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Commit7759eb23fd("block: remove bio_rewind_iter()") removed a similar API for the following reasons: ``` It is pointed that bio_rewind_iter() is one very bad API[1]: 1) bio size may not be restored after rewinding 2) it causes some bogus change, such as5151842b9d(block: reset bi_iter.bi_done after splitting bio) 3) rewinding really makes things complicated wrt. bio splitting 4) unnecessary updating of .bi_done in fast path [1] https://marc.info/?t=153549924200005&r=1&w=2 So this patch takes Kent's suggestion to restore one bio into its original state via saving bio iterator(struct bvec_iter) in bio_integrity_prep(), given now bio_rewind_iter() is only used by bio integrity code. ``` However, saving off a copy of the 32 bytes bio->bi_iter in case rewind needed isn't efficient because it bloats per-bio-data for what is an unlikely case. That suggestion also ignores the need to restore crypto and integrity info. Add dm_bio_rewind() API for a specific use-case that is much more narrow than the previous more generic rewind code that was reverted: 1) most bios have a fixed end sector since bio split is done from front of the bio, if driver just records how many sectors between current bio's start sector and the original bio's end sector, the original position can be restored. Keeping the original bio's end sector fixed is a _hard_ requirement for this interface! 2) if a bio's end sector won't change (usually bio_trim() isn't called, or in the case of DM it preserves original bio), user can restore the original position by storing sector offset from the current ->bi_iter.bi_sector to bio's end sector; together with saving bio size, only 8 bytes is needed to restore to original bio. 3) DM's requeue use case: when BLK_STS_DM_REQUEUE happens, DM core needs to restore to an "original bio" which represents the current dm_io to be requeued (which may be a subset of the original bio). By storing the sector offset from the original bio's end sector and dm_io's size, dm_bio_rewind() can restore such original bio. See commit7dd76d1fee("dm: improve bio splitting and associated IO accounting") for more details on how DM does this. Leveraging this, allows DM core to shift the need for bio cloning from bio-split time (during IO submission) to the less likely BLK_STS_DM_REQUEUE handling (after IO completes with that error). 4) Unlike the original rewind API, dm_bio_rewind() doesn't add .bi_done to bvec_iter and there is no effect on the fast path. Implement dm_bio_rewind() by factoring out clear helpers that it calls: dm_bio_integrity_rewind, dm_bio_crypt_rewind and dm_bio_rewind_iter. DM is able to ensure that dm_bio_rewind() is used safely but, given the constraint that the bio's end must never change, other hypothetical future callers may not take the same care. So make dm_bio_rewind() and all supporting code local to DM to avoid risk of hypothetical abuse. A "dm_" prefix was added to all functions to avoid any namespace collisions. Suggested-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Mike Snitzer <snitzer@kernel.org>
114 lines
3.8 KiB
Makefile
114 lines
3.8 KiB
Makefile
# SPDX-License-Identifier: GPL-2.0
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#
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# Makefile for the kernel software RAID and LVM drivers.
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#
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dm-mod-y += dm.o dm-table.o dm-target.o dm-linear.o dm-stripe.o \
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dm-ioctl.o dm-io.o dm-kcopyd.o dm-sysfs.o dm-stats.o \
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dm-rq.o dm-io-rewind.o
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dm-multipath-y += dm-path-selector.o dm-mpath.o
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dm-historical-service-time-y += dm-ps-historical-service-time.o
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dm-io-affinity-y += dm-ps-io-affinity.o
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dm-queue-length-y += dm-ps-queue-length.o
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dm-round-robin-y += dm-ps-round-robin.o
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dm-service-time-y += dm-ps-service-time.o
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dm-snapshot-y += dm-snap.o dm-exception-store.o dm-snap-transient.o \
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dm-snap-persistent.o
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dm-mirror-y += dm-raid1.o
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dm-log-userspace-y += dm-log-userspace-base.o dm-log-userspace-transfer.o
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dm-bio-prison-y += dm-bio-prison-v1.o dm-bio-prison-v2.o
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dm-thin-pool-y += dm-thin.o dm-thin-metadata.o
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dm-cache-y += dm-cache-target.o dm-cache-metadata.o dm-cache-policy.o \
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dm-cache-background-tracker.o
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dm-cache-smq-y += dm-cache-policy-smq.o
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dm-ebs-y += dm-ebs-target.o
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dm-era-y += dm-era-target.o
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dm-clone-y += dm-clone-target.o dm-clone-metadata.o
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dm-verity-y += dm-verity-target.o
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dm-zoned-y += dm-zoned-target.o dm-zoned-metadata.o dm-zoned-reclaim.o
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md-mod-y += md.o md-bitmap.o
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raid456-y += raid5.o raid5-cache.o raid5-ppl.o
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linear-y += md-linear.o
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multipath-y += md-multipath.o
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faulty-y += md-faulty.o
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# Note: link order is important. All raid personalities
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# and must come before md.o, as they each initialise
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# themselves, and md.o may use the personalities when it
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# auto-initialised.
