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Message-ID: <20220123100448.GA1468@haolee.io>
Date: Sun, 23 Jan 2022 10:04:48 +0000
From: Hao Lee <haolee.swjtu@...il.com>
To: viro@...iv.linux.org.uk
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
haolee.swjtu@...il.com
Subject: [PATCH] fs/namespace: eliminate unnecessary mount counting
propagate_one() counts the number of propagated mounts in each
propagation. We can count them in advance and use the number in
subsequent propagation.
Signed-off-by: Hao Lee <haolee.swjtu@...il.com>
---
fs/namespace.c | 27 +++++++++++++++++++--------
fs/pnode.c | 12 +++++++-----
fs/pnode.h | 5 +++--
3 files changed, 29 insertions(+), 15 deletions(-)
diff --git a/fs/namespace.c b/fs/namespace.c
index c6feb92209a6..5d05392854ca 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2082,18 +2082,15 @@ static int invent_group_ids(struct mount *mnt, bool recurse)
return 0;
}
-int count_mounts(struct mnt_namespace *ns, struct mount *mnt)
+int update_pending_mounts(struct mnt_namespace *ns, unsigned int mounts)
{
unsigned int max = READ_ONCE(sysctl_mount_max);
- unsigned int mounts = 0, old, pending, sum;
- struct mount *p;
-
- for (p = mnt; p; p = next_mnt(p, mnt))
- mounts++;
+ unsigned int old, pending, sum;
old = ns->mounts;
pending = ns->pending_mounts;
sum = old + pending;
+
if ((old > sum) ||
(pending > sum) ||
(max < sum) ||
@@ -2104,6 +2101,17 @@ int count_mounts(struct mnt_namespace *ns, struct mount *mnt)
return 0;
}
+unsigned int count_mounts(struct mount *mnt)
+{
+ unsigned int mounts = 0;
+ struct mount *p;
+
+ for (p = mnt; p; p = next_mnt(p, mnt))
+ mounts++;
+
+ return mounts;
+}
+
/*
* @source_mnt : mount tree to be attached
* @nd : place the mount tree @source_mnt is attached
@@ -2178,6 +2186,7 @@ static int attach_recursive_mnt(struct mount *source_mnt,
struct mountpoint *smp;
struct mount *child, *p;
struct hlist_node *n;
+ unsigned int nr_mounts;
int err;
/* Preallocate a mountpoint in case the new mounts need
@@ -2187,9 +2196,10 @@ static int attach_recursive_mnt(struct mount *source_mnt,
if (IS_ERR(smp))
return PTR_ERR(smp);
+ nr_mounts = count_mounts(source_mnt);
/* Is there space to add these mounts to the mount namespace? */
if (!moving) {
- err = count_mounts(ns, source_mnt);
+ err = update_pending_mounts(ns, nr_mounts);
if (err)
goto out;
}
@@ -2198,7 +2208,8 @@ static int attach_recursive_mnt(struct mount *source_mnt,
err = invent_group_ids(source_mnt, true);
if (err)
goto out;
- err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list);
+ err = propagate_mnt(dest_mnt, dest_mp, source_mnt, nr_mounts,
+ &tree_list);
lock_mount_hash();
if (err)
goto out_cleanup_ids;
diff --git a/fs/pnode.c b/fs/pnode.c
index 1106137c747a..877de718fc35 100644
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -222,7 +222,7 @@ static inline bool peers(struct mount *m1, struct mount *m2)
return m1->mnt_group_id == m2->mnt_group_id && m1->mnt_group_id;
}
-static int propagate_one(struct mount *m)
+static int propagate_one(struct mount *m, unsigned int nr_mounts)
{
struct mount *child;
int type;
@@ -269,7 +269,7 @@ static int propagate_one(struct mount *m)
last_dest = m;
last_source = child;
hlist_add_head(&child->mnt_hash, list);
- return count_mounts(m->mnt_ns, child);
+ return update_pending_mounts(m->mnt_ns, nr_mounts);
}
/*
@@ -284,9 +284,11 @@ static int propagate_one(struct mount *m)
* @dest_dentry: destination dentry.
* @source_mnt: source mount.
* @tree_list : list of heads of trees to be attached.
+ * @nr_mounts : the number of mounts in source_mnt
*/
int propagate_mnt(struct mount *dest_mnt, struct mountpoint *dest_mp,
- struct mount *source_mnt, struct hlist_head *tree_list)
+ struct mount *source_mnt, unsigned int nr_mounts,
+ struct hlist_head *tree_list)
{
struct mount *m, *n;
int ret = 0;
@@ -305,7 +307,7 @@ int propagate_mnt(struct mount *dest_mnt, struct mountpoint *dest_mp,
/* all peers of dest_mnt, except dest_mnt itself */
for (n = next_peer(dest_mnt); n != dest_mnt; n = next_peer(n)) {
- ret = propagate_one(n);
+ ret = propagate_one(n, nr_mounts);
if (ret)
goto out;
}
@@ -316,7 +318,7 @@ int propagate_mnt(struct mount *dest_mnt, struct mountpoint *dest_mp,
/* everything in that slave group */
n = m;
do {
- ret = propagate_one(n);
+ ret = propagate_one(n, nr_mounts);
if (ret)
goto out;
n = next_peer(n);
diff --git a/fs/pnode.h b/fs/pnode.h
index 988f1aa9b02a..005355c0dd49 100644
--- a/fs/pnode.h
+++ b/fs/pnode.h
@@ -38,7 +38,7 @@ static inline void set_mnt_shared(struct mount *mnt)
void change_mnt_propagation(struct mount *, int);
int propagate_mnt(struct mount *, struct mountpoint *, struct mount *,
- struct hlist_head *);
+ unsigned int, struct hlist_head *);
int propagate_umount(struct list_head *);
int propagate_mount_busy(struct mount *, int);
void propagate_mount_unlock(struct mount *);
@@ -52,5 +52,6 @@ void mnt_change_mountpoint(struct mount *parent, struct mountpoint *mp,
struct mount *copy_tree(struct mount *, struct dentry *, int);
bool is_path_reachable(struct mount *, struct dentry *,
const struct path *root);
-int count_mounts(struct mnt_namespace *ns, struct mount *mnt);
+int update_pending_mounts(struct mnt_namespace *ns, unsigned int mounts);
+unsigned int count_mounts(struct mount *mnt);
#endif /* _LINUX_PNODE_H */
--
2.34.1
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