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Date: Thu, 13 Jan 2011 11:09:13 -0600
From: Alex Elder <aelder@....com>
To: Ian Kent <raven@...maw.net>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
Nick Piggin <npiggin@...nel.dk>,
Al Viro <viro@...iv.linux.org.uk>,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [announce] vfs-scale git tree update
On Thu, 2011-01-13 at 11:03 +0800, Ian Kent wrote:
> On Thu, 2011-01-13 at 10:23 +0800, Ian Kent wrote:
> > On Wed, 2011-01-12 at 14:11 -0600, Alex Elder wrote:
> > > On Wed, 2011-01-12 at 12:15 +0800, Ian Kent wrote:
> > > > On Wed, 2011-01-12 at 11:59 +0800, Ian Kent wrote:
. . .
> > > > Could you try this patch please.
> > >
> > > OK, sorry for the delay. I tried the patch. I applied
> > > it against 4162cf64973df51fc885825bc9ca4d055891c49f,
> > > which is the linus/master branch I had on hand. This
> > > time I got a different failure due to a null pointer
> > > dereference. Console capture below. I can log
> > > in still but the boot sequence never got to the
> > > login prompt on the console as it normally does.
> >
> >
> > Sorry, that is rather an obvious mistake on my part.
> > There's a call to d_op->d_revalidate() just below where the dentry
> > operations are set. I'm tempted to just call the revalidate function
> > directly since it is always called anyway. But let me check we've done
> > in the our current of tree autofs patch series first.
>
> Ha, there is no revalidate in the current not yet merged autofs.
> So I think we just need to work around it.
>
> Try this and see if it resolves the issue.
This one works. I am able to boot without
hitting the BUG_ON() in d_set_d_op() and
there is no longer the null pointer dereference
that occurred with the last one.
-Alex
> autofs4 - set dentry op in ->lookup() only
>
> From: Ian Kent <raven@...maw.net>
>
> With the introduction of the vfs-scale patch series setting dentry
> operations more than once (or changing them) triggers a BUG_ON().
> Since the two dentry operations used are the same, just set the
> operations in ->lookup() and remove the set in ->symlink() and
> ->mkdir().
>
> Also, move the d_add() in ->symlink() and ->mkdir() to the end of
> the function.
> ---
>
> fs/autofs4/root.c | 40 +++++++---------------------------------
> 1 files changed, 7 insertions(+), 33 deletions(-)
>
>
> diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
> index 651e4ef..0897706 100644
> --- a/fs/autofs4/root.c
> +++ b/fs/autofs4/root.c
> @@ -419,12 +419,6 @@ void autofs4_dentry_release(struct dentry *de)
> }
> }
>
> -/* For dentries of directories in the root dir */
> -static const struct dentry_operations autofs4_root_dentry_operations = {
> - .d_revalidate = autofs4_revalidate,
> - .d_release = autofs4_dentry_release,
> -};
> -
> /* For other dentries */
> static const struct dentry_operations autofs4_dentry_operations = {
> .d_revalidate = autofs4_revalidate,
> @@ -568,19 +562,6 @@ static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, s
> ino = autofs4_dentry_ino(dentry);
> } else {
> /*
> - * Mark the dentry incomplete but don't hash it. We do this
> - * to serialize our inode creation operations (symlink and
> - * mkdir) which prevents deadlock during the callback to
> - * the daemon. Subsequent user space lookups for the same
> - * dentry are placed on the wait queue while the daemon
> - * itself is allowed passage unresticted so the create
> - * operation itself can then hash the dentry. Finally,
> - * we check for the hashed dentry and return the newly
> - * hashed dentry.
> - */
> - d_set_d_op(dentry, &autofs4_root_dentry_operations);
> -
> - /*
> * And we need to ensure that the same dentry is used for
> * all following lookup calls until it is hashed so that
> * the dentry flags are persistent throughout the request.
> @@ -589,6 +570,8 @@ static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, s
> if (!ino)
> return ERR_PTR(-ENOMEM);
>
> + d_set_d_op(dentry, &autofs4_dentry_operations);
> +
> dentry->d_fsdata = ino;
> ino->dentry = dentry;
>
> @@ -714,12 +697,6 @@ static int autofs4_dir_symlink(struct inode *dir,
> kfree(ino);
> return -ENOMEM;
> }
> - d_add(dentry, inode);
> -
> - if (dir == dir->i_sb->s_root->d_inode)
> - d_set_d_op(dentry, &autofs4_root_dentry_operations);
> - else
> - d_set_d_op(dentry, &autofs4_dentry_operations);
>
> dentry->d_fsdata = ino;
> ino->dentry = dget(dentry);
> @@ -732,6 +709,8 @@ static int autofs4_dir_symlink(struct inode *dir,
> ino->u.symlink = cp;
> dir->i_mtime = CURRENT_TIME;
>
> + d_add(dentry, inode);
> +
> return 0;
> }
>
> @@ -849,12 +828,6 @@ static int autofs4_dir_mkdir(struct inode *dir, struct dentry *dentry, int mode)
> kfree(ino);
> return -ENOMEM;
> }
> - d_add(dentry, inode);
> -
> - if (dir == dir->i_sb->s_root->d_inode)
> - d_set_d_op(dentry, &autofs4_root_dentry_operations);
> - else
> - d_set_d_op(dentry, &autofs4_dentry_operations);
>
> dentry->d_fsdata = ino;
> ino->dentry = dget(dentry);
> @@ -866,6 +839,8 @@ static int autofs4_dir_mkdir(struct inode *dir, struct dentry *dentry, int mode)
> inc_nlink(dir);
> dir->i_mtime = CURRENT_TIME;
>
> + d_add(dentry, inode);
> +
> return 0;
> }
>
> @@ -944,8 +919,7 @@ static inline int autofs4_ask_umount(struct vfsmount *mnt, int __user *p)
> int is_autofs4_dentry(struct dentry *dentry)
> {
> return dentry && dentry->d_inode &&
> - (dentry->d_op == &autofs4_root_dentry_operations ||
> - dentry->d_op == &autofs4_dentry_operations) &&
> + (dentry->d_op == &autofs4_dentry_operations) &&
> dentry->d_fsdata != NULL;
> }
>
>
>
--
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