2007-02-22 12:41:19

by Pekka Enberg

Subject: [PATCH 2/2] unionfs: fix slab abuses with krealloc

From: Pekka Enberg <[email protected]>

This changes unionfs to use krealloc() for reallocating memory so that
we don't need to play tricks with slab internals.

Cc: Josef Sipek <[email protected]>
Signed-off-by: Pekka Enberg <[email protected]>
---
fs/unionfs/copyup.c | 35 +++++++++++++----------------------
fs/unionfs/lookup.c | 33 +++++++++++++--------------------
2 files changed, 26 insertions(+), 42 deletions(-)

Index: 2.6/fs/unionfs/copyup.c
===================================================================
--- 2.6.orig/fs/unionfs/copyup.c 2007-02-22 11:33:52.000000000 +0200
+++ 2.6/fs/unionfs/copyup.c 2007-02-22 11:33:53.000000000 +0200
@@ -603,23 +603,16 @@
const char *childname;
unsigned int childnamelen;

- int old_kmalloc_size;
- int kmalloc_size;
- int num_dentry;
+ int nr_dentry;
int count;

int old_bstart;
int old_bend;
struct dentry **path = NULL;
- struct dentry **tmp_path;
struct super_block *sb;

verify_locked(dentry);

- /* There is no sense allocating any less than the minimum. */
- kmalloc_size = malloc_sizes[0].cs_size;
- num_dentry = kmalloc_size / sizeof(struct dentry *);
-
if ((err = is_robranch_super(dir->i_sb, bindex))) {
hidden_dentry = ERR_PTR(err);
goto out;
@@ -629,7 +622,10 @@
old_bend = dbend(dentry);

hidden_dentry = ERR_PTR(-ENOMEM);
- path = kzalloc(kmalloc_size, GFP_KERNEL);
+
+ /* There is no sense allocating any less than the minimum. */
+ nr_dentry = 1;
+ path = kmalloc(nr_dentry * sizeof(struct dentry *), GFP_KERNEL);
if (!path)
goto out;

@@ -655,26 +651,21 @@
/* find out the hidden_parent_dentry in the given branch */
hidden_parent_dentry = unionfs_lower_dentry_idx(parent_dentry, bindex);

- /* store the child dentry */
- path[count++] = child_dentry;
-
/* grow path table */
- if (count == num_dentry) {
- old_kmalloc_size = kmalloc_size;
- kmalloc_size *= 2;
- num_dentry = kmalloc_size / sizeof(struct dentry *);
+ if (count == nr_dentry) {
+ void *p;

- tmp_path = kzalloc(kmalloc_size, GFP_KERNEL);
- if (!tmp_path) {
+ nr_dentry *= 2;
+ p = krealloc(path, nr_dentry * sizeof(struct dentry *), GFP_KERNEL);
+ if (!p) {
hidden_dentry = ERR_PTR(-ENOMEM);
goto out;
}
- memcpy(tmp_path, path, old_kmalloc_size);
- kfree(path);
- path = tmp_path;
- tmp_path = NULL;
+ path = p;
}

+ /* store the child dentry */
+ path[count++] = child_dentry;
} while (!hidden_parent_dentry);
count--;

Index: 2.6/fs/unionfs/lookup.c
===================================================================
--- 2.6.orig/fs/unionfs/lookup.c 2007-02-22 11:33:52.000000000 +0200
+++ 2.6/fs/unionfs/lookup.c 2007-02-22 11:33:53.000000000 +0200
@@ -428,9 +428,8 @@
/* allocate new dentry private data, free old one if necessary */
int new_dentry_private_data(struct dentry *dentry)
{
- int newsize;
- int oldsize = 0;
struct unionfs_dentry_info *info = UNIONFS_D(dentry);
+ int new_size, size;

spin_lock(&dentry->d_lock);
if (!info) {
@@ -445,8 +444,9 @@
mutex_lock(&info->lock);

info->lower_paths = NULL;
+ size = 0;
} else
- oldsize = sizeof(struct path) * info->bcount;
+ size = sizeof(struct path) * info->bcount;

info->bstart = -1;
info->bend = -1;
@@ -454,28 +454,21 @@
info->bcount = sbmax(dentry->d_sb);
atomic_set(&info->generation,
atomic_read(&UNIONFS_SB(dentry->d_sb)->generation));
- newsize = sizeof(struct path) * sbmax(dentry->d_sb);
+
+ new_size = sizeof(struct path) * sbmax(dentry->d_sb);

/* Don't reallocate when we already have enough space. */
- /* It would be ideal if we could actually use the slab macros to
- * determine what our object sizes is, but those are not exported.
- */
- if (oldsize) {
- int minsize = malloc_sizes[0].cs_size;
-
- if (!newsize || ((oldsize < newsize) && (newsize > minsize))) {
- kfree(info->lower_paths);
- info->lower_paths = NULL;
- }
- }
+ if (new_size > size) {
+ void *p;

- if (!info->lower_paths && newsize) {
- info->lower_paths = kmalloc(newsize, GFP_ATOMIC);
- if (!info->lower_paths)
+ p = krealloc(info->lower_paths, new_size, GFP_ATOMIC);
+ if (!p)
goto out_free;
- }

- memset(info->lower_paths, 0, (oldsize > newsize ? oldsize : newsize));
+ info->lower_paths = p;
+ size = new_size;
+ }
+ memset(info->lower_paths, 0, size);

spin_unlock(&dentry->d_lock);
return 0;

2007-02-23 06:53:32

by Josef Sipek

Subject: Re: [PATCH 2/2] unionfs: fix slab abuses with krealloc

On Thu, Feb 22, 2007 at 02:41:16PM +0200, Pekka J Enberg wrote:
> From: Pekka Enberg <[email protected]>
>
> This changes unionfs to use krealloc() for reallocating memory so that
> we don't need to play tricks with slab internals.
>
> Cc: Josef Sipek <[email protected]>
> Signed-off-by: Pekka Enberg <[email protected]>

I guess I should have Acked both patches...

Acked-by: Josef 'Jeff' Sipek <[email protected]>