[PATCH 09/23] vfs: Teach poll and select to use file_hotplug_lock

Eric W. Biederman
2009-06-01T21:55:53Z

From: Eric W. Biederman <ebiederm@maxwell.arastra.com>

Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com>
---
fs/select.c | 24 +++++++++++++++++-------
include/linux/poll.h | 1 +
2 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/fs/select.c b/fs/select.c
index 99e4145..fd68da0 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -416,10 +416,15 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
continue;
file = fget_light(i, &fput_needed);
if (file) {
- f_op = file->f_op;
- mask = DEFAULT_POLLMASK;
- if (f_op && f_op->poll)
- mask = (*f_op->poll)(file, retval ? NULL : wait);
+ mask = DEAD_POLLMASK;
+ if (file_hotplug_read_trylock(file)) {
+ f_op = file->f_op;
+ mask = DEFAULT_POLLMASK;
+ if (f_op && f_op->poll)
+ mask = (*f_op->poll)(file, retval ? NULL : wait);
+
+ file_hotplug_read_unlock(file);
+ }
fput_light(file, fput_needed);
if ((mask & POLLIN_SET) && (in & bit)) {
res_in |= bit;
@@ -684,9 +689,14 @@ static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait)
file = fget_light(fd, &fput_needed);
mask = POLLNVAL;
if (file != NULL) {
- mask = DEFAULT_POLLMASK;
- if (file->f_op && file->f_op->poll)
- mask = file->f_op->poll(file, pwait);
+ mask = DEAD_POLLMASK;
+ if (file_hotplug_read_trylock(file)) {
+ mask = DEFAULT_POLLMASK;
+ if (file->f_op && file->f_op->poll)
+ mask = file->f_op->poll(file, pwait);
+
+ file_hotplug_read_unlock(file);
+ }
/* Mask out unneeded events. */
mask &= pollfd->events | POLLERR | POLLHUP;
fput_light(file, fput_needed);
diff --git a/include/linux/poll.h b/include/linux/poll.h
index d388620..f0512f4 100644
--- a/include/linux/poll.h
+++ b/include/linux/poll.h
@@ -22,6 +22,7 @@
#define N_INLINE_POLL_ENTRIES (WQUEUES_STACK_ALLOC / sizeof(struct poll_table_entry))

#define DEFAULT_POLLMASK (POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM)
+#define DEAD_POLLMASK (DEFAULT_POLLMASK | POLLERR)

struct poll_table_struct;

--
1.6.3.1.54.g99dd.dirty