user/sven/linux.git, branch v4.8.4

Linux 4.8.4

2016-10-22T10:41:00Z

cfq: fix starvation of asynchronous writes

2016-10-22T10:40:26Z

commit 3932a86b4b9d1f0b049d64d4591ce58ad18b44ec upstream. While debugging timeouts happening in my application workload (ScyllaDB), I have observed calls to open() taking a long time, ranging everywhere from 2 seconds - the first ones that are enough to time out my application - to more than 30 seconds. The problem seems to happen because XFS may block on pending metadata updates under certain circumnstances, and that's confirmed with the following backtrace taken by the offcputime tool (iovisor/bcc): ffffffffb90c57b1 finish_task_switch ffffffffb97dffb5 schedule ffffffffb97e310c schedule_timeout ffffffffb97e1f12 __down ffffffffb90ea821 down ffffffffc046a9dc xfs_buf_lock ffffffffc046abfb _xfs_buf_find ffffffffc046ae4a xfs_buf_get_map ffffffffc046babd xfs_buf_read_map ffffffffc0499931 xfs_trans_read_buf_map ffffffffc044a561 xfs_da_read_buf ffffffffc0451390 xfs_dir3_leaf_read.constprop.16 ffffffffc0452b90 xfs_dir2_leaf_lookup_int ffffffffc0452e0f xfs_dir2_leaf_lookup ffffffffc044d9d3 xfs_dir_lookup ffffffffc047d1d9 xfs_lookup ffffffffc0479e53 xfs_vn_lookup ffffffffb925347a path_openat ffffffffb9254a71 do_filp_open ffffffffb9242a94 do_sys_open ffffffffb9242b9e sys_open ffffffffb97e42b2 entry_SYSCALL_64_fastpath 00007fb0698162ed [unknown] Inspecting my run with blktrace, I can see that the xfsaild kthread exhibit very high "Dispatch wait" times, on the dozens of seconds range and consistent with the open() times I have saw in that run. Still from the blktrace output, we can after searching a bit, identify the request that wasn't dispatched: 8,0 11 152 81.092472813 804 A WM 141698288 + 8 <- (8,1) 141696240 8,0 11 153 81.092472889 804 Q WM 141698288 + 8 [xfsaild/sda1] 8,0 11 154 81.092473207 804 G WM 141698288 + 8 [xfsaild/sda1] 8,0 11 206 81.092496118 804 I WM 141698288 + 8 ( 22911) [xfsaild/sda1] <==== 'I' means Inserted (into the IO scheduler) ===================================> 8,0 0 289372 96.718761435 0 D WM 141698288 + 8 (15626265317) [swapper/0] <==== Only 15s later the CFQ scheduler dispatches the request ======================> As we can see above, in this particular example CFQ took 15 seconds to dispatch this request. Going back to the full trace, we can see that the xfsaild queue had plenty of opportunity to run, and it was selected as the active queue many times. It would just always be preempted by something else (example): 8,0 1 0 81.117912979 0 m N cfq1618SN / insert_request 8,0 1 0 81.117913419 0 m N cfq1618SN / add_to_rr 8,0 1 0 81.117914044 0 m N cfq1618SN / preempt 8,0 1 0 81.117914398 0 m N cfq767A / slice expired t=1 8,0 1 0 81.117914755 0 m N cfq767A / resid=40 8,0 1 0 81.117915340 0 m N / served: vt=1948520448 min_vt=1948520448 8,0 1 0 81.117915858 0 m N cfq767A / sl_used=1 disp=0 charge=0 iops=1 sect=0 where cfq767 is the xfsaild queue and cfq1618 corresponds to one of the ScyllaDB IO dispatchers. The requests preempting the xfsaild queue are synchronous requests. That's a characteristic of ScyllaDB workloads, as we only ever issue O_DIRECT requests. While it can be argued that preempting ASYNC requests in favor of SYNC is part of the CFQ logic, I don't believe that doing so for 15+ seconds is anyone's goal. Moreover, unless I am misunderstanding something, that breaks the expectation set by the "fifo_expire_async" tunable, which in my system is set to the default. Looking at the code, it seems to me that the issue is that after we make an async queue active, there is no guarantee that it will execute any request. When the queue itself tests if it cfq_may_dispatch() it can bail if it sees SYNC requests in flight. An incoming request from another queue can also preempt it in such situation before we have the chance to execute anything (as seen in the trace above). This patch sets the must_dispatch flag if we notice that we have requests that are already fifo_expired. This flag is always cleared after cfq_dispatch_request() returns from cfq_dispatch_requests(), so it won't pin the queue for subsequent requests (unless they are themselves expired) Care is taken during preempt to still allow rt requests to preempt us regardless. Testing my workload with this patch applied produces much better results. From the application side I see no timeouts, and the open() latency histogram generated by systemtap looks much better, with the worst outlier at 131ms: Latency histogram of xfs_buf_lock acquisition (microseconds): value |-------------------------------------------------- count 0 | 11 1 |@@@@ 161 2 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ 1966 4 |@ 54 8 | 36 16 | 7 32 | 0 64 | 0 ~ 1024 | 0 2048 | 0 4096 | 1 8192 | 1 16384 | 2 32768 | 0 65536 | 0 131072 | 1 262144 | 0 524288 | 0 Signed-off-by: Glauber Costa CC: Jens Axboe CC: linux-block@vger.kernel.org CC: linux-kernel@vger.kernel.org Signed-off-by: Glauber Costa Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman

acpi, nfit: check for the correct event code in notifications

2016-10-22T10:40:26Z

commit c09f12186d6b03b798832d95289af76495990192 upstream. Commit 209851649dc4 "acpi: nfit: Add support for hot-add" added support for _FIT notifications, but it neglected to verify the notification event code matches the one in the ACPI spec for "NFIT Update". Currently there is only one code in the spec, but once additional codes are added, older kernels (without this fix) will misbehave by assuming all event notifications are for an NFIT Update. Fixes: 209851649dc4 ("acpi: nfit: Add support for hot-add") Cc: Cc: Dan Williams Reported-by: Linda Knippers Signed-off-by: Vishal Verma Signed-off-by: Dan Williams Signed-off-by: Greg Kroah-Hartman

drm: virtio: reinstate drm_virtio_set_busid()

2016-10-22T10:40:26Z

commit c2cbc38b9715bd8318062e600668fc30e5a3fbfa upstream. Before commit a325725633c2 ("drm: Lobotomize set_busid nonsense for !pci drivers"), several DRM drivers for platform devices used to expose an explicit "drm_driver.set_busid" callback, invariably backed by drm_platform_set_busid(). Commit a325725633c2 removed drm_platform_set_busid(), along with the referring .set_busid field initializations. This was justified because interchangeable functionality had been implemented in drm_dev_alloc() / drm_dev_init(), which DRM_IOCTL_SET_VERSION would rely on going forward. However, commit a325725633c2 also removed drm_virtio_set_busid(), for which the same consolidation was not appropriate: this .set_busid callback had been implemented with drm_pci_set_busid(), and not drm_platform_set_busid(). The error regressed Xorg/xserver on QEMU's "virtio-vga" card; the drmGetBusid() function from libdrm would no longer return stable PCI identifiers like "pci:0000:00:02.0", but rather unstable platform ones like "virtio0". Reinstate drm_virtio_set_busid() with judicious use of git checkout -p a325725633c2^ -- drivers/gpu/drm/virtio Cc: Daniel Vetter Cc: Emil Velikov Cc: Gerd Hoffmann Cc: Gustavo Padovan Cc: Hans de Goede Cc: Joachim Frieben Reported-by: Joachim Frieben Fixes: a325725633c26aa66ab940f762a6b0778edf76c0 Ref: https://bugzilla.redhat.com/show_bug.cgi?id=1366842 Signed-off-by: Laszlo Ersek Reviewed-by: Emil Velikov Signed-off-by: Dave Airlie Signed-off-by: Greg Kroah-Hartman

cachefiles: Fix attempt to read i_blocks after deleting file [ver #2]

2016-10-22T10:40:26Z

commit a818101d7b92e76db2f9a597e4830734767473b9 upstream. An NULL-pointer dereference happens in cachefiles_mark_object_inactive() when it tries to read i_blocks so that it can tell the cachefilesd daemon how much space it's making available. The problem is that cachefiles_drop_object() calls cachefiles_mark_object_inactive() after calling cachefiles_delete_object() because the object being marked active staves off attempts to (re-)use the file at that filename until after it has been deleted. This means that d_inode is NULL by the time we come to try to access it. To fix the problem, have the caller of cachefiles_mark_object_inactive() supply the number of blocks freed up. Without this, the following oops may occur: BUG: unable to handle kernel NULL pointer dereference at 0000000000000098 IP: [] cachefiles_mark_object_inactive+0x61/0xb0 [cachefiles] ... CPU: 11 PID: 527 Comm: kworker/u64:4 Tainted: G I ------------ 3.10.0-470.el7.x86_64 #1 Hardware name: Hewlett-Packard HP Z600 Workstation/0B54h, BIOS 786G4 v03.19 03/11/2011 Workqueue: fscache_object fscache_object_work_func [fscache] task: ffff880035edaf10 ti: ffff8800b77c0000 task.ti: ffff8800b77c0000 RIP: 0010:[] cachefiles_mark_object_inactive+0x61/0xb0 [cachefiles] RSP: 0018:ffff8800b77c3d70 EFLAGS: 00010246 RAX: 0000000000000000 RBX: ffff8800bf6cc400 RCX: 0000000000000034 RDX: 0000000000000000 RSI: ffff880090ffc710 RDI: ffff8800bf761ef8 RBP: ffff8800b77c3d88 R08: 2000000000000000 R09: 0090ffc710000000 R10: ff51005d2ff1c400 R11: 0000000000000000 R12: ffff880090ffc600 R13: ffff8800bf6cc520 R14: ffff8800bf6cc400 R15: ffff8800bf6cc498 FS: 0000000000000000(0000) GS:ffff8800bb8c0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b CR2: 0000000000000098 CR3: 00000000019ba000 CR4: 00000000000007e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Stack: ffff880090ffc600 ffff8800bf6cc400 ffff8800867df140 ffff8800b77c3db0 ffffffffa06c48cb ffff880090ffc600 ffff880090ffc180 ffff880090ffc658 ffff8800b77c3df0 ffffffffa085d846 ffff8800a96b8150 ffff880090ffc600 Call Trace: [] cachefiles_drop_object+0x6b/0xf0 [cachefiles] [] fscache_drop_object+0xd6/0x1e0 [fscache] [] fscache_object_work_func+0xa5/0x200 [fscache] [] process_one_work+0x17b/0x470 [] worker_thread+0x126/0x410 [] ? rescuer_thread+0x460/0x460 [] kthread+0xcf/0xe0 [] ? kthread_create_on_node+0x140/0x140 [] ret_from_fork+0x58/0x90 [] ? kthread_create_on_node+0x140/0x140 The oopsing code shows: callq 0xffffffff810af6a0 mov 0xf8(%r12),%rax mov 0x30(%rax),%rax mov 0x98(%rax),%rax <---- oops here lock add %rax,0x130(%rbx) where this is: d_backing_inode(object->dentry)->i_blocks Fixes: a5b3a80b899bda0f456f1246c4c5a1191ea01519 (CacheFiles: Provide read-and-reset release counters for cachefilesd) Reported-by: Jianhong Yin Signed-off-by: David Howells Reviewed-by: Jeff Layton Reviewed-by: Steve Dickson Signed-off-by: Al Viro Signed-off-by: Greg Kroah-Hartman

