If the next discard range is contiguous with the current range being
considered, it's cheaper to expand the current range than to append an
additional bio.
Signed-off-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The data segment gaps the block layer tracks doesn't apply to bio's that
don't have data. Skip calculating this to fix a NULL pointer access.
Fixes: 2f6b2565d4 ("block: accumulate memory segment gaps per bio")
Reported-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Yu Kuai <yukuai@fnnas.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The blk-mq dma iterator has an optimization for requests that align to
the device's iommu merge boundary. This boundary may be larger than the
device's virtual boundary, but the code had been depending on that queue
limit to know ahead of time if the request is guaranteed to align to
that optimization.
Rather than rely on that queue limit, which many devices may not report,
save the lowest set bit of any boundary gap between each segment in the
bio while checking the segments. The request stores the value for
merging and quickly checking per io if the request can use iova
optimizations.
Signed-off-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Despite its name, the block layer is fine with segments smaller that the
"min_segment_size" limit. The value is an optimization limit indicating
the largest segment that can be used without considering boundary
limits. Smaller segments can take a fast path, so give it a name that
reflects that: max_fast_segment_size.
Signed-off-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Currently, split bio will be chained to original bio, and original bio
will be resubmitted to the tail of current->bio_list, waiting for
split bio to be issued. However, if split bio get split again, the IO
order will be messed up. This problem, on the one hand, will cause
performance degradation, especially for mdraid with large IO size; on
the other hand, will cause write errors for zoned block devices[1].
For example, in raid456 IO will first be split by max_sector from
md_submit_bio(), and then later be split again by chunksize for internal
handling:
For example, assume max_sectors is 1M, and chunksize is 512k
1) issue a 2M IO:
bio issuing: 0+2M
current->bio_list: NULL
2) md_submit_bio() split by max_sector:
bio issuing: 0+1M
current->bio_list: 1M+1M
3) chunk_aligned_read() split by chunksize:
bio issuing: 0+512k
current->bio_list: 1M+1M -> 512k+512k
4) after first bio issued, __submit_bio_noacct() will contuine issuing
next bio:
bio issuing: 1M+1M
current->bio_list: 512k+512k
bio issued: 0+512k
5) chunk_aligned_read() split by chunksize:
bio issuing: 1M+512k
current->bio_list: 512k+512k -> 1536k+512k
bio issued: 0+512k
6) no split afterwards, finally the issue order is:
0+512k -> 1M+512k -> 512k+512k -> 1536k+512k
This behaviour will cause large IO read on raid456 endup to be small
discontinuous IO in underlying disks. Fix this problem by placing split
bio to the head of current->bio_list.
Test script: test on 8 disk raid5 with 64k chunksize
dd if=/dev/md0 of=/dev/null bs=4480k iflag=direct
Test results:
Before this patch
1) iostat results:
Device r/s rMB/s rrqm/s %rrqm r_await rareq-sz aqu-sz %util
md0 52430.00 3276.87 0.00 0.00 0.62 64.00 32.60 80.10
sd* 4487.00 409.00 2054.00 31.40 0.82 93.34 3.68 71.20
2) blktrace G stage:
8,0 0 486445 11.357392936 843 G R 14071424 + 128 [dd]
8,0 0 486451 11.357466360 843 G R 14071168 + 128 [dd]
8,0 0 486454 11.357515868 843 G R 14071296 + 128 [dd]
8,0 0 486468 11.357968099 843 G R 14072192 + 128 [dd]
8,0 0 486474 11.358031320 843 G R 14071936 + 128 [dd]
8,0 0 486480 11.358096298 843 G R 14071552 + 128 [dd]
8,0 0 486490 11.358303858 843 G R 14071808 + 128 [dd]
3) io seek for sdx:
Noted io seek is the result from blktrace D stage, statistic of:
ABS((offset of next IO) - (offset + len of previous IO))
Read|Write seek
cnt 55175, zero cnt 25079
>=(KB) .. <(KB) : count ratio |distribution |
0 .. 1 : 25079 45.5% |########################################|
1 .. 2 : 0 0.0% | |
2 .. 4 : 0 0.0% | |
4 .. 8 : 0 0.0% | |
