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Date: Fri, 8 May 2009 11:53:58 +0900 From: Tejun Heo <tj@...nel.org> To: linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org, linux-ide@...r.kernel.org, rusty@...tcorp.com.au, James.Bottomley@...senPartnership.com, mike.miller@...com, donari75@...il.com, paul.clements@...eleye.com, tim@...erelk.net, Geert.Uytterhoeven@...ycom.com, davem@...emloft.net, Laurent@...vier.info, jgarzik@...ox.com, jeremy@...source.com, grant.likely@...retlab.ca, adrian@...en.demon.co.uk, sfr@...b.auug.org.au, bzolnier@...il.com, petkovbb@...glemail.com, sshtylyov@...mvista.com, oakad@...oo.com, drzeus@...eus.cx, dwmw2@...radead.org, Markus.Lidel@...dowconnect.com, wein@...ibm.com, schwidefsky@...ibm.com, zaitcev@...hat.com, fujita.tomonori@....ntt.co.jp, axboe@...nel.dk Subject: [GIT PATCH] block: unify request processing model and implement peek/fetch Hello, Upon ack, please pull from the following git tree. git://git.kernel.org/pub/scm/linux/kernel/git/tj/misc.git block-peek-fetch Block layer has allowed two different models of request processing. elv_next_request() is used to peek at the top of the queue, after peeking, a LLD could start processing it immediately or dequeue and then start processing. The non-dequeuing behavior is mostly useful for simpler device drivers (usually PIO based) which process requests on segment basis. By using the block layer queue tip as the current request pointer, they don't have to care about request boundaries and just process things segment-by-segment. However, this dual mode of operations complicates and ambiguates block layer API. Block layer can't tell whether a request has begun processing or not in deterministic manner. This makes accounting inaccurate and implementing high level features in block layer difficult. For example, it isn't clear when a block layer timeout timer should be started or how queue queiscing for EH should be implemented. Even when problems can be worked aroudn, it makes the implementation fragile. Although allowing llds ignore request boundaries makes things simpler for certain drivers, the number of drivers benefit form it aren't too many and driver stacks which are even mildly complex have to deal with request boundaries anyway. Also, the benefit itself isn't that significant. In most cases, it is just another way of doing things rather than the definitively better way. IOW, if there were no such alternative, nobody would have missed it. This patchset converts all block layer llds to dequeuing model and then clean up API to simplify a bit and enforce dequeueing model. This patchset contains the following patches. 0001-ide-dequeue-in-flight-request.patch 0002-mg_disk-fix-queue-hang-infinite-retry-on-fs-requ.patch 0003-mg_disk-dequeue-and-track-in-flight-request.patch 0004-hd-dequeue-and-track-in-flight-request.patch 0005-ataflop-dequeue-and-track-in-flight-request.patch 0006-swim3-dequeue-in-flight-request.patch 0007-xsysace-dequeue-in-flight-request.patch 0008-paride-dequeue-in-flight-request.patch 0009-ps3disk-dequeue-in-flight-request.patch 0010-amiflop-dequeue-in-flight-request.patch 0011-swim-dequeue-in-flight-request.patch 0012-xd-dequeue-in-flight-request.patch 0013-mtd_blkdevs-dequeue-in-flight-request.patch 0014-jsflash-dequeue-in-flight-request.patch 0015-z2ram-dequeue-in-flight-request.patch 0016-gdrom-dequeue-in-flight-request.patch 0017-block-convert-to-dequeueing-model-easy-ones.patch 0018-block-implement-and-enforce-request-peek-start-fetc.patch 0001 converts ide to dequeueing model. 0002 fixes a bug in mg_disk spotted during conversion. 0003-0005 make llds which used elv_next_request() to track in-flight request to dequeue and track it themselves. 0006-0008 convert llds which already track in-flight request to dequeueing model. 0009 converts ps3disk. 0010-0015 convert llds which process requests one-by-one sequentially to dequeueing model. 0016 converts gdrom which already used dequeueing model in normal path. 0017 converts plat-omap/mailbox, floppy, viocd, mspro_block, i2o_block and mmc/card/queue which are already pretty close to dequeueing model. 0018 changes block layer issue API such that there are three functions - blk_peek_request(), blk_start_request() and blk_fetch_request() where blk_fetch_request() is combination of the prevoius two. It also enforces dequeueing model. Trying to complete a queued request will trigger BUG. Please note that conversions in 0001-0016 might not look optimal. They're done in such a way that 0018 can mechanically convert to blk_fetch_request() where applicable. All changes have been compile tested. libata, ide, hd and ubd_kern are verified to work. Waiting for floppy media to test it. This patchset is on top of linux-2.6-block#for-2.6.31 (f68adec3c7155a8bbf32a90cb4c4d0737df045d9) + linux-2.6-ide#for-next (03682411b1ccd38cbde2e9a6ab43884ff34fbefc) + block-unify-sector-and-data-len (1df2a196e28cc8f97919dc530dc1c019e1d3a968) and contains the following changes. arch/arm/plat-omap/mailbox.c | 9 +- arch/um/drivers/ubd_kern.c | 3 block/blk-barrier.c | 4 - block/blk-core.c | 105 ++++++++++++++++++++++++-------- block/blk-tag.c | 2 block/blk.h | 1 drivers/block/DAC960.c | 4 - drivers/block/amiflop.c | 47 +++++++------- drivers/block/ataflop.c | 62 ++++++++++--------- drivers/block/cciss.c | 4 - drivers/block/cpqarray.c | 4 - drivers/block/floppy.c | 4 - drivers/block/hd.c | 62 ++++++++++++------- drivers/block/mg_disk.c | 115 +++++++++++++++++++----------------- drivers/block/nbd.c | 4 - drivers/block/paride/pcd.c | 17 +++-- drivers/block/paride/pd.c | 13 ++-- drivers/block/paride/pf.c | 13 +--- drivers/block/ps3disk.c | 8 +- drivers/block/sunvdc.c | 3 drivers/block/swim.c | 41 +++++------- drivers/block/swim3.c | 46 ++++++++++---- drivers/block/sx8.c | 8 -- drivers/block/ub.c | 8 +- drivers/block/viodasd.c | 4 - drivers/block/virtio_blk.c | 4 - drivers/block/xd.c | 23 +++---- drivers/block/xen-blkfront.c | 15 ++-- drivers/block/xsysace.c | 19 +++-- drivers/block/z2ram.c | 13 ++-- drivers/cdrom/gdrom.c | 28 +++----- drivers/cdrom/viocd.c | 2 drivers/ide/ide-atapi.c | 14 +++- drivers/ide/ide-cd.c | 8 -- drivers/ide/ide-io.c | 33 +++++++--- drivers/memstick/core/mspro_block.c | 9 +- drivers/message/i2o/i2o_block.c | 10 +-- drivers/mmc/card/queue.c | 11 --- drivers/mtd/mtd_blkdevs.c | 14 ++-- drivers/s390/block/dasd.c | 16 +---- drivers/s390/char/tape_block.c | 7 -- drivers/sbus/char/jsflash.c | 22 +++--- drivers/scsi/scsi_lib.c | 10 +-- drivers/scsi/scsi_transport_sas.c | 4 - include/linux/blkdev.h | 9 ++ include/linux/elevator.h | 2 46 files changed, 486 insertions(+), 378 deletions(-) Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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