Implement extended device numbers. A block driver can tell block
layer that it wants to use extended device numbers. After the usual
minor space is used up, block layer automatically allocates devt's
from EXT_BLOCK_MAJOR.
Currently only one major number is allocated for this but as the
allocation is strictly on-demand, ~1mil minor space under it should
suffice unless the system actually has more than ~1mil partitions and
if that ever happens adding more majors to the extended devt area is
easy.
Due to internal implementation issues, the first partition can't be
allocated on the extended area. In other words, genhd->minors should
at least be 1. This limitation will be lifted by later changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
There are two variants of stat functions - ones prefixed with double
underbars which don't care about preemption and ones without which
disable preemption before manipulating per-cpu counters. It's unclear
whether the underbarred ones assume that preemtion is disabled on
entry as some callers don't do that.
This patch unifies diskstats access by implementing disk_stat_lock()
and disk_stat_unlock() which take care of both RCU (for partition
access) and preemption (for per-cpu counter access). diskstats access
should always be enclosed between the two functions. As such, there's
no need for the versions which disables preemption. They're removed
and double underbars ones are renamed to drop the underbars. As an
extra argument is added, there's no danger of using the old version
unconverted.
disk_stat_lock() uses get_cpu() and returns the cpu index and all
diskstat functions which access per-cpu counters now has @cpu
argument to help RT.
This change adds RCU or preemption operations at some places but also
collapses several preemption ops into one at others. Overall, the
performance difference should be negligible as all involved ops are
very lightweight per-cpu ones.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
disk->part[] is protected by its matching bdev's lock. However,
non-critical accesses like collecting stats and printing out sysfs and
proc information used to be performed without any locking. As
partitions can come and go dynamically, partitions can go away
underneath those non-critical accesses. As some of those accesses are
writes, this theoretically can lead to silent corruption.
This patch fixes the race by using RCU for the partition array and dev
reference counter to hold partitions.
* Rename disk->part[] to disk->__part[] to make sure no one outside
genhd layer proper accesses it directly.
* Use RCU for disk->__part[] dereferencing.
* Implement disk_{get|put}_part() which can be used to get and put
partitions from gendisk respectively.
* Iterators are implemented to help iterate through all partitions
safely.
* Functions which require RCU readlock are marked with _rcu suffix.
* Use disk_put_part() in __blkdev_put() instead of directly putting
the contained kobject.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* Implement disk_devt() and part_devt() and use them to directly
access devt instead of computing it from ->major and ->first_minor.
Note that all references to ->major and ->first_minor outside of
block layer is used to determine devt of the disk (the part0) and as
->major and ->first_minor will continue to represent devt for the
disk, converting these users aren't strictly necessary. However,
convert them for consistency.
* Implement disk_max_parts() to avoid directly deferencing
genhd->minors.
* Update bdget_disk() such that it doesn't assume consecutive minor
space.
* Move devt computation from register_disk() to add_disk() and make it
the only one (all other usages use the initially determined value).
These changes clean up the code and will help disk->part dereference
fix and extended block device numbers.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
In hd_struct, @partno is used to denote partition number and a number
of other places use @part to denote hd_struct. Functions use @part
and @index instead. This causes confusion and makes it difficult to
use consistent variable names for hd_struct. Always use @partno if a
variable represents partition number.
Also, print out functions use @f or @part for seq_file argument. Use
@seqf uniformly instead.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This patch makes the following misc updates in preparation for
disk->part dereference fix and extended block devt support.
* implment part_to_disk()
* fix comment about gendisk->part indexing
* rename get_part() to disk_map_sector()
* don't use n which is always zero while printing disk information in
diskstats_show()
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Recent block_class iteration updates 5c6f35c5..27f3025 converted all
class device iteration to class_for_each_device() and
class_find_device(), which are correct but pain in the ass to use.
This pach converts them to newly introduced class_dev_iterator so that
they can use more natural control structures instead of separate
callbacks and struct to pass parameters to them.
This results in smaller and easier code.
This patch also restores the original behavior of not printing header
in /proc/partitions if there's no partition to print. This is trivial
but still user-visible behavior.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
block_class_lock protects major_names array and bdev_map and doesn't
have anything to do with block class devices. Don't grab them while
iterating over block class devices.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Recent block_class iteration updates 5c6f35c5..27f3025 broke partition
info printouts.
* printk_all_partitions(): Partition print out stops when it meets a
partition hole. Partition printing inner loop should continue
instead of exiting on empty partition slot.
* /proc/partitions and /proc/diskstats: If all information can't be
read in single read(), the information is truncated. This is
because find_start() doesn't actually update the counter containing
the initial seek. It runs to the end and ends up always reporting
EOF on the second read.