8 .. 16 : 0 0.0% | |
16 .. 32 : 0 0.0% | |
32 .. 64 : 12540 22.7% |##################### |
64 .. 128 : 2508 4.5% |##### |
128 .. 256 : 0 0.0% | |
256 .. 512 : 10032 18.2% |################# |
512 .. 1024 : 5016 9.1% |######### |
After this patch:
1) iostat results:
Device r/s rMB/s rrqm/s %rrqm r_await rareq-sz aqu-sz %util
md0 87965.00 5271.88 0.00 0.00 0.16 61.37 14.03 90.60
sd* 6020.00 658.44 5117.00 45.95 0.44 112.00 2.68 86.50
2) blktrace G stage:
8,0 0 206296 5.354894072 664 G R 7156992 + 128 [dd]
8,0 0 206305 5.355018179 664 G R 7157248 + 128 [dd]
8,0 0 206316 5.355204438 664 G R 7157504 + 128 [dd]
8,0 0 206319 5.355241048 664 G R 7157760 + 128 [dd]
8,0 0 206333 5.355500923 664 G R 7158016 + 128 [dd]
8,0 0 206344 5.355837806 664 G R 7158272 + 128 [dd]
8,0 0 206353 5.355960395 664 G R 7158528 + 128 [dd]
8,0 0 206357 5.356020772 664 G R 7158784 + 128 [dd]
3) io seek for sdx
Read|Write seek
cnt 28644, zero cnt 21483
>=(KB) .. <(KB) : count ratio |distribution |
0 .. 1 : 21483 75.0% |########################################|
1 .. 2 : 0 0.0% | |
2 .. 4 : 0 0.0% | |
4 .. 8 : 0 0.0% | |
8 .. 16 : 0 0.0% | |
16 .. 32 : 0 0.0% | |
32 .. 64 : 7161 25.0% |############## |
BTW, this looks like a long term problem from day one, and large
sequential IO read is pretty common case like video playing.
And even with this patch, in this test case IO is merged to at most 128k
is due to block layer plug limit BLK_PLUG_FLUSH_SIZE, increase such
limit can get even better performance. However, we'll figure out how to do
this properly later.
[1] https://lore.kernel.org/all/e40b076d-583d-406b-b223-005910a9f46f@acm.org/
Fixes: d89d87965d ("When stacked block devices are in-use (e.g. md or dm), the recursive calls")
Reported-by: Tie Ren <tieren@fnnas.com>
Closes: https://lore.kernel.org/all/7dro5o7u5t64d6bgiansesjavxcuvkq5p2pok7dtwkav7b7ape@3isfr44b6352/
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Lots of checks are already done while submitting this bio the first
time, and there is no need to check them again when this bio is
resubmitted after split.
Hence open code should_fail_bio() and blk_throtl_bio() that are still
necessary from submit_bio_split_bioset().
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
No functional changes are intended, some drivers like mdraid will split
bio by internal processing, prepare to unify bio split codes.
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
bio->issue_time_ns is only used by blk-iolatency, which can only be
enabled for rq-based disk, hence it's not necessary to initialize
the time for bio-based disk.
Meanwhile, if bio is split by blk_crypto_fallback_split_bio_if_needed(),
the issue time is not initialized for new split bio, this can be fixed
as well.
Noted the next patch will optimize better that bio issue time will
only be used when blk-iolatency is really enabled by the disk.
Fixes: 488f6682c8 ("block: blk-crypto-fallback for Inline Encryption")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We're already iterating every segment, so check these for a valid IO
lengths at the same time. Individual segment lengths will not be checked
on passthrough commands. The read/write command segments must be sized
to the dma alignment.
Signed-off-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Previously, the block layer stored the requests in the plug list in
LIFO order. For this reason, blk_attempt_plug_merge() would check
just the head entry for a back merge attempt, and abort after that
unless requests for multiple queues existed in the plug list. If more
than one request is present in the plug list, this makes the one-shot
back merging less useful than before, as it'll always fail to find a
quick merge candidate.
Use the tail entry for the one-shot merge attempt, which is the last
added request in the list. If that fails, abort immediately unless
there are multiple queues available. If multiple queues are available,
then scan the list. Ideally the latter scan would be a backwards scan
of the list, but as it currently stands, the plug list is singly linked
and hence this isn't easily feasible.
