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path: root/drivers/md/dm-delay.c
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2019-04-26dm delay: fix a crash when invalid device is specifiedMikulas Patocka
When the target line contains an invalid device, delay_ctr() will call delay_dtr() with NULL workqueue. Attempting to destroy the NULL workqueue causes a crash. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Cc: stable@vger.kernel.org Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2018-12-18dm: Check for device sector overflow if CONFIG_LBDAF is not setMilan Broz
Reference to a device in device-mapper table contains offset in sectors. If the sector_t is 32bit integer (CONFIG_LBDAF is not set), then several device-mapper targets can overflow this offset and validity check is then performed on a wrong offset and a wrong table is activated. See for example (on 32bit without CONFIG_LBDAF) this overflow: # dmsetup create test --table "0 2048 linear /dev/sdg 4294967297" # dmsetup table test 0 2048 linear 8:96 1 This patch adds explicit check for overflow if the offset is sector_t type. Signed-off-by: Milan Broz <gmazyland@gmail.com> Reviewed-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2018-07-27dm delay: add flush as a third class of IOMikulas Patocka
Add a new class for dm-delay that delays flush requests. Previously, flushes were delayed as writes, but it caused problems if the user needed to create a device with one or a few slow sectors for the purpose of testing - all flushes would be forwarded to this device and delayed, and that skews the test results. Fix this by allowing to select 0 delay for flushes. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2018-07-27dm delay: refactor repetitive codeMikulas Patocka
dm-delay has a lot of code that is repeated for delaying read and write bios. Repetitive code is generally bad; refactor out the repetitive code in preperation for adding another delay class for flush bios. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2018-01-17dm: backfill missing calls to mutex_destroy()Mike Snitzer
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2017-11-14md: Convert timers to use timer_setup()Kees Cook
In preparation for unconditionally passing the struct timer_list pointer to all timer callbacks, switch to using the new timer_setup() and from_timer() to pass the timer pointer explicitly. Cc: Kent Overstreet <kent.overstreet@gmail.com> Cc: Shaohua Li <shli@kernel.org> Cc: Alasdair Kergon <agk@redhat.com> Cc: Mike Snitzer <snitzer@redhat.com> Cc: dm-devel@redhat.com Cc: linux-bcache@vger.kernel.org Cc: linux-raid@vger.kernel.org Signed-off-by: Kees Cook <keescook@chromium.org> Reviewed-by: Michael Lyle <mlyle@lyle.org> Reviewed-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2017-08-23block: replace bi_bdev with a gendisk pointer and partitions indexChristoph Hellwig
This way we don't need a block_device structure to submit I/O. The block_device has different life time rules from the gendisk and request_queue and is usually only available when the block device node is open. Other callers need to explicitly create one (e.g. the lightnvm passthrough code, or the new nvme multipathing code). For the actual I/O path all that we need is the gendisk, which exists once per block device. But given that the block layer also does partition remapping we additionally need a partition index, which is used for said remapping in generic_make_request. Note that all the block drivers generally want request_queue or sometimes the gendisk, so this removes a layer of indirection all over the stack. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2017-04-24dm: mark targets that pass integrity dataMikulas Patocka
A dm-crypt on dm-integrity device incorrectly advertises an integrity profile on the DM crypt device. It can be seen in the files "/sys/block/dm-*/integrity/*" that both dm-integrity and dm-crypt target advertise the integrity profile. That is incorrect, only the dm-integrity target should advertise the integrity profile. A general problem in DM is that if we have a DM device that depends on another device with an integrity profile, the upper device will always advertise the integrity profile, even when the target driver doesn't support handling integrity data. Most targets don't support integrity data, so we provide a whitelist of targets that support it (linear, delay and striped). The targets that support passing integrity data to the lower device are marked with the flag DM_TARGET_PASSES_INTEGRITY. The DM core will now advertise integrity data on a DM device only if all the targets support the integrity data. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2016-02-22dm: rename target's per_bio_data_size to per_io_data_sizeMike Snitzer
