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SubjectRe: Linux 2.6.26-rc4
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On Tue, 2008-06-03 at 08:01 -0700, Linus Torvalds wrote:
>
> On Tue, 3 Jun 2008, Ian Kent wrote:
> > >
> > > > I think it must be autofs4 doing something weird. Like this in
> > > > autofs4_lookup_unhashed():
> > > >
> > > > /*
> > > > * Make the rehashed dentry negative so the VFS
> > > > * behaves as it should.
> > > > */
> > > > if (inode) {
> > > > dentry->d_inode = NULL;
>
> Uhhuh. Yeah, that's not allowed.
>
> A dentry inode can start _out_ as NULL, but it can never later become NULL
> again until it is totally unused.

Here is a patch for autofs4 to, hopefully, resolve this.

Keep in mind this doesn't address any other autofs4 issues but I it
should allow us to identify if this was in fact the root cause of the
problem Jesper reported.

autofs4 - leave rehashed dentry positive

From: Ian Kent <raven@themaw.net>

Correct the error of making a positive dentry negative after it has been
instantiated.

This involves removing the code in autofs4_lookup_unhashed() that
makes the dentry negative and updating autofs4_dir_symlink() and
autofs4_dir_mkdir() to recognise they have been given a postive
dentry (previously the dentry was always negative) and deal with
it. In addition the dentry info struct initialization, autofs4_init_ino(),
and the symlink free function, ino_lnkfree(), have been made aware
of this possible re-use. This is needed because the current case
re-uses a dentry in order to preserve it's flags as described in
commit f50b6f8691cae2e0064c499dd3ef3f31142987f0.

Signed-off-by: Ian Kent <raven@themaw.net>
---

fs/autofs4/inode.c | 23 +++++++------
fs/autofs4/root.c | 95 ++++++++++++++++++++++++++++++----------------------
2 files changed, 67 insertions(+), 51 deletions(-)


diff --git a/fs/autofs4/inode.c b/fs/autofs4/inode.c
index 2fdcf5e..ec9a641 100644
--- a/fs/autofs4/inode.c
+++ b/fs/autofs4/inode.c
@@ -24,8 +24,10 @@

static void ino_lnkfree(struct autofs_info *ino)
{
- kfree(ino->u.symlink);
- ino->u.symlink = NULL;
+ if (ino->u.symlink) {
+ kfree(ino->u.symlink);
+ ino->u.symlink = NULL;
+ }
}

struct autofs_info *autofs4_init_ino(struct autofs_info *ino,
@@ -41,16 +43,17 @@ struct autofs_info *autofs4_init_ino(struct autofs_info *ino,
if (ino == NULL)
return NULL;

- ino->flags = 0;
- ino->mode = mode;
- ino->inode = NULL;
- ino->dentry = NULL;
- ino->size = 0;
-
- INIT_LIST_HEAD(&ino->rehash);
+ if (!reinit) {
+ ino->flags = 0;
+ ino->mode = mode;
+ ino->inode = NULL;
+ ino->dentry = NULL;
+ ino->size = 0;
+ INIT_LIST_HEAD(&ino->rehash);
+ atomic_set(&ino->count, 0);
+ }

ino->last_used = jiffies;
- atomic_set(&ino->count, 0);

ino->sbi = sbi;

diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index edf5b6b..6ce603b 100644
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -555,24 +555,8 @@ static struct dentry *autofs4_lookup_unhashed(struct autofs_sb_info *sbi, struct
goto next;

if (d_unhashed(dentry)) {
- struct inode *inode = dentry->d_inode;
-
- ino = autofs4_dentry_ino(dentry);
list_del_init(&ino->rehash);
dget(dentry);
- /*
- * Make the rehashed dentry negative so the VFS
- * behaves as it should.
- */
- if (inode) {
- dentry->d_inode = NULL;
- list_del_init(&dentry->d_alias);
- spin_unlock(&dentry->d_lock);
- spin_unlock(&sbi->rehash_lock);
- spin_unlock(&dcache_lock);
- iput(inode);
- return dentry;
- }
spin_unlock(&dentry->d_lock);
spin_unlock(&sbi->rehash_lock);
spin_unlock(&dcache_lock);
@@ -728,35 +712,50 @@ static int autofs4_dir_symlink(struct inode *dir,
return -EACCES;

ino = autofs4_init_ino(ino, sbi, S_IFLNK | 0555);
- if (ino == NULL)
+ if (!ino)
return -ENOSPC;