This patch fixes both problems.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
/proc/partitions didn't use to write out the header if there was no
partition. However, recent commit 66c64afe changed the behavior.
This is nothing major but there's no reason to change user visible
behavior without a good rationale. Restore the original behavior.
Note that 2.6.28 has clean up changes scheduled which will replace
this rather hacky implementation.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Greg KH <greg@kroah.com>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This patch remove blk_register_filter and blk_unregister_filter in
gendisk, and adds them to sd.c, sr.c. and ide-cd.c
The commit abf5439370 moved cmdfilter
from gendisk to request_queue. It turned out that in some subsystems
multiple gendisks share a single request_queue. So we get:
Using physmap partition information
Creating 3 MTD partitions on "physmap-flash":
0x00000000-0x01c00000 : "User FS"
0x01c00000-0x01c40000 : "booter"
kobject (8511c410): tried to init an initialized object, something is seriously wrong.
Call Trace:
[<8036644c>] dump_stack+0x8/0x34
[<8021f050>] kobject_init+0x50/0xcc
[<8021fa18>] kobject_init_and_add+0x24/0x58
[<8021d20c>] blk_register_filter+0x4c/0x64
[<8021c194>] add_disk+0x78/0xe0
[<8027d14c>] add_mtd_blktrans_dev+0x254/0x278
[<8027c8f0>] blktrans_notify_add+0x40/0x78
[<80279c00>] add_mtd_device+0xd0/0x150
[<8027b090>] add_mtd_partitions+0x568/0x5d8
[<80285458>] physmap_flash_probe+0x2ac/0x334
[<802644f8>] driver_probe_device+0x12c/0x244
[<8026465c>] __driver_attach+0x4c/0x84
[<80263c64>] bus_for_each_dev+0x58/0xac
[<802633ec>] bus_add_driver+0xc4/0x24c
[<802648e0>] driver_register+0xcc/0x184
[<80100460>] _stext+0x60/0x1bc
In the long term, we need to fix such subsystems but we need a quick
fix now. This patch add the command filter support to only sd and sr
though it might be useful for other SG_IO users (such as cciss).
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Reported-by: Manuel Lauss <mano@roarinelk.homelinux.net>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Otherwise we leak references, which is not a good thing to do.
Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
The proc files get truncated if they do not fit into the buffer with
a single read(). We need to move the seq_file index from the callback
of class_find_device() to the caller of class_find_device(), to keep
its value across multiple invocations of the callback.
Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Use the proper class iterator function instead of mucking around in the
internals of the class structures.
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
The seq_start call is the better place for the header for the file, that
way we don't have to be mucking in the class structure to try to figure
out if this is the first partition or not.
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Use the proper class iterator function instead of mucking around in the
internals of the class structures.
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
These functions are only needed if CONFIG_PROC_FS is enabled, so save
the space when it is not.
This also makes it easier for a patch later in this series to work
properly if CONFIG_PROC_FS is not enabled.
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Use the proper class iterator function instead of mucking around in the
internals of the class structures.
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Use the proper class iterator function instead of mucking around in the
internals of the class structures.
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Warn if something really bad happens if we can't create this link.
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Why?:
There are occasions where userspace would like to access sysfs
attributes for a device but it may not know how sysfs has named the
device or the path. For example what is the sysfs path for
/dev/disk/by-id/ata-ST3160827AS_5MT004CK? With this change a call to
stat(2) returns the major:minor then userspace can see that
/sys/dev/block/8:32 links to /sys/block/sdc.
What are the alternatives?:
1/ Add an ioctl to return the path: Doable, but sysfs is meant to reduce
the need to proliferate ioctl interfaces into the kernel, so this
seems counter productive.
2/ Use udev to create these symlinks: Also doable, but it adds a
udev dependency to utilities that might be running in a limited
environment like an initramfs.
3/ Do a full-tree search of sysfs.
[kay.sievers@vrfy.org: fix duplicate registrations]
[kay.sievers@vrfy.org: cleanup suggestions]
Cc: Neil Brown <neilb@suse.de>
Cc: Tejun Heo <htejun@gmail.com>
Acked-by: Kay Sievers <kay.sievers@vrfy.org>
Reviewed-by: SL Baur <steve@xemacs.org>
Acked-by: Kay Sievers <kay.sievers@vrfy.org>
Acked-by: Mark Lord <lkml@rtr.ca>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This patch exports the per-gendisk command filter to user space through
sysfs, so it can be changed by the system administrator.
All users of the old cmd filter have been converted to use the new one.
Original patch from Peter Jones.
