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SubjectRe: [PATCH] proc: avoid extra pde_put() in proc_fill_super()
On Tue, Jan 22, 2013 at 09:03:26PM +0400, Maxim Patlasov wrote:
> If proc_get_inode() succeeded, but d_make_root() failed, pde_put() for
> proc_root will be called twice: the first time due to iput() called from
> d_make_root() and the second time directly in the end of proc_fill_super().

I don't like that solution, TBH. How about making proc_get_inode() call
pde_put() on failure instead? Note that it already does so if inode had
been found in icache, so this will just make the refcounting consistent.
Completely untested patch follows:

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index 76ddae8..8b487e5 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -413,31 +413,24 @@ struct dentry *proc_lookup_de(struct proc_dir_entry *de, struct inode *dir,
struct dentry *dentry)
{
struct inode *inode = NULL;
- int error = -ENOENT;

spin_lock(&proc_subdir_lock);
for (de = de->subdir; de ; de = de->next) {
if (de->namelen != dentry->d_name.len)
continue;
- if (!memcmp(dentry->d_name.name, de->name, de->namelen)) {
- pde_get(de);
- spin_unlock(&proc_subdir_lock);
- error = -ENOMEM;
- inode = proc_get_inode(dir->i_sb, de);
- goto out_unlock;
- }
- }
- spin_unlock(&proc_subdir_lock);
-out_unlock:
-
- if (inode) {
+ if (memcmp(dentry->d_name.name, de->name, de->namelen))
+ continue;
+ pde_get(de);
+ spin_unlock(&proc_subdir_lock);
+ inode = proc_get_inode(dir->i_sb, de);
+ if (!inode)
+ return ERR_PTR(-ENOMEM);
d_set_d_op(dentry, &proc_dentry_operations);
d_add(dentry, inode);
return NULL;
}
- if (de)
- pde_put(de);
- return ERR_PTR(error);
+ spin_unlock(&proc_subdir_lock);
+ return ERR_PTR(-ENOENT);
}

struct dentry *proc_lookup(struct inode *dir, struct dentry *dentry,
diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index 439ae688..e2bbe20 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -448,9 +448,7 @@ struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
struct inode * inode;

inode = iget_locked(sb, de->low_ino);
- if (!inode)
- return NULL;
- if (inode->i_state & I_NEW) {
+ if (inode && inode->i_state & I_NEW) {
inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
PROC_I(inode)->pde = de;

@@ -499,6 +497,5 @@ int proc_fill_super(struct super_block *s)
return 0;

printk("proc_read_super: get root inode failed\n");
- pde_put(&proc_root);
return -ENOMEM;
}

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