block: do not merge requests without consulting with io scheduler

Before merging a bio into an existing request, io scheduler is called to
get its approval first. However, the requests that come fro

block: do not merge requests without consulting with io scheduler

Before merging a bio into an existing request, io scheduler is called to
get its approval first. However, the requests that come from a plug
flush may get merged by block layer without consulting with io
scheduler.

In case of CFQ, this can cause fairness problems. For instance, if a
request gets merged into a low weight cgroup's request, high weight cgroup
now will depend on low weight cgroup to get scheduled. If high weigt cgroup
needs that io request to complete before submitting more requests, then it
will also lose its timeslice.

Following script demonstrates the problem. Group g1 has a low weight, g2
and g3 have equal high weights but g2's requests are adjacent to g1's
requests so they are subject to merging. Due to these merges, g2 gets
poor disk time allocation.

cat > cfq-merge-repro.sh << "EOF"
#!/bin/bash
set -e

IO_ROOT=/mnt-cgroup/io

mkdir -p $IO_ROOT

if ! mount | grep -qw $IO_ROOT; then
mount -t cgroup none -oblkio $IO_ROOT
fi

cd $IO_ROOT

for i in g1 g2 g3; do
if [ -d $i ]; then
rmdir $i
fi
done

mkdir g1 && echo 10 > g1/blkio.weight
mkdir g2 && echo 495 > g2/blkio.weight
mkdir g3 && echo 495 > g3/blkio.weight

RUNTIME=10

(echo $BASHPID > g1/cgroup.procs &&
fio --readonly --name name1 --filename /dev/sdb \
--rw read --size 64k --bs 64k --time_based \
--runtime=$RUNTIME --offset=0k &> /dev/null)&

(echo $BASHPID > g2/cgroup.procs &&
fio --readonly --name name1 --filename /dev/sdb \
--rw read --size 64k --bs 64k --time_based \
--runtime=$RUNTIME --offset=64k &> /dev/null)&

(echo $BASHPID > g3/cgroup.procs &&
fio --readonly --name name1 --filename /dev/sdb \
--rw read --size 64k --bs 64k --time_based \
--runtime=$RUNTIME --offset=256k &> /dev/null)&

sleep $((RUNTIME+1))

for i in g1 g2 g3; do
echo ---- $i ----
cat $i/blkio.time
done

EOF
# ./cfq-merge-repro.sh
---- g1 ----
8:16 162
---- g2 ----
8:16 165
---- g3 ----
8:16 686

After applying the patch:

# ./cfq-merge-repro.sh
---- g1 ----
8:16 90
---- g2 ----
8:16 445
---- g3 ----
8:16 471

Signed-off-by: Tahsin Erdogan <tahsin@google.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

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block: add a separate operation type for secure erase

Instead of overloading the discard support with the REQ_SECURE flag.
Use the opportunity to rename the queue flag as well, and remove the
dead c

block: add a separate operation type for secure erase

Instead of overloading the discard support with the REQ_SECURE flag.
Use the opportunity to rename the queue flag as well, and remove the
dead checks for this flag in the RAID 1 and RAID 10 drivers that don't
claim support for secure erase.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>

show more ...

block: convert merge/insert code to check for REQ_OPs.

This patch converts the block layer merging code to use separate variables
for the operation and flags, and to check req_op for the REQ_OP.

Si

block: convert merge/insert code to check for REQ_OPs.

This patch converts the block layer merging code to use separate variables
for the operation and flags, and to check req_op for the REQ_OP.

Signed-off-by: Mike Christie <mchristi@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

show more ...

block, fs, mm, drivers: use bio set/get op accessors

This patch converts the simple bi_rw use cases in the block,
drivers, mm and fs code to set/get the bio operation using
bio_set_op_attrs/bio_op

block, fs, mm, drivers: use bio set/get op accessors

This patch converts the simple bi_rw use cases in the block,
drivers, mm and fs code to set/get the bio operation using
bio_set_op_attrs/bio_op

These should be simple one or two liner cases, so I just did them
in one patch. The next patches handle the more complicated
cases in a module per patch.

Signed-off-by: Mike Christie <mchristi@redhat.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

show more ...

block, drivers, cgroup: use op_is_write helper instead of checking for REQ_WRITE

We currently set REQ_WRITE/WRITE for all non READ IOs
like discard, flush, writesame, etc. In the next patches where

block, drivers, cgroup: use op_is_write helper instead of checking for REQ_WRITE

We currently set REQ_WRITE/WRITE for all non READ IOs
like discard, flush, writesame, etc. In the next patches where we
no longer set up the op as a bitmap, we will not be able to
detect a operation direction like writesame by testing if REQ_WRITE is
set.

