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Without this fix (and another to the userspace component itself
described later), the kernel will be unable to process any OrangeFS
requests after the userspace component is restarted (due to a crash or
at the administrator's behest).
The bug here is that inside orangefs_remount, the orangefs_request_mutex
is locked. When the userspace component restarts while the filesystem
is mounted, it sends a ORANGEFS_DEV_REMOUNT_ALL ioctl to the device,
which causes the kernel to send it a few requests aimed at synchronizing
the state between the two. While this is happening the
orangefs_request_mutex is locked to prevent any other requests going
through.
This is only half of the bugfix. The other half is in the userspace
component which outright ignores(!) requests made before it considers
the filesystem remounted, which is after the ioctl returns. Of course
the ioctl doesn't return until after the userspace component responds to
the request it ignores. The userspace component has been changed to
allow ORANGEFS_VFS_OP_FEATURES regardless of the mount status.
Mike Marshall says:
"I've tested this patch against the fixed userspace part. This patch is
real important, I hope it can make it into 4.11...
Here's what happens when the userspace daemon is restarted, without
the patch:
=============================================
[ INFO: possible recursive locking detected ]
[ 4.10.0-00007-ge98bdb3 #1 Not tainted ]
---------------------------------------------
pvfs2-client-co/29032 is trying to acquire lock:
(orangefs_request_mutex){+.+.+.}, at: service_operation+0x3c7/0x7b0 [orangefs]
but task is already holding lock:
(orangefs_request_mutex){+.+.+.}, at: dispatch_ioctl_command+0x1bf/0x330 [orangefs]
CPU: 0 PID: 29032 Comm: pvfs2-client-co Not tainted 4.10.0-00007-ge98bdb3 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.3-1.fc25 04/01/2014
Call Trace:
__lock_acquire+0x7eb/0x1290
lock_acquire+0xe8/0x1d0
mutex_lock_killable_nested+0x6f/0x6e0
service_operation+0x3c7/0x7b0 [orangefs]
orangefs_remount+0xea/0x150 [orangefs]
dispatch_ioctl_command+0x227/0x330 [orangefs]
orangefs_devreq_ioctl+0x29/0x70 [orangefs]
do_vfs_ioctl+0xa3/0x6e0
SyS_ioctl+0x79/0x90"
Signed-off-by: Martin Brandenburg <martin@omnibond.com>
Acked-by: Mike Marshall <hubcap@omnibond.com>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.