- ino->size = strlen(symname);
- ino->u.symlink = cp = kmalloc(ino->size + 1, GFP_KERNEL);
-
- if (cp == NULL) {
- kfree(ino);
+ cp = kmalloc(ino->size + 1, GFP_KERNEL);
+ if (!cp) {
+ if (!dentry->d_fsdata)
+ kfree(ino);
return -ENOSPC;
}

strcpy(cp, symname);

- inode = autofs4_get_inode(dir->i_sb, ino);
- d_add(dentry, inode);
+ inode = dentry->d_inode;
+ if (inode)
+ d_rehash(dentry);
+ else {
+ inode = autofs4_get_inode(dir->i_sb, ino);
+ if (!inode) {
+ kfree(cp);
+ if (!dentry->d_fsdata)
+ kfree(ino);
+ return -ENOSPC;
+ }
+
+ d_add(dentry, inode);

- if (dir == dir->i_sb->s_root->d_inode)
- dentry->d_op = &autofs4_root_dentry_operations;
- else
- dentry->d_op = &autofs4_dentry_operations;
+ if (dir == dir->i_sb->s_root->d_inode)
+ dentry->d_op = &autofs4_root_dentry_operations;
+ else
+ dentry->d_op = &autofs4_dentry_operations;
+
+ dentry->d_fsdata = ino;
+ ino->dentry = dentry;
+ ino->inode = inode;
+ }
+ dget(dentry);

- dentry->d_fsdata = ino;
- ino->dentry = dget(dentry);
atomic_inc(&ino->count);
p_ino = autofs4_dentry_ino(dentry->d_parent);
if (p_ino && dentry->d_parent != dentry)
atomic_inc(&p_ino->count);
- ino->inode = inode;

+ ino->u.symlink = cp;
+ ino->size = strlen(symname);
dir->i_mtime = CURRENT_TIME;

return 0;
@@ -866,24 +865,38 @@ static int autofs4_dir_mkdir(struct inode *dir, struct dentry *dentry, int mode)
dentry, dentry->d_name.len, dentry->d_name.name);

ino = autofs4_init_ino(ino, sbi, S_IFDIR | 0555);
- if (ino == NULL)
+ if (!ino)
return -ENOSPC;

- inode = autofs4_get_inode(dir->i_sb, ino);
- d_add(dentry, inode);
+ inode = dentry->d_inode;
+ if (inode)
+ d_rehash(dentry);
+ else {
+ inode = autofs4_get_inode(dir->i_sb, ino);
+ if (!inode) {
+ if (!dentry->d_fsdata)
+ kfree(ino);
+ return -ENOSPC;
+ }

- if (dir == dir->i_sb->s_root->d_inode)
- dentry->d_op = &autofs4_root_dentry_operations;
- else
- dentry->d_op = &autofs4_dentry_operations;
+ d_add(dentry, inode);
+
+ if (dir == dir->i_sb->s_root->d_inode)
+ dentry->d_op = &autofs4_root_dentry_operations;
+ else
+ dentry->d_op = &autofs4_dentry_operations;
+
+ dentry->d_fsdata = ino;
+ ino->dentry = dentry;
+ ino->inode = inode;
+ }
+ dget(dentry);

- dentry->d_fsdata = ino;
- ino->dentry = dget(dentry);
atomic_inc(&ino->count);
p_ino = autofs4_dentry_ino(dentry->d_parent);
if (p_ino && dentry->d_parent != dentry)
atomic_inc(&p_ino->count);
- ino->inode = inode;
+
inc_nlink(dir);
dir->i_mtime = CURRENT_TIME;




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