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Date: Thu, 18 Aug 2022 12:12:30 +0300
From: Vasily Averin <vvs@...nvz.org>
To: Roman Gushchin <roman.gushchin@...ux.dev>, mkoutny@...e.com,
tj@...nel.org
Cc: gregkh@...uxfoundation.org, hannes@...xchg.org, kernel@...nvz.org,
linux-kernel@...r.kernel.org, mhocko@...e.com, shakeelb@...gle.com,
songmuchun@...edance.com, viro@...iv.linux.org.uk,
Christian Brauner <brauner@...nel.org>
Subject: [RFC PATCH] simple_xattr: switch from list to rb_tree
The patch was announced here:
https://lore.kernel.org/all/62188f37-f816-08e9-cdd5-8df23131746d@openvz.org/
"5) simple_xattrs: replace list to rb-tree
This significantly reduces the search time for existing entries."
It was compiled but was not tested yet.
---
Currently simple_xattr uses a list to store existing entries.
If the list grows, the presence check may be slow and potentially
lead to problems. Red-black tree should work more efficiently
in this situation.
This patch replaces list to rb_tree and switches simple_xattr_* calls
to its using.
Signed-off-by: Vasily Averin <vvs@...nvz.org>
---
fs/xattr.c | 109 ++++++++++++++++++++++++++++++++----------
include/linux/xattr.h | 13 +++--
2 files changed, 92 insertions(+), 30 deletions(-)
diff --git a/fs/xattr.c b/fs/xattr.c
index 6401703707f2..672f2214fcfd 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -1021,6 +1021,60 @@ struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
return new_xattr;
}
+static struct simple_xattr *simple_xattr_rb_search(struct rb_root *root,
+ const char* name)
+{
+ struct rb_node **new = &(root->rb_node), *parent = NULL;
+
+ /* Figure out where to put new node */
+ while (*new)
+ {
+ struct simple_xattr *xattr;
+ int result;
+
+ xattr = container_of(*new, struct simple_xattr, node);
+ result = strcmp(xattr->name, name);
+
+ parent = *new;
+ if (result < 0)
+ new = &((*new)->rb_left);
+ else if (result > 0)
+ new = &((*new)->rb_right);
+ else
+ return xattr;
+ }
+ return NULL;
+}
+
+static bool simple_xattr_rb_insert(struct rb_root *root,
+ struct simple_xattr *new_xattr)
+{
+ struct rb_node **new = &(root->rb_node), *parent = NULL;
+
+ /* Figure out where to put new node */
+ while (*new) {
+ struct simple_xattr *xattr;
+ int result;
+
+ xattr = container_of(*new, struct simple_xattr, node);
+ result = strcmp(xattr->name, new_xattr->name);
+
+ parent = *new;
+ if (result < 0)
+ new = &((*new)->rb_left);
+ else if (result > 0)
+ new = &((*new)->rb_right);
+ else
+ return false;
+ }
+
+ /* Add new node and rebalance tree. */
+ rb_link_node(&new_xattr->node, parent, new);
+ rb_insert_color(&new_xattr->node, root);
+
+ return true;
+}
+
/*
* xattr GET operation for in-memory/pseudo filesystems
*/
@@ -1031,10 +1085,8 @@ int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
int ret = -ENODATA;
spin_lock(&xattrs->lock);
- list_for_each_entry(xattr, &xattrs->head, list) {
- if (strcmp(name, xattr->name))
- continue;
-
+ xattr = simple_xattr_rb_search(&xattrs->rb_root, name);
+ if (xattr) {
ret = xattr->size;
if (buffer) {
if (size < xattr->size)
@@ -1042,7 +1094,6 @@ int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
else
memcpy(buffer, xattr->value, xattr->size);
}
- break;
}
spin_unlock(&xattrs->lock);
return ret;
@@ -1067,7 +1118,7 @@ int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
const void *value, size_t size, int flags,
ssize_t *removed_size)
{
- struct simple_xattr *xattr;
+ struct simple_xattr *xattr = NULL;