vfs: move permission checking into notify_change() for utimes(NULL)

2016-10-22T10:40:26Z

commit f2b20f6ee842313a0d681dbbf7f87b70291a6a3b upstream. This fixes a bug where the permission was not properly checked in overlayfs. The testcase is ltp/utimensat01. It is also cleaner and safer to do the permission checking in the vfs helper instead of the caller. This patch introduces an additional ia_valid flag ATTR_TOUCH (since touch(1) is the most obvious user of utimes(NULL)) that is passed into notify_change whenever the conditions for this special permission checking mode are met. Reported-by: Aihua Zhang Signed-off-by: Miklos Szeredi Tested-by: Aihua Zhang Signed-off-by: Greg Kroah-Hartman

dlm: free workqueues after the connections

2016-10-22T10:40:26Z

commit 3a8db79889ce16930aff19b818f5b09651bb7644 upstream. After backporting commit ee44b4bc054a ("dlm: use sctp 1-to-1 API") series to a kernel with an older workqueue which didn't use RCU yet, it was noticed that we are freeing the workqueues in dlm_lowcomms_stop() too early as free_conn() will try to access that memory for canceling the queued works if any. This issue was introduced by commit 0d737a8cfd83 as before it such attempt to cancel the queued works wasn't performed, so the issue was not present. This patch fixes it by simply inverting the free order. Fixes: 0d737a8cfd83 ("dlm: fix race while closing connections") Signed-off-by: Marcelo Ricardo Leitner Signed-off-by: David Teigland Signed-off-by: Greg Kroah-Hartman

crypto: vmx - Fix memory corruption caused by p8_ghash

2016-10-22T10:40:26Z

commit 80da44c29d997e28c4442825f35f4ac339813877 upstream. This patch changes the p8_ghash driver to use ghash-generic as a fixed fallback implementation. This allows the correct value of descsize to be defined directly in its shash_alg structure and avoids problems with incorrect buffer sizes when its state is exported or imported. Reported-by: Jan Stancek Fixes: cc333cd68dfa ("crypto: vmx - Adding GHASH routines for VMX module") Signed-off-by: Marcelo Cerri Signed-off-by: Herbert Xu Signed-off-by: Greg Kroah-Hartman

crypto: ghash-generic - move common definitions to a new header file

2016-10-22T10:40:25Z

commit a397ba829d7f8aff4c90af3704573a28ccd61a59 upstream. Move common values and types used by ghash-generic to a new header file so drivers can directly use ghash-generic as a fallback implementation. Fixes: cc333cd68dfa ("crypto: vmx - Adding GHASH routines for VMX module") Signed-off-by: Marcelo Cerri Signed-off-by: Herbert Xu Signed-off-by: Greg Kroah-Hartman

ext4: unmap metadata when zeroing blocks

2016-10-22T10:40:25Z

commit 9b623df614576680cadeaa4d7e0b5884de8f7c17 upstream. When zeroing blocks for DAX allocations, we also have to unmap aliases in the block device mappings. Otherwise writeback can overwrite zeros with stale data from block device page cache. Signed-off-by: Jan Kara Signed-off-by: Theodore Ts'o Signed-off-by: Greg Kroah-Hartman