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/linux-block/20250611121626.7252-1-abuehaze@amazon.com/
Reported-by: Hazem Mohamed Abuelfotoh <abuehaze@amazon.com>
Fixes: e70c301fae ("block: don't reorder requests in blk_add_rq_to_plug")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Pull block updates from Jens Axboe:
- Fixes for integrity handling
- NVMe pull request via Keith:
- Secure concatenation for TCP transport (Hannes)
- Multipath sysfs visibility (Nilay)
- Various cleanups (Qasim, Baruch, Wang, Chen, Mike, Damien, Li)
- Correct use of 64-bit BARs for pci-epf target (Niklas)
- Socket fix for selinux when used in containers (Peijie)
- MD pull request via Yu:
- fix recovery can preempt resync (Li Nan)
- fix md-bitmap IO limit (Su Yue)
- fix raid10 discard with REQ_NOWAIT (Xiao Ni)
- fix raid1 memory leak (Zheng Qixing)
- fix mddev uaf (Yu Kuai)
- fix raid1,raid10 IO flags (Yu Kuai)
- some refactor and cleanup (Yu Kuai)
- Series cleaning up and fixing bugs in the bad block handling code
- Improve support for write failure simulation in null_blk
- Various lock ordering fixes
- Fixes for locking for debugfs attributes
- Various ublk related fixes and improvements
- Cleanups for blk-rq-qos wait handling
- blk-throttle fixes
- Fixes for loop dio and sync handling
- Fixes and cleanups for the auto-PI code
- Block side support for hardware encryption keys in blk-crypto
- Various cleanups and fixes
* tag 'for-6.15/block-20250322' of git://git.kernel.dk/linux: (105 commits)
nvmet: replace max(a, min(b, c)) by clamp(val, lo, hi)
nvme-tcp: fix selinux denied when calling sock_sendmsg
nvmet: pci-epf: Always configure BAR0 as 64-bit
nvmet: Remove duplicate uuid_copy
nvme: zns: Simplify nvme_zone_parse_entry()
nvmet: pci-epf: Remove redundant 'flush_workqueue()' calls
nvmet-fc: Remove unused functions
nvme-pci: remove stale comment
nvme-fc: Utilise min3() to simplify queue count calculation
nvme-multipath: Add visibility for queue-depth io-policy
nvme-multipath: Add visibility for numa io-policy
nvme-multipath: Add visibility for round-robin io-policy
nvmet: add tls_concat and tls_key debugfs entries
nvmet-tcp: support secure channel concatenation
nvmet: Add 'sq' argument to alloc_ctrl_args
nvme-fabrics: reset admin connection for secure concatenation
nvme-tcp: request secure channel concatenation
nvme-keyring: add nvme_tls_psk_refresh()
nvme: add nvme_auth_derive_tls_psk()
nvme: add nvme_auth_generate_digest()
...
blk_rq_map_sg is maze of nested loops. Untangle it by creating an
iterator that returns [paddr,len] tuples for DMA mapping, and then
implement the DMA logic on top of this. This not only removes code
at the source level, but also generates nicer binary code:
$ size block/blk-merge.o.*
text data bss dec hex filename
10001 432 0 10433 28c1 block/blk-merge.o.new
10317 468 0 10785 2a21 block/blk-merge.o.old
Last but not least it will be used as a building block for a new
DMA mapping helper that doesn't rely on struct scatterlist.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20250106081609.798289-1-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Replace the semi-open coded request list helpers with a proper rq_list
type that mirrors the bio_list and has head and tail pointers. Besides
better type safety this actually allows to insert at the tail of the
list, which will be useful soon.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20241113152050.157179-5-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
max_zone_append_sectors differs from all other queue limits in that the
final value used is not stored in the queue_limits but needs to be
obtained using queue_limits_max_zone_append_sectors helper. This not
only adds (tiny) extra overhead to the I/O path, but also can be easily
forgotten in file system code.
