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proc: use slower rb_first()

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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.

Link: http://lkml.kernel.org/r/20180314231032.GA15854@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Alexey Dobriyan 2018-04-10 16:32:20 -07:00 committed by Linus Torvalds
parent 05c3f29283
commit 4f1134370a
4 changed files with 17 additions and 19 deletions
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26
fs/proc/generic.c
View File

@ -52,8 +52,8 @@ 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)
@ -66,7 +66,7 @@ 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,
@ -87,9 +87,8 @@ 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) {
@ -101,16 +100,15 @@ 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;
}
@ -401,7 +399,7 @@ 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);
@ -577,7 +575,7 @@ 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);
@ -614,13 +612,13 @@ 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;
}

6
fs/proc/internal.h
View File

@ -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;

2
fs/proc/proc_net.c
View File

@ -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;

2
fs/proc/root.c
View File

@ -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",
};