This patch converts the drivers and cgroup to use the
op_is_write helper. This should just cover the simple
cases. I did dm, md and bcache in their own patches
because they were more involved.

Signed-off-by: Mike Christie <mchristi@redhat.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

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block: merge: get the 1st and last bvec via helpers

This patch applies the two introduced helpers to
figure out the 1st and last bvec.

Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Reviewed-by: C

block: merge: get the 1st and last bvec via helpers

This patch applies the two introduced helpers to
figure out the 1st and last bvec.

Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

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block: fix bio splitting on max sectors

After commit e36f62042880(block: split bios to maxpossible length),
bio can be splitted in the middle of a vector entry, then it
is easy to split out one bio

block: fix bio splitting on max sectors

After commit e36f62042880(block: split bios to maxpossible length),
bio can be splitted in the middle of a vector entry, then it
is easy to split out one bio which size isn't aligned with block
size, especially when the block size is bigger than 512.

This patch fixes the issue by making the max io size aligned
to logical block size.

Fixes: e36f62042880(block: split bios to maxpossible length)
Reported-by: Stefan Haberland <sth@linux.vnet.ibm.com>
Cc: Keith Busch <keith.busch@intel.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

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block: split bios to max possible length

This splits bio in the middle of a vector to form the largest possible
bio at the h/w's desired alignment, and guarantees the bio being split
will have some

block: split bios to max possible length

This splits bio in the middle of a vector to form the largest possible
bio at the h/w's desired alignment, and guarantees the bio being split
will have some data.

The criteria for splitting is changed from the max sectors to the h/w's
optimal sector alignment if it is provided. For h/w that advertise their
block storage's underlying chunk size, it's a big performance win to not
submit commands that cross them. If sector alignment is not provided,
this patch uses the max sectors as before.

This addresses the performance issue commit d380561113 attempted to
fix, but was reverted due to splitting logic error.

Signed-off-by: Keith Busch <keith.busch@intel.com>
Cc: Jens Axboe <axboe@fb.com>
Cc: Ming Lei <tom.leiming@gmail.com>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Cc: <stable@vger.kernel.org> # 4.4.x-
Signed-off-by: Jens Axboe <axboe@fb.com>

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Revert "block: Split bios on chunk boundaries"

This reverts commit d3805611130af9b911e908af9f67a3f64f4f0914.

If we end up splitting on the first segment, we don't adjust
the sector count. That resu

Revert "block: Split bios on chunk boundaries"

This reverts commit d3805611130af9b911e908af9f67a3f64f4f0914.

If we end up splitting on the first segment, we don't adjust
the sector count. That results in hitting a BUG() with attempting
to split 0 sectors.

As this is just a performance issue and not a regression since
4.3 release, let's just rever this change. That gives us more
time to test a real fix for 4.5, which would be marked for
stable anyway.

show more ...

block: Split bios on chunk boundaries

For h/w that advertise their block storage's underlying chunk size, it's
a big performance win to not submit commands that cross them. This patch
uses that crit

block: Split bios on chunk boundaries

For h/w that advertise their block storage's underlying chunk size, it's
a big performance win to not submit commands that cross them. This patch
uses that criteria if it is provided. If it is not provided, this patch
uses the max sectors as before.

Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

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block: add call to split trace point

There is a split tracepoint that is supposed to be called when
bio is splitted, and it was called in bio_split function until
commit 4b1faf931650d4a35b2a ("block

block: add call to split trace point

There is a split tracepoint that is supposed to be called when
bio is splitted, and it was called in bio_split function until
commit 4b1faf931650d4a35b2a ("block: Kill bio_pair_split()").
But now, no one reports splits, so this patch adds call to
trace_block_split back in blk_queue_split right after split.

Signed-off-by: Mike Krinkin <krinkin.m.u@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

show more ...

blk-merge: fix computing bio->bi_seg_front_size in case of single segment

When bio has only one physical segment, we should set bio's
bi_seg_front_size as the real(final) size of the single segment.

blk-merge: fix computing bio->bi_seg_front_size in case of single segment

When bio has only one physical segment, we should set bio's
bi_seg_front_size as the real(final) size of the single segment.

