On Wed, Mar 14, 2012 at 10:17:37AM -0400, Zach Brown wrote: > > >We could do this if we have two b-trees, one indexed by filename and > >one indexed by inode number, which is what JFS (and I believe btrfs) > >does. > > Typically the inode number of the destination inode isn't used to index > entries for a readdir tree because of (wait for it) hard links. You end > up right back where you started with multiple entries per key. Well, if you are using 32-bit (or even 48-bit) inode numbers and a 64-bit telldir cookie, it's possible to make the right thing happen. But yes, if you are using 32-bit inode numbers and a 32-bit telldir cookie, dealing with what happens when you have multiple hard links to the same inode in the same directory gets tricky. > A painful solution is to have the key in the readdir tree allocated by > the tree itself -- count key populations in subtrees per child pointer > and use that to find free keys. One thing that might work is to have a 16-bit extra field in the directory entry that gives an signed offset to the inode number so that such that inode+offset is a unique value within the btree sorted by inode+offset number. Since this tree is only used for returning entries in an optimal (or as close to optimal as can be arranged) order, we could get away with that. - Ted -- 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
