables in order. Currently, e2fsprogs has two commands that report how badly fragmented a file might be. So, it is smart for e2fsprogs to drop -c option from e4defrag. e4defrag -c shows whether we need to execute e4defrag or not. For this, I think we should add "fragmentation score" included in e4defrag -c to the output of filefrag. However, sometimes we want to check the fragmentation not only for a single file but also for many files in the same directory. e4defrag -c gets the extent information of all files in a directory, and calculates the fragmentation score based on this information. But I'm not sure that I should add this feature to filefrag by adding new option or some other way. Regards, Kazuya Mio -- 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
