BMC/Intel-BMC/linux.git/block/bfq-cgroup.c, branch dev-5.7

block, bfq: invoke flush_idle_tree after reparent_active_queues in pd_offline

2020-03-21T20:31:03+00:00

In bfq_pd_offline(), the function bfq_flush_idle_tree() is invoked to flush the rb tree that contains all idle entities belonging to the pd (cgroup) being destroyed. In particular, bfq_flush_idle_tree() is invoked before bfq_reparent_active_queues(). Yet the latter may happen to add some entities to the idle tree. It happens if, in some of the calls to bfq_bfqq_move() performed by bfq_reparent_active_queues(), the queue to move is empty and gets expired. This commit simply reverses the invocation order between bfq_flush_idle_tree() and bfq_reparent_active_queues(). Tested-by: cki-project@redhat.com Signed-off-by: Paolo Valente Signed-off-by: Jens Axboe

block, bfq: make reparent_leaf_entity actually work only on leaf entities

2020-03-21T20:31:02+00:00

bfq_reparent_leaf_entity() reparents the input leaf entity (a leaf entity represents just a bfq_queue in an entity tree). Yet, the input entity is guaranteed to always be a leaf entity only in two-level entity trees. In this respect, because of the error fixed by commit 14afc5936197 ("block, bfq: fix overwrite of bfq_group pointer in bfq_find_set_group()"), all (wrongly collapsed) entity trees happened to actually have only two levels. After the latter commit, this does not hold any longer. This commit fixes this problem by modifying bfq_reparent_leaf_entity(), so that it searches an active leaf entity down the path that stems from the input entity. Such a leaf entity is guaranteed to exist when bfq_reparent_leaf_entity() is invoked. Tested-by: cki-project@redhat.com Signed-off-by: Paolo Valente Signed-off-by: Jens Axboe

block, bfq: turn put_queue into release_process_ref in __bfq_bic_change_cgroup

2020-03-21T20:31:00+00:00

A bfq_put_queue() may be invoked in __bfq_bic_change_cgroup(). The goal of this put is to release a process reference to a bfq_queue. But process-reference releases may trigger also some extra operation, and, to this goal, are handled through bfq_release_process_ref(). So, turn the invocation of bfq_put_queue() into an invocation of bfq_release_process_ref(). Tested-by: cki-project@redhat.com Signed-off-by: Paolo Valente Signed-off-by: Jens Axboe

block, bfq: move forward the getting of an extra ref in bfq_bfqq_move

2020-03-21T20:30:58+00:00

Commit ecedd3d7e199 ("block, bfq: get extra ref to prevent a queue from being freed during a group move") gets an extra reference to a bfq_queue before possibly deactivating it (temporarily), in bfq_bfqq_move(). This prevents the bfq_queue from disappearing before being reactivated in its new group. Yet, the bfq_queue may also be expired (i.e., its service may be stopped) before the bfq_queue is deactivated. And also an expiration may lead to a premature freeing. This commit fixes this issue by simply moving forward the getting of the extra reference already introduced by commit ecedd3d7e199 ("block, bfq: get extra ref to prevent a queue from being freed during a group move"). Reported-by: cki-project@redhat.com Tested-by: cki-project@redhat.com Signed-off-by: Paolo Valente Signed-off-by: Jens Axboe

block, bfq: fix overwrite of bfq_group pointer in bfq_find_set_group()

