aoe: user can ask driver to forget previously detected devices

When an AoE device is detected, the kernel is informed, and a new block device
is created.  If the device is unused, the block device corresponding to remote
device that is no longer available may be removed from the system by telling
the aoe driver to "flush" its list of devices.

Without this patch, software like GPFS and LVM may attempt to read from AoE
devices that were discovered earlier but are no longer present, blocking until
the I/O attempt times out.

Signed-off-by: Ed L. Cashin <ecashin@coraid.com>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/drivers/block/aoe/aoechr.c b/drivers/block/aoe/aoechr.c
index f1124664c5c9..1bc85aa2271f 100644
--- a/drivers/block/aoe/aoechr.c
+++ b/drivers/block/aoe/aoechr.c
@@ -15,6 +15,7 @@ enum {
         MINOR_DISCOVER,
         MINOR_INTERFACES,
         MINOR_REVALIDATE,
+        MINOR_FLUSH,
         MSGSZ = 2048,
         NMSG = 100,             /* message backlog to retain */
 };
@@ -43,6 +44,7 @@ static struct aoe_chardev chardevs[] = {
         { MINOR_DISCOVER, "discover" },
         { MINOR_INTERFACES, "interfaces" },
         { MINOR_REVALIDATE, "revalidate" },
+        { MINOR_FLUSH, "flush" },
 };
 
 static int
@@ -158,6 +160,9 @@ aoechr_write(struct file *filp, const char __user *buf, size_t cnt, loff_t *offp
                 break;
         case MINOR_REVALIDATE:
                 ret = revalidate(buf, cnt);
+                break;
+        case MINOR_FLUSH:
+                ret = aoedev_flush(buf, cnt);
         }
         if (ret == 0)
                 ret = cnt;