On Fri, Apr 01, 2016 at 01:44:13PM +1100, Dave Chinner wrote:
> On Wed, Mar 30, 2016 at 11:55:18PM -0400, Joe Lawrence wrote:
> > Hi Dave,
> >
> > Upon loading 4.6-rc1, I noticed a few linked list corruption messages in
> > dmesg shortly after boot up. I bisected the kernel, landing on:
> >
> > [c19b3b05ae440de50fffe2ac2a9b27392a7448e9] xfs: mode di_mode to vfs inode
> >
> > If I revert c19b3b05ae44 from 4.6-rc1, the warnings stop.
> >
> > WARNING: CPU: 35 PID: 6715 at lib/list_debug.c:29 __list_add+0x65/0xc0
> > list_add corruption. next->prev should be prev (ffff882030928a00), but was ffff88103f00c300. (next=ffff88100fde5ce8).
> .....
> > [<ffffffff812488f0>] ? bdev_test+0x20/0x20
> > [<ffffffff813551a5>] __list_add+0x65/0xc0
> > [<ffffffff81249bd8>] bd_acquire+0xc8/0xd0
> > [<ffffffff8124aa59>] blkdev_open+0x39/0x70
> > [<ffffffff8120bc27>] do_dentry_open+0x227/0x320
> > [<ffffffff8124aa20>] ? blkdev_get_by_dev+0x50/0x50
> > [<ffffffff8120d057>] vfs_open+0x57/0x60
> > [<ffffffff8121c9fa>] path_openat+0x1ba/0x1340
> > [<ffffffff8121eff1>] do_filp_open+0x91/0x100
> > [<ffffffff8122c806>] ? __alloc_fd+0x46/0x180
> > [<ffffffff8120d3b4>] do_sys_open+0x124/0x210
> > [<ffffffff8120d4be>] SyS_open+0x1e/0x20
> > [<ffffffff81003c12>] do_syscall_64+0x62/0x110
> > [<ffffffff8169ade1>] entry_SYSCALL64_slow_path+0x25/0x25
> ....
> > According to the bd_acquire+0xc8 offset, we're in bd_acquire()
> > attempting the list add:
> ....
> > 713 bdev = bdget(inode->i_rdev);
> > 714 if (bdev) {
> > 715 spin_lock(&bdev_lock);
> > 716 if (!inode->i_bdev) {
> > 717 /*
> > 718 * We take an additional reference to bd_inode,
> > 719 * and it's released in clear_inode() of inode.
> > 720 * So, we can access it via ->i_mapping always
> > 721 * without igrab().
> > 722 */
> > 723 bdgrab(bdev);
> > 724 inode->i_bdev = bdev;
> > 725 inode->i_mapping = bdev->bd_inode->i_mapping;
> > 726 list_add(&inode->i_devices, &bdev->bd_inodes);
>
> So the bdev->bd_inodes list is corrupt, and this call trace is
> just the messenger.
....
> > I'm not really sure why the bisect landed on c19b3b05ae44 "xfs: mode
> > di_mode to vfs inode", but as I mentioned, reverting it made the list
> > warnings go away.
>
> Neither am I at this point as it's the bdev inode (not an xfs
> inode) that has a corrupted list. I'll have to try to reproduce this.
Patch below should fix the problem. Smoke tested only at this point.
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
xfs: we don't need no steekin ->evict_inode
From: Dave Chinner <dchinner@xxxxxxxxxx>
Joe Lawrence reported a list_add corruption with 4.6-rc1 when
testing some custom md administration code that made it's own
block device nodes for the md array. The simple test loop of:
for i in {0..100}; do
mknod --mode=0600 $tmp/tmp_node b $MAJOR $MINOR
mdadm --detail --export $tmp/tmp_node > /dev/null
rm -f $tmp/tmp_node
done
Would produce this warning in bd_acquire() when mdadm opened the
device node:
list_add double add: new=ffff88043831c7b8, prev=ffff8804380287d8, next=ffff88043831c7b8.
And then produce this from bd_forget from kdevtmpfs evicting a block
dev inode:
list_del corruption. prev->next should be ffff8800bb83eb10, but was ffff88043831c7b8
This is a regression caused by commit c19b3b05 ("xfs: mode di_mode
to vfs inode"). The issue is that xfs_inactive() frees the
unlinked inode, and the above commit meant that this freeing zeroed
the mode in the struct inode. The problem is that after evict() has
called ->evict_inode, it expects the i_mode to be intact so that it
can call bd_forget() or cd_forget() to drop the reference to the
block device inode attached to the XFS inode.
In reality, the only thing we do in xfs_fs_evict_inode() that is not
generic is call xfs_inactive(). We can move the xfs_inactive() call
to xfs_fs_destroy_inode() without any problems at all, and this
will leave the VFS inode intact until it is completely done with it.
So, remove xfs_fs_evict_inode(), and do the work it used to do in
->destroy_inode instead.
Reported-by: Joe Lawrence <joe.lawrence@xxxxxxxxxxx>
Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
---
fs/xfs/xfs_super.c | 28 +++++++---------------------
1 file changed, 7 insertions(+), 21 deletions(-)
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index b412bb1..d8424f5 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -928,7 +928,7 @@ xfs_fs_alloc_inode(
/*
* Now that the generic code is guaranteed not to be accessing
- * the linux inode, we can reclaim the inode.
+ * the linux inode, we can inactivate and reclaim the inode.
*/
STATIC void
xfs_fs_destroy_inode(
@@ -938,9 +938,14 @@ xfs_fs_destroy_inode(
trace_xfs_destroy_inode(ip);
- XFS_STATS_INC(ip->i_mount, vn_reclaim);
+ ASSERT(!rwsem_is_locked(&ip->i_iolock.mr_lock));
+ XFS_STATS_INC(ip->i_mount, vn_rele);
+ XFS_STATS_INC(ip->i_mount, vn_remove);
+
+ xfs_inactive(ip);
ASSERT(XFS_FORCED_SHUTDOWN(ip->i_mount) || ip->i_delayed_blks == 0);
+ XFS_STATS_INC(ip->i_mount, vn_reclaim);
/*
* We should never get here with one of the reclaim flags already set.
@@ -987,24 +992,6 @@ xfs_fs_inode_init_once(
"xfsino", ip->i_ino);
}
-STATIC void
-xfs_fs_evict_inode(
- struct inode *inode)
-{
- xfs_inode_t *ip = XFS_I(inode);
-
- ASSERT(!rwsem_is_locked(&ip->i_iolock.mr_lock));
-
- trace_xfs_evict_inode(ip);
-
- truncate_inode_pages_final(&inode->i_data);
- clear_inode(inode);
- XFS_STATS_INC(ip->i_mount, vn_rele);
- XFS_STATS_INC(ip->i_mount, vn_remove);
-
- xfs_inactive(ip);
-}
-
/*
* We do an unlocked check for XFS_IDONTCACHE here because we are already
* serialised against cache hits here via the inode->i_lock and igrab() in
@@ -1673,7 +1660,6 @@ xfs_fs_free_cached_objects(
static const struct super_operations xfs_super_operations = {
.alloc_inode = xfs_fs_alloc_inode,
.destroy_inode = xfs_fs_destroy_inode,
- .evict_inode = xfs_fs_evict_inode,
.drop_inode = xfs_fs_drop_inode,
.put_super = xfs_fs_put_super,
.sync_fs = xfs_fs_sync_fs,
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