vfs, fdtable: Add fget_task helper

This introduces a function which can be used to fetch a file, given an arbitrary task. As long as the user holds a reference (refcnt) to the task_struct it is safe to call, and will either return NULL on failure, or a pointer to the file, with a refcnt. This patch is based on Oleg Nesterov's (cf. [1]) patch from September 2018. [1]: Link: https://lore.kernel.org/r/20180915160423.GA31461@redhat.com

Sargun Dhillon committed 6 years ago

Commit 5e876fb1 parent c79f46a2 files · +22 −2Browse files

Showing the changes to include/linux (1 of 2 files). Show all

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include/linux/file.h+2−0

@@ -16,6 +16,7 @@ extern void fput(struct file *); · 15 unmodified lines
16	16	extern void fput_many(struct file *, unsigned int);
17	17
18	18	struct file_operations;
	19	+struct task_struct;
19	20	struct vfsmount;
20	21	struct dentry;
21	22	struct inode;
@@ -47,6 +48,7 @@ static inline void fdput(struct fd fd) · 25 unmodified lines
47	48	extern struct file *fget(unsigned int fd);
48	49	extern struct file *fget_many(unsigned int fd, unsigned int refs);
49	50	extern struct file *fget_raw(unsigned int fd);
	51	+extern struct file fget_task(struct task_struct task, unsigned int fd);
50	52	extern unsigned long __fdget(unsigned int fd);
51	53	extern unsigned long __fdget_raw(unsigned int fd);
52	54	extern unsigned long __fdget_pos(unsigned int fd);