Large Package Updates

When building kernel modules against the full Red Hat Enterprise Linux 6 source tree (instead of just kernel-devel), modules would be signed by a locally generated key. However, Red Hat Enterprise Linux 6 refused to load modules created in this way as it did not recognize the key. This update disables module signing while building out-of-tree modules, thus, in the aforementioned case, kernel module loading works as expected.

With this update, the upper limit of the log_mtts_per_seg variable was increased from five to seven, increasing the amount of memory that can be registered. As a result, the Mellanox driver (mlx4) can now use up to 64 GB of physical memory for RDMA (remote direct memory access). This provides better scalability for example when using the Mellanox adapter in NFS/RDMA, or on machines with a lot of physical memory.

Due to a mix-up between FMODE_ and O_ flags, an NFSv4 client could get a WRITE lock on a file that another NFSv4 client already had a READ lock on. As a result, data could be corrupted. With this update, FMODE_ and O_ flags are properly handled and getting a WRITE lock fails in the aforementioned case.

Booting Red Hat Enterprise Linux 6 debug kernel on a system with the Dell PowerEdge RAID Controller H700 adapter caused the megaraid_sas driver to reset the controller multiple times leading to a faulty controller state. On rebooting the system, the faulty controller state could cause the firmware to detect an incorrect memory condition. This could be especially confusing since the message could be a faulty DIMM (Dual In-line Memory Module) condition prompting the administrator to replace the DIMMs. This occurred due to a leak in the mfi_sgl dma'ed frame when the firmware supported IEEE frames. The mfi_sgl would draw memory from the slab cache and any use of freed memory would result in incorrect pages being read in the ISR (Interrupt Service Routine). This caused the controller resets and the ensuing DIMM error condition. This update fixes the leak in mfi_sgl when the firmware supports IEEE frames. Faulty controller states and faulty DIMM conditions no longer occur.

Running VDSM and performing an lvextend operation during an intensive Virtual Guest power up caused this operation to fail. Since lvextend was blocked, all components became non-responsive: vgs and lvs commands froze the session, Virtual Guests became Paused or Not Responding. This was caused due to a faulty use of a lock. With this update, performing an lvextend operation works as expected.

Due to a faulty memory allocator, on Non-Uniform Memory Architecture (NUMA) platforms, an OOM (Out Of Memory) condition would occur when a user changed a cpuset's /etc/dev/mems file (list of memory nodes in that cpuset) even though the specified node had enough free memory. With this update, the memory allocator no longer causes an OOM condition when a node has enough free memory.

When using a VIRT-IO (Virtual Input/Output) NIC (Network Interface Controller), its state was reported as unknown instead of its real state (up or down). This was due to the fact that the device could not report the state status. With this update, when a device is not capable of reporting the current state, it is assumed the state is up or the state is read from the config file.

A previously released patch fixed the external module compiling when using the full source tree, however, it was discovered it resulted in breaking the build in the kernel-devel only case. With this update, the patch has been fixed to avoid any external module compiling errors.

Running certain workload tests on a NUMA (Non-Uniform Memory Architecture) system could cause kernel panic at mm/migrate.c:113. This was due to a false positive BUG_ON. With this update, the false positive BUG_ON has been removed.

Updated partner qualification injecting target faults uncovered a flaw where the Emulex lpfc driver would incorrectly panic due to a null pnode dereference. This update addresses the issue and was tested successfully under the same test conditions without the panic occurring.

Updated partner qualification injecting controller faults uncovered a flaw where the Emulex lpfc driver panicked during error handling. With this update, kernel panic no longer occurs.

Updated partner qualification injecting controller faults uncovered a flaw where Fibre Channel ports would go offline while testing with Emulex LPFC controllers due to a faulty LPFC heartbeat functionality. This update changes the default behavior of the LPFC heartbeat to off.