Signed-off-by: Adel Gadllah <adel.gadllah@gmail.com>
Signed-off-by: Peter Jones <pjones@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Commit 30f2f0eb4b ("block: do_mounts -
accept root=<non-existant partition>") extended blk_lookup_devt() to be
able to look up partitions that had not yet been registered, but in the
process made the assumption that the '&block_class.devices' list only
contains disk devices and that you can do 'dev_to_disk(dev)' on them.
That isn't actually true. The block_class device list also contains the
partitions we've discovered so far, and you can't just do a
'dev_to_disk()' on those.
So make sure to only work on devices that block/genhd.c has registered
itself, something we can test by checking the 'dev->type' member. This
makes the loop in blk_lookup_devt() match the other such loops in this
file.
[ We may want to do an alternate version that knows to handle _either_
whole-disk devices or partitions, but for now this is the minimal fix
for a series of crashes reported by Mariusz Kozlowski in
http://lkml.org/lkml/2008/5/25/25
and Ingo in
http://lkml.org/lkml/2008/6/9/39 ]
Reported-by: Mariusz Kozlowski <m.kozlowski@tuxland.pl>
Reported-by: Ingo Molnar <mingo@elte.hu>
Cc: Neil Brown <neilb@suse.de>
Cc: Joao Luis Meloni Assirati <assirati@nonada.if.usp.br>
Acked-by: Kay Sievers <kay.sievers@vrfy.org>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Some devices, like md, may create partitions only at first access,
so allow root= to be set to a valid non-existant partition of an
existing disk. This applies only to non-initramfs root mounting.
This fixes a regression from 2.6.24 which did allow this to happen and
broke some users machines :(
Acked-by: Neil Brown <neilb@suse.de>
Tested-by: Joao Luis Meloni Assirati <assirati@nonada.if.usp.br>
Cc: stable <stable@kernel.org>
Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Provide a place in sysfs (/sys/class/bdi) for the backing_dev_info object.
This allows us to see and set the various BDI specific variables.
In particular this properly exposes the read-ahead window for all relevant
users and /sys/block/<block>/queue/read_ahead_kb should be deprecated.
With patient help from Kay Sievers and Greg KH
[mszeredi@suse.cz]
- split off NFS and FUSE changes into separate patches
- document new sysfs attributes under Documentation/ABI
- do bdi_class_init as a core_initcall, otherwise the "default" BDI
won't be initialized
- remove bdi_init_fmt macro, it's not used very much
[akpm@linux-foundation.org: fix ia64 warning]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Acked-by: Greg KH <greg@kroah.com>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fixes:
block/genhd.c:361: warning: ignoring return value of ‘class_register’, declared with attribute warn_unused_result
Signed-off-by: Roland McGrath <roland@redhat.com>
Acked-by: Jeff Garzik <jeff@garzik.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch contains the following cleanups:
- make the needlessly global struct disk_type static
- #if 0 the unused genhd_media_change_notify()
Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This patch adds a proper prototye for blk_dev_init() in block/blk.h
Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This moves the block devices to /sys/class/block. It will create a
flat list of all block devices, with the disks and partitions in one
directory. For compatibility /sys/block is created and contains symlinks
to the disks.
/sys/class/block
|-- sda -> ../../devices/pci0000:00/0000:00:1f.2/host0/target0:0:0/0:0:0:0/block/sda
|-- sda1 -> ../../devices/pci0000:00/0000:00:1f.2/host0/target0:0:0/0:0:0:0/block/sda/sda1
|-- sda10 -> ../../devices/pci0000:00/0000:00:1f.2/host0/target0:0:0/0:0:0:0/block/sda/sda10
|-- sda5 -> ../../devices/pci0000:00/0000:00:1f.2/host0/target0:0:0/0:0:0:0/block/sda/sda5
|-- sda6 -> ../../devices/pci0000:00/0000:00:1f.2/host0/target0:0:0/0:0:0:0/block/sda/sda6
|-- sda7 -> ../../devices/pci0000:00/0000:00:1f.2/host0/target0:0:0/0:0:0:0/block/sda/sda7
|-- sda8 -> ../../devices/pci0000:00/0000:00:1f.2/host0/target0:0:0/0:0:0:0/block/sda/sda8
|-- sda9 -> ../../devices/pci0000:00/0000:00:1f.2/host0/target0:0:0/0:0:0:0/block/sda/sda9
`-- sr0 -> ../../devices/pci0000:00/0000:00:1f.2/host1/target1:0:0/1:0:0:0/block/sr0
/sys/block/
|-- sda -> ../devices/pci0000:00/0000:00:1f.2/host0/target0:0:0/0:0:0:0/block/sda
`-- sr0 -> ../devices/pci0000:00/0000:00:1f.2/host1/target1:0:0/1:0:0:0/block/sr0
Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Dynamically create the kset instead of declaring it statically. We also
rename block_subsys to block_kset to catch all users of this symbol
with a build error instead of an easy-to-ignore build warning.
