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Subject[PATCH -mm] proc: use slower rb_first()
In a typical for /proc "open+read+close" usecase, dentry is looked up
successfully on open only to be killed in dput() on close. In fact dentries
which aren't /proc/*/... and /proc/sys/* were almost NEVER CACHED.
Simple printk in proc_lookup_de() shows that.

Now that ->delete hook intelligently picks which dentries should live
in dcache and which should not, rbtree caching is not necessary as
dcache does it job, at last!

As a side effect, struct proc_dir_entry shrinks by one pointer
which can go into inline name.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---

fs/proc/generic.c | 26 ++++++++++++--------------
fs/proc/internal.h | 6 +++---
fs/proc/proc_net.c | 2 +-
fs/proc/root.c | 2 +-
4 files changed, 17 insertions(+), 19 deletions(-)

--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -53,8 +53,8 @@ static int proc_match(const char *name, struct proc_dir_entry *de, unsigned int

static struct proc_dir_entry *pde_subdir_first(struct proc_dir_entry *dir)
{
- return rb_entry_safe(rb_first_cached(&dir->subdir),
- struct proc_dir_entry, subdir_node);
+ return rb_entry_safe(rb_first(&dir->subdir), struct proc_dir_entry,
+ subdir_node);
}

static struct proc_dir_entry *pde_subdir_next(struct proc_dir_entry *dir)
@@ -67,7 +67,7 @@ static struct proc_dir_entry *pde_subdir_find(struct proc_dir_entry *dir,
const char *name,
unsigned int len)
{
- struct rb_node *node = dir->subdir.rb_root.rb_node;
+ struct rb_node *node = dir->subdir.rb_node;

while (node) {
struct proc_dir_entry *de = rb_entry(node,
@@ -88,9 +88,8 @@ static struct proc_dir_entry *pde_subdir_find(struct proc_dir_entry *dir,
static bool pde_subdir_insert(struct proc_dir_entry *dir,
struct proc_dir_entry *de)
{
- struct rb_root_cached *root = &dir->subdir;
- struct rb_node **new = &root->rb_root.rb_node, *parent = NULL;
- bool leftmost = true;
+ struct rb_root *root = &dir->subdir;
+ struct rb_node **new = &root->rb_node, *parent = NULL;

/* Figure out where to put new node */
while (*new) {
@@ -102,16 +101,15 @@ static bool pde_subdir_insert(struct proc_dir_entry *dir,
parent = *new;
if (result < 0)
new = &(*new)->rb_left;
- else if (result > 0) {
+ else if (result > 0)
new = &(*new)->rb_right;
- leftmost = false;
- } else
+ else
return false;
}

/* Add new node and rebalance tree. */
rb_link_node(&de->subdir_node, parent, new);
- rb_insert_color_cached(&de->subdir_node, root, leftmost);
+ rb_insert_color(&de->subdir_node, root);
return true;
}

@@ -422,7 +420,7 @@ static struct proc_dir_entry *__proc_create(struct proc_dir_entry **parent,
ent->namelen = qstr.len;
ent->mode = mode;
ent->nlink = nlink;
- ent->subdir = RB_ROOT_CACHED;
+ ent->subdir = RB_ROOT;
refcount_set(&ent->refcnt, 1);
spin_lock_init(&ent->pde_unload_lock);
INIT_LIST_HEAD(&ent->pde_openers);
@@ -598,7 +596,7 @@ void remove_proc_entry(const char *name, struct proc_dir_entry *parent)

de = pde_subdir_find(parent, fn, len);
if (de)
- rb_erase_cached(&de->subdir_node, &parent->subdir);
+ rb_erase(&de->subdir_node, &parent->subdir);
write_unlock(&proc_subdir_lock);
if (!de) {
WARN(1, "name '%s'\n", name);
@@ -635,13 +633,13 @@ int remove_proc_subtree(const char *name, struct proc_dir_entry *parent)
write_unlock(&proc_subdir_lock);
return -ENOENT;
}
- rb_erase_cached(&root->subdir_node, &parent->subdir);
+ rb_erase(&root->subdir_node, &parent->subdir);

de = root;
while (1) {
next = pde_subdir_first(de);
if (next) {
- rb_erase_cached(&next->subdir_node, &de->subdir);
+ rb_erase(&next->subdir_node, &de->subdir);
de = next;
continue;
}
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -51,15 +51,15 @@ struct proc_dir_entry {
kgid_t gid;
loff_t size;
struct proc_dir_entry *parent;
- struct rb_root_cached subdir;
+ struct rb_root subdir;
struct rb_node subdir_node;
char *name;
umode_t mode;
u8 namelen;
#ifdef CONFIG_64BIT
-#define SIZEOF_PDE_INLINE_NAME (192-147)
+#define SIZEOF_PDE_INLINE_NAME (192-139)
#else
-#define SIZEOF_PDE_INLINE_NAME (128-91)
+#define SIZEOF_PDE_INLINE_NAME (128-87)
#endif
char inline_name[SIZEOF_PDE_INLINE_NAME];
} __randomize_layout;
--- a/fs/proc/proc_net.c
+++ b/fs/proc/proc_net.c
@@ -196,7 +196,7 @@ static __net_init int proc_net_ns_init(struct net *net)
if (!netd)
goto out;

- netd->subdir = RB_ROOT_CACHED;
+ netd->subdir = RB_ROOT;
netd->data = net;
netd->nlink = 2;
netd->namelen = 3;
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -203,7 +203,7 @@ struct proc_dir_entry proc_root = {
.proc_iops = &proc_root_inode_operations,
.proc_fops = &proc_root_operations,
.parent = &proc_root,
- .subdir = RB_ROOT_CACHED,
+ .subdir = RB_ROOT,
.name = proc_root.inline_name,
.inline_name = "/proc",
};
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