user/sven/linux.git/include/linux/elevator.h, branch v4.9.243

elevator: fix truncation of icq_cache_name

2018-11-10T15:42:48Z

[ Upstream commit 9bd2bbc01d17ddd567cc0f81f77fe1163e497462 ] gcc 7.1 reports the following warning: block/elevator.c: In function ‘elv_register’: block/elevator.c:898:5: warning: ‘snprintf’ output may be truncated before the last format character [-Wformat-truncation=] "%s_io_cq", e->elevator_name); ^~~~~~~~~~ block/elevator.c:897:3: note: ‘snprintf’ output between 7 and 22 bytes into a destination of size 21 snprintf(e->icq_cache_name, sizeof(e->icq_cache_name), ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ "%s_io_cq", e->elevator_name); ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The bug is that the name of the icq_cache is 6 characters longer than the elevator name, but only ELV_NAME_MAX + 5 characters were reserved for it --- so in the case of a maximum-length elevator name, the 'q' character in "_io_cq" would be truncated by snprintf(). Fix it by reserving ELV_NAME_MAX + 6 characters instead. Signed-off-by: Eric Biggers Reviewed-by: Bart Van Assche Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin

block: do not merge requests without consulting with io scheduler

2016-07-21T03:35:12Z

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 Signed-off-by: Jens Axboe

block: prepare elevator to use REQ_OPs.

2016-06-07T19:41:38Z

This patch converts the elevator code to use separate variables for the operation and flags, and to check req_op for the REQ_OP. Signed-off-by: Mike Christie Reviewed-by: Christoph Hellwig Reviewed-by: Hannes Reinecke Signed-off-by: Jens Axboe

cfq-iosched: fix the setting of IOPS mode on SSDs

2015-06-10T14:01:20Z

A previous commit wanted to make CFQ default to IOPS mode on non-rotational storage, however it did so when the queue was initialized and the non-rotational flag is only set later on in the probe. Add an elevator hook that gets called off the add_disk() path, at that point we know that feature probing has finished, and we can reliably check for the various flags that drivers can set. Fixes: 41c0126b ("block: Make CFQ default to IOPS mode on SSDs") Tested-by: Romain Francoise Signed-off-by: Jens Axboe

Revert "block: add __init to elv_register"

2014-06-22T22:34:11Z

This reverts commit b5097e956a4d2919ee248d6481e4204c5568ed5c. The original commit is buggy, we do use the registration functions at runtime, for instance when loading IO schedulers through sysfs. Reported-by: Damien Wyart

block: remove elv_abort_queue and blk_abort_flushes

2014-06-11T21:31:21Z

elv_abort_queue has no callers, and blk_abort_flushes is only called by elv_abort_queue. Signed-off-by: Christoph Hellwig Signed-off-by: Jens Axboe

block: add __init to elv_register

2014-06-10T19:13:11Z

elv_register is only called by elevator init functions: __init cfq_init __init deadline_init __init noop_init Cc: Andrew Morton Signed-off-by: Fabian Frederick Signed-off-by: Jens Axboe

block: Remove useless IPI struct initialization

2014-02-24T22:46:38Z

rq_fifo_clear() reset the csd.list through INIT_LIST_HEAD for no clear purpose. The csd.list doesn't need to be initialized as a list head because it's only ever used as a list node. Lets remove this useless initialization. Reviewed-by: Jan Kara Cc: Andrew Morton Cc: Christoph Hellwig Cc: Ingo Molnar Cc: Jan Kara Cc: Jens Axboe Signed-off-by: Frederic Weisbecker Signed-off-by: Jens Axboe

block: Stop abusing csd.list for fifo_time

2014-02-24T22:46:32Z

Block layer currently abuses rq->csd.list.next for storing fifo_time. That is a terrible hack and completely unnecessary as well. Union achieves the same space saving in a cleaner way. Signed-off-by: Jan Kara Cc: Andrew Morton Cc: Christoph Hellwig Cc: Ingo Molnar Cc: Jens Axboe Signed-off-by: Frederic Weisbecker Signed-off-by: Jens Axboe

elevator: Fix a race in elevator switching

2013-07-03T11:25:24Z

There's a race between elevator switching and normal io operation. Because the allocation of struct elevator_queue and struct elevator_data don't in a atomic operation.So there are have chance to use NULL ->elevator_data. For example: Thread A: Thread B blk_queu_bio elevator_switch spin_lock_irq(q->queue_block) elevator_alloc elv_merge elevator_init_fn Because call elevator_alloc, it can't hold queue_lock and the ->elevator_data is NULL.So at the same time, threadA call elv_merge and nedd some info of elevator_data.So the crash happened. Move the elevator_alloc into func elevator_init_fn, it make the operations in a atomic operation. Using the follow method can easy reproduce this bug 1:dd if=/dev/sdb of=/dev/null 2:while true;do echo noop > scheduler;echo deadline > scheduler;done The test method also use this method. Signed-off-by: Jianpeng Ma Signed-off-by: Jens Axboe