Commit fa67bf88 authored Nov 20, 2020 by Eric W. Biederman

file: Remove get_files_struct

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>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
v1: https://lkml.kernel.org/r/20200817220425.9389-13-ebiederm@xmission.com
Link: https://lkml.kernel.org/r/20201120231441.29911-24-ebiederm@xmission.com


Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

parent 9fe83c43

fs/file.c

+0 −13

Original line number	Diff line number	Diff line
		@@ -411,19 +411,6 @@ 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)) {

include/linux/fdtable.h

+0 −1

Original line number	Diff line number	Diff line
		@@ -115,7 +115,6 @@ struct file task_lookup_next_fd_rcu(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;

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