On Tue, 22 May 2007 21:43:49 +0400
Alexey Dobriyan <[email protected]> wrote:
> On Sun, May 20, 2007 at 08:41:02PM -0700, [email protected] wrote:
> > Subject: procfs directory entry cleanup
> > From: "Changli Gao" <[email protected]>
> >
> > Function proc_register() will assign proc_dir_operations and
> > proc_dir_inode_operations to ent's members proc_fops and proc_iops
> > correctly if ent is a directory. So the early assignment isn't
> > necessary.
>
> > --- a/fs/proc/generic.c~procfs-directory-entry-cleanup
> > +++ a/fs/proc/generic.c
> > @@ -649,9 +649,6 @@ struct proc_dir_entry *proc_mkdir_mode(c
> >
> > ent = proc_create(&parent, name, S_IFDIR | mode, 2);
> > if (ent) {
> > - ent->proc_fops = &proc_dir_operations;
> > - ent->proc_iops = &proc_dir_inode_operations;
> > -
> > if (proc_register(parent, ent) < 0) {
> > kfree(ent);
> > ent = NULL;
> > @@ -686,10 +683,6 @@ struct proc_dir_entry *create_proc_entry
> >
> > ent = proc_create(&parent,name,mode,nlink);
> > if (ent) {
> > - if (S_ISDIR(mode)) {
> > - ent->proc_fops = &proc_dir_operations;
> > - ent->proc_iops = &proc_dir_inode_operations;
> > - }
> > if (proc_register(parent, ent) < 0) {
> > kfree(ent);
> > ent = NULL;
>
> This should add race because new PDE for directory will be glued to tree
> with NULL ->proc_iops and, at least, vfs_getattr() doesn't check for
> NULL ->i_op.
>
> I've tried to reproduce this scenario with udelay() inserted before
> S_ISDIR checks in proc_register() but got some panic while in X,
> so no cookie for me. Maybe it's impossible, indeed.
>
> Anyway, this patch + moving ->proc_fops and ->proc_iops initialization
> before gluing is OK with me.
Like this?
diff -puN fs/proc/generic.c~procfs-directory-entry-cleanup-fix fs/proc/generic.c
--- a/fs/proc/generic.c~procfs-directory-entry-cleanup-fix
+++ a/fs/proc/generic.c
@@ -529,12 +529,6 @@ static int proc_register(struct proc_dir
return -EAGAIN;
dp->low_ino = i;
- spin_lock(&proc_subdir_lock);
- dp->next = dir->subdir;
- dp->parent = dir;
- dir->subdir = dp;
- spin_unlock(&proc_subdir_lock);
-
if (S_ISDIR(dp->mode)) {
if (dp->proc_iops == NULL) {
dp->proc_fops = &proc_dir_operations;
@@ -550,6 +544,13 @@ static int proc_register(struct proc_dir
if (dp->proc_iops == NULL)
dp->proc_iops = &proc_file_inode_operations;
}
+
+ spin_lock(&proc_subdir_lock);
+ dp->next = dir->subdir;
+ dp->parent = dir;
+ dir->subdir = dp;
+ spin_unlock(&proc_subdir_lock);
+
return 0;
}
_
-
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