Add a new max_hw_zone_append_sectors value to queue_limits which is
set by the driver, and calculate max_zone_append_sectors from that and
the other inputs in blk_validate_zoned_limits, similar to how
max_sectors is calculated to fix this.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20241104073955.112324-3-hch@lst.de
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/20241108154657.845768-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
For zoned devices, write zeroes must be split at the zone boundary
which is represented as chunk_sectors. For other uses like the
internally RAIDed NVMe devices it is probably at least useful.
Enhance get_max_io_size to know about write zeroes and use it in
bio_split_write_zeroes. Also add a comment about the seemingly
nonsensical zero max_write_zeroes limit.
Fixes: 885fa13f65 ("block: implement splitting of REQ_OP_WRITE_ZEROES bios")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/20241104062647.91160-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
max_zone_append_sectors differs from all other queue limits in that the
final value used is not stored in the queue_limits but needs to be
obtained using queue_limits_max_zone_append_sectors helper. This not
only adds (tiny) extra overhead to the I/O path, but also can be easily
forgotten in file system code.
Add a new max_hw_zone_append_sectors value to queue_limits which is
set by the driver, and calculate max_zone_append_sectors from that and
the other inputs in blk_validate_zoned_limits, similar to how
max_sectors is calculated to fix this.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20241104073955.112324-3-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
It's now just checking whether or not RQF_IO_STAT is set, so let's get
rid of it and just open-code the specific flag that is being checked.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Both types of merging when integrity data is used are miscounting the
segments:
Merging two requests wasn't accounting for the new segment count, so add
the "next" segment count to the first on a successful merge to ensure
this value is accurate.
Merging a bio into an existing request was double counting the bio's
segments, even if the merge failed later on. Move the segment accounting
to the end when the merge is successful.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Link: https://lore.kernel.org/r/20240913182854.2445457-4-kbusch@meta.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Currently REQ_OP_ZONE_APPEND is handled by the bio_split_rw case in
__bio_split_to_limits. This is harmful because REQ_OP_ZONE_APPEND
bios do not adhere to the soft max_limits value but instead use their
own capped version of max_hw_sectors, leading to incorrect splits that
later blow up in bio_split.
We still need the bio_split_rw logic to count nr_segs for blk-mq code,
so add a new wrapper that passes in the right limit, and turns any bio
that would need a split into an error as an additional debugging aid.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Tested-by: Hans Holmberg <hans.holmberg@wdc.com>
Reviewed-by: Hans Holmberg <hans.holmberg@wdc.com>
Link: https://lore.kernel.org/r/20240826173820.1690925-4-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The current setup with bio_may_exceed_limit and __bio_split_to_limits
is a bit of a mess.
Change it so that __bio_split_to_limits does all the work and is just
a variant of bio_split_to_limits that returns nr_segs. This is done
by inlining it and instead have the various bio_split_* helpers directly
submit the potentially split bios.
To support btrfs, the rw version has a lower level helper split out
that just returns the offset to split. This turns out to nicely clean
up the btrfs flow as well.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: David Sterba <dsterba@suse.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Tested-by: Hans Holmberg <hans.holmberg@wdc.com>
Reviewed-by: Hans Holmberg <hans.holmberg@wdc.com>
Link: https://lore.kernel.org/r/20240826173820.1690925-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Correct the parameter name in the comment of get_max_segment_size()
to fix following warning:-
block/blk-merge.c:220: warning: Function parameter or struct member 'len' not described in 'get_max_segment_size'
block/blk-merge.c:220: warning: Excess function parameter 'max_len' description in 'get_max_segment_size'
Signed-off-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/20240709045432.8688-1-kch@nvidia.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Add atomic write support, as follows:
- add helper functions to get request_queue atomic write limits
- report request_queue atomic write support limits to sysfs and update Doc
- support to safely merge atomic writes
- deal with splitting atomic writes
- misc helper functions
- add a per-request atomic write flag
New request_queue limits are added, as follows:
- atomic_write_hw_max is set by the block driver and is the maximum length
of an atomic write which the device may support. It is not
necessarily a power-of-2.
- atomic_write_max_sectors is derived from atomic_write_hw_max_sectors and
max_hw_sectors. It is always a power-of-2. Atomic writes may be merged,
and atomic_write_max_sectors would be the limit on a merged atomic write
request size. This value is not capped at max_sectors, as the value in
max_sectors can be controlled from userspace, and it would only cause
trouble if userspace could limit atomic_write_unit_max_bytes and the
other atomic write limits.
