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| author | Sargun Dhillon <sargun@sargun.me> | 2020-01-07 09:59:24 -0800 |
|---|---|---|
| committer | Christian Brauner <christian.brauner@ubuntu.com> | 2020-01-13 21:48:42 +0100 |
| commit | 5e876fb43dbf24c941a323139752bcb2f0a80da0 (patch) | |
| tree | 79948c06e4f93aeb83eb698d2409ca4997bd942a /fs/file.c | |
| parent | c79f46a282390e0f5b306007bf7b11a46d529538 (diff) | |
| download | linux-5e876fb43dbf24c941a323139752bcb2f0a80da0.tar.bz2 | |
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
Signed-off-by: Sargun Dhillon <sargun@sargun.me>
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20200107175927.4558-2-sargun@sargun.me
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Diffstat (limited to 'fs/file.c')
| -rw-r--r-- | fs/file.c | 22 |
1 files changed, 20 insertions, 2 deletions
diff --git a/fs/file.c b/fs/file.c index 3da91a112bab..d044a32c030e 100644 --- a/fs/file.c +++ b/fs/file.c @@ -706,9 +706,9 @@ void do_close_on_exec(struct files_struct *files) spin_unlock(&files->file_lock); } -static struct file *__fget(unsigned int fd, fmode_t mask, unsigned int refs) +static struct file *__fget_files(struct files_struct *files, unsigned int fd, + fmode_t mask, unsigned int refs) { - struct files_struct *files = current->files; struct file *file; rcu_read_lock(); @@ -729,6 +729,12 @@ loop: return file; } +static inline struct file *__fget(unsigned int fd, fmode_t mask, + unsigned int refs) +{ + return __fget_files(current->files, fd, mask, refs); +} + struct file *fget_many(unsigned int fd, unsigned int refs) { return __fget(fd, FMODE_PATH, refs); @@ -746,6 +752,18 @@ struct file *fget_raw(unsigned int fd) } EXPORT_SYMBOL(fget_raw); +struct file *fget_task(struct task_struct *task, unsigned int fd) +{ + struct file *file = NULL; + + task_lock(task); + if (task->files) + file = __fget_files(task->files, fd, 0, 1); + task_unlock(task); + + return file; +} + /* * Lightweight file lookup - no refcnt increment if fd table isn't shared. * |