On Fri, Sep 07, 2007 at 01:39:41PM -0400, Josef 'Jeff' Sipek wrote: > On Fri, Sep 07, 2007 at 01:28:55PM +0530, Bharata B Rao wrote: > > On Fri, Sep 07, 2007 at 04:31:26PM +0900, hooanon05@xxxxxxxxxxx wrote: > > > > > > When the first readdir is issued: > > > - call vfs_readdir for every underlying opened dir (file) object. > > > - store every entry to either the hash table for the result or the > > > whiteout, when the same-named entry didn't exist in the tables. > > > - to improvement the performance, the allocated memory for the hash > > > tables are managed in a pointer array. and the elements are > > > concatinated logically by the pointer. > > > - the pointer for the result-table, the version, and the currect jiffies > > > are set to vdir, which is a cache in an inode. > > > - all cache are copied to a member in a file object. > > > - the index of the cache memory block and the offset in an array is > > > handled as the seek position. > > > > Ok, interesting approach. So you define the seek behaviour on your > > directory cache rather than allowing the underlying filesystems to > > interpret the seek. I guess we can do something similar with Union > > Mounts also. > > Unless I missunderstood something, Unionfs uses the same approach. Even But in the version of unionfs present in -mm, lseek on directories is still limited in functionality as it allows seeking to only the beginning and to the current position. > Unionfs's ODF branch does the same thing. The major difference is that we > keep the cache in a file on a disk. And as Erez explained, it is ODF which is allowing you to have a complete lseek behaviour. Regards, Bharata. - 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
