Applications that require a unified event loop occasionally have a need
to interface with libraries or other code that require notification on a
file descriptor becoming ready for read or write via poll. Add support
for the aio poll operation to enable these use-cases by way of the
thread based aio helpers.
Signed-off-by: Benjamin LaHaise <ben.lahaise@xxxxxxxxxxxxxxxxx>
Signed-off-by: Benjamin LaHaise <bcrl@xxxxxxxxx>
---
fs/aio.c | 46 ++++++++++++++++++++++++++++++++++++++++++++
include/uapi/linux/aio_abi.h | 2 +-
2 files changed, 47 insertions(+), 1 deletion(-)
diff --git a/fs/aio.c b/fs/aio.c
index 576b780..4384df4 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -200,6 +200,7 @@ struct aio_kiocb {
struct task_struct *ki_submit_task;
#if IS_ENABLED(CONFIG_AIO_THREAD)
struct task_struct *ki_cancel_task;
+ unsigned long ki_data;
unsigned long ki_rlimit_fsize;
aio_thread_work_fn_t ki_work_fn;
struct work_struct ki_work;
@@ -225,6 +226,7 @@ static const struct address_space_operations aio_ctx_aops;
static void aio_complete(struct kiocb *kiocb, long res, long res2);
ssize_t aio_fsync(struct kiocb *iocb, int datasync);
+long aio_poll(struct aio_kiocb *iocb);
static __always_inline bool aio_may_use_threads(void)
{
@@ -1675,6 +1677,45 @@ ssize_t aio_fsync(struct kiocb *iocb, int datasync)
return aio_thread_queue_iocb(req, datasync ? aio_thread_op_fdatasync
: aio_thread_op_fsync, 0);
}
+
+static long aio_thread_op_poll(struct aio_kiocb *iocb)
+{
+ struct file *file = iocb->common.ki_filp;
+ short events = iocb->ki_data;
+ struct poll_wqueues table;
+ unsigned int mask;
+ ssize_t ret = 0;
+
+ poll_initwait(&table);
+ events |= POLLERR | POLLHUP;
+
+ for (;;) {
+ mask = DEFAULT_POLLMASK;
+ if (file->f_op && file->f_op->poll) {
+ table.pt._key = events;
+ mask = file->f_op->poll(file, &table.pt);
+ }
+ /* Mask out unneeded events. */
+ mask &= events;
+ ret = mask;
+ if (mask)
+ break;
+
+ ret = -EINTR;
+ if (signal_pending(current))
+ break;
+
+ poll_schedule_timeout(&table, TASK_INTERRUPTIBLE, NULL, 0);
+ }
+
+ poll_freewait(&table);
+ return ret;
+}
+
+long aio_poll(struct aio_kiocb *req)
+{
+ return aio_thread_queue_iocb(req, aio_thread_op_poll, 0);
+}
#endif /* IS_ENABLED(CONFIG_AIO_THREAD) */
/*
@@ -1764,6 +1805,11 @@ rw_common:
ret = aio_fsync(&req->common, 0);
break;
+ case IOCB_CMD_POLL:
+ if (aio_may_use_threads())
+ ret = aio_poll(req);
+ break;
+
default:
pr_debug("EINVAL: no operation provided\n");
return -EINVAL;
diff --git a/include/uapi/linux/aio_abi.h b/include/uapi/linux/aio_abi.h
index bb2554f..7639fb1 100644
--- a/include/uapi/linux/aio_abi.h
+++ b/include/uapi/linux/aio_abi.h
@@ -39,8 +39,8 @@ enum {
IOCB_CMD_FDSYNC = 3,
/* These two are experimental.
* IOCB_CMD_PREADX = 4,
- * IOCB_CMD_POLL = 5,
*/
+ IOCB_CMD_POLL = 5,
IOCB_CMD_NOOP = 6,
IOCB_CMD_PREADV = 7,
IOCB_CMD_PWRITEV = 8,
--
2.5.0
--
"Thought is the essence of where you are now."
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