- atomic_write_hw_unit_{min,max} are set by the block driver and are the
min/max length of an atomic write unit which the device may support. They
both must be a power-of-2. Typically atomic_write_hw_unit_max will hold
the same value as atomic_write_hw_max.
- atomic_write_unit_{min,max} are derived from
atomic_write_hw_unit_{min,max}, max_hw_sectors, and block core limits.
Both min and max values must be a power-of-2.
- atomic_write_hw_boundary is set by the block driver. If non-zero, it
indicates an LBA space boundary at which an atomic write straddles no
longer is atomically executed by the disk. The value must be a
power-of-2. Note that it would be acceptable to enforce a rule that
atomic_write_hw_boundary_sectors is a multiple of
atomic_write_hw_unit_max, but the resultant code would be more
complicated.
All atomic writes limits are by default set 0 to indicate no atomic write
support. Even though it is assumed by Linux that a logical block can always
be atomically written, we ignore this as it is not of particular interest.
Stacked devices are just not supported either for now.
An atomic write must always be submitted to the block driver as part of a
single request. As such, only a single BIO must be submitted to the block
layer for an atomic write. When a single atomic write BIO is submitted, it
cannot be split. As such, atomic_write_unit_{max, min}_bytes are limited
by the maximum guaranteed BIO size which will not be required to be split.
This max size is calculated by request_queue max segments and the number
of bvecs a BIO can fit, BIO_MAX_VECS. Currently we rely on userspace
issuing a write with iovcnt=1 for pwritev2() - as such, we can rely on each
segment containing PAGE_SIZE of data, apart from the first+last, which each
can fit logical block size of data. The first+last will be LBS
length/aligned as we rely on direct IO alignment rules also.
New sysfs files are added to report the following atomic write limits:
- atomic_write_unit_max_bytes - same as atomic_write_unit_max_sectors in
bytes
- atomic_write_unit_min_bytes - same as atomic_write_unit_min_sectors in
bytes
- atomic_write_boundary_bytes - same as atomic_write_hw_boundary_sectors in
bytes
- atomic_write_max_bytes - same as atomic_write_max_sectors in bytes
Atomic writes may only be merged with other atomic writes and only under
the following conditions:
- total resultant request length <= atomic_write_max_bytes
- the merged write does not straddle a boundary
Helper function bdev_can_atomic_write() is added to indicate whether
atomic writes may be issued to a bdev. If a bdev is a partition, the
partition start must be aligned with both atomic_write_unit_min_sectors
and atomic_write_hw_boundary_sectors.
FSes will rely on the block layer to validate that an atomic write BIO
submitted will be of valid size, so add blk_validate_atomic_write_op_size()
for this purpose. Userspace expects an atomic write which is of invalid
size to be rejected with -EINVAL, so add BLK_STS_INVAL for this. Also use
BLK_STS_INVAL for when a BIO needs to be split, as this should mean an
invalid size BIO.
Flag REQ_ATOMIC is used for indicating an atomic write.
Co-developed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: John Garry <john.g.garry@oracle.com>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Link: https://lore.kernel.org/r/20240620125359.2684798-6-john.g.garry@oracle.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Currently, io_ticks is accounted based on sampling, specifically
update_io_ticks() will always account io_ticks by 1 jiffies from
bdev_start_io_acct()/blk_account_io_start(), and the result can be
inaccurate, for example(HZ is 250):
Test script:
fio -filename=/dev/sda -bs=4k -rw=write -direct=1 -name=test -thinktime=4ms
Test result: util is about 90%, while the disk is really idle.
This behaviour is introduced by commit 5b18b5a737 ("block: delete
part_round_stats and switch to less precise counting"), however, there
was a key point that is missed that this patch also improve performance
a lot:
Before the commit:
part_round_stats:
if (part->stamp != now)
stats |= 1;
part_in_flight()
-> there can be lots of task here in 1 jiffies.
part_round_stats_single()
__part_stat_add()
part->stamp = now;
After the commit:
update_io_ticks:
stamp = part->bd_stamp;
if (time_after(now, stamp))
if (try_cmpxchg())
__part_stat_add()
-> only one task can reach here in 1 jiffies.
