[PATCH v4 1/3] fs: prepare for adding LSM blob to backing_file

Paul Moore
2026-04-03T03:09:09Z

From: Amir Goldstein <amir73il@gmail.com>

In preparation to adding LSM blob to backing_file struct, factor out
helpers init_backing_file() and backing_file_free().

Cc: stable@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-unionfs@vger.kernel.org
Cc: linux-erofs@lists.ozlabs.org
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
[PM: use the term "LSM blob", fix comment style to match file]
Signed-off-by: Paul Moore <paul@paul-moore.com>
---
fs/file_table.c | 22 ++++++++++++++++++++--
1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/fs/file_table.c b/fs/file_table.c
index aaa5faaace1e..3b3792903185 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -66,6 +66,12 @@ void backing_file_set_user_path(struct file *f, const struct path *path)
}
EXPORT_SYMBOL_GPL(backing_file_set_user_path);

+static inline void backing_file_free(struct backing_file *ff)
+{
+ path_put(&ff->user_path);
+ kmem_cache_free(bfilp_cachep, ff);
+}
+
static inline void file_free(struct file *f)
{
security_file_free(f);
@@ -73,8 +79,7 @@ static inline void file_free(struct file *f)
percpu_counter_dec(&nr_files);
put_cred(f->f_cred);
if (unlikely(f->f_mode & FMODE_BACKING)) {
- path_put(backing_file_user_path(f));
- kmem_cache_free(bfilp_cachep, backing_file(f));
+ backing_file_free(backing_file(f));
} else {
kmem_cache_free(filp_cachep, f);
}
@@ -283,6 +288,12 @@ struct file *alloc_empty_file_noaccount(int flags, const struct cred *cred)
return f;
}

+static int init_backing_file(struct backing_file *ff)
+{
+ memset(&ff->user_path, 0, sizeof(ff->user_path));
+ return 0;
+}
+
/*
* Variant of alloc_empty_file() that allocates a backing_file container
* and doesn't check and modify nr_files.
@@ -305,7 +316,14 @@ struct file *alloc_empty_backing_file(int flags, const struct cred *cred)
return ERR_PTR(error);
}

+ /* The f_mode flags must be set before fput(). */
ff->file.f_mode |= FMODE_BACKING | FMODE_NOACCOUNT;
+ error = init_backing_file(ff);
+ if (unlikely(error)) {
+ fput(&ff->file);
+ return ERR_PTR(error);
+ }
+
return &ff->file;
}
EXPORT_SYMBOL_GPL(alloc_empty_backing_file);
--
2.53.0