On Wed, Jun 14, 2023 at 10:49:06AM +0300, Amir Goldstein wrote:
> Overlayfs and cachefiles use open_with_fake_path() to allocate internal
> files, where overlayfs also puts a "fake" path in f_path - a path which
> is not on the same fs as f_inode.
>
> Allocate a container struct backing_file for those internal files, that
> is used to hold the "fake" ovl path along with the real path.
>
> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
> ---
> fs/cachefiles/namei.c | 4 +--
> fs/file_table.c | 74 +++++++++++++++++++++++++++++++++++++------
> fs/internal.h | 5 +--
> fs/open.c | 30 +++++++++++-------
> fs/overlayfs/file.c | 4 +--
> include/linux/fs.h | 24 +++++++++++---
> 6 files changed, 109 insertions(+), 32 deletions(-)
>
> diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
> index 82219a8f6084..283534c6bc8d 100644
> --- a/fs/cachefiles/namei.c
> +++ b/fs/cachefiles/namei.c
> @@ -560,8 +560,8 @@ static bool cachefiles_open_file(struct cachefiles_object *object,
> */
> path.mnt = cache->mnt;
> path.dentry = dentry;
> - file = open_with_fake_path(&path, O_RDWR | O_LARGEFILE | O_DIRECT,
> - d_backing_inode(dentry), cache->cache_cred);
> + file = open_backing_file(&path, O_RDWR | O_LARGEFILE | O_DIRECT,
> + &path, cache->cache_cred);
> if (IS_ERR(file)) {
> trace_cachefiles_vfs_error(object, d_backing_inode(dentry),
> PTR_ERR(file),
> diff --git a/fs/file_table.c b/fs/file_table.c
> index 372653b92617..138d5d405df7 100644
> --- a/fs/file_table.c
> +++ b/fs/file_table.c
> @@ -44,18 +44,40 @@ static struct kmem_cache *filp_cachep __read_mostly;
>
> static struct percpu_counter nr_files __cacheline_aligned_in_smp;
>
> +/* Container for backing file with optional real path */
> +struct backing_file {
> + struct file file;
> + struct path real_path;
> +};
> +
> +static inline struct backing_file *backing_file(struct file *f)
> +{
> + return container_of(f, struct backing_file, file);
> +}
> +
> +struct path *backing_file_real_path(struct file *f)
> +{
> + return &backing_file(f)->real_path;
> +}
> +EXPORT_SYMBOL_GPL(backing_file_real_path);
> +
> static void file_free_rcu(struct rcu_head *head)
> {
> struct file *f = container_of(head, struct file, f_rcuhead);
>
> put_cred(f->f_cred);
> - kmem_cache_free(filp_cachep, f);
> + if (unlikely(f->f_mode & FMODE_BACKING))
> + kfree(backing_file(f));
> + else
> + kmem_cache_free(filp_cachep, f);
> }
>
> static inline void file_free(struct file *f)
> {
> security_file_free(f);
> - if (!(f->f_mode & FMODE_NOACCOUNT))
> + if (unlikely(f->f_mode & FMODE_BACKING))
> + path_put(backing_file_real_path(f));
> + else
> percpu_counter_dec(&nr_files);
I think this needs to be:
if (unlikely(f->f_mode & FMODE_BACKING))
path_put(backing_file_real_path(f));
if (likely(!(f->f_mode & FMODE_NOACCOUNT)))
percpu_counter_dec(&nr_files);
as we do have FMODE_NOACCOUNT without FMODE_BACKING.
No need to resend though.