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
We don't need a "default" ktype for a kset. We should set this
explicitly every time for each kset. This change is needed so that we
can make ksets dynamic, and cleans up one of the odd, undocumented
assumption that the kset/kobject/ktype model has.
This patch is based on a lot of help from Kay Sievers.
Nasty bug in the block code was found by Dave Young
<hidave.darkstar@gmail.com>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: Dave Young <hidave.darkstar@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Fix a memory leak in alloc_disk_node(). Don't forget to free 'dkstats' when the allocation of 'part' failed.
Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This changes the uevent buffer functions to use a struct instead of a
long list of parameters. It does no longer require the caller to do the
proper buffer termination and size accounting, which is currently wrong
in some places. It fixes a known bug where parts of the uevent
environment are overwritten because of wrong index calculations.
Many thanks to Mathieu Desnoyers for finding bugs and improving the
error handling.
Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Put WARN_ON and fixed all callers of unregister_blkdev(). Now we can make
unregister_blkdev return void.
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When unregister_blkdev() has failed, something wrong happened. This patch
adds WARN_ON to notify of such badness.
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
kmalloc_node() and kmem_cache_alloc_node() were not available in a zeroing
variant in the past. But with __GFP_ZERO it is possible now to do zeroing
while allocating.
Use __GFP_ZERO to remove the explicit clearing of memory via memset whereever
we can.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Send an uevent to user space to indicate that a media change event has
occurred.
Signed-off-by: Kristen Carlson Accardi <kristen.c.accardi@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Allow user space to determine if a disk supports Asynchronous Notification of
media changes. This is done by adding a new sysfs file "capability_flags",
which is documented in (insert file name). This sysfs file will export all
disk capabilities flags to user space. We also define a new flag to define
the media change notification capability.
Signed-off-by: Kristen Carlson Accardi <kristen.c.accardi@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Display all possible partitions when the root filesystem is not mounted.
This helps to track spell'o's and missing drivers.
Updated to work with newer kernels.
Example output:
VFS: Cannot open root device "foobar" or unknown-block(0,0)
Please append a correct "root=" boot option; here are the available partitions:
0800 8388608 sda driver: sd
0801 192748 sda1
0802 8193150 sda2
0810 4194304 sdb driver: sd
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)
[akpm@linux-foundation.org: cleanups, fix printk warnings]
Signed-off-by: Jan Engelhardt <jengelh@gmx.de>
Cc: Dave Gilbert <linux@treblig.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We need to work on cleaning up the relationship between kobjects, ksets and
ktypes. The removal of 'struct subsystem' is the first step of this,
especially as it is not really needed at all.
Thanks to Kay for fixing the bugs in this patch.
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Revert all this. It can cause device-mapper to receive a different major from
earlier kernels and it turns out that the Amanda backup program (via GNU tar,
apparently) checks major numbers on files when performing incremental backups.
Which is a bit broken of Amanda (or tar), but this feature isn't important
enough to justify the churn.
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Several people have reported failures in dynamic major device number handling
due to the recent changes in there to avoid handing out the local/experimental
majors.
Rolf reports that this is due to a gcc-4.1.0 bug.
The patch refactors that code a lot in an attempt to provoke the compiler into
behaving.
Cc: Rolf Eike Beer <eike-kernel@sf-tec.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
As pointed out in http://bugzilla.kernel.org/show_bug.cgi?id=7922, dynamic
blockdev major allocation can hand out majors which LANANA has defined as
being for local/experimental use.
Cc: Torben Mathiasen <device@lanana.org>
Cc: Greg KH <greg@kroah.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Tomas Klas <tomas.klas@mepatek.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch provides fault-injection capability for disk IO.
Boot option:
fail_make_request=<probability>,<interval>,<space>,<times>
<interval> -- specifies the interval of failures.
<probability> -- specifies how often it should fail in percent.
<space> -- specifies the size of free space where disk IO can be issued
safely in bytes.
<times> -- specifies how many times failures may happen at most.
Debugfs:
/debug/fail_make_request/interval
/debug/fail_make_request/probability
/debug/fail_make_request/specifies
/debug/fail_make_request/times
Example:
fail_make_request=10,100,0,-1
echo 1 > /sys/blocks/hda/hda1/make-it-fail
generic_make_request() on /dev/hda1 fails once per 10 times.
Cc: Jens Axboe <axboe@suse.de>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Tejun Heo