kernel/linux.git/drivers/md/raid5.h, branch v6.1.168

md/raid5: Cleanup prototype of raid5_get_active_stripe()

2022-09-22T07:05:04+00:00

Drop the three bools in the prototype of raid5_get_active_stripe() and replace them with a flags parameter. At the same time, drop the distinction with __raid5_get_active_stripe(). Suggested-by: Christoph Hellwig Signed-off-by: Logan Gunthorpe Signed-off-by: Song Liu

md/raid5: Drop extern on function declarations in raid5.h

2022-09-22T07:05:04+00:00

externs should not be used in function declarations, so clean those up. Signed-off-by: Logan Gunthorpe Signed-off-by: Song Liu

md/raid5: Ensure batch_last is released before sleeping for quiesce

2022-08-03T03:08:53+00:00

A race condition exists where if raid5_quiesce() is called in the middle of a request that has set batch_last, it will deadlock. batch_last will hold a reference to a stripe when raid5_quiesce() is called. This will cause the next raid5_get_active_stripe() call to sleep waiting for the quiesce to finish, but the raid5_quiesce() thread will wait for active_stripes to go to zero which will never happen because request thread is waiting for the quiesce to stop. Fix this by creating a special __raid5_get_active_stripe() function which takes the request context and clears the last_batch before sleeping. While we're at it, change the arguments of raid5_get_active_stripe() to bools. Fixes: 3312e6c887fe ("md/raid5: Keep a reference to last stripe_head for batch") Reported-by: David Sloan Signed-off-by: Logan Gunthorpe Signed-off-by: Song Liu Signed-off-by: Jens Axboe

md/raid5: Add __rcu annotation to struct disk_info

2022-04-25T21:00:36+00:00

rdev and replacement are protected in some circumstances with rcu_dereference and synchronize_rcu (in raid5_remove_disk()). However, they were not annotated with __rcu so a sparse warning is emitted for every rcu_dereference() call. Add the __rcu annotation and fix up the initialization with RCU_INIT_POINTER, all pointer modifications with rcu_assign_pointer(), a few cases where the pointer value is tested with rcu_access_pointer() and one case where READ_ONCE() is used instead of rcu_dereference(), a case in print_raid5_conf() that should have rcu_dereference() and rcu_read_[un]lock() calls. Additional sparse issues will be fixed up in further commits. Signed-off-by: Logan Gunthorpe Reviewed-by: Christoph Hellwig Signed-off-by: Song Liu

md/raid5: Un-nest struct raid5_percpu definition

2022-04-25T21:00:36+00:00

Sparse reports many warnings of the form: drivers/md/raid5.c:1476:16: warning: dereference of noderef expression This is because all struct raid5_percpu definitions get marked as __percpu when really only the pointer in r5conf should have that annotation. Fix this by moving the defnition of raid5_precpu out of the definition of struct r5conf. Signed-off-by: Logan Gunthorpe Reviewed-by: Christoph Hellwig Signed-off-by: Song Liu

md/raid5: play nice with PREEMPT_RT

2022-01-06T16:37:02+00:00

raid_run_ops() relies on the implicitly disabled preemption for its percpu ops, although this is really about CPU locality. This breaks RT semantics as it can take regular (and thus sleeping) spinlocks, such as stripe_lock. Add a local_lock such that non-RT does not change and continues to be just map to preempt_disable/enable, but makes RT happy as the region will use a per-CPU spinlock and thus be preemptible and still guarantee CPU locality. Signed-off-by: Davidlohr Bueso Signed-off-by: Song Liu

md/raid5: let multiple devices of stripe_head share page

2020-09-24T23:44:44+00:00

In current implementation, grow_buffers() uses alloc_page() to allocate the buffers for each stripe_head, i.e. allocate a page for each dev[i] in stripe_head. After setting stripe_size as a configurable value by writing sysfs entry, it means that we always allocate 64K buffers, but just use 4K of them when stripe_size is 4K in 64KB arm64. To avoid wasting memory, we try to let multiple sh->dev share one real page. That means, multiple sh->dev[i].page will point to the only page with different offset. Example of 64K PAGE_SIZE and 4K stripe_size as following: 64K PAGE_SIZE +---+---+---+---+------------------------------+ | | | | | | | | | | +-+-+-+-+-+-+-+-+------------------------------+ ^ ^ ^ ^ | | | +----------------------------+ | | | | | | +-------------------+ | | | | | | +----------+ | | | | | | +-+ | | | | | | | +-----+-----+------+-----+------+-----+------+------+ sh | offset(0) | offset(4K) | offset(8K) | offset(12K) | + +-----------+------------+------------+-------------+ +----> dev[0].page dev[1].page dev[2].page dev[3].page A new 'pages' array will be added into stripe_head to record shared page used by this stripe_head. Allocate them when grow_buffers() and free them when shrink_buffers(). After trying to share page, the users of sh->dev[i].page need to take care of the related page offset: page of issued bio and page passed to xor compution functions. But thanks for previous different page offset supported. Here, we just need to set correct dev[i].offset. Signed-off-by: Yufen Yu Signed-off-by: Song Liu

md/raid5: add a new member of offset into r5dev

2020-09-24T23:44:44+00:00

Add a new member of offset into struct r5dev. It indicates the offset of related dev[i].page. For now, since each device have a privated page, the value is always 0. Thus, we set offset as 0 when allcate page in grow_buffers() and resize_stripes(). To support following different page offset, we try to use the page offset rather than '0' directly for async_memcpy() and ops_run_io(). We try to support different page offset for xor compution functions in the following. To avoid repeatly allocate a new array each time, we add a memory region into scribble buffer to record offset. No functional change. Signed-off-by: Yufen Yu Signed-off-by: Song Liu

Merge tag 'locking-urgent-2020-08-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2020-08-11T02:07:44+00:00

Pull locking updates from Thomas Gleixner: "A set of locking fixes and updates: - Untangle the header spaghetti which causes build failures in various situations caused by the lockdep additions to seqcount to validate that the write side critical sections are non-preemptible. - The seqcount associated lock debug addons which were blocked by the above fallout. seqcount writers contrary to seqlock writers must be externally serialized, which usually happens via locking - except for strict per CPU seqcounts. As the lock is not part of the seqcount, lockdep cannot validate that the lock is held. This new debug mechanism adds the concept of associated locks. sequence count has now lock type variants and corresponding initializers which take a pointer to the associated lock used for writer serialization. If lockdep is enabled the pointer is stored and write_seqcount_begin() has a lockdep assertion to validate that the lock is held. Aside of the type and the initializer no other code changes are required at the seqcount usage sites. The rest of the seqcount API is unchanged and determines the type at compile time with the help of _Generic which is possible now that the minimal GCC version has been moved up. Adding this lockdep coverage unearthed a handful of seqcount bugs which have been addressed already independent of this. While generally useful this comes with a Trojan Horse twist: On RT kernels the write side critical section can become preemtible if the writers are serialized by an associated lock, which leads to the well known reader preempts writer livelock. RT prevents this by storing the associated lock pointer independent of lockdep in the seqcount and changing the reader side to block on the lock when a reader detects that a writer is in the write side critical section. - Conversion of seqcount usage sites to associated types and initializers" * tag 'locking-urgent-2020-08-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (25 commits) locking/seqlock, headers: Untangle the spaghetti monster locking, arch/ia64: Reduce header dependencies by moving XTP bits into the new header x86/headers: Remove APIC headers from seqcount: More consistent seqprop names seqcount: Compress SEQCNT_LOCKNAME_ZERO() seqlock: Fold seqcount_LOCKNAME_init() