From: Mateusz Guzik <mjguzik@gmail.com>
To: ebiggers@kernel.org
Cc: tytso@mit.edu, jaegeuk@kernel.org, linux-kernel@vger.kernel.org,
linux-fscrypt@vger.kernel.org, Mateusz Guzik <mjguzik@gmail.com>
Subject: [PATCH] fscrypto: try to avoid refing parent dentry in fscrypt_file_open
Date: Tue, 7 May 2024 11:36:53 +0200 [thread overview]
Message-ID: <20240507093653.297402-1-mjguzik@gmail.com> (raw)
Merely checking if the directory is encrypted happens for every open
when using ext4, at the moment refing and unrefing the parent, costing 2
atomics and serializing opens of different files.
The most common case of encryption not being used can be checked for
with RCU instead.
Sample result from open1_processes -t 20 ("Separate file open/close") from
will-it-scale on Sapphire Rapids (ops/s):
before: 12539898
after: 25575494 (+103%)
Arguably a vfs helper would be nice here.
Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
---
fs/crypto/hooks.c | 23 +++++++++++++++++------
1 file changed, 17 insertions(+), 6 deletions(-)
diff --git a/fs/crypto/hooks.c b/fs/crypto/hooks.c
index 104771c3d3f6..16328ec14266 100644
--- a/fs/crypto/hooks.c
+++ b/fs/crypto/hooks.c
@@ -30,21 +30,32 @@
int fscrypt_file_open(struct inode *inode, struct file *filp)
{
int err;
- struct dentry *dir;
+ struct dentry *dentry, *dentry_parent;
+ struct inode *inode_parent;
err = fscrypt_require_key(inode);
if (err)
return err;
- dir = dget_parent(file_dentry(filp));
- if (IS_ENCRYPTED(d_inode(dir)) &&
- !fscrypt_has_permitted_context(d_inode(dir), inode)) {
+ dentry = file_dentry(filp);
+ rcu_read_lock();
+ dentry_parent = READ_ONCE(dentry->d_parent);
+ inode_parent = d_inode_rcu(dentry_parent);
+ if (inode_parent != NULL && !IS_ENCRYPTED(inode_parent)) {
+ rcu_read_unlock();
+ return 0;
+ }
+ rcu_read_unlock();
+
+ dentry_parent = dget_parent(dentry);
+ if (IS_ENCRYPTED(d_inode(dentry_parent)) &&
+ !fscrypt_has_permitted_context(d_inode(dentry_parent), inode)) {
fscrypt_warn(inode,
"Inconsistent encryption context (parent directory: %lu)",
- d_inode(dir)->i_ino);
+ d_inode(dentry_parent)->i_ino);
err = -EPERM;
}
- dput(dir);
+ dput(dentry_parent);
return err;
}
EXPORT_SYMBOL_GPL(fscrypt_file_open);
--
2.39.2
next reply other threads:[~2024-05-07 9:37 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-07 9:36 Mateusz Guzik [this message]
2024-05-07 17:56 ` [PATCH] fscrypto: try to avoid refing parent dentry in fscrypt_file_open Eric Biggers
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