Hence in order to account io_ticks precisely, we only need to know if
there are IO inflight at most once in one jiffies. Noted that for
rq-based device, iterating tags should not be used here because
'tags->lock' is grabbed in blk_mq_find_and_get_req(), hence
part_stat_lock_inc/dec() and part_in_flight() is used to trace inflight.
The additional overhead is quite little:
- per cpu add/dec for each IO for rq-based device;
- per cpu sum for each jiffies;
And it's verified by null-blk that there are no performance degration
under heavy IO pressure.
Fixes: 5b18b5a737 ("block: delete part_round_stats and switch to less precise counting")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20240509123717.3223892-2-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
With the block layer zone write plugging being automatically done for
any write operation to a zone of a zoned block device, a regular request
plugging handled through current->plug can only ever see at most a
single write request per zone. In such case, any potential reordering
of the plugged requests will be harmless. We can thus remove the special
casing for write operations to zones and have these requests plugged as
well. This allows removing the function blk_mq_plug and instead directly
using current->plug where needed.
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Tested-by: Hans Holmberg <hans.holmberg@wdc.com>
Tested-by: Dennis Maisenbacher <dennis.maisenbacher@wdc.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20240408014128.205141-29-dlemoal@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Zone write plugging implements a per-zone "plug" for write operations
to control the submission and execution order of write operations to
sequential write required zones of a zoned block device. Per-zone
plugging guarantees that at any time there is at most only one write
request per zone being executed. This mechanism is intended to replace
zone write locking which implements a similar per-zone write throttling
at the scheduler level, but is implemented only by mq-deadline.
Unlike zone write locking which operates on requests, zone write
plugging operates on BIOs. A zone write plug is simply a BIO list that
is atomically manipulated using a spinlock and a kblockd submission
work. A write BIO to a zone is "plugged" to delay its execution if a
write BIO for the same zone was already issued, that is, if a write
request for the same zone is being executed. The next plugged BIO is
unplugged and issued once the write request completes.
This mechanism allows to:
- Untangle zone write ordering from block IO schedulers. This allows
removing the restriction on using mq-deadline for writing to zoned
block devices. Any block IO scheduler, including "none" can be used.
- Zone write plugging operates on BIOs instead of requests. Plugged
BIOs waiting for execution thus do not hold scheduling tags and thus
are not preventing other BIOs from executing (reads or writes to
other zones). Depending on the workload, this can significantly
improve the device use (higher queue depth operation) and
performance.
- Both blk-mq (request based) zoned devices and BIO-based zoned devices
(e.g. device mapper) can use zone write plugging. It is mandatory
for the former but optional for the latter. BIO-based drivers can
use zone write plugging to implement write ordering guarantees, or
the drivers can implement their own if needed.
- The code is less invasive in the block layer and is mostly limited to
blk-zoned.c with some small changes in blk-mq.c, blk-merge.c and
bio.c.
Zone write plugging is implemented using struct blk_zone_wplug. This
structure includes a spinlock, a BIO list and a work structure to
handle the submission of plugged BIOs. Zone write plugs structures are
managed using a per-disk hash table.
Plugging of zone write BIOs is done using the function
blk_zone_write_plug_bio() which returns false if a BIO execution does
not need to be delayed and true otherwise. This function is called
from blk_mq_submit_bio() after a BIO is split to avoid large BIOs
spanning multiple zones which would cause mishandling of zone write
plugs. This ichange enables by default zone write plugging for any mq
request-based block device. BIO-based device drivers can also use zone
write plugging by expliclty calling blk_zone_write_plug_bio() in their
->submit_bio method. For such devices, the driver must ensure that a
BIO passed to blk_zone_write_plug_bio() is already split and not
straddling zone boundaries.
Only write and write zeroes BIOs are plugged. Zone write plugging does
not introduce any significant overhead for other operations. A BIO that
is being handled through zone write plugging is flagged using the new
BIO flag BIO_ZONE_WRITE_PLUGGING. A request handling a BIO flagged with
this new flag is flagged with the new RQF_ZONE_WRITE_PLUGGING flag.
