Hi, any comment ?
On 2017/4/13 21:49, Hou Tao wrote:
> After the invocation of remove_proc_entry() for a proc fs directory,
> if the related dentry had been held by some processes (eg., by chdir),
> the lookup afterwards will still return the old proc_dir_entry. The
> new created proc fs files under the proc fs directory will not be
> visible until the old dentry is released, and this makes our hotplug
> process to fail which needs to access the new proc fs files.
>
> To fix it, we need to mark the deleting or deleted proc_dir_entry
> as invalid and the lookup afterwards will use the new proc_dir_entry
> regardless of the status of the old dentry.
>
> Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
> ---
> fs/proc/generic.c | 21 ++++++++++++++++++++-
> fs/proc/inode.c | 5 +++++
> fs/proc/internal.h | 1 +
> 3 files changed, 26 insertions(+), 1 deletion(-)
>
> diff --git a/fs/proc/generic.c b/fs/proc/generic.c
> index ee27feb..92c9dd4 100644
> --- a/fs/proc/generic.c
> +++ b/fs/proc/generic.c
> @@ -23,11 +23,19 @@
> #include <linux/spinlock.h>
> #include <linux/completion.h>
> #include <linux/uaccess.h>
> +#include <linux/namei.h>
>
> #include "internal.h"
>
> +static int proc_dentry_revalidate(struct dentry *dentry, unsigned int flags);
> +
> static DEFINE_RWLOCK(proc_subdir_lock);
>
> +static const struct dentry_operations proc_dentry_operations = {
> + .d_revalidate = proc_dentry_revalidate,
> + .d_delete = always_delete_dentry,
> +};
> +
> static int proc_match(unsigned int len, const char *name, struct proc_dir_entry *de)
> {
> if (len < de->namelen)
> @@ -223,6 +231,17 @@ void proc_free_inum(unsigned int inum)
> spin_unlock_irqrestore(&proc_inum_lock, flags);
> }
>
> +static int proc_dentry_revalidate(struct dentry *dentry, unsigned int flags)
> +{
> + struct proc_dir_entry *de;
> +
> + if (flags & LOOKUP_RCU)
> + return -ECHILD;
> +
> + de = PDE(d_inode(dentry));
> + return !proc_entry_is_removing(de);
> +}
> +
> /*
> * Don't create negative dentries here, return -ENOENT by hand
> * instead.
> @@ -240,7 +259,7 @@ struct dentry *proc_lookup_de(struct proc_dir_entry *de, struct inode *dir,
> inode = proc_get_inode(dir->i_sb, de);
> if (!inode)
> return ERR_PTR(-ENOMEM);
> - d_set_d_op(dentry, &simple_dentry_operations);
> + d_set_d_op(dentry, &proc_dentry_operations);
> d_add(dentry, inode);
> return NULL;
> }
> diff --git a/fs/proc/inode.c b/fs/proc/inode.c
> index 2cc7a80..84232d0 100644
> --- a/fs/proc/inode.c
> +++ b/fs/proc/inode.c
> @@ -171,6 +171,11 @@ static void close_pdeo(struct proc_dir_entry *pde, struct pde_opener *pdeo)
> }
> }
>
> +bool proc_entry_is_removing(struct proc_dir_entry *de)
> +{
> + return (atomic_read(&de->in_use) == BIAS);
> +}
> +
> void proc_entry_rundown(struct proc_dir_entry *de)
> {
> DECLARE_COMPLETION_ONSTACK(c);
> diff --git a/fs/proc/internal.h b/fs/proc/internal.h
> index c5ae09b..646b3f6 100644
> --- a/fs/proc/internal.h
> +++ b/fs/proc/internal.h
> @@ -205,6 +205,7 @@ void set_proc_pid_nlink(void);
> extern struct inode *proc_get_inode(struct super_block *, struct proc_dir_entry *);
> extern int proc_fill_super(struct super_block *, void *data, int flags);
> extern void proc_entry_rundown(struct proc_dir_entry *);
> +extern bool proc_entry_is_removing(struct proc_dir_entry *de);
>
> /*
> * proc_namespaces.c
>
