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Subject[PATCH] fget: Do not loop with rcu lock held
Date
Unlock RCU before running another loop iteration

Signed-off-by: Sergey Temerkhanov <s.temerkhanov@gmail.com>
---
fs/file.c | 34 ++++++++++++++++++++--------------
1 file changed, 20 insertions(+), 14 deletions(-)

diff --git a/fs/file.c b/fs/file.c
index 4559b5fec3bd..49d57752e7a6 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -823,21 +823,27 @@ static struct file *__fget_files(struct files_struct *files, unsigned int fd,
fmode_t mask, unsigned int refs)
{
struct file *file;
+ bool again = false;

- rcu_read_lock();
-loop:
- file = fcheck_files(files, fd);
- if (file) {
- /* File object ref couldn't be taken.
- * dup2() atomicity guarantee is the reason
- * we loop to catch the new file (or NULL pointer)
- */
- if (file->f_mode & mask)
- file = NULL;
- else if (!get_file_rcu_many(file, refs))
- goto loop;
- }
- rcu_read_unlock();
+ do {
+ rcu_read_lock();
+
+ file = fcheck_files(files, fd);
+ if (file) {
+ /* File object ref couldn't be taken.
+ * dup2() atomicity guarantee is the reason
+ * we loop to catch the new file (or NULL pointer)
+ */
+ if (file->f_mode & mask)
+ file = NULL;
+ else if (!get_file_rcu_many(file, refs))
+ again = true;
+ }
+ rcu_read_unlock();
+
+ if (unlikely(again))
+ schedule();
+ } while (again);

return file;
}
--
2.25.1
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