From 93e6442c76a0d26ad028c5df9b4a1e3096d9c36b Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Mon, 16 Jan 2017 16:05:59 -0500 Subject: [PATCH] dm: add basic support for using the select or poll function Add the ability to poll on the /dev/mapper/control device. The select or poll function waits until any event happens on any dm device since opening the /dev/mapper/control device. When select or poll returns the device as readable, we must close and reopen the device to wait for new dm events. Usage: 1. open the /dev/mapper/control device 2. scan the event numbers of all devices we are interested in and process them 3. call select, poll or epoll on the handle (it waits until some new event happens since opening the device) 4. close the /dev/mapper/control handle 5. go to step 1 The next commit allows to re-arm the polling without closing and reopening the device. Signed-off-by: Mikulas Patocka Signed-off-by: Andy Grover Signed-off-by: Mike Snitzer --- drivers/md/dm-core.h | 3 +++ drivers/md/dm-ioctl.c | 49 ++++++++++++++++++++++++++++++++++++++++++- drivers/md/dm.c | 5 +++++ 3 files changed, 56 insertions(+), 1 deletion(-) diff --git a/drivers/md/dm-core.h b/drivers/md/dm-core.h index 52ca8d059e82..24eddbdf2ab4 100644 --- a/drivers/md/dm-core.h +++ b/drivers/md/dm-core.h @@ -147,4 +147,7 @@ static inline bool dm_message_test_buffer_overflow(char *result, unsigned maxlen return !maxlen || strlen(result) + 1 >= maxlen; } +extern atomic_t dm_global_event_nr; +extern wait_queue_head_t dm_global_eventq; + #endif diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c index 41852ae287a5..6b65a538d91d 100644 --- a/drivers/md/dm-ioctl.c +++ b/drivers/md/dm-ioctl.c @@ -23,6 +23,14 @@ #define DM_MSG_PREFIX "ioctl" #define DM_DRIVER_EMAIL "dm-devel@redhat.com" +struct dm_file { + /* + * poll will wait until the global event number is greater than + * this value. + */ + unsigned global_event_nr; +}; + /*----------------------------------------------------------------- * The ioctl interface needs to be able to look up devices by * name or uuid. @@ -1868,8 +1876,47 @@ static long dm_compat_ctl_ioctl(struct file *file, uint command, ulong u) #define dm_compat_ctl_ioctl NULL #endif +static int dm_open(struct inode *inode, struct file *filp) +{ + int r; + struct dm_file *priv; + + r = nonseekable_open(inode, filp); + if (unlikely(r)) + return r; + + priv = filp->private_data = kmalloc(sizeof(struct dm_file), GFP_KERNEL); + if (!priv) + return -ENOMEM; + + priv->global_event_nr = atomic_read(&dm_global_event_nr); + + return 0; +} + +static int dm_release(struct inode *inode, struct file *filp) +{ + kfree(filp->private_data); + return 0; +} + +static unsigned dm_poll(struct file *filp, poll_table *wait) +{ + struct dm_file *priv = filp->private_data; + unsigned mask = 0; + + poll_wait(filp, &dm_global_eventq, wait); + + if ((int)(atomic_read(&dm_global_event_nr) - priv->global_event_nr) > 0) + mask |= POLLIN; + + return mask; +} + static const struct file_operations _ctl_fops = { - .open = nonseekable_open, + .open = dm_open, + .release = dm_release, + .poll = dm_poll, .unlocked_ioctl = dm_ctl_ioctl, .compat_ioctl = dm_compat_ctl_ioctl, .owner = THIS_MODULE, diff --git a/drivers/md/dm.c b/drivers/md/dm.c index fbd06b9f9467..ff22aa2a07b5 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -58,6 +58,9 @@ static DECLARE_WORK(deferred_remove_work, do_deferred_remove); static struct workqueue_struct *deferred_remove_workqueue; +atomic_t dm_global_event_nr = ATOMIC_INIT(0); +DECLARE_WAIT_QUEUE_HEAD(dm_global_eventq); + /* * One of these is allocated per bio. */ @@ -1760,7 +1763,9 @@ static void event_callback(void *context) dm_send_uevents(&uevents, &disk_to_dev(md->disk)->kobj); atomic_inc(&md->event_nr); + atomic_inc(&dm_global_event_nr); wake_up(&md->eventq); + wake_up(&dm_global_eventq); } /* -- 2.20.1