Request-based DM will also make use of per_bio_data_size. Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2015-10-31dm delay: document that offsets are specified in sectorsTomohiro Kusumi
Only delay params are mentioned in delay.txt. Mention offsets just like documents for linear and flakey do. Signed-off-by: Tomohiro Kusumi <kusumi.tomohiro@gmail.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2015-10-31dm delay: capitalize the start of an delay_ctr() error messageTomohiro Kusumi
All other error messages start capitalized. Signed-off-by: Tomohiro Kusumi <kusumi.tomohiro@gmail.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2015-10-31dm delay: Use DM_MAPIO macros instead of open-coded equivalentsTomohiro Kusumi
.map function of dm-delay returns return value of delay_bio(), hence it's supposed to return using a defined DM_MAPIO macro. Signed-off-by: Tomohiro Kusumi <kusumi.tomohiro@gmail.com> Acked-By: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2015-08-12dm: do not override error code returned from dm_get_device()Vivek Goyal
Some of the device mapper targets override the error code returned by dm_get_device() and return either -EINVAL or -ENXIO. There is nothing gained by this override. It is better to propagate the returned error code unchanged to caller. This work was motivated by hitting an issue where the underlying device was busy but -EINVAL was being returned. After this change we get -EBUSY instead and it is easier to figure out the problem. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2015-04-15dm delay: use msecs_to_jiffies for time conversionNicholas Mc Guire
Converting milliseconds to jiffies by "val * HZ / 1000" is technically OK but msecs_to_jiffies(val) is the cleaner solution and handles all corner cases correctly. Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2014-01-30Merge branch 'for-3.14/core' of git://git.kernel.dk/linux-blockLinus Torvalds
Pull core block IO changes from Jens Axboe: "The major piece in here is the immutable bio_ve series from Kent, the rest is fairly minor. It was supposed to go in last round, but various issues pushed it to this release instead. The pull request contains: - Various smaller blk-mq fixes from different folks. Nothing major here, just minor fixes and cleanups. - Fix for a memory leak in the error path in the block ioctl code from Christian Engelmayer. - Header export fix from CaiZhiyong. - Finally the immutable biovec changes from Kent Overstreet. This enables some nice future work on making arbitrarily sized bios possible, and splitting more efficient. Related fixes to immutable bio_vecs: - dm-cache immutable fixup from Mike Snitzer. - btrfs immutable fixup from Muthu Kumar. - bio-integrity fix from Nic Bellinger, which is also going to stable" * 'for-3.14/core' of git://git.kernel.dk/linux-block: (44 commits) xtensa: fixup simdisk driver to work with immutable bio_vecs block/blk-mq-cpu.c: use hotcpu_notifier() blk-mq: for_each_* macro correctness block: Fix memory leak in rw_copy_check_uvector() handling bio-integrity: Fix bio_integrity_verify segment start bug block: remove unrelated header files and export symbol blk-mq: uses page->list incorrectly blk-mq: use __smp_call_function_single directly btrfs: fix missing increment of bi_remaining Revert "block: Warn and free bio if bi_end_io is not set" block: Warn and free bio if bi_end_io is not set blk-mq: fix initializing request's start time block: blk-mq: don't export blk_mq_free_queue() block: blk-mq: make blk_sync_queue support mq block: blk-mq: support draining mq queue dm cache: increment bi_remaining when bi_end_io is restored block: fixup for generic bio chaining block: Really silence spurious compiler warnings block: Silence spurious compiler warnings block: Kill bio_pair_split() ...