struct simple_xattr *new_xattr = NULL;
int err = 0;
@@ -1088,31 +1139,36 @@ int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
}
spin_lock(&xattrs->lock);
- list_for_each_entry(xattr, &xattrs->head, list) {
- if (!strcmp(name, xattr->name)) {
- if (flags & XATTR_CREATE) {
- xattr = new_xattr;
- err = -EEXIST;
- } else if (new_xattr) {
- list_replace(&xattr->list, &new_xattr->list);
+ if ((flags & XATTR_CREATE) && new_xattr) {
+ /* create new */
+ if (!simple_xattr_rb_insert(&xattrs->rb_root, new_xattr)) {
+ /* already exist */
+ xattr = new_xattr;
+ err = -EEXIST;
+ }
+ } else {
+ /* replace or remove */
+ xattr = simple_xattr_rb_search(&xattrs->rb_root, name);
+ if (xattr) {
+ /* found */
+ if (!new_xattr) {
+ /* remove existing */
+ rb_erase(&xattr->node, &xattrs->rb_root);
if (removed_size)
*removed_size = xattr->size;
} else {
- list_del(&xattr->list);
+ /* replace existing */
+ rb_replace_node(&xattr->node, &new_xattr->node,
+ &xattrs->rb_root);
if (removed_size)
*removed_size = xattr->size;
}
- goto out;
+ } else if (new_xattr) {
+ /* not found, incorrect replace */
+ xattr = new_xattr;
+ err = -ENODATA;
}
}
- if (flags & XATTR_REPLACE) {
- xattr = new_xattr;
- err = -ENODATA;
- } else {
- list_add(&new_xattr->list, &xattrs->head);
- xattr = NULL;
- }
-out:
spin_unlock(&xattrs->lock);
if (xattr) {
kfree(xattr->name);
@@ -1149,6 +1205,7 @@ ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs,
{
bool trusted = capable(CAP_SYS_ADMIN);
struct simple_xattr *xattr;
+ struct rb_node *node;
ssize_t remaining_size = size;
int err = 0;
@@ -1170,7 +1227,9 @@ ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs,
#endif
spin_lock(&xattrs->lock);
- list_for_each_entry(xattr, &xattrs->head, list) {
+ for (node = rb_first(&xattrs->rb_root); node; node = rb_next(node)) {
+ xattr = container_of(node, struct simple_xattr, node);
+
/* skip "trusted." attributes for unprivileged callers */
if (!trusted && xattr_is_trusted(xattr->name))
continue;
@@ -1191,6 +1250,6 @@ void simple_xattr_list_add(struct simple_xattrs *xattrs,
struct simple_xattr *new_xattr)
{
spin_lock(&xattrs->lock);
- list_add(&new_xattr->list, &xattrs->head);
+ simple_xattr_rb_insert(&xattrs->rb_root, new_xattr);
spin_unlock(&xattrs->lock);
}
diff --git a/include/linux/xattr.h b/include/linux/xattr.h
index 979a9d3e5bfb..bbe81cfb7a4d 100644
--- a/include/linux/xattr.h
+++ b/include/linux/xattr.h
@@ -80,12 +80,12 @@ static inline const char *xattr_prefix(const struct xattr_handler *handler)
}
struct simple_xattrs {
- struct list_head head;
+ struct rb_root rb_root;
spinlock_t lock;
};
struct simple_xattr {
- struct list_head list;
+ struct rb_node node;
char *name;
size_t size;
char value[];
@@ -96,7 +96,7 @@ struct simple_xattr {
*/
static inline void simple_xattrs_init(struct simple_xattrs *xattrs)
{
- INIT_LIST_HEAD(&xattrs->head);
+ xattrs->rb_root = RB_ROOT;
spin_lock_init(&xattrs->lock);
}
@@ -105,9 +105,12 @@ static inline void simple_xattrs_init(struct simple_xattrs *xattrs)
*/
static inline void simple_xattrs_free(struct simple_xattrs *xattrs)
{
- struct simple_xattr *xattr, *node;
+ struct simple_xattr *xattr;
+ struct rb_node *node;
- list_for_each_entry_safe(xattr, node, &xattrs->head, list) {
+ while ((node = rb_first(&xattrs->rb_root))) {
+ rb_erase(node, &xattrs->rb_root);
+ xattr = container_of(node, struct simple_xattr, node);
kfree(xattr->name);
kvfree(xattr);
}
--
2.34.1
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