On Mon, Apr 19, 2010 at 04:12:48PM +0200, Jan Blunck wrote: > On Mon, Apr 19, Jamie Lokier wrote: > > > Jan Blunck wrote: > > > On Mon, Apr 19, David Woodhouse wrote: > > > > > > > On Mon, 2010-04-19 at 14:40 +0200, Jan Blunck wrote: > > > > > On Thu, Apr 15, Valerie Aurora wrote: > > > > > > > > > > > Add support for fallthru directory entries to ext2. > > > > > > > > > > > > XXX - Makes up inode number for fallthru entry > > > > > > XXX - Might be better implemented as special symlinks > > > > > > > > > > Better not. David Woodhouse actually convinced me of moving away from the > > > > > special symlink approach. The whiteouts have been implemented as special > > > > > symlinks before. > > > > > > > > I certainly asked whether you really need a real 'struct inode' for > > > > whiteouts, and suggested that they should be represented _purely_ as a > > > > dentry with type DT_WHT. > > > > > > > > I don't much like the manifestation of that in this patch though, > > > > especially with the made-up inode number. (ISTR I had other > > > > jffs2-specific objections too, which I'll dig out and forward). > > > > > > Yes, this patches still have issues that Val and me are aware off. I can't > > > remember anything jffs2-specific though. > > > > > > We return that inode number because we don't want to lookup the name on the > > > other filesystem during readdir. Therefore returning DT_UNKNOWN to let the > > > userspace decide if it needs to stat the file was the easiest workaround. I > > > know that POSIX requires d_ino and d_name but on the other hand it does not > > > require anything more on how long d_ino is valid. > > > > Although the lifetime of d_ino might very, I know some programs (not > > public) that will break if they see a d_ino which is wrongly matching > > the st_ino of another file somewhere on the same st_dev. They will > > assume the name is a hard link to the other file, without calling > > stat(), which I think is a reasonable assumption and a useful optimisation. > > > > So the made-up d_ino should at least be careful to not match an inode > > number of another file which has a stable st_ino. > > > > Why not zero for d_ino? > > > > Hmm, why not. Or even the ino of the directory we are reading from ... I don't recall there being any technical reason not to look up the real inode number. I just wrote it that we because I was lazy. So I like returning the directory's d_ino better than a single magic number, but I'd at least like to try returning the real inode number too. -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
