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Date: Wed, 22 Dec 2021 23:23:32 +0000
From: David Howells <dhowells@...hat.com>
To: linux-cachefs@...hat.com
Cc: dhowells@...hat.com, Trond Myklebust <trondmy@...merspace.com>,
Anna Schumaker <anna.schumaker@...app.com>,
Steve French <sfrench@...ba.org>,
Dominique Martinet <asmadeus@...ewreck.org>,
Jeff Layton <jlayton@...nel.org>,
Matthew Wilcox <willy@...radead.org>,
Alexander Viro <viro@...iv.linux.org.uk>,
Omar Sandoval <osandov@...ndov.com>,
JeffleXu <jefflexu@...ux.alibaba.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
linux-afs@...ts.infradead.org, linux-nfs@...r.kernel.org,
linux-cifs@...r.kernel.org, ceph-devel@...r.kernel.org,
v9fs-developer@...ts.sourceforge.net,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v4 38/68] vfs,
cachefiles: Mark a backing file in use with an inode flag
Use an inode flag, S_KERNEL_FILE, to mark that a backing file is in use by
the kernel to prevent cachefiles or other kernel services from interfering
with that file.
Alter rmdir to reject attempts to remove a directory marked with this flag.
This is used by cachefiles to prevent cachefilesd from removing them.
Using S_SWAPFILE instead isn't really viable as that has other effects in
the I/O paths.
Changes
=======
ver #3:
- Check for the object pointer being NULL in the tracepoints rather than
the caller.
Signed-off-by: David Howells <dhowells@...hat.com>
cc: linux-cachefs@...hat.com
Link: https://lore.kernel.org/r/163819630256.215744.4815885535039369574.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906931596.143852.8642051223094013028.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967141000.1823006.12920680657559677789.stgit@warthog.procyon.org.uk/ # v3
---
fs/cachefiles/Makefile | 1 +
fs/cachefiles/namei.c | 43 +++++++++++++++++++++++++++++++++++++
fs/namei.c | 3 ++-
include/linux/fs.h | 1 +
include/trace/events/cachefiles.h | 42 ++++++++++++++++++++++++++++++++++++
5 files changed, 89 insertions(+), 1 deletion(-)
create mode 100644 fs/cachefiles/namei.c
diff --git a/fs/cachefiles/Makefile b/fs/cachefiles/Makefile
index 463e3d608b75..e0b092ca077f 100644
--- a/fs/cachefiles/Makefile
+++ b/fs/cachefiles/Makefile
@@ -7,6 +7,7 @@ cachefiles-y := \
cache.o \
daemon.o \
main.o \
+ namei.o \
security.o
cachefiles-$(CONFIG_CACHEFILES_ERROR_INJECTION) += error_inject.o
diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
new file mode 100644
index 000000000000..913f83f1c900
--- /dev/null
+++ b/fs/cachefiles/namei.c
@@ -0,0 +1,43 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* CacheFiles path walking and related routines
+ *
+ * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@...hat.com)
+ */
+
+#include <linux/fs.h>
+#include "internal.h"
+
+/*
+ * Mark the backing file as being a cache file if it's not already in use. The
+ * mark tells the culling request command that it's not allowed to cull the
+ * file or directory. The caller must hold the inode lock.
+ */
+static bool __cachefiles_mark_inode_in_use(struct cachefiles_object *object,
+ struct dentry *dentry)
+{
+ struct inode *inode = d_backing_inode(dentry);
+ bool can_use = false;
+
+ if (!(inode->i_flags & S_KERNEL_FILE)) {
+ inode->i_flags |= S_KERNEL_FILE;
+ trace_cachefiles_mark_active(object, inode);
+ can_use = true;
+ } else {
+ pr_notice("cachefiles: Inode already in use: %pd\n", dentry);
+ }
+
+ return can_use;
+}
+
+/*
+ * Unmark a backing inode. The caller must hold the inode lock.
+ */
+static void __cachefiles_unmark_inode_in_use(struct cachefiles_object *object,
+ struct dentry *dentry)
+{
+ struct inode *inode = d_backing_inode(dentry);
+
+ inode->i_flags &= ~S_KERNEL_FILE;
+ trace_cachefiles_mark_inactive(object, inode);
+}
diff --git a/fs/namei.c b/fs/namei.c
index 1f9d2187c765..d81f04f8d818 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3958,7 +3958,8 @@ int vfs_rmdir(struct user_namespace *mnt_userns, struct inode *dir,
inode_lock(dentry->d_inode);
error = -EBUSY;
- if (is_local_mountpoint(dentry))
+ if (is_local_mountpoint(dentry) ||
+ (dentry->d_inode->i_flags & S_KERNEL_FILE))
goto out;
error = security_inode_rmdir(dir, dentry);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 2c0b8e77d9ab..bcf1ca430139 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2249,6 +2249,7 @@ struct super_operations {
#define S_ENCRYPTED (1 << 14) /* Encrypted file (using fs/crypto/) */
#define S_CASEFOLD (1 << 15) /* Casefolded file */
#define S_VERITY (1 << 16) /* Verity file (using fs/verity/) */
+#define S_KERNEL_FILE (1 << 17) /* File is in use by the kernel (eg. fs/cachefiles) */
/*
* Note that nosuid etc flags are inode-specific: setting some file-system
diff --git a/include/trace/events/cachefiles.h b/include/trace/events/cachefiles.h
index 9bd5a8a60801..6331cd29880d 100644
--- a/include/trace/events/cachefiles.h
+++ b/include/trace/events/cachefiles.h
@@ -83,6 +83,48 @@ cachefiles_error_traces;
#define E_(a, b) { a, b }
+TRACE_EVENT(cachefiles_mark_active,
+ TP_PROTO(struct cachefiles_object *obj,
+ struct inode *inode),
+
+ TP_ARGS(obj, inode),
+
+ /* Note that obj may be NULL */
+ TP_STRUCT__entry(
+ __field(unsigned int, obj )
+ __field(ino_t, inode )
+ ),
+
+ TP_fast_assign(
+ __entry->obj = obj ? obj->debug_id : 0;
+ __entry->inode = inode->i_ino;
+ ),
+
+ TP_printk("o=%08x i=%lx",
+ __entry->obj, __entry->inode)
+ );
+
+TRACE_EVENT(cachefiles_mark_inactive,
+ TP_PROTO(struct cachefiles_object *obj,
+ struct inode *inode),
+
+ TP_ARGS(obj, inode),
+
+ /* Note that obj may be NULL */
+ TP_STRUCT__entry(
+ __field(unsigned int, obj )
+ __field(ino_t, inode )
+ ),
+
+ TP_fast_assign(
+ __entry->obj = obj ? obj->debug_id : 0;
+ __entry->inode = inode->i_ino;
+ ),
+
+ TP_printk("o=%08x i=%lx",
+ __entry->obj, __entry->inode)
+ );
+
TRACE_EVENT(cachefiles_vfs_error,
TP_PROTO(struct cachefiles_object *obj, struct inode *backer,
int error, enum cachefiles_error_trace where),
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