2014-01-07dm delay: use per-bio data instead of a mempool and slab cacheMikulas Patocka
Starting with commit c0820cf5ad095 ("dm: introduce per_bio_data"), device mapper has the capability to pre-allocate a target-specific structure with the bio. This patch changes dm-delay to use this facility instead of a slab cache and mempool. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2013-12-31Merge tag 'v3.13-rc6' into for-3.14/coreJens Axboe
Needed to bring blk-mq uptodate, since changes have been going in since for-3.14/core was established. Fixup merge issues related to the immutable biovec changes. Signed-off-by: Jens Axboe <axboe@kernel.dk> Conflicts: block/blk-flush.c fs/btrfs/check-integrity.c fs/btrfs/extent_io.c fs/btrfs/scrub.c fs/logfs/dev_bdev.c
2013-11-23block: Abstract out bvec iteratorKent Overstreet
Immutable biovecs are going to require an explicit iterator. To implement immutable bvecs, a later patch is going to add a bi_bvec_done member to this struct; for now, this patch effectively just renames things. Signed-off-by: Kent Overstreet <kmo@daterainc.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: "Ed L. Cashin" <ecashin@coraid.com> Cc: Nick Piggin <npiggin@kernel.dk> Cc: Lars Ellenberg <drbd-dev@lists.linbit.com> Cc: Jiri Kosina <jkosina@suse.cz> Cc: Matthew Wilcox <willy@linux.intel.com> Cc: Geoff Levand <geoff@infradead.org> Cc: Yehuda Sadeh <yehuda@inktank.com> Cc: Sage Weil <sage@inktank.com> Cc: Alex Elder <elder@inktank.com> Cc: ceph-devel@vger.kernel.org Cc: Joshua Morris <josh.h.morris@us.ibm.com> Cc: Philip Kelleher <pjk1939@linux.vnet.ibm.com> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Jeremy Fitzhardinge <jeremy@goop.org> Cc: Neil Brown <neilb@suse.de> Cc: Alasdair Kergon <agk@redhat.com> Cc: Mike Snitzer <snitzer@redhat.com> Cc: dm-devel@redhat.com Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: linux390@de.ibm.com Cc: Boaz Harrosh <bharrosh@panasas.com> Cc: Benny Halevy <bhalevy@tonian.com> Cc: "James E.J. Bottomley" <JBottomley@parallels.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: "Nicholas A. Bellinger" <nab@linux-iscsi.org> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Chris Mason <chris.mason@fusionio.com> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Andreas Dilger <adilger.kernel@dilger.ca> Cc: Jaegeuk Kim <jaegeuk.kim@samsung.com> Cc: Steven Whitehouse <swhiteho@redhat.com> Cc: Dave Kleikamp <shaggy@kernel.org> Cc: Joern Engel <joern@logfs.org> Cc: Prasad Joshi <prasadjoshi.linux@gmail.com> Cc: Trond Myklebust <Trond.Myklebust@netapp.com> Cc: KONISHI Ryusuke <konishi.ryusuke@lab.ntt.co.jp> Cc: Mark Fasheh <mfasheh@suse.com> Cc: Joel Becker <jlbec@evilplan.org> Cc: Ben Myers <bpm@sgi.com> Cc: xfs@oss.sgi.com Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Len Brown <len.brown@intel.com> Cc: Pavel Machek <pavel@ucw.cz> Cc: "Rafael J. Wysocki" <rjw@sisk.pl> Cc: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com> Cc: Ben Hutchings <ben@decadent.org.uk> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Guo Chao <yan@linux.vnet.ibm.com> Cc: Tejun Heo <tj@kernel.org> Cc: Asai Thambi S P <asamymuthupa@micron.com> Cc: Selvan Mani <smani@micron.com> Cc: Sam Bradshaw <sbradshaw@micron.com> Cc: Wei Yongjun <yongjun_wei@trendmicro.com.cn> Cc: "Roger Pau Monné" <roger.pau@citrix.com> Cc: Jan Beulich <jbeulich@suse.com> Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com> Cc: Ian Campbell <Ian.Campbell@citrix.com> Cc: Sebastian Ott <sebott@linux.vnet.ibm.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Jiang Liu <jiang.liu@huawei.com> Cc: Nitin Gupta <ngupta@vflare.org> Cc: Jerome Marchand <jmarchand@redhat.com> Cc: Joe Perches <joe@perches.com> Cc: Peng Tao <tao.peng@emc.com> Cc: Andy Adamson <andros@netapp.com> Cc: fanchaoting <fanchaoting@cn.fujitsu.com> Cc: Jie Liu <jeff.liu@oracle.com> Cc: Sunil Mushran <sunil.mushran@gmail.com> Cc: "Martin K. Petersen" <martin.petersen@oracle.com> Cc: Namjae Jeon <namjae.jeon@samsung.com> Cc: Pankaj Kumar <pankaj.km@samsung.com> Cc: Dan Magenheimer <dan.magenheimer@oracle.com> Cc: Mel Gorman <mgorman@suse.de>6
2013-11-18dm delay: fix a possible deadlock due to shared workqueueMikulas Patocka
The dm-delay target uses a shared workqueue for multiple instances. This can cause deadlock if two or more dm-delay targets are stacked on the top of each other. This patch changes dm-delay to use a per-instance workqueue. Cc: stable@vger.kernel.org # 2.6.22+ Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2013-03-01dm: rename request variables to biosAlasdair G Kergon
