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SubjectRe: problems with reiserfs + nfs using 2.4.2-pre4


On Tuesday, February 20, 2001 11:40:24 AM +1100 Neil Brown
<neilb@cse.unsw.edu.au> wrote:
>
> When reiserfs came along, it abused this, and re-interpreted the
> opaque datum to contain information for recalling (locating) an
> inode - if read_inode2 was defined. I think this is wrong.
>

I suggested to Al Viro a while ago to break iget up into two calls, and
then got sucked into something else and didn't follow up. Independently,
he came up with the below message during a thread on fs-devel about
read_inode. I think it is very similar to what you've described, and it
should work. I'm willing to help integrate/code once things settle down
for 2.4.

His last paragraph is also important, I'd rather see this as a new
call...BTW, I believe XFS and GFS actually have 64 bit inode numbers, while
reiserfs has a unique 32 bit inode number (objectid) and a unique 32 bit
packing locality that are both required to find the object.

Cut n' paste from Viro's mail, beware of newline munging:

> From: Alexander Viro <viro@math.psu.edu>
> To: Steve Whitehouse <Steve@ChyGwyn.com>
> cc: linux-fsdevel@vger.kernel.org
> Subject: Re: read_inode() extra argument ?
> Date-Sent: Tuesday, December 19, 2000 06:41:42 AM -0500
>
[snip]
> Basically, read_inode() (and iget()) is _not_ a universal API. It's
> a conveniency thing for filesystems that are comfortable with it. Notice
> that quite a few filesystems do not have ->read_inode() at all.
>
> If you need more than just an inumber to fill the inode - don't use
> iget() at all. It's just a wrong API for that kind of situations.
>
> In all fairness, ->read_inode() should not be a method. Correct way to
> deal with that would be along the lines
>
> --- fs/inode.c Tue Dec 19 09:42:41 2000
> +++ fs/inode.c.new Tue Dec 19 09:59:37 2000
> @@ -661,22 +661,10 @@
> inode->i_ino = ino;
> inode->i_flags = 0;
> atomic_set(&inode->i_count, 1);
> - inode->i_state = I_LOCK;
> + inode->i_state = I_LOCK | I_NEW;
> spin_unlock(&inode_lock);
>
> clean_inode(inode);
> - sb->s_op->read_inode(inode);
> -
> - /*
> - * This is special! We do not need the spinlock
> - * when clearing I_LOCK, because we're guaranteed
> - * that nobody else tries to do anything about the
> - * state of the inode when it is locked, as we
> - * just created it (so there can be no old holders
> - * that haven't tested I_LOCK).
> - */
> - inode->i_state &= ~I_LOCK;
> - wake_up(&inode->i_wait);
>
> return inode;
> }
> @@ -693,6 +681,20 @@
> wait_on_inode(inode);
> }
> return inode;
> +}
> +
> +void unlock_new_inode(struct inode *inode)
> +{
> + /*
> + * This is special! We do not need the spinlock
> + * when clearing I_LOCK, because we're guaranteed
> + * that nobody else tries to do anything about the
> + * state of the inode when it is locked, as we
> + * just created it (so there can be no old holders
> + * that haven't tested I_LOCK).
> + */
> + inode->i_state &= ~(I_LOCK|I_NEW);
> + wake_up(&inode->i_wait);
> }
>
> static inline unsigned long hash(struct super_block *sb, unsigned long
> i_ino) --- fs/ext2/namei.c Tue Dec 19 09:59:54 2000
> +++ fs/ext2/namei.c.new Tue Dec 19 10:01:22 2000
> @@ -175,9 +175,12 @@
> unsigned long ino = le32_to_cpu(de->inode);
> brelse (bh);
> inode = iget(dir->i_sb, ino);
> -
> if (!inode)
> return ERR_PTR(-EACCES);
> + if (inode->i_state & I_NEW) {
> + ext2_read_inode(inode);
> + unlock_new_inode(inode);
> + }
> }
> d_add(dentry, inode);
> return NULL;
>
> (modulo obvious changes to fs.h, exporting (or inlining)
> unlock_new_inode(), etc.)
>
> The point being: allow filesystems to use whatever means they find
> convenient for filling the inode. All we really need from icache is an
> analog of iget() that would leave new struct inode locked, recognizable
> as new and would _not_ do anything fs-specific. Quite possibly we want a
> new function for that leaving iget() as-is so that existing callers would
> stay intact - patch above just describes the general idea.




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