The completion of BIOs and requests flagged trigger respectively calls
to the functions blk_zone_write_bio_endio() and
blk_zone_write_complete_request(). The latter function is used to
trigger submission of the next plugged BIO using the zone plug work.
blk_zone_write_bio_endio() does the same for BIO-based devices.
This ensures that at any time, at most one request (blk-mq devices) or
one BIO (BIO-based devices) is being executed for any zone. The
handling of zone write plugs using a per-zone plug spinlock maximizes
parallelism and device usage by allowing multiple zones to be writen
simultaneously without lock contention.
Zone write plugging ignores flush BIOs without data. Hovever, any flush
BIO that has data is always plugged so that the write part of the flush
sequence is serialized with other regular writes.
Given that any BIO handled through zone write plugging will be the only
BIO in flight for the target zone when it is executed, the unplugging
and submission of a BIO will have no chance of successfully merging with
plugged requests or requests in the scheduler. To overcome this
potential performance degradation, blk_mq_submit_bio() calls the
function blk_zone_write_plug_attempt_merge() to try to merge other
plugged BIOs with the one just unplugged and submitted. Successful
merging is signaled using blk_zone_write_plug_bio_merged(), called from
bio_attempt_back_merge(). Furthermore, to avoid recalculating the number
of segments of plugged BIOs to attempt merging, the number of segments
of a plugged BIO is saved using the new struct bio field
__bi_nr_segments. To avoid growing the size of struct bio, this field is
added as a union with the bio_cookie field. This is safe to do as
polling is always disabled for plugged BIOs.
When BIOs are plugged in a zone write plug, the device request queue
usage counter is always incremented. This reference is kept and reused
for blk-mq devices when the plugged BIO is unplugged and submitted
again using submit_bio_noacct_nocheck(). For this case, the unplugged
BIO is already flagged with BIO_ZONE_WRITE_PLUGGING and
blk_mq_submit_bio() proceeds directly to allocating a new request for
the BIO, re-using the usage reference count taken when the BIO was
plugged. This extra reference count is dropped in
blk_zone_write_plug_attempt_merge() for any plugged BIO that is
successfully merged. Given that BIO-based devices will not take this
path, the extra reference is dropped after a plugged BIO is unplugged
and submitted.
Zone write plugs are dynamically allocated and managed using a hash
table (an array of struct hlist_head) with RCU protection.
A zone write plug is allocated when a write BIO is received for the
zone and not freed until the zone is fully written, reset or finished.
To detect when a zone write plug can be freed, the write state of each
zone is tracked using a write pointer offset which corresponds to the
offset of a zone write pointer relative to the zone start. Write
operations always increment this write pointer offset. Zone reset
operations set it to 0 and zone finish operations set it to the zone
size.
If a write error happens, the wp_offset value of a zone write plug may
become incorrect and out of sync with the device managed write pointer.
This is handled using the zone write plug flag BLK_ZONE_WPLUG_ERROR.
The function blk_zone_wplug_handle_error() is called from the new disk
zone write plug work when this flag is set. This function executes a
report zone to update the zone write pointer offset to the current
value as indicated by the device. The disk zone write plug work is
scheduled whenever a BIO flagged with BIO_ZONE_WRITE_PLUGGING completes
with an error or when bio_zone_wplug_prepare_bio() detects an unaligned
write. Once scheduled, the disk zone write plugs work keeps running
until all zone errors are handled.
To match the new data structures used for zoned disks, the function
disk_free_zone_bitmaps() is renamed to the more generic
disk_free_zone_resources(). The function disk_init_zone_resources() is
also introduced to initialize zone write plugs resources when a gendisk
is allocated.
In order to guarantee that the user can simultaneously write up to a
number of zones equal to a device max active zone limit or max open zone
limit, zone write plugs are allocated using a mempool sized to the
maximum of these 2 device limits. For a device that does not have
active and open zone limits, 128 is used as the default mempool size.
If a change to the device active and open zone limits is detected, the
disk mempool is resized when blk_revalidate_disk_zones() is executed.
This commit contains contributions from Christoph Hellwig <hch@lst.de>.