Use 'bio' in the name of variables and functions that deal with bios rather than 'request' to avoid confusion with the normal block layer use of 'request'. No functional changes. Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2013-03-01dm: fix truncated status stringsMikulas Patocka
Avoid returning a truncated table or status string instead of setting the DM_BUFFER_FULL_FLAG when the last target of a table fills the buffer. When processing a table or status request, the function retrieve_status calls ti->type->status. If ti->type->status returns non-zero, retrieve_status assumes that the buffer overflowed and sets DM_BUFFER_FULL_FLAG. However, targets don't return non-zero values from their status method on overflow. Most targets returns always zero. If a buffer overflow happens in a target that is not the last in the table, it gets noticed during the next iteration of the loop in retrieve_status; but if a buffer overflow happens in the last target, it goes unnoticed and erroneously truncated data is returned. In the current code, the targets behave in the following way: * dm-crypt returns -ENOMEM if there is not enough space to store the key, but it returns 0 on all other overflows. * dm-thin returns errors from the status method if a disk error happened. This is incorrect because retrieve_status doesn't check the error code, it assumes that all non-zero values mean buffer overflow. * all the other targets always return 0. This patch changes the ti->type->status function to return void (because most targets don't use the return code). Overflow is detected in retrieve_status: if the status method fills up the remaining space completely, it is assumed that buffer overflow happened. Cc: stable@vger.kernel.org Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2012-12-21dm: remove map_infoMikulas Patocka
This patch removes map_info from bio-based device mapper targets. map_info is still used for request-based targets. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2012-07-27dm thin: commit before gathering statusAlasdair G Kergon
Commit outstanding metadata before returning the status for a dm thin pool so that the numbers reported are as up-to-date as possible. The commit is not performed if the device is suspended or if the DM_NOFLUSH_FLAG is supplied by userspace and passed to the target through a new 'status_flags' parameter in the target's dm_status_fn. The userspace dmsetup tool will support the --noflush flag with the 'dmsetup status' and 'dmsetup wait' commands from version 1.02.76 onwards. Tested-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2012-03-28dm: reject trailing characters in sccanf inputMikulas Patocka
Device mapper uses sscanf to convert arguments to numbers. The problem is that the way we use it ignores additional unmatched characters in the scanned string. For example, this `if (sscanf(string, "%d", &number) == 1)' will match a number, but also it will match number with some garbage appended, like "123abc". As a result, device mapper accepts garbage after some numbers. For example the command `dmsetup create vg1-new --table "0 16384 linear 254:1bla 34816bla"' will pass without an error. This patch fixes all sscanf uses in device mapper. It appends "%c" with a pointer to a dummy character variable to every sscanf statement. The construct `if (sscanf(string, "%d%c", &number, &dummy) == 1)' succeeds only if string is a null-terminated number (optionally preceded by some whitespace characters). If there is some character appended after the number, sscanf matches "%c", writes the character to the dummy variable and returns 2. We check the return value for 1 and consequently reject numbers with some garbage appended. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Acked-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2011-01-13dm: convert workqueues to alloc_orderedTejun Heo
Convert all create[_singlethread]_work() users to the new alloc[_ordered]_workqueue(). This conversion is mechanical and doesn't introduce any behavior change. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2010-08-12dm delay: support discardMike Snitzer
Enable discard support for the delay target. Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2010-08-12dm: use dm_target_offset macroAlasdair G Kergon
