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-rw-r--r--fs/file_table.c19
1 files changed, 14 insertions, 5 deletions
diff --git a/fs/file_table.c b/fs/file_table.c
index 5c7d10ead4ad..edecd36fed9b 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -289,11 +289,20 @@ struct file *fget(unsigned int fd)
289EXPORT_SYMBOL(fget); 289EXPORT_SYMBOL(fget);
290 290
291/* 291/*
292 * Lightweight file lookup - no refcnt increment if fd table isn't shared. 292 * Lightweight file lookup - no refcnt increment if fd table isn't shared.
293 * You can use this only if it is guranteed that the current task already 293 *
294 * holds a refcnt to that file. That check has to be done at fget() only 294 * You can use this instead of fget if you satisfy all of the following
295 * and a flag is returned to be passed to the corresponding fput_light(). 295 * conditions:
296 * There must not be a cloning between an fget_light/fput_light pair. 296 * 1) You must call fput_light before exiting the syscall and returning control
297 * to userspace (i.e. you cannot remember the returned struct file * after
298 * returning to userspace).
299 * 2) You must not call filp_close on the returned struct file * in between
300 * calls to fget_light and fput_light.
301 * 3) You must not clone the current task in between the calls to fget_light
302 * and fput_light.
303 *
304 * The fput_needed flag returned by fget_light should be passed to the
305 * corresponding fput_light.
297 */ 306 */
298struct file *fget_light(unsigned int fd, int *fput_needed) 307struct file *fget_light(unsigned int fd, int *fput_needed)
299{ 308{