Instead of requiring a thread for each device to sleep in ioctl(DEV_WAIT)
to receive dm events, allow a single thread to:
1) Open /dev/mapper/control multiple times
2) Associate each of these open file descriptors with different DM devices
3) poll() on all of these
4) When an event occurs, use TABLE_STATUS ioctl to get device's state
This requires:
a) Implementing open, release, and poll file operations
b) Defining a per-file context struct called dm_file
c) Adding a new DEV_ASSOC ioctl to associate a file with a single dm device
d) Handle if fd w/association is closed or referenced device is destroyed
Associating a fd with a device for polling limits the use of other
ioctls besides VERSION, using that fd. There is no mechanism to query
associations, userspace must track this itself.
Signed-off-by: Andy Grover <agrover@xxxxxxxxxx>
---
drivers/md/dm-core.h | 10 +++++
drivers/md/dm-ioctl.c | 98 ++++++++++++++++++++++++++++++++++++++++++-
drivers/md/dm.c | 12 ++++++
include/uapi/linux/dm-ioctl.h | 6 ++-
4 files changed, 122 insertions(+), 4 deletions(-)
diff --git a/drivers/md/dm-core.h b/drivers/md/dm-core.h
index 40ceba1..8aeb292 100644
--- a/drivers/md/dm-core.h
+++ b/drivers/md/dm-core.h
@@ -24,6 +24,12 @@ struct dm_kobject_holder {
struct completion completion;
};
+struct dm_file {
+ struct mapped_device *md;
+ uint32_t event_nr;
+ struct list_head assoc_files_node;
+};
+
/*
* DM core internal structure that used directly by dm.c and dm-rq.c
* DM targets must _not_ deference a mapped_device to directly access its members!
@@ -80,6 +86,10 @@ struct mapped_device {
struct list_head uevent_list;
spinlock_t uevent_lock; /* Protect access to uevent_list */
+ /* Track the fds set to track this device */
+ struct mutex assoc_files_list_lock;
+ struct list_head assoc_files_list;
+
/* the number of internal suspends */
unsigned internal_suspend_count;
diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 17c9bf9..c5fc53c 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1207,6 +1207,45 @@ static int dev_wait(struct file *filp, struct dm_ioctl *param, size_t param_size
return r;
}
+/*
+ * Associates a given open file with a specific mapped device.
+ * This lets the file be used to poll for events on the device.
+ */
+static int dev_assoc_set(struct file *filp, struct dm_ioctl *param, size_t param_size)
+{
+ struct dm_file *priv = filp->private_data;
+ struct mapped_device *md;
+
+ /* Can only associate once */
+ if (priv)
+ return -EINVAL;
+
+ priv = kzalloc(sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ INIT_LIST_HEAD(&priv->assoc_files_node);
+
+ md = find_device(param);
+ if (!md) {
+ kfree(priv);
+ return -ENXIO;
+ }
+
+ priv->md = md;
+ priv->event_nr = dm_get_event_nr(priv->md);
+
+ mutex_lock(&md->assoc_files_list_lock);
+ list_add_tail(&priv->assoc_files_node, &md->assoc_files_list);
+ mutex_unlock(&md->assoc_files_list_lock);
+
+ filp->private_data = priv;
+
+ /* No dm_put(), we're keeping a reference to the mapped_device */
+
+ return 0;
+}
+
static inline fmode_t get_mode(struct dm_ioctl *param)
{
fmode_t mode = FMODE_READ | FMODE_WRITE;
@@ -1635,7 +1674,8 @@ static ioctl_fn lookup_ioctl(unsigned int cmd, int *ioctl_flags)
{DM_LIST_VERSIONS_CMD, 0, list_versions},
{DM_TARGET_MSG_CMD, 0, target_message},
- {DM_DEV_SET_GEOMETRY_CMD, 0, dev_set_geometry}
+ {DM_DEV_SET_GEOMETRY_CMD, 0, dev_set_geometry},
+ {DM_DEV_ASSOC_CMD, IOCTL_FLAGS_NO_PARAMS, dev_assoc_set},
};
if (unlikely(cmd >= ARRAY_SIZE(_ioctls)))
@@ -1828,6 +1868,13 @@ static int ctl_ioctl(struct file *file, uint command, struct dm_ioctl __user *us
if (cmd == DM_VERSION_CMD)
return 0;
+ /*
+ * Cannot use files that have been associated for most ioctls.
+ * See dev_assoc_set().
