On Sun, 2008-08-17 at 18:21 +0530, Balaji Rao wrote: > On Sunday 17 August 2008 05:23:22 pm David Woodhouse wrote: > > On Mon, 2008-07-21 at 02:01 +0530, Balaji Rao wrote: > > > Here's an implementation of NFS support for btrfs. It does not work in > > > one particular case as described in > > > http://www.mail-archive.com/linux-btrfs@xxxxxxxxxxxxxxx/msg00298.html. > > > > I can't get it to work properly. The simple case of exporting and using > > a file system works -- but that doesn't exercise the get_parent() or > > dentry_to_fh() code paths. To test those, you need to clear the server's > > dcache completely -- I prefer just rebooting the server. > > > > OK. I was not very sure if NFS worked across server reboots. It definitely should. > > Note that the first problem you'll hit is the lack of stable fsid -- > > because btrfs uses an anonymous superblock, it might cause stale file > > handles after a reboot, unless your test setup mounts exactly the same > > anonymous file systems each time. That bit me when I context switched > > from something else and had debugfs mounted before btrfs, then rebooted > > and didn't mount debugfs first. I'll deal with the fsid problem > > separately; just be aware of it and avoid it for now. > > > Hmmm.. how do we deal with that ? I'm not entirely sure yet. I had a patch to make the kernel automatically set a uuid on the export, which was simple enough. Unfortunately that isn't sufficient, because although we then return an appropriate root fh to the mount request, we then aren't capable of _interpreting_ that fh when the client immediately gives it back to us in a subsequent fsinfo request. Because we're relying on mountd to do the initial fh->dentry conversion for us, and mountd is very limited in its uuid handling -- it assumes that - there is a block device - there is a 1:1 mapping between block device and uuid - libuuid can cope with new file systems. > > The second problem is that btrfs_fh_to_dentry() fails -- it seems we > > need to set the key type BTRFS_INODE_ITEM_KEY in btrfs_get_dentry(), > > rather than BTRFS_INODE_REF_KEY. I still haven't learned enough to know > > precisely what the implications of that are -- but unless I make that > > change, btrfs_lookup_inode() fails and btrfs_read_locked_inode() marks > > the resulting inode as bad. > > > Right. Again, my bad. That's a silly mistake, which didn't surface because of > bad testing! > > > You can test that by mounting the exported file system, then rebooting > > the server, then running 'ls' in the NFS-mounted file system. > > > > My next test was to make a deep directory path: mkdir -p a/b/c/d/e/f/g > > and then change directory into it. Again reboot the server and run 'ls'. > > This time, I see 'ls: cannot open directory .'. In this csse, it seems > > to be because btrfs_get_parent() is failing. In my case, it seems to be > > because the 'if (slot >= nritems)' check is triggering -- both are set > > to 14. I'm now trying to work out precisely what that means... > > I think this means that the inode ref is not found, which is weird. I remember > that it worked with it a really deep path. I'll try to reproduce the problem > and see what's going on.. See below... it seems to be working now. diff --git a/export.c b/export.c index 1b8875c..6209f35 100644 --- a/export.c +++ b/export.c @@ -72,7 +72,7 @@ static struct dentry *btrfs_get_dentry(struct super_block *sb, u64 objectid, struct btrfs_key key; key.objectid = objectid; - btrfs_set_key_type(&key, BTRFS_INODE_REF_KEY); + btrfs_set_key_type(&key, BTRFS_INODE_ITEM_KEY); key.offset = 0; root = btrfs_lookup_fs_root(btrfs_sb(sb)->fs_info, root_objectid); @@ -164,14 +164,22 @@ static struct dentry *btrfs_get_parent(struct dentry *child) leaf = path->nodes[0]; slot = path->slots[0]; nritems = btrfs_header_nritems(leaf); - if (slot >= nritems) - goto out; + if (slot >= nritems) { + ret = btrfs_next_leaf(root, path); + if (ret) { + btrfs_free_path(path); + goto out; + } + leaf = path->nodes[0]; + slot = path->slots[0]; + } + + btrfs_free_path(path); btrfs_item_key_to_cpu(leaf, &key, slot); if (key.objectid != dir->i_ino || key.type != BTRFS_INODE_REF_KEY) goto out; - btrfs_free_path(path); objectid = key.offset; /* Build a new key for the inode item */ -- David Woodhouse Open Source Technology Centre David.Woodhouse@xxxxxxxxx Intel Corporation -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
