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fs: cache first and last mount

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Speed up listmount() by caching the first and last node making retrieval
of the first and last mount of each mount namespace O(1).

Link: https://lore.kernel.org/r/20241215-vfs-6-14-mount-work-v1-2-fd55922c4af8@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Christian Brauner 2024-12-15 21:17:06 +01:00
parent 5a4e727d1a
commit b782c5efe7
No known key found for this signature in database
GPG Key ID: 91C61BC06578DCA2
2 changed files with 24 additions and 6 deletions
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13
fs/mount.h
View File

@ -8,7 +8,11 @@
struct mnt_namespace {
struct ns_common ns;
struct mount * root;
struct rb_root mounts; /* Protected by namespace_sem */
struct {
struct rb_root mounts; /* Protected by namespace_sem */
struct rb_node *mnt_last_node; /* last (rightmost) mount in the rbtree */
struct rb_node *mnt_first_node; /* first (leftmost) mount in the rbtree */
};
struct user_namespace *user_ns;
struct ucounts *ucounts;
u64 seq; /* Sequence number to prevent loops */
@ -154,8 +158,13 @@ static inline bool mnt_ns_attached(const struct mount *mnt)
static inline void move_from_ns(struct mount *mnt, struct list_head *dt_list)
{
struct mnt_namespace *ns = mnt->mnt_ns;
WARN_ON(!mnt_ns_attached(mnt));
rb_erase(&mnt->mnt_node, &mnt->mnt_ns->mounts);
if (ns->mnt_last_node == &mnt->mnt_node)
ns->mnt_last_node = rb_prev(&mnt->mnt_node);
if (ns->mnt_first_node == &mnt->mnt_node)
ns->mnt_first_node = rb_next(&mnt->mnt_node);
rb_erase(&mnt->mnt_node, &ns->mounts);
RB_CLEAR_NODE(&mnt->mnt_node);
list_add_tail(&mnt->mnt_list, dt_list);
}

17
fs/namespace.c
View File

@ -1155,16 +1155,25 @@ static void mnt_add_to_ns(struct mnt_namespace *ns, struct mount *mnt)
{
struct rb_node **link = &ns->mounts.rb_node;
struct rb_node *parent = NULL;
bool mnt_first_node = true, mnt_last_node = true;
WARN_ON(mnt_ns_attached(mnt));
mnt->mnt_ns = ns;
while (*link) {
parent = *link;
if (mnt->mnt_id_unique < node_to_mount(parent)->mnt_id_unique)
if (mnt->mnt_id_unique < node_to_mount(parent)->mnt_id_unique) {
link = &parent->rb_left;
else
mnt_last_node = false;
} else {
link = &parent->rb_right;
mnt_first_node = false;
}
}
if (mnt_last_node)
ns->mnt_last_node = &mnt->mnt_node;
if (mnt_first_node)
ns->mnt_first_node = &mnt->mnt_node;
rb_link_node(&mnt->mnt_node, parent, link);
rb_insert_color(&mnt->mnt_node, &ns->mounts);
}
@ -5559,9 +5568,9 @@ static ssize_t do_listmount(struct mnt_namespace *ns, u64 mnt_parent_id,
if (!last_mnt_id) {
if (reverse)
first = node_to_mount(rb_last(&ns->mounts));
first = node_to_mount(ns->mnt_last_node);
else
first = node_to_mount(rb_first(&ns->mounts));
first = node_to_mount(ns->mnt_first_node);
} else {
if (reverse)
first = mnt_find_id_at_reverse(ns, last_mnt_id - 1);