On Fri, Jun 18, 2010 at 03:04:08AM +0900, J. R. Okajima wrote: > > David Dillow: > > For example, our main Lustre scratch space has over 285 million files in > > it, and using find -inum takes over 72 hours to walk the tree using > ::: > > Using ne2scan -- which uses libext2fs and combines the inode scan and > > the name lookup -- takes over 48 hours to generate a list of candidate > > files for the purge example. With an optimized inode scan and the custom > ::: > > While I've never heard of ne2scan, I am interested in this simplified > problem such as "find the pathname(s) from an inum in a huge fs." > Is ne2scan essentially equivalent to "debugfs ncheck inum"? > > About Valeris's patch, as long as "ls -i" is useful/helpful, > > + /* Use of d_ino without st_dev is always buggy. */ > is not true. What I'm hearing again and again is that d_ino is useful to improve performance. As Andreas put it to me, if d_ino is the same, the referenced file may or may not be the same, but if it's different, the files are definitely different. Only in well-controlled environments known not to have submounts or bind mounts do people trust d_ino to be from the same file system as the other entries in a directory. I only submitted this patch half-seriously - mainly I wanted to find out how people are using d_ino, and therefore what I need to do for fallthru directory entries in union mounts. In order to get the correct inode number for a directory entry referring to a lower layer file or directory, we have to do a ->lookup() from the fs-specific readdir code (or else require that fallthrus store an arbitrarily sized integer - which seriously restricts the implementation). Now, doing a ->lookup() to get d_ino makes no sense if we are using d_ino as a way to avoid the cost stat(), which is mainly the ->lookup(). And you definitely can't use d_ino by itself in a union mount. I'm inclined to save the trouble and just return 1 in d_ino for fallthru directory entries, especially now that I've tested it system-wide and had no obvious problems. -VAL -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
