[PATCH 46/64] cachefiles: Mark a backing file in use with an inode flag

From: David Howells
Date: Mon Nov 29 2021 - 09:36:11 EST


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.

Using S_SWAPFILE instead isn't really viable as that has other effects in
the I/O paths.

Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
---

fs/cachefiles/internal.h | 2 ++
fs/cachefiles/namei.c | 35 +++++++++++++++++++++++++++++++++++
2 files changed, 37 insertions(+)

diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h
index fbb38d3e6cac..ebb39373716b 100644
--- a/fs/cachefiles/internal.h
+++ b/fs/cachefiles/internal.h
@@ -187,6 +187,8 @@ extern struct kmem_cache *cachefiles_object_jar;
/*
* namei.c
*/
+extern void cachefiles_unmark_inode_in_use(struct cachefiles_object *object,
+ struct file *file);
extern struct dentry *cachefiles_get_directory(struct cachefiles_cache *cache,
struct dentry *dir,
const char *name);
diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
index 25ca41952dab..2e209e403713 100644
--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -32,6 +32,18 @@ static bool __cachefiles_mark_inode_in_use(struct cachefiles_object *object,
return can_use;
}

+static bool cachefiles_mark_inode_in_use(struct cachefiles_object *object,
+ struct dentry *dentry)
+{
+ struct inode *inode = d_backing_inode(dentry);
+ bool can_use;
+
+ inode_lock(inode);
+ can_use = __cachefiles_mark_inode_in_use(object, dentry);
+ inode_unlock(inode);
+ return can_use;
+}
+
/*
* Unmark a backing inode. The caller must hold the inode lock.
*/
@@ -44,6 +56,29 @@ static void __cachefiles_unmark_inode_in_use(struct cachefiles_object *object,
trace_cachefiles_mark_inactive(object, inode);
}

+/*
+ * Unmark a backing inode and tell cachefilesd that there's something that can
+ * be culled.
+ */
+void cachefiles_unmark_inode_in_use(struct cachefiles_object *object,
+ struct file *file)
+{
+ struct cachefiles_cache *cache = object->volume->cache;
+ struct inode *inode = file_inode(file);
+
+ if (inode) {
+ inode_lock(inode);
+ __cachefiles_unmark_inode_in_use(object, file->f_path.dentry);
+ inode_unlock(inode);
+
+ if (!test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags)) {
+ atomic_long_add(inode->i_blocks, &cache->b_released);
+ if (atomic_inc_return(&cache->f_released))
+ cachefiles_state_changed(cache);
+ }
+ }
+}
+
/*
* get a subdirectory
*/