linux/include
Milan Broz 0e435ac26e block: fix setting of max_segment_size and seg_boundary mask
Fix setting of max_segment_size and seg_boundary mask for stacked md/dm
devices.

When stacking devices (LVM over MD over SCSI) some of the request queue
parameters are not set up correctly in some cases by default, namely
max_segment_size and and seg_boundary mask.

If you create MD device over SCSI, these attributes are zeroed.

Problem become when there is over this mapping next device-mapper mapping
- queue attributes are set in DM this way:

request_queue   max_segment_size  seg_boundary_mask
SCSI                65536             0xffffffff
MD RAID1                0                      0
LVM                 65536                 -1 (64bit)

Unfortunately bio_add_page (resp.  bio_phys_segments) calculates number of
physical segments according to these parameters.

During the generic_make_request() is segment cout recalculated and can
increase bio->bi_phys_segments count over the allowed limit.  (After
bio_clone() in stack operation.)

Thi is specially problem in CCISS driver, where it produce OOPS here

    BUG_ON(creq->nr_phys_segments > MAXSGENTRIES);

(MAXSEGENTRIES is 31 by default.)

Sometimes even this command is enough to cause oops:

  dd iflag=direct if=/dev/<vg>/<lv> of=/dev/null bs=128000 count=10

This command generates bios with 250 sectors, allocated in 32 4k-pages
(last page uses only 1024 bytes).

For LVM layer, it allocates bio with 31 segments (still OK for CCISS),
unfortunatelly on lower layer it is recalculated to 32 segments and this
violates CCISS restriction and triggers BUG_ON().

The patch tries to fix it by:

 * initializing attributes above in queue request constructor
   blk_queue_make_request()

 * make sure that blk_queue_stack_limits() inherits setting

 (DM uses its own function to set the limits because it
 blk_queue_stack_limits() was introduced later.  It should probably switch
 to use generic stack limit function too.)

 * sets the default seg_boundary value in one place (blkdev.h)

 * use this mask as default in DM (instead of -1, which differs in 64bit)

Bugs related to this:
https://bugzilla.redhat.com/show_bug.cgi?id=471639
http://bugzilla.kernel.org/show_bug.cgi?id=8672

Signed-off-by: Milan Broz <mbroz@redhat.com>
Reviewed-by: Alasdair G Kergon <agk@redhat.com>
Cc: Neil Brown <neilb@suse.de>
Cc: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Tejun Heo <htejun@gmail.com>
Cc: Mike Miller <mike.miller@hp.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-12-03 12:55:55 +01:00
..
acpi ACPICA: disable _BIF warning 2008-11-27 02:17:30 -05:00
asm-arm
asm-frv ide: fix support for IDE PCI controllers using MMIO on frv 2008-10-17 18:09:14 +02:00
asm-generic Fix __pfn_to_page(pfn) for CONFIG_DISCONTIGMEM=y 2008-11-08 10:02:48 -08:00
asm-h8300 h8300: update timer handler - new files 2008-10-16 11:21:29 -07:00
asm-m32r [PATCH] remove unused ibcs2/PER_SVR4 in SET_PERSONALITY 2008-10-16 15:40:05 +02:00
asm-m68k proc: move /proc/hardware to m68k-specific code 2008-10-23 14:24:03 +04:00
asm-mn10300 [PATCH] remove unused ibcs2/PER_SVR4 in SET_PERSONALITY 2008-10-16 15:40:05 +02:00
asm-xtensa Merge git://git.kernel.org/pub/scm/linux/kernel/git/czankel/xtensa-2.6 2008-10-23 09:16:56 -07:00
crypto
drm drm: move drm vblank initialization/cleanup to driver load/unload 2008-11-25 09:49:03 +10:00
keys
linux block: fix setting of max_segment_size and seg_boundary mask 2008-12-03 12:55:55 +01:00
math-emu math-emu: Fix thinko in _FP_DIV 2008-10-22 22:09:59 -07:00
media V4L/DVB (9335): videobuf: split unregister bus creating self-contained frontend de-allocator 2008-10-21 14:32:08 -02:00
mtd
net net: Fix soft lockups/OOM issues w/ unix garbage collector 2008-11-26 15:32:27 -08:00
pcmcia
rdma
rxrpc
scsi [SCSI] fc_transport: fix old bug on bitflag definitions 2008-11-21 17:30:53 +09:00
sound Merge branches 'topic/fix/misc' and 'topic/fix/hda' into for-linus 2008-11-10 17:58:46 +01:00
trace sched: clean up tracepoints 2008-10-14 10:33:14 +02:00
video atmel_lcdfb: change irq_base definition to allow error reporting 2008-11-12 17:17:16 -08:00
xen
Kbuild