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dbe3ece128
DM currently has a statically allocated bio that it uses to issue empty
flushes. It doesn't submit this bio, it just uses it for maintaining
state while setting up clones. Multiple users can access this bio at the
same time. This wasn't previously an issue, even if it was a bit iffy,
but with the blkg associations it can become one.
We setup the blkg association, then clone bio's and submit, then remove
the blkg assocation again. But since we can have multiple tasks doing
this at the same time, against multiple blkg's, then we can either lose
references to a blkg, or put it twice. The latter causes complaints on
the percpu ref being <= 0 when released, and can cause use-after-free as
well. Ming reports that xfstest generic/475 triggers this:
------------[ cut here ]------------
percpu ref (blkg_release) <= 0 (0) after switching to atomic
WARNING: CPU: 13 PID: 0 at lib/percpu-refcount.c:155 percpu_ref_switch_to_atomic_rcu+0x2c9/0x4a0
Switch to just using an on-stack bio for this, and get rid of the
embedded bio.
Fixes: 5cdf2e3fea ("blkcg: associate blkg when associating a device")
Reported-by: Ming Lei <ming.lei@redhat.com>
Tested-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
138 lines
2.9 KiB
C
138 lines
2.9 KiB
C
/*
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* Internal header file _only_ for device mapper core
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*
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* Copyright (C) 2016 Red Hat, Inc. All rights reserved.
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*
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* This file is released under the LGPL.
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*/
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#ifndef DM_CORE_INTERNAL_H
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#define DM_CORE_INTERNAL_H
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#include <linux/kthread.h>
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#include <linux/ktime.h>
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#include <linux/blk-mq.h>
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#include <trace/events/block.h>
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#include "dm.h"
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#define DM_RESERVED_MAX_IOS 1024
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struct dm_kobject_holder {
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struct kobject kobj;
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struct completion completion;
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};
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/*
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* DM core internal structure that used directly by dm.c and dm-rq.c
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* DM targets must _not_ deference a mapped_device to directly access its members!
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*/
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struct mapped_device {
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struct mutex suspend_lock;
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struct mutex table_devices_lock;
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struct list_head table_devices;
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/*
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* The current mapping (struct dm_table *).
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* Use dm_get_live_table{_fast} or take suspend_lock for
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* dereference.
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*/
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void __rcu *map;
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unsigned long flags;
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/* Protect queue and type against concurrent access. */
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struct mutex type_lock;
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enum dm_queue_mode type;
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int numa_node_id;
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struct request_queue *queue;
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atomic_t holders;
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atomic_t open_count;
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struct dm_target *immutable_target;
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struct target_type *immutable_target_type;
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char name[16];
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struct gendisk *disk;
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struct dax_device *dax_dev;
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/*
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* A list of ios that arrived while we were suspended.
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*/
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struct work_struct work;
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wait_queue_head_t wait;
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spinlock_t deferred_lock;
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struct bio_list deferred;
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void *interface_ptr;
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/*
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* Event handling.
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*/
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wait_queue_head_t eventq;
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atomic_t event_nr;
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atomic_t uevent_seq;
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struct list_head uevent_list;
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spinlock_t uevent_lock; /* Protect access to uevent_list */
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/* the number of internal suspends */
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unsigned internal_suspend_count;
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/*
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* io objects are allocated from here.
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*/
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struct bio_set io_bs;
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struct bio_set bs;
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/*
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* Processing queue (flush)
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*/
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struct workqueue_struct *wq;
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/*
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* freeze/thaw support require holding onto a super block
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*/
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struct super_block *frozen_sb;
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/* forced geometry settings */
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struct hd_geometry geometry;
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/* kobject and completion */
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struct dm_kobject_holder kobj_holder;
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struct block_device *bdev;
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struct dm_stats stats;
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/* for blk-mq request-based DM support */
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struct blk_mq_tag_set *tag_set;
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bool init_tio_pdu:1;
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struct srcu_struct io_barrier;
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};
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void disable_write_same(struct mapped_device *md);
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void disable_write_zeroes(struct mapped_device *md);
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static inline struct completion *dm_get_completion_from_kobject(struct kobject *kobj)
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{
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return &container_of(kobj, struct dm_kobject_holder, kobj)->completion;
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}
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unsigned __dm_get_module_param(unsigned *module_param, unsigned def, unsigned max);
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static inline bool dm_message_test_buffer_overflow(char *result, unsigned maxlen)
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{
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return !maxlen || strlen(result) + 1 >= maxlen;
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}
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extern atomic_t dm_global_event_nr;
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extern wait_queue_head_t dm_global_eventq;
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void dm_issue_global_event(void);
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#endif
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