Fixes: 02e707424c2ea(blk-merge: fix blk_bio_segment_split)
Reported-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Tested-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

show more ...

blk-merge: warn if figured out segment number is bigger than nr_phys_segments

We had seen lots of reports of this kind issue, so add one
warnning in blk-merge, then it can be triggered easily and
av

blk-merge: warn if figured out segment number is bigger than nr_phys_segments

We had seen lots of reports of this kind issue, so add one
warnning in blk-merge, then it can be triggered easily and
avoid to depend on warning/bug from drivers.

Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

show more ...

blk-merge: fix blk_bio_segment_split

Commit bdced438acd83a(block: setup bi_phys_segments after
splitting) introduces function of computing bio->bi_phys_segments
during bio splitting.

Unfortunately

blk-merge: fix blk_bio_segment_split

Commit bdced438acd83a(block: setup bi_phys_segments after
splitting) introduces function of computing bio->bi_phys_segments
during bio splitting.

Unfortunately both bio->bi_seg_front_size and bio->bi_seg_back_size
arn't computed, so too many physical segments may be obtained
for one request since both the two are used to check if one segment
across two bios can be possible.

This patch fixes the issue by computing the two variables in
blk_bio_segment_split().

Fixes: bdced438acd83a(block: setup bi_phys_segments after splitting)
Reported-by: Michael Ellerman <mpe@ellerman.id.au>
Reported-by: Mark Salter <msalter@redhat.com>
Tested-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
Tested-by: Mark Salter <msalter@redhat.com>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

show more ...

block: fix segment split

Inside blk_bio_segment_split(), previous bvec pointer(bvprvp)
always points to the iterator local variable, which is obviously
wrong, so fix it by pointing to the local vari

block: fix segment split

Inside blk_bio_segment_split(), previous bvec pointer(bvprvp)
always points to the iterator local variable, which is obviously
wrong, so fix it by pointing to the local variable of 'bvprv'.

Fixes: 5014c311baa2b(block: fix bogus compiler warnings in blk-merge.c)
Cc: stable@kernel.org #4.3
Reported-by: Michael Ellerman <mpe@ellerman.id.au>
Reported-by: Mark Salter <msalter@redhat.com>
Tested-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
Tested-by: Mark Salter <msalter@redhat.com>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

show more ...

block: avoid to merge splitted bio

The splitted bio has been already too fat to merge, so mark it
as NOMERGE.

Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Ming Lei <ming.lei@canonical

block: avoid to merge splitted bio

The splitted bio has been already too fat to merge, so mark it
as NOMERGE.

Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

show more ...

block: setup bi_phys_segments after splitting

The number of bio->bi_phys_segments is always obtained
during bio splitting, so it is natural to setup it
just after bio splitting, then we can avoid to

block: setup bi_phys_segments after splitting

The number of bio->bi_phys_segments is always obtained
during bio splitting, so it is natural to setup it
just after bio splitting, then we can avoid to compute
nr_segment again during merge.

Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

show more ...

block: blk-merge: fast-clone bio when splitting rw bios

biovecs has become immutable since v3.13, so it isn't necessary
to allocate biovecs for the new cloned bios, then we can save
one extra biovec

block: blk-merge: fast-clone bio when splitting rw bios

biovecs has become immutable since v3.13, so it isn't necessary
to allocate biovecs for the new cloned bios, then we can save
one extra biovecs allocation/copy, and the allocation is often
not fixed-length and a bit more expensive.

For example, if the 'max_sectors_kb' of null blk's queue is set
as 16(32 sectors) via sysfs just for making more splits, this patch
can increase throught about ~70% in the sequential read test over
null_blk(direct io, bs: 1M).

Cc: Christoph Hellwig <hch@infradead.org>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Cc: Ming Lin <ming.l@ssi.samsung.com>
Cc: Dongsu Park <dpark@posteo.net>
Signed-off-by: Ming Lei <ming.lei@canonical.com>

This fixes a performance regression introduced by commit 54efd50bfd,
and allows us to take full advantage of the fact that we have immutable
bio_vecs. Hand applied, as it rejected violently with commit
5014c311baa2.

Signed-off-by: Jens Axboe <axboe@fb.com>

show more ...

block: Refuse request/bio merges with gaps in the integrity payload

If a driver sets the block queue virtual boundary mask, it means that
it cannot handle gaps so we must not allow those in the inte

block: Refuse request/bio merges with gaps in the integrity payload

If a driver sets the block queue virtual boundary mask, it means that
it cannot handle gaps so we must not allow those in the integrity
payload as well.

Signed-off-by: Sagi Grimberg <sagig@mellanox.com>

Fixed up by me to have duplicate integrity merge functions, depending
on whether block integrity is enabled or not. Fixes a compilations
issue with CONFIG_BLK_DEV_INTEGRITY unset.

