Attachment 358245 Details for Bug 589788

[patch] tentative fix

1013-blktap-teardown.patch (text/plain), 3.28 KB, created by Jan Beulich on 2010-04-30 14:40:16 UTC

(hide)

Description:

Filename:

MIME Type:

Creator: Jan Beulich

Created: 2010-04-30 14:40:16 UTC

Size: 3.28 KB

patch

obsolete

>From: http://xenbits.xensource.com/linux-2.6.18-xen.hg?rev/eb21d96a6aae
># HG changeset patch
># User Keir Fraser <keir.fraser@citrix.com>
># Date 1271693963 -3600
># Node ID eb21d96a6aaef9719a3c83501e52e21dede2c7a4
># Parent  fbe371367af64674d8eefa59924890a7b783f769
>Subject: xen/blktap: fix cleanup after unclean application exit
>References: bnc#569194, bnc#589788
>Patch-mainline: n/a
>
>When an application using blktap devices doesn't close the file handle
>(or mmap-s) of /dev/xen/blktapN, we cannot defer the mmput() on the
>stored mm until blktap_release(), as that will never be called without
>the mm's reference count dropping to zero.
>
>Signed-off-by: Jan Beulich <jbeulich@novell.com>
>
>From: http://xenbits.xensource.com/linux-2.6.18-xen.hg?rev/2a4b455b1fba
># HG changeset patch
># User Keir Fraser <keir.fraser@citrix.com>
># Date 1271925346 -3600
># Node ID 2a4b455b1fbab6405d06f446484d9fe9b20be619
># Parent  347237fd42d855bb301159c85e9f962d8521a21f
>blktap: fix cleanup after unclean application exit #2
>
>When an application using blktap devices doesn't close the mmap-s of
>/dev/xen/blktapN and the frontend driver never connects, we cannot
>defer the mmput() on the stored mm until blktap_release() or the exit
>path of the worker thread, as the former will never be called without
>the mm's reference count dropping to zero, and the worker thread
>would never get started.
>
>Also remove a left-over from c/s 1013.
>
>Signed-off-by: Jan Beulich <jbeulich@novell.com>
>
>--- 11.2-2010-04-22.orig/drivers/xen/blktap/blktap.c	2010-04-22 16:53:36.000000000 +0200
>+++ 11.2-2010-04-22/drivers/xen/blktap/blktap.c	2010-04-22 17:02:05.000000000 +0200
>@@ -548,6 +548,7 @@ void signal_tapdisk(int idx) 
> {
> 	tap_blkif_t *info;
> 	struct task_struct *ptask;
>+	struct mm_struct *mm;
> 
> 	/*
> 	 * if the userland tools set things up wrong, this could be negative;
>@@ -567,7 +568,9 @@ void signal_tapdisk(int idx) 
> 	}
> 	info->blkif = NULL;
> 
>-	return;
>+	mm = xchg(&info->mm, NULL);
>+	if (mm)
>+		mmput(mm);
> }
> 
> static int blktap_open(struct inode *inode, struct file *filp)
>@@ -632,6 +635,7 @@ static int blktap_open(struct inode *ino
> static int blktap_release(struct inode *inode, struct file *filp)
> {
> 	tap_blkif_t *info = filp->private_data;
>+	struct mm_struct *mm;
> 	
> 	/* check for control device */
> 	if (!info)
>@@ -640,8 +644,9 @@ static int blktap_release(struct inode *
> 	info->ring_ok = 0;
> 	smp_wmb();
> 
>-	mmput(info->mm);
>-	info->mm = NULL;
>+	mm = xchg(&info->mm, NULL);
>+	if (mm)
>+		mmput(mm);
> 	kfree(info->foreign_map.map);
> 	info->foreign_map.map = NULL;
> 
>@@ -1083,7 +1088,7 @@ static void fast_flush_area(pending_req_
> 				>> PAGE_SHIFT, INVALID_P2M_ENTRY);
> 		}
> 
>-		if (khandle->user != INVALID_GRANT_HANDLE) {
>+		if (mm != NULL && khandle->user != INVALID_GRANT_HANDLE) {
> 			BUG_ON(xen_feature(XENFEAT_auto_translated_physmap));
> 			if (!locked++)
> 				down_write(&mm->mmap_sem);
>@@ -1140,6 +1145,7 @@ static void print_stats(blkif_t *blkif)
> int tap_blkif_schedule(void *arg)
> {
> 	blkif_t *blkif = arg;
>+	tap_blkif_t *info;
> 
> 	blkif_get(blkif);
> 
>@@ -1173,8 +1179,16 @@ int tap_blkif_schedule(void *arg)
> 		printk(KERN_DEBUG "%s: exiting\n", current->comm);
> 
> 	blkif->xenblkd = NULL;
>+	info = tapfds[blkif->dev_num];
> 	blkif_put(blkif);
> 
>+	if (info) {
>+		struct mm_struct *mm = xchg(&info->mm, NULL);
>+
>+		if (mm)
>+			mmput(mm);
>+	}
>+
> 	return 0;
> }
>

Actions: View | Diff

Attachments on bug 589788: 349791 | 349854 | 349855 | 349856 | 350294 | 358189 | 358245