+ */
+ if (file->private_data)
+ return -EINVAL;
+
fn = lookup_ioctl(cmd, &ioctl_flags);
if (!fn) {
DMWARN("dm_ctl_ioctl: unknown command 0x%x", command);
@@ -1879,8 +1926,55 @@ static long dm_compat_ctl_ioctl(struct file *file, uint command, ulong u)
#define dm_compat_ctl_ioctl NULL
#endif
+int dm_open(struct inode *inode, struct file *filp)
+{
+ filp->private_data = NULL;
+ return nonseekable_open(inode, filp);
+}
+
+int dm_release(struct inode *inode, struct file *filp)
+{
+ struct dm_file *priv = filp->private_data;
+
+ if (priv->md) {
+ mutex_lock(&priv->md->assoc_files_list_lock);
+ list_del(&priv->assoc_files_node);
+ mutex_unlock(&priv->md->assoc_files_list_lock);
+
+ dm_put(priv->md);
+ }
+
+ kfree(priv);
+
+ return 0;
+}
+
+static unsigned int dm_poll(struct file *filp, poll_table *wait)
+{
+ struct dm_file *priv = filp->private_data;
+ unsigned int mask = 0;
+ uint32_t cur_event;
+
+ /* fd has not been associated with a device with DEV_EVENT_SET */
+ if (!priv->md)
+ return 0;
+
+ poll_wait(filp, &priv->md->eventq, wait);
+
+ cur_event = dm_get_event_nr(priv->md);
+
+ if (priv->event_nr < cur_event) {
+ priv->event_nr = cur_event;
+ 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 3086da5..e847094 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1489,6 +1489,8 @@ static struct mapped_device *alloc_dev(int minor)
INIT_LIST_HEAD(&md->uevent_list);
INIT_LIST_HEAD(&md->table_devices);
spin_lock_init(&md->uevent_lock);
+ mutex_init(&md->assoc_files_list_lock);
+ INIT_LIST_HEAD(&md->assoc_files_list);
md->queue = blk_alloc_queue_node(GFP_KERNEL, numa_node_id);
if (!md->queue)
@@ -1878,6 +1880,7 @@ static void __dm_destroy(struct mapped_device *md, bool wait)
struct request_queue *q = dm_get_md_queue(md);
struct dm_table *map;
int srcu_idx;
+ struct dm_file *dm_f, *tmp;
might_sleep();
@@ -1905,6 +1908,15 @@ static void __dm_destroy(struct mapped_device *md, bool wait)
dm_put_live_table(md, srcu_idx);
mutex_unlock(&md->suspend_lock);
+ /* Disassociate event fds linked to this md */
+ mutex_lock(&md->assoc_files_list_lock);
+ list_for_each_entry_safe(dm_f, tmp, &md->assoc_files_list, assoc_files_node) {
+ dm_f->md = NULL;
+ dm_f->event_nr = 0;
+ list_del(&dm_f->assoc_files_node);
+ }
+ mutex_unlock(&md->assoc_files_list_lock);
+
/*
* Rare, but there may be I/O requests still going to complete,
* for example. Wait for all references to disappear.
diff --git a/include/uapi/linux/dm-ioctl.h b/include/uapi/linux/dm-ioctl.h
index 4bf9f1e..b3731b8 100644
--- a/include/uapi/linux/dm-ioctl.h
+++ b/include/uapi/linux/dm-ioctl.h
@@ -240,7 +240,8 @@ enum {
/* Added later */
DM_LIST_VERSIONS_CMD,
DM_TARGET_MSG_CMD,
- DM_DEV_SET_GEOMETRY_CMD
+ DM_DEV_SET_GEOMETRY_CMD,
+ DM_DEV_ASSOC_CMD,
};
#define DM_IOCTL 0xfd
@@ -255,6 +256,7 @@ enum {
#define DM_DEV_SUSPEND _IOWR(DM_IOCTL, DM_DEV_SUSPEND_CMD, struct dm_ioctl)
#define DM_DEV_STATUS _IOWR(DM_IOCTL, DM_DEV_STATUS_CMD, struct dm_ioctl)
#define DM_DEV_WAIT _IOWR(DM_IOCTL, DM_DEV_WAIT_CMD, struct dm_ioctl)
+#define DM_DEV_ASSOC _IOWR(DM_IOCTL, DM_DEV_ASSOC_CMD, struct dm_ioctl)
#define DM_TABLE_LOAD _IOWR(DM_IOCTL, DM_TABLE_LOAD_CMD, struct dm_ioctl)
#define DM_TABLE_CLEAR _IOWR(DM_IOCTL, DM_TABLE_CLEAR_CMD, struct dm_ioctl)
@@ -267,7 +269,7 @@ enum {
#define DM_DEV_SET_GEOMETRY _IOWR(DM_IOCTL, DM_DEV_SET_GEOMETRY_CMD, struct dm_ioctl)
#define DM_VERSION_MAJOR 4
-#define DM_VERSION_MINOR 35
+#define DM_VERSION_MINOR 36
#define DM_VERSION_PATCHLEVEL 0
#define DM_VERSION_EXTRA "-ioctl (2016-06-23)"
--
2.9.3
--
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