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    SubjectRe: 3.0-rcX BUG at fs/btrfs/ioctl.c:432 - bisected
    Hi,

    a candidate fix:

    http://git.kernel.org/?p=linux/kernel/git/mason/btrfs-unstable.git;a=commit;h=aa0467d8d2a00e75b2bb6a56a4ee6d70c5d1928f

    "
    With Linus' tree, today's linux-next build (powercp ppc64_defconfig)
    produced this warning:

    fs/btrfs/delayed-inode.c: In function 'btrfs_delayed_update_inode':
    fs/btrfs/delayed-inode.c:1598:6: warning: 'ret' may be used
    uninitialized in this function
    Introduced by commit 16cdcec736cd ("btrfs: implement delayed inode items
    operation").

    This fixes a bug in btrfs_update_inode(): if the returned value from
    btrfs_delayed_update_inode is a nonzero garbage, inode stat data are not
    updated and several call paths may hit a BUG_ON or fail with strange
    code.
    "

    if you can reproduce it reliably, add this patch on top of the delayed inodes.



    On Thu, Jun 09, 2011 at 03:52:43PM -0600, Jim Schutt wrote:
    > Hi,
    >
    > I've run into the following BUG on 3.0-rcX kernels when
    > running mkcephfs:
    >
    > Jun 9 15:14:50 an1 [ 299.446615] ------------[ cut here ]------------
    > Jun 9 15:14:50 an1 [ 299.447357] kernel BUG at fs/btrfs/ioctl.c:432!

    ioctl.c:
    431 ret = btrfs_update_inode(trans, root, dir);
    432 BUG_ON(ret);

    > Jun 9 15:14:50 an1 [ 299.447357] RSP: 0018:ffff88021b163c48 EFLAGS: 00010206
    > Jun 9 15:14:50 an1 [ 299.447357] RAX: 0000000019b201a0 RBX: ffff88022402d800 RCX: ffff88019206c028
    ^^^^^^^^^^^^^^^^
    ret, which seems to contain value of delayed_node from previous return value
    (deduced from assembly):

    delayed-node.c:
    1600 delayed_node = btrfs_get_or_create_delayed_node(inode);
    1601 if (IS_ERR(delayed_node))
    1602 return PTR_ERR(delayed_node);


    > Please let me know what other information I can provide, or
    > any testing I can do, that will help to resolve this issue.

    thanks, I think the stacktrace contains everything important. I was trying to
    trigger the bugon myself when the report arrived, but did not succeed. the
    issue is quite recent and seeing this report was a "cache" hit :)

    Note: there are two more possibilities to hit the bugon in the ioctl: ENOMEM
    and ENOENT being retunred from btrfs_update_inode, but the symptoms fit the
    case described above.


    david


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