2.6.33 merge window part 2

User-visible changes include:

• If there are any remaining reiserfs users out there: that filesystem has seen a major rework of its internal locking to eliminate use of the big kernel lock.

• The Super-H architecture has gained perf events support for a number of system types.

• The exofs filesystem (for object storage devices) now has multi-device mirror support.

• There is a new "discard" mount option for ext4 filesystems, controlling whether ext4 issues TRIM commands for newly-freed space. It defaults to off due to fears about how well this feature will really work once hardware begins to support it.

• It is now possible to configure a kernel without ext2 or ext3 support, but still mount filesystems with those formats using the ext4 code.

• The Nouveau reverse-engineered NVIDIA driver has been merged, but without the accompanying firmware; see this article for more information.

• The "ramzswap" device, formerly known as compcache, has been merged into the staging tree.

• There is now support for the "BATMAN" mesh network protocol in the staging tree.

• The "perf" tool now has a "diff" mode which will calculate the change in performance between two different runs and generate a report.

• The semantics for the O_SYNC and O_DSYNC open-time flags have been rationalized, as described in this article.

• The MD layer now supports barrier requests for all RAID types. The device mapper, too, has improved barrier support.

• The snapshot merge target for the device mapper has been merged.

• An extensive set of tracepoints has been added to the XFS filesystem, allowing fine-grained visibility into most aspects of its operation.

• Memory pages shared with the kernel shared memory (KSM) mechanism are now swappable.

• New hardware support:
  • Block devices: The VMware paravirtualized SCSI HBA device, LSI 3ware SAS/SATA-RAID controllers, PMC-Sierra SPC 8001 SAS/SATA based host adapters, Apple PowerMac/PowerBook internal 'MacIO' IDE controllers, Blackfin Secure Digital host controllers, TI DAVINCI multimedia card interfaces, and BCM Reference Board NAND flash controllers.

  • Miscellaneous: Dynapro serial touchscreens, Altera University Program PS/2 ports, Samsung S3C2410 touchscreens, National Semiconductor LM73 temperature sensors, Nuvoton NUC900 series SPI controllers SuperH MSIOF SPI controllers, OMAP SPI 100K master controllers, ST-Ericsson AB4500 Mixed Signal Power management chips, Freescale MC13783 realtime clocks, Freescale MC13783 touchscreen devices, SHARP LQ035Q1DH02 TFT displays, and TI BQ32000 I2C realtime clocks.

  • Networking: RealTek RTL8192U Wireless LAN NICs, Agere Systems HERMES II Wireless PC Cards (Model 0110), and Analog Devices Blackfin on-chip CAN controllers.

  • Sound: AD525x digital potentiometers and Texas Instruments DAC7512 digital-to-analog converters.

  • Systems and processors: Neuros OSD 2.0 devices, Nintendo GameCubes, Freescale P1020RDB processors, Freescale p4080ds reference boards, Arcom/Eurotech ZEUS single-board SBC systems, ATNGW100 mkII Network Gateway boards, and Acvilon BF561 boards.

  • USB: Xilinx USB host controllers and OMAP34xx USBHOST 3 port EHCI controllers.

  • Video4Linux: OmniVision OV2610, OV3610, and OV96xx sensors, Sharp RJ54N1CB0C sensors, E3C EC168 DVB-T USB2.0 receivers, E3C EC100 DVB-T demodulators, Maxim MAX2165 silicon tuners, Aptina MT9T112 cameras, and DiBcom DiB0090 tuners.

Changes visible to kernel developers include:

• The scsi_debug module can now emulate "thin provisioning" devices.

• The detect() callback in struct i2c_driver has lost the unused kind parameter. Also, struct i2c_client_address_data is no more; address lists are represented with simple unsigned short arrays instead.

• The spinlock renaming patch has been applied. Developers working near low-level code will see the new arch_spin_lock_t type being used with non-sleeping (even in the realtime tree) locks.

• Video4Linux2 has a new subdevice API, called media-bus, intended to help in the negotiation of image formats between the sensor and the controller.

• There is a new mechanism for grabbing and saving kernel messages on a system crash; see this article for more information.

• The per-CPU variable allocator has been replaced, and there is a new set of operations for working with these variables; see this article for a brief introduction.

This merge window should close in the very near future, so the 2.6.33 kernel is, at this point, close to being feature-complete. Any final additions will be noted in next week's edition.