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obj-$(CONFIG_MD_LINEAR) += linear.o
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obj-$(CONFIG_MD_RAID0) += raid0.o
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obj-$(CONFIG_MD_RAID1) += raid1.o
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obj-$(CONFIG_MD_RAID10) += raid10.o
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obj-$(CONFIG_MD_RAID456) += raid456.o
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obj-$(CONFIG_MD_MULTIPATH) += multipath.o
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obj-$(CONFIG_MD_FAULTY) += faulty.o
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obj-$(CONFIG_MD_CLUSTER) += md-cluster.o
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obj-$(CONFIG_BCACHE) += bcache/
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obj-$(CONFIG_BLK_DEV_MD) += md-mod.o
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ifeq ($(CONFIG_BLK_DEV_MD),y)
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obj-y += md-autodetect.o
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endif
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obj-$(CONFIG_BLK_DEV_DM) += dm-mod.o
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obj-$(CONFIG_BLK_DEV_DM_BUILTIN) += dm-builtin.o
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obj-$(CONFIG_DM_UNSTRIPED) += dm-unstripe.o
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obj-$(CONFIG_DM_BUFIO) += dm-bufio.o
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obj-$(CONFIG_DM_BIO_PRISON) += dm-bio-prison.o
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obj-$(CONFIG_DM_CRYPT) += dm-crypt.o
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obj-$(CONFIG_DM_DELAY) += dm-delay.o
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obj-$(CONFIG_DM_DUST) += dm-dust.o
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obj-$(CONFIG_DM_FLAKEY) += dm-flakey.o
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obj-$(CONFIG_DM_MULTIPATH) += dm-multipath.o dm-round-robin.o
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obj-$(CONFIG_DM_MULTIPATH_QL) += dm-queue-length.o
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obj-$(CONFIG_DM_MULTIPATH_ST) += dm-service-time.o
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obj-$(CONFIG_DM_MULTIPATH_HST) += dm-historical-service-time.o
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obj-$(CONFIG_DM_MULTIPATH_IOA) += dm-io-affinity.o
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obj-$(CONFIG_DM_SWITCH) += dm-switch.o
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obj-$(CONFIG_DM_SNAPSHOT) += dm-snapshot.o
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obj-$(CONFIG_DM_PERSISTENT_DATA) += persistent-data/
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obj-$(CONFIG_DM_MIRROR) += dm-mirror.o dm-log.o dm-region-hash.o
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obj-$(CONFIG_DM_LOG_USERSPACE) += dm-log-userspace.o
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obj-$(CONFIG_DM_ZERO) += dm-zero.o
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obj-$(CONFIG_DM_RAID) += dm-raid.o
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obj-$(CONFIG_DM_THIN_PROVISIONING) += dm-thin-pool.o
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obj-$(CONFIG_DM_VERITY) += dm-verity.o
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obj-$(CONFIG_DM_CACHE) += dm-cache.o
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obj-$(CONFIG_DM_CACHE_SMQ) += dm-cache-smq.o
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obj-$(CONFIG_DM_EBS) += dm-ebs.o
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obj-$(CONFIG_DM_ERA) += dm-era.o
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obj-$(CONFIG_DM_CLONE) += dm-clone.o
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obj-$(CONFIG_DM_LOG_WRITES) += dm-log-writes.o
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obj-$(CONFIG_DM_INTEGRITY) += dm-integrity.o
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obj-$(CONFIG_DM_ZONED) += dm-zoned.o
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obj-$(CONFIG_DM_WRITECACHE) += dm-writecache.o
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ifeq ($(CONFIG_DM_INIT),y)
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dm-mod-objs += dm-init.o
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endif
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ifeq ($(CONFIG_DM_UEVENT),y)
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dm-mod-objs += dm-uevent.o
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endif
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ifeq ($(CONFIG_BLK_DEV_ZONED),y)
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dm-mod-objs += dm-zone.o
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endif
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ifeq ($(CONFIG_IMA),y)
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dm-mod-objs += dm-ima.o
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endif
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ifeq ($(CONFIG_DM_VERITY_FEC),y)
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dm-verity-objs += dm-verity-fec.o
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endif
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ifeq ($(CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG),y)
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dm-verity-objs += dm-verity-verify-sig.o
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endif
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ifeq ($(CONFIG_DM_AUDIT),y)
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dm-mod-objs += dm-audit.o
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endif
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