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file: Implement task_lookup_fd_rcu

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[ Upstream commit 3a879fb38082125cc0d8aa89b70c7f3a7cdf584b ]

As a companion to lookup_fd_rcu implement task_lookup_fd_rcu for
querying an arbitrary process about a specific file.

Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
v1: https://lkml.kernel.org/r/20200818103713.aw46m7vprsy4vlve@wittgenstein
Link: https://lkml.kernel.org/r/20201120231441.29911-11-ebiederm@xmission.com
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Eric W. Biederman 2020-11-20 17:14:28 -06:00 committed by Ksawlii
parent 566924f14c
commit d1c2b8d006
2 changed files with 17 additions and 0 deletions
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15
fs/file.c
View file

@ -911,6 +911,21 @@ struct file *fget_task(struct task_struct *task, unsigned int fd)
return file;
}
struct file *task_lookup_fd_rcu(struct task_struct *task, unsigned int fd)
{
/* Must be called with rcu_read_lock held */
struct files_struct *files;
struct file *file = NULL;
task_lock(task);
files = task->files;
if (files)
file = files_lookup_fd_rcu(files, fd);
task_unlock(task);
return file;
}
/*
* Lightweight file lookup - no refcnt increment if fd table isn't shared.
*

2
include/linux/fdtable.h
View file

@ -110,6 +110,8 @@ static inline struct file *lookup_fd_rcu(unsigned int fd)
return files_lookup_fd_rcu(current->files, fd);
}
struct file *task_lookup_fd_rcu(struct task_struct *task, unsigned int fd);
struct task_struct;
struct files_struct *get_files_struct(struct task_struct *);