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 <[email protected]> > --- > 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 >