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Tested-by: Hans Holmberg <hans.holmberg@wdc.com>
Tested-by: Dennis Maisenbacher <dennis.maisenbacher@wdc.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20240408014128.205141-8-dlemoal@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Restore support for passing data lifetime information from filesystems to
block drivers. This patch reverts commit b179c98f76 ("block: Remove
request.write_hint") and commit c75e707fe1 ("block: remove the
per-bio/request write hint").
This patch does not modify the size of struct bio because the new
bi_write_hint member fills a hole in struct bio. pahole reports the
following for struct bio on an x86_64 system with this patch applied:
/* size: 112, cachelines: 2, members: 20 */
/* sum members: 110, holes: 1, sum holes: 2 */
/* last cacheline: 48 bytes */
Reviewed-by: Kanchan Joshi <joshi.k@samsung.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20240202203926.2478590-7-bvanassche@acm.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
Once all I/O using a blk_crypto_key has completed, filesystems can call
blk_crypto_evict_key(). However, the block layer currently doesn't call
blk_crypto_put_keyslot() until the request is being freed, which happens
after upper layers have been told (via bio_endio()) the I/O has
completed. This causes a race condition where blk_crypto_evict_key()
can see 'slot_refs != 0' without there being an actual bug.
This makes __blk_crypto_evict_key() hit the
'WARN_ON_ONCE(atomic_read(&slot->slot_refs) != 0)' and return without
doing anything, eventually causing a use-after-free in
blk_crypto_reprogram_all_keys(). (This is a very rare bug and has only
been seen when per-file keys are being used with fscrypt.)
There are two options to fix this: either release the keyslot before
bio_endio() is called on the request's last bio, or make
__blk_crypto_evict_key() ignore slot_refs. Let's go with the first
solution, since it preserves the ability to report bugs (via
WARN_ON_ONCE) where a key is evicted while still in-use.
Fixes: a892c8d52c ("block: Inline encryption support for blk-mq")
Cc: stable@vger.kernel.org
Reviewed-by: Nathan Huckleberry <nhuck@google.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20230315183907.53675-2-ebiggers@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Pull block fixes from Jens Axboe:
- NVMe pull request via Christoph:
- Don't access released socket during error recovery (Akinobu
Mita)
- Bring back auto-removal of deleted namespaces during sequential
scan (Christoph Hellwig)
- Fix an error code in nvme_auth_process_dhchap_challenge (Dan
Carpenter)
- Show well known discovery name (Daniel Wagner)
- Add a missing endianess conversion in effects masking (Keith
Busch)
- Fix for a regression introduced in blk-rq-qos during init in this
merge window (Breno)
- Reorder a few fields in struct blk_mq_tag_set, eliminating a few
holes and shrinking it (Christophe)
- Remove redundant bdev_get_queue() NULL checks (Juhyung)
- Add sed-opal single user mode support flag (Luca)
- Remove SQE128 check in ublk as it isn't needed, saving some memory
(Ming)
- Op specific segment checking for cloned requests (Uday)
- Exclusive open partition scan fixes (Yu)
- Loop offset/size checking before assigning them in the device (Zhong)
- Bio polling fixes (me)
* tag 'block-6.3-2023-03-03' of git://git.kernel.dk/linux:
blk-mq: enforce op-specific segment limits in blk_insert_cloned_request
nvme-fabrics: show well known discovery name
nvme-tcp: don't access released socket during error recovery
nvme-auth: fix an error code in nvme_auth_process_dhchap_challenge()
nvme: bring back auto-removal of deleted namespaces during sequential scan
blk-iocost: Pass gendisk to ioc_refresh_params
nvme: fix sparse warning on effects masking
block: be a bit more careful in checking for NULL bdev while polling
block: clear bio->bi_bdev when putting a bio back in the cache
loop: loop_set_status_from_info() check before assignment
ublk: remove check IO_URING_F_SQE128 in ublk_ch_uring_cmd
block: remove more NULL checks after bdev_get_queue()
blk-mq: Reorder fields in 'struct blk_mq_tag_set'
block: fix scan partition for exclusively open device again
block: Revert "block: Do not reread partition table on exclusively open device"
sed-opal: add support flag for SUM in status ioctl
