[Xen-changelog] [xen-unstable] blktapctrl: Fix too early close of pipes

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1236883586 0
# Node ID d8741d4dd05a4aec44bbdbf67deb2f26e1c934ad
# Parent  f603aeef08086aa735d58d788000781e4736d6b5
blktapctrl: Fix too early close of pipes

Connections to ioemu have single_handler set, so they are closed as
soon as all images of a certain type are closed. This is wrong with
ioemu: All images that belong to the same domain are handled by the
same backend process (usually qemu-dm, but also tapdisk-ioemu for
domains without device model), regardless of the image type.

This patch checks for the same-domain condition for ioemu connections.

Signed-off-by: Kevin Wolf <kwolf@xxxxxxx>
---
 tools/blktap/drivers/blktapctrl.c |   27 +++++++++++++++++++++++++++
 1 files changed, 27 insertions(+)

diff -r f603aeef0808 -r d8741d4dd05a tools/blktap/drivers/blktapctrl.c
--- a/tools/blktap/drivers/blktapctrl.c Thu Mar 12 18:42:59 2009 +0000
+++ b/tools/blktap/drivers/blktapctrl.c Thu Mar 12 18:46:26 2009 +0000
@@ -231,6 +231,24 @@ static void add_disktype(blkif_t *blkif,
        entry->pprev = pprev;
 }
 
+static int qemu_instance_has_disks(pid_t pid)
+{
+       int i;
+       int count = 0;
+       driver_list_entry_t *entry;
+
+       for (i = 0; i < MAX_DISK_TYPES; i++) {
+               entry = active_disks[i];
+               while (entry) {
+                       if ((entry->blkif->tappid == pid) && 
dtypes[i]->use_ioemu)
+                               count++;
+                       entry = entry->next;
+               }
+       }
+
+       return (count != 0);
+}
+
 static int del_disktype(blkif_t *blkif)
 {
        driver_list_entry_t *entry, **pprev;
@@ -254,6 +272,14 @@ static int del_disktype(blkif_t *blkif)
 
        DPRINTF("DEL_DISKTYPE: Freeing entry\n");
        free(entry);
+
+       /*
+        * When using ioemu, all disks of one VM are connected to the same
+        * qemu-dm instance. We may close the file handle only if there is
+        * no other disk left for this domain.
+        */
+       if (dtypes[type]->use_ioemu)
+               return !qemu_instance_has_disks(blkif->tappid);
 
        /* Caller should close() if no single controller, or list is empty. */
        return (!dtypes[type]->single_handler || (active_disks[type] == NULL));
@@ -721,6 +747,7 @@ static int unmap_blktapctrl(blkif_t *blk
        }
 
        if (del_disktype(blkif)) {
+               DPRINTF("Closing communication pipe to pid %d\n", 
blkif->tappid);
                close(blkif->fds[WRITE]);
                close(blkif->fds[READ]);
        }

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