2020-03-06T14:00:58+00:00

The bfq_find_set_group() function takes as input a blkcg (which represents a cgroup) and retrieves the corresponding bfq_group, then it updates the bfq internal group hierarchy (see comments inside the function for why this is needed) and finally it returns the bfq_group. In the hierarchy update cycle, the pointer holding the correct bfq_group that has to be returned is mistakenly used to traverse the hierarchy bottom to top, meaning that in each iteration it gets overwritten with the parent of the current group. Since the update cycle stops at root's children (depth = 2), the overwrite becomes a problem only if the blkcg describes a cgroup at a hierarchy level deeper than that (depth > 2). In this case the root's child that happens to be also an ancestor of the correct bfq_group is returned. The main consequence is that processes contained in a cgroup at depth greater than 2 are wrongly placed in the group described above by BFQ. This commits fixes this problem by using a different bfq_group pointer in the update cycle in order to avoid the overwrite of the variable holding the original group reference. Reported-by: Kwon Je Oh Signed-off-by: Carlo Nonato Signed-off-by: Paolo Valente Signed-off-by: Jens Axboe

block, bfq: get a ref to a group when adding it to a service tree

2020-02-03T13:58:15+00:00

BFQ schedules generic entities, which may represent either bfq_queues or groups of bfq_queues. When an entity is inserted into a service tree, a reference must be taken, to make sure that the entity does not disappear while still referred in the tree. Unfortunately, such a reference is mistakenly taken only if the entity represents a bfq_queue. This commit takes a reference also in case the entity represents a group. Tested-by: Oleksandr Natalenko Tested-by: Chris Evich Signed-off-by: Paolo Valente Signed-off-by: Jens Axboe

block, bfq: remove ifdefs from around gets/puts of bfq groups

2020-02-03T13:58:15+00:00

ifdefs around gets and puts of bfq groups reduce readability, remove them. Tested-by: Oleksandr Natalenko Reported-by: Jens Axboe Signed-off-by: Paolo Valente Signed-off-by: Jens Axboe

block, bfq: extend incomplete name of field on_st

2020-02-03T13:58:15+00:00

The flag on_st in the bfq_entity data structure is true if the entity is on a service tree or is in service. Yet the name of the field, confusingly, does not mention the second, very important case. Extend the name to mention the second case too. Tested-by: Oleksandr Natalenko Signed-off-by: Paolo Valente Signed-off-by: Jens Axboe

block, bfq: get extra ref to prevent a queue from being freed during a group move

2020-02-03T13:58:15+00:00

In bfq_bfqq_move(), the bfq_queue, say Q, to be moved to a new group may happen to be deactivated in the scheduling data structures of the source group (and then activated in the destination group). If Q is referred only by the data structures in the source group when the deactivation happens, then Q is freed upon the deactivation. This commit addresses this issue by getting an extra reference before the possible deactivation, and releasing this extra reference after Q has been moved. Tested-by: Chris Evich Tested-by: Oleksandr Natalenko Signed-off-by: Paolo Valente Signed-off-by: Jens Axboe

bfq-iosched: Ensure bio->bi_blkg is valid before using it

2019-12-05T14:10:09+00:00

bio->bi_blkg will be NULL when the issue of the request has bypassed the block layer as shown in the following oops: Internal error: Oops: 96000005 [#1] SMP CPU: 17 PID: 2996 Comm: scsi_id Not tainted 5.4.0 #4 Call trace: percpu_counter_add_batch+0x38/0x4c8 bfqg_stats_update_legacy_io+0x9c/0x280 bfq_insert_requests+0xbac/0x2190 blk_mq_sched_insert_request+0x288/0x670 blk_execute_rq_nowait+0x140/0x178 blk_execute_rq+0x8c/0x140 sg_io+0x604/0x9c0 scsi_cmd_ioctl+0xe38/0x10a8 scsi_cmd_blk_ioctl+0xac/0xe8 sd_ioctl+0xe4/0x238 blkdev_ioctl+0x590/0x20e0 block_ioctl+0x60/0x98 do_vfs_ioctl+0xe0/0x1b58 ksys_ioctl+0x80/0xd8 __arm64_sys_ioctl+0x40/0x78 el0_svc_handler+0xc4/0x270 so ensure its validity before using it. Fixes: fd41e60331b1 ("bfq-iosched: stop using blkg->stat_bytes and ->stat_ios") Signed-off-by: Hou Tao Signed-off-by: Jens Axboe