Signed-off-by: Jens Axboe <axboe@fb.com>

show more ...

block: Check for gaps on front and back merges

We are checking for gaps to previous bio_vec, which can
only detect back merges gaps. Moreover, at the point where
we check for a gap, we don't know if

block: Check for gaps on front and back merges

We are checking for gaps to previous bio_vec, which can
only detect back merges gaps. Moreover, at the point where
we check for a gap, we don't know if we will attempt a back
or a front merge. Thus, check for gap to prev in a back merge
attempt and check for a gap to next in a front merge attempt.

Signed-off-by: Jens Axboe <axboe@fb.com>
[sagig: Minor rename change]
Signed-off-by: Sagi Grimberg <sagig@mellanox.com>

show more ...

block: fix bogus compiler warnings in blk-merge.c

The compiler can't figure out that bvprv is initialized whenever 'prev'
is set to 1 as well. Use a pointer to bvprv instead, setting it to NULL
init

block: fix bogus compiler warnings in blk-merge.c

The compiler can't figure out that bvprv is initialized whenever 'prev'
is set to 1 as well. Use a pointer to bvprv instead, setting it to NULL
initially, and get rid of the 'prev' tracking. This dumbs it down
enough that gcc is happy.

Signed-off-by: Jens Axboe <axboe@fb.com>

show more ...

blk: Fix bio_io_vec index when checking bvec gaps

Corrects a coding error from earlier patch.

Reported by: Sagi Grimberg <sagig@dev.mellanox.co.il>
Signed-off-by: Keith Busch <keith.busch@intel.com

blk: Fix bio_io_vec index when checking bvec gaps

Corrects a coding error from earlier patch.

Reported by: Sagi Grimberg <sagig@dev.mellanox.co.il>
Signed-off-by: Keith Busch <keith.busch@intel.com>
Fixes: 03100aada96f ("block: Replace SG_GAPS with new queue limits mask")
Signed-off-by: Jens Axboe <axboe@fb.com>

show more ...

block: Replace SG_GAPS with new queue limits mask

The SG_GAPS queue flag caused checks for bio vector alignment against
PAGE_SIZE, but the device may have different constraints. This patch
adds a qu

block: Replace SG_GAPS with new queue limits mask

The SG_GAPS queue flag caused checks for bio vector alignment against
PAGE_SIZE, but the device may have different constraints. This patch
adds a queue limits so a driver with such constraints can set to allow
requests that would have been unnecessarily split. The new gaps check
takes the request_queue as a parameter to simplify the logic around
invoking this function.

This new limit makes the queue flag redundant, so removing it and
all usage. Device-mappers will inherit the correct settings through
blk_stack_limits().

Signed-off-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>

show more ...

scatterlist: remove open coded sg_unmark_end instances

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
[hch: split from a larger patch by Dan]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Si

scatterlist: remove open coded sg_unmark_end instances

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
[hch: split from a larger patch by Dan]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>

show more ...

block: kill merge_bvec_fn() completely

As generic_make_request() is now able to handle arbitrarily sized bios,
it's no longer necessary for each individual block driver to define its
own ->merge_bve

block: kill merge_bvec_fn() completely

As generic_make_request() is now able to handle arbitrarily sized bios,
it's no longer necessary for each individual block driver to define its
own ->merge_bvec_fn() callback. Remove every invocation completely.

Cc: Jens Axboe <axboe@kernel.dk>
Cc: Lars Ellenberg <drbd-dev@lists.linbit.com>
Cc: drbd-user@lists.linbit.com
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Yehuda Sadeh <yehuda@inktank.com>
Cc: Sage Weil <sage@inktank.com>
Cc: Alex Elder <elder@kernel.org>
Cc: ceph-devel@vger.kernel.org
Cc: Alasdair Kergon <agk@redhat.com>
Cc: Mike Snitzer <snitzer@redhat.com>
Cc: dm-devel@redhat.com
Cc: Neil Brown <neilb@suse.de>
Cc: linux-raid@vger.kernel.org
Cc: Christoph Hellwig <hch@infradead.org>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Acked-by: NeilBrown <neilb@suse.de> (for the 'md' bits)
Acked-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
[dpark: also remove ->merge_bvec_fn() in dm-thin as well as
dm-era-target, and resolve merge conflicts]
Signed-off-by: Dongsu Park <dpark@posteo.net>
Signed-off-by: Ming Lin <ming.l@ssi.samsung.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

show more ...