From: Tony Battersby <tonyb@xxxxxxxxxxxxxxx>
Improve the description of fget_light(), which is currently incorrect
about needing a prior refcnt (judging by the way it is actually used).
Signed-off-by: Tony Battersby <tonyb@xxxxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/file_table.c | 19 ++++++++++++++-----
1 file changed, 14 insertions(+), 5 deletions(-)
diff -puN fs/file_table.c~vfs-improve-comment-describing-fget_light fs/file_table.c
--- a/fs/file_table.c~vfs-improve-comment-describing-fget_light
+++ a/fs/file_table.c
@@ -315,11 +315,20 @@ struct file *fget(unsigned int fd)
EXPORT_SYMBOL(fget);
/*
- * Lightweight file lookup - no refcnt increment if fd table isn't shared.
- * You can use this only if it is guranteed that the current task already
- * holds a refcnt to that file. That check has to be done at fget() only
- * and a flag is returned to be passed to the corresponding fput_light().
- * There must not be a cloning between an fget_light/fput_light pair.
+ * Lightweight file lookup - no refcnt increment if fd table isn't shared.
+ *
+ * You can use this instead of fget if you satisfy all of the following
+ * conditions:
+ * 1) You must call fput_light before exiting the syscall and returning control
+ * to userspace (i.e. you cannot remember the returned struct file * after
+ * returning to userspace).
+ * 2) You must not call filp_close on the returned struct file * in between
+ * calls to fget_light and fput_light.
+ * 3) You must not clone the current task in between the calls to fget_light
+ * and fput_light.
+ *
+ * The fput_needed flag returned by fget_light should be passed to the
+ * corresponding fput_light.
*/
struct file *fget_light(unsigned int fd, int *fput_needed)
{
_
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