Use new dm_target_offset() macro to avoid most references to ti->begin in dm targets. Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2010-03-06dm table: remove unused dm_get_device range parametersNikanth Karthikesan
Remove unused parameters(start and len) of dm_get_device() and fix the callers. Signed-off-by: Nikanth Karthikesan <knikanth@suse.de> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-07-23dm table: pass correct dev area size to device_area_is_validMike Snitzer
Incorrect device area lengths are being passed to device_area_is_valid(). The regression appeared in 2.6.31-rc1 through commit 754c5fc7ebb417b23601a6222a6005cc2e7f2913. With the dm-stripe target, the size of the target (ti->len) was used instead of the stripe_width (ti->len/#stripes). An example of a consequent incorrect error message is: device-mapper: table: 254:0: sdb too small for target Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-06-22dm target:s introduce iterate devices fnMike Snitzer
Add .iterate_devices to 'struct target_type' to allow a function to be called for all devices in a DM target. Implemented it for all targets except those in dm-snap.c (origin and snapshot). (The raid1 version number jumps to 1.12 because we originally reserved 1.1 to 1.11 for 'block_on_error' but ended up using 'handle_errors' instead.) Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com> Cc: martin.petersen@oracle.com
2009-06-22dm delay: support barriersMikulas Patocka
Flush support for dm-delay target. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-04-15block: move bio list helpers into bio.hChristoph Hellwig
It's used by DM and MD and generally useful, so move the bio list helpers into bio.h. Signed-off-by: Christoph Hellwig <hch@lst.de> Acked-by: Alasdair G Kergon <agk@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-01-06dm: consolidate target deregistration error handlingMikulas Patocka
Change dm_unregister_target to return void and use BUG() for error reporting. dm_unregister_target can only fail because of programming bug in the target driver. It can't fail because of user's behavior or disk errors. This patch changes unregister_target to return void and use BUG if someone tries to unregister non-registered target or unregister target that is in use. This patch removes code duplication (testing of error codes in all dm targets) and reports bugs in just one place, in dm_unregister_target. In some target drivers, these return codes were ignored, which could lead to a situation where bugs could be missed. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2008-10-21dm: remove dm header from targetsMikulas Patocka
Change #include "dm.h" to #include <linux/device-mapper.h> in all targets. Targets should not need direct access to internal DM structures. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2007-10-20dm: bio_list macro renamingAlasdair G Kergon
Remove BIO_LIST and DEFINE_BIO_LIST macros that gain us nothing since contents are initialised to NULL. Cc: Jan Engelhardt <jengelh@linux01.gwdg.de> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2007-10-20dm delay: fix statusMilan Broz
Fix missing space in dm-delay target status output if separate read and write delay are configured. Signed-off-by: Milan Broz <mbroz@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2007-10-20dm delay: fix ctr error pathsDmitry Monakhov
Add missing 'dm_put_device' to dm-delay target constructor. Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org> Signed-off-by: Milan Broz <mbroz@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2007-07-12dm delay: cleanupAlasdair G Kergon
Use setup_timer(). Replace semaphore with mutex. Signed-off-by: Alasdair G Kergon <agk@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-12dm: use kmem_cache macroAlasdair G Kergon
Use new KMEM_CACHE() macro and make the newly-exposed structure names more meaningful. Also remove some superfluous casts and inlines (let a modern compiler be the judge). Acked-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-05-09dm: delay targetHeinz Mauelshagen
New device-mapper target that can delay I/O (for testing). Reads can be separated from writes, redirected to different underlying devices and delayed by differing amounts of time. Signed-off-by: Heinz Mauelshagen <mauelshagen@redhat.com> Signed-off-by: Milan Broz <mbroz@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>