1 files changed, 57 insertions, 5 deletions

diff --git a/fs/select.c b/fs/select.c
index 6b14dc7df3a4..f9f49c40cfd4 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -28,6 +28,7 @@
 #include <linux/hrtimer.h>
 #include <linux/sched/rt.h>
 #include <linux/freezer.h>
+#include <net/ll_poll.h>
 
 #include <asm/uaccess.h>
 
@@ -386,9 +387,10 @@ get_max:
 #define POLLEX_SET (POLLPRI)
 
 static inline void wait_key_set(poll_table *wait, unsigned long in,
-                                unsigned long out, unsigned long bit)
+                                unsigned long out, unsigned long bit,
+                                unsigned int ll_flag)
 {
-        wait->_key = POLLEX_SET;
+        wait->_key = POLLEX_SET | ll_flag;
         if (in & bit)
                 wait->_key |= POLLIN_SET;
         if (out & bit)
@@ -402,6 +404,8 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
         poll_table *wait;
         int retval, i, timed_out = 0;
         unsigned long slack = 0;
+        unsigned int busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0;
+        unsigned long busy_end = 0;
 
         rcu_read_lock();
         retval = max_select_fd(n, fds);
@@ -424,6 +428,7 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
         retval = 0;
         for (;;) {
                 unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;
+                bool can_busy_loop = false;
 
                 inp = fds->in; outp = fds->out; exp = fds->ex;
                 rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex;
@@ -451,7 +456,8 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
                                         f_op = f.file->f_op;
                                         mask = DEFAULT_POLLMASK;
                                         if (f_op && f_op->poll) {
-                                                wait_key_set(wait, in, out, bit);
+                                                wait_key_set(wait, in, out,
+                                                             bit, busy_flag);
                                                 mask = (*f_op->poll)(f.file, wait);
                                         }
                                         fdput(f);
@@ -470,6 +476,18 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
                                                 retval++;
                                                 wait->_qproc = NULL;
                                         }
+                                        /* got something, stop busy polling */
+                                        if (retval) {
+                                                can_busy_loop = false;
+                                                busy_flag = 0;
+
+                                        /*
+                                         * only remember a returned
+                                         * POLL_BUSY_LOOP if we asked for it
+                                         */
+                                        } else if (busy_flag & mask)
+                                                can_busy_loop = true;
+
                                 }
                         }
                         if (res_in)
@@ -488,6 +506,17 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
                         break;
                 }
 
+                /* only if found POLL_BUSY_LOOP sockets && not out of time */
+                if (can_busy_loop && !need_resched()) {
+                        if (!busy_end) {
+                                busy_end = busy_loop_end_time();
+                                continue;
+                        }
+                        if (!busy_loop_timeout(busy_end))
+                                continue;
+                }
+                busy_flag = 0;
+
                 /*
                  * If this is the first loop and we have a timeout
                  * given, then we convert to ktime_t and set the to
@@ -719,7 +748,9 @@ struct poll_list {
  * pwait poll_table will be used by the fd-provided poll handler for waiting,
  * if pwait->_qproc is non-NULL.
  */
-static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait)
+static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait,
+                                     bool *can_busy_poll,
+                                     unsigned int busy_flag)
 {
         unsigned int mask;
         int fd;
@@ -733,7 +764,10 @@ static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait)
                         mask = DEFAULT_POLLMASK;
                         if (f.file->f_op && f.file->f_op->poll) {
                                 pwait->_key = pollfd->events|POLLERR|POLLHUP;
+                                pwait->_key |= busy_flag;
                                 mask = f.file->f_op->poll(f.file, pwait);
+                                if (mask & busy_flag)
+                                        *can_busy_poll = true;
                         }
                         /* Mask out unneeded events. */
                         mask &= pollfd->events | POLLERR | POLLHUP;
@@ -752,6 +786,8 @@ static int do_poll(unsigned int nfds,  struct poll_list *list,
         ktime_t expire, *to = NULL;
         int timed_out = 0, count = 0;
         unsigned long slack = 0;
+        unsigned int busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0;
+        unsigned long busy_end = 0;
 
         /* Optimise the no-wait case */
         if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
@@ -764,6 +800,7 @@ static int do_poll(unsigned int nfds,  struct poll_list *list,
 
         for (;;) {
                 struct poll_list *walk;
+                bool can_busy_loop = false;
 
                 for (walk = list; walk != NULL; walk = walk->next) {
                         struct pollfd * pfd, * pfd_end;
@@ -778,9 +815,13 @@ static int do_poll(unsigned int nfds,  struct poll_list *list,
                                  * this. They'll get immediately deregistered
                                  * when we break out and return.
                                  */
-                                if (do_pollfd(pfd, pt)) {
+                                if (do_pollfd(pfd, pt, &can_busy_loop,
+                                              busy_flag)) {
                                         count++;
                                         pt->_qproc = NULL;
+                                        /* found something, stop busy polling */
+                                        busy_flag = 0;
+                                        can_busy_loop = false;
                                 }
                         }
                 }
@@ -797,6 +838,17 @@ static int do_poll(unsigned int nfds,  struct poll_list *list,
                 if (count || timed_out)
                         break;
 
+                /* only if found POLL_BUSY_LOOP sockets && not out of time */
+                if (can_busy_loop && !need_resched()) {
+                        if (!busy_end) {
+                                busy_end = busy_loop_end_time();
+                                continue;
+                        }
+                        if (!busy_loop_timeout(busy_end))
+                                continue;
+                }
+                busy_flag = 0;
+
                 /*
                  * If this is the first loop and we have a timeout
                  * given, then we convert to ktime_t and set the to