Jerome Marchand 09e099d4ba block: fix accounting bug on cross partition merges ... /proc/diskstats would display a strange output as follows. $ cat /proc/diskstats |grep sda 8 0 sda 90524 7579 102154 20464 0 0 0 0 0 14096 20089 8 1 sda1 19085 1352 21841 4209 0 0 0 0 4294967064 15689 4293424691 ~~~~~~~~~~ 8 2 sda2 71252 3624 74891 15950 0 0 0 0 232 23995 1562390 8 3 sda3 54 487 2188 92 0 0 0 0 0 88 92 8 4 sda4 4 0 8 0 0 0 0 0 0 0 0 8 5 sda5 81 2027 2130 138 0 0 0 0 0 87 137 Its reason is the wrong way of accounting hd_struct->in_flight. When a bio is merged into a request belongs to different partition by ELEVATOR_FRONT_MERGE. The detailed root cause is as follows. Assuming that there are two partition, sda1 and sda2. 1. A request for sda2 is in request_queue. Hence sda1's hd_struct->in_flight is 0 and sda2's one is 1. | hd_struct->in_flight --------------------------- sda1 | 0 sda2 | 1 --------------------------- 2. A bio belongs to sda1 is issued and is merged into the request mentioned on step1 by ELEVATOR_BACK_MERGE. The first sector of the request is changed from sda2 region to sda1 region. However the two partition's hd_struct->in_flight are not changed. | hd_struct->in_flight --------------------------- sda1 | 0 sda2 | 1 --------------------------- 3. The request is finished and blk_account_io_done() is called. In this case, sda2's hd_struct->in_flight, not a sda1's one, is decremented. | hd_struct->in_flight --------------------------- sda1 | -1 sda2 | 1 --------------------------- The patch fixes the problem by caching the partition lookup inside the request structure, hence making sure that the increment and decrement will always happen on the same partition struct. This also speeds up IO with accounting enabled, since it cuts down on the number of lookups we have to do. Also add a refcount to struct hd_struct to keep the partition in memory as long as users exist. We use kref_test_and_get() to ensure we don't add a reference to a partition which is going away. Signed-off-by: Jerome Marchand <jmarchan@redhat.com> Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com> Cc: stable@kernel.org Signed-off-by: Jens Axboe <jaxboe@fusionio.com>		2011-01-05 16:57:38 +01:00
..
acorn.c	partitions: fix sometimes unreadable partition strings	2010-08-11 08:59:20 -07:00
acorn.h	block: use struct parsed_partitions *state universally in partition check code	2010-05-21 20:01:02 +02:00
amiga.c	partitions: fix sometimes unreadable partition strings	2010-08-11 08:59:20 -07:00
amiga.h	block: use struct parsed_partitions *state universally in partition check code	2010-05-21 20:01:02 +02:00
atari.c	partitions: fix sometimes unreadable partition strings	2010-08-11 08:59:20 -07:00
atari.h	block: use struct parsed_partitions *state universally in partition check code	2010-05-21 20:01:02 +02:00
check.c	block: fix accounting bug on cross partition merges	2011-01-05 16:57:38 +01:00
check.h	block, partition: add partition_meta_info to hd_struct	2010-09-15 16:13:18 +02:00
efi.c	genhd, efi: add efi partition metadata to hd_structs	2010-09-15 16:13:28 +02:00
efi.h	block: use struct parsed_partitions *state universally in partition check code	2010-05-21 20:01:02 +02:00
ibm.c	[S390] partitions: fix build error in ibm partition detection code	2010-08-13 10:06:55 +02:00
ibm.h	block: use struct parsed_partitions *state universally in partition check code	2010-05-21 20:01:02 +02:00
karma.c	partitions: fix sometimes unreadable partition strings	2010-08-11 08:59:20 -07:00
karma.h	block: use struct parsed_partitions *state universally in partition check code	2010-05-21 20:01:02 +02:00
Kconfig	partition: use DEFAULT_SGI_PARTITION for SGI_PARTION default	2008-02-06 10:41:08 -08:00
ldm.c	Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial	2010-10-24 13:41:39 -07:00
ldm.h	Update broken web addresses in the kernel.	2010-10-18 11:03:14 +02:00
mac.c	partitions: fix sometimes unreadable partition strings	2010-08-11 08:59:20 -07:00
mac.h	block: use struct parsed_partitions *state universally in partition check code	2010-05-21 20:01:02 +02:00
Makefile	partition: add support for sysv68 partitions	2007-05-08 11:15:09 -07:00
msdos.c	partitions: fix sometimes unreadable partition strings	2010-08-11 08:59:20 -07:00
msdos.h	block: use struct parsed_partitions *state universally in partition check code	2010-05-21 20:01:02 +02:00
osf.c	partitions: fix sometimes unreadable partition strings	2010-08-11 08:59:20 -07:00
osf.h	block: use struct parsed_partitions *state universally in partition check code	2010-05-21 20:01:02 +02:00
sgi.c	partitions: fix sometimes unreadable partition strings	2010-08-11 08:59:20 -07:00
sgi.h	block: use struct parsed_partitions *state universally in partition check code	2010-05-21 20:01:02 +02:00
sun.c	partitions: fix sometimes unreadable partition strings	2010-08-11 08:59:20 -07:00
sun.h	block: use struct parsed_partitions *state universally in partition check code	2010-05-21 20:01:02 +02:00
sysv68.c	partitions: fix sometimes unreadable partition strings	2010-08-11 08:59:20 -07:00
sysv68.h	block: use struct parsed_partitions *state universally in partition check code	2010-05-21 20:01:02 +02:00
ultrix.c	partitions: fix sometimes unreadable partition strings	2010-08-11 08:59:20 -07:00
ultrix.h	block: use struct parsed_partitions *state universally in partition check code	2010-05-21 20:01:02 +02:00