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dm: allow remove to be deferred

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This patch allows the removal of an open device to be deferred until
it is closed.  (Previously such a removal attempt would fail.)

The deferred remove functionality is enabled by setting the flag
DM_DEFERRED_REMOVE in the ioctl structure on DM_DEV_REMOVE or
DM_REMOVE_ALL ioctl.

On return from DM_DEV_REMOVE, the flag DM_DEFERRED_REMOVE indicates if
the device was removed immediately or flagged to be removed on close -
if the flag is clear, the device was removed.

On return from DM_DEV_STATUS and other ioctls, the flag
DM_DEFERRED_REMOVE is set if the device is scheduled to be removed on
closure.

A device that is scheduled to be deleted can be revived using the
message "@cancel_deferred_remove". This message clears the
DMF_DEFERRED_REMOVE flag so that the device won't be deleted on close.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Mikulas Patocka
2013-11-01 18:27:41 -04:00
committed by Mike Snitzer
parent 7833b08e18
commit 2c140a246d
4 changed files with 99 additions and 12 deletions
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15
include/uapi/linux/dm-ioctl.h
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@@ -267,9 +267,9 @@ 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 26
#define DM_VERSION_MINOR 27
#define DM_VERSION_PATCHLEVEL 0
#define DM_VERSION_EXTRA "-ioctl (2013-08-15)"
#define DM_VERSION_EXTRA "-ioctl (2013-10-30)"
/* Status bits */
#define DM_READONLY_FLAG (1 << 0) /* In/Out */
@@ -341,4 +341,15 @@ enum {
*/
#define DM_DATA_OUT_FLAG (1 << 16) /* Out */
/*
* If set with DM_DEV_REMOVE or DM_REMOVE_ALL this indicates that if
* the device cannot be removed immediately because it is still in use
* it should instead be scheduled for removal when it gets closed.
*
* On return from DM_DEV_REMOVE, DM_DEV_STATUS or other ioctls, this
* flag indicates that the device is scheduled to be removed when it
* gets closed.
*/
#define DM_DEFERRED_REMOVE (1 << 17) /* In/Out */
#endif /* _LINUX_DM_IOCTL_H */