[13/17] file: Remove get_files_struct

Submitted by Eric W. Biederman on Aug. 17, 2020, 10:04 p.m.

Details

Message ID 20200817220425.9389-13-ebiederm@xmission.com
State New
Series "Series without cover letter"
Headers show

Commit Message

Eric W. Biederman Aug. 17, 2020, 10:04 p.m.
When discussing[1] exec and posix file locks it was realized that none
of the callers of get_files_struct fundamentally needed to call
get_files_struct, and that by switching them to helper functions
instead it will both simplify their code and remove unnecessary
increments of files_struct.count.  Those unnecessary increments can
result in exec unnecessarily unsharing files_struct which breaking
posix locks, and it can result in fget_light having to fallback to
fget reducing system performance.

Now that get_files_struct has no more users and can not cause the
problems for posix file locking and fget_light remove get_files_struct
so that it does not gain any new users.

[1] https://lkml.kernel.org/r/20180915160423.GA31461@redhat.com
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
 fs/file.c               | 13 -------------
 include/linux/fdtable.h |  1 -
 2 files changed, 14 deletions(-)

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diff --git a/fs/file.c b/fs/file.c
index 88f9f78869f8..605e756f3c63 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -410,19 +410,6 @@  static struct fdtable *close_files(struct files_struct * files)
 	return fdt;
 }
 
-struct files_struct *get_files_struct(struct task_struct *task)
-{
-	struct files_struct *files;
-
-	task_lock(task);
-	files = task->files;
-	if (files)
-		atomic_inc(&files->count);
-	task_unlock(task);
-
-	return files;
-}
-
 void put_files_struct(struct files_struct *files)
 {
 	if (atomic_dec_and_test(&files->count)) {
diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h
index a3a054084f49..8c4bc6aa19c9 100644
--- a/include/linux/fdtable.h
+++ b/include/linux/fdtable.h
@@ -108,7 +108,6 @@  struct file *fnext_task(struct task_struct *task, unsigned int *fd);
 
 struct task_struct;
 
-struct files_struct *get_files_struct(struct task_struct *);
 void put_files_struct(struct files_struct *fs);
 int unshare_files(void);
 struct files_struct *dup_fd(struct files_struct *, unsigned, int *) __latent_entropy;

Comments

Christian Brauner Aug. 18, 2020, 10:39 a.m.
On Mon, Aug 17, 2020 at 05:04:21PM -0500, Eric W. Biederman wrote:
> When discussing[1] exec and posix file locks it was realized that none
> of the callers of get_files_struct fundamentally needed to call
> get_files_struct, and that by switching them to helper functions
> instead it will both simplify their code and remove unnecessary
> increments of files_struct.count.  Those unnecessary increments can
> result in exec unnecessarily unsharing files_struct which breaking
> posix locks, and it can result in fget_light having to fallback to
> fget reducing system performance.
> 
> Now that get_files_struct has no more users and can not cause the
> problems for posix file locking and fget_light remove get_files_struct
> so that it does not gain any new users.
> 
> [1] https://lkml.kernel.org/r/20180915160423.GA31461@redhat.com
> Suggested-by: Oleg Nesterov <oleg@redhat.com>
> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
> ---

Acked-by: Christian Brauner <christian.brauner@ubuntu.com>