When configuring an SIT (Simple Internet Transition) tunnel while a remote address is configured, kernel panic occurred, caused by an execution of a NULL header_ops pointer in the neigh_update_hhs() function. With this update, a check is introduced that makes sure the header_ops pointer is not of the value NULL, thus, kernel panic no longer occurs.

When booting a Red Hat Enterprise Linux 5.5 kernel on a guest on an AMD host system running Red Hat Enterprise Linux 6, the guest kernel crashes due to an unsupported MSR (Model Specific Registers) read of the MSR_K7_CLK_CTL model. With this update, KVM support was added for the MSR_K7_CLK_CTL model specific register used in the AMD K7 CPU models, thus, the kernel crashes no longer occur.

Previously, the s390 tape block driver crashed whenever it tried to switch the I/O scheduler. With this update, an official in-kernel API (elevator_change()) is used to switch the I/O scheduler safely, thus, the crashes no longer occurs.

Previously, a kernel module not shipped by Red Hat was successfully loaded when the FIPS boot option was enabled. With this update, kernel self-integrity is improved by rejecting to load kernel modules which are not shipped by Red Hat when the FIPS boot option is enabled.

A regression was discovered that caused kernel panic during the booting of any SGI UV100 and UV1000 system unless the virtefi command line option was passed to the kernel by GRUB. With this update, the need for the virtefi command line option is removed and the kernel will boots as expected without it.

Previously, a Windows XP host experienced the stop error screen (i.e. the "Blue Screen Of Death" error) when booted with the CPU mode name. With this update, a Windows XP host no longer experiences the aforementioned error due to added KVM (Kernel-based Virtual Machine) support for the MSR_EBC_FREQUENCY_ID model specific register.

Previously the cxgb3 (Chelsio Communications T3 10Gb Ethernet) adapter experienced parity errors. With this update, the parity errors are correctly detected and the cxgb3 adapter successfully recovers from them.

Systems with an updated Video BIOS for the AMD RS880 would not properly boot with KMS (Kernel mode-setting) enabled. With this update, the Video BIOS boots successfully when KMS is enabled.

The zfcpdump (kdump) kernel on IBM System z could not be debugged using the dump analysis tool crash, because the vmlinux file in the kernel-kdump-debuginfo RPM did not contain DWARF debug information. With this update, the CONFIG_DEBUG_KERNEL parameter is set to yes and the needed debug information is provided.

Previously, MADV_HUGEPAGE was missing in the include/asm-generic/mman-common.h file which caused madvise to fail to utilize TPH. With this update, the madvise option was removed from /sys/kernel/mm/redhat_transparent_hugepage/enabled since MADV_HUGEPAGE was removed from the madvise system call.

The kernel panicked when booting the kdump kernel on a s390 system with an initramfs that contained an odd number of bytes. With this update, an initramfs with sufficient padding such that it contains an even number of bytes is generated, thus, the kernel no longer panics.

Previously, in order to install Snapshot 13, boot parameter nomodeset xforcevesa had to be added to the kernel command line, otherwise, the screen turned black and and prevented the installation. With this update, the aforementioned boot parameter no longer has to be specified and the installation works as expected.

Previously, a write request may have merged with a discard request. This could have posed a potential risk for 3rd party drivers which could possibly issue a discard without waiting properly. With this update, discarding of write block I/O requests by preventing merges of discard and write requests in one block I/O has been introduced, thus, resolving the possible risks.

The fork() system call led to an rmap walk finding the parent huge-pmd twice instead of once, thus causing a discrepancy between the mapcount and page_mapcount check, which could have led to erratic page counts for subpages. This fix ensures that that the rmap walk is accurate when a process is forked, thus resolving the issue.

Running a fsstress test which issues various operations on a ext4 filesystem when usrquota is enabled, the following JBD (Journaling Block Device) error was output in /var/log/messages:

JBD: Spotted dirty metadata buffer (dev = sda10, blocknr = 17635). There's a risk of filesystem corruption in case of system crash.

With this update, by always journaling the quota file modification in an ext4 file system the aforementioned message no longer appears in the logs.

Previously, the destination MAC address validation was not checking for NPIV (N_Port ID Virtualization) addresses, which results in FCoE (Fibre Channel over Ethernet) frames being dropped. With this update, the destination MAC address check for FCoE frames has been modified so that multiple N_port IDs can be multiplexed on a single physical N_port.

During an installation through Cisco NPV (N port virtualization) to Brocade, adding a LUN (Logical Unit Number) through Add Advanced Target did not work properly. This was caused by the faulty resending of FLOGI (Fabric Login) when a Fibre Channel switch in the NPV mode rejected requests with zero Destination ID. With this update, the LUN is seen and able to be selected for installation.

Previously, timing issues could cause the FIP (FCoE Initialization Protocol) FLOGIs to timeout even if there were no problems. This caused the kernel to go into a non-FIP mode even though it should have been in the FIP mode. With this update, the timing issues no longer occur and the kernel no longer switches to the non-FIP mode when logging to the Fibre Channel Switch/Forwarder.

Previously, the vmstat (virtual memory statistics) tool incorrectly reported the disk I/O as swap-in on ppc64 and other architectures that do not support the TRANSPARENT_HUGEPAGE configuration option in the kernel. With this update, the vmstat tool no longer reports incorrect statistics and works as expected.

Previously, building under memory pressure with KSM (Kernel Shared Memory) caused KSM to collapse with an internal compiler error indicating an error in swapping. With this update, data corruption during swapping no longer occurs.

Occasionally, the anon_vma variable could contain the value null in the page_address_in_vma function and cause kernel panic. With this update, kernel panic no longer occurs.

Previously, the /proc/maps file which is read by LVM2 (Logical Volume Manager 2) contained inconsistencies caused by LVM2 incorrectly deciding which memory to mlock and munlock. With this update, LVM2 correctly decides between the mlock and munlock operations and no longer causes inconsistencies.

Systems that have an Emulex FC controller (with SLI-3 based firmware) installed could return a kernel panic during installation. With this update, kernel panic no longer occurs during installation.

This update fixes the slow memory leak in the i915 module in DRM (Direct Rendering Manager) and GEM (Graphics Execution Manager).

Previously, a race condition in the TTM (Translation Table Maps) module of the DRM (Direct Rendering Manager) between the object destruction thread and object eviction could result in a major loss of large objects reference counts. Consequently, this caused a major amount of memory leak. With this update, the race condition no longer occurs and any memory leaks are prevented.

Previously, an operation such as madvise(MADV_MERGEABLE) may have split VMAs (Virtual Memory Area) without checking if any huge page had to be split into regular pages, leading to huge pages to be still mapped in VMA ranges that would not be large enough to fit huge pages. With this update, huge pages are checked whether they have been split when any VMA is being truncated.

Previously, accounting of reclaimable inodes did not work correctly. When an inode was reclaimed it was only deleted from the per-AG (per Allocation Group) tree. Neither the counter was decreased, nor was the parent tree's AG entry untagged properly. This caused the system to hang indefinitely. With this update, the accounting of reclaimable inodes works properly and the system remains responsive.

A race condition occurred when Xen was presented with an inconsistent page type resulting in the crash of the kernel. With this update, the race condition is prevented and kernel crashes no longer occur.

Previously, Red Hat Enterprise Linux 6 enabled the CONFIG_IMA option in the kernel. This caused the kernel to track all inodes in the system in a radix tree, leading to a huge waste of memory. With this update, an optimized version of a tree (rbtree) is used and memory is no longer wasted.

Previously, calling the elevator_change function immediately after the blk_init_queue function resulted in a null pointer dereference. With this update, the null pointer dereference no longer occurs.

When booting the latest Red Hat Enterprise Linux 6 kernel (-78.el6), the system hanged shortly after the booting. Access to the file system died and the console started outputting soft lockup messages from the TTM code. With this update, the aforementioned behavior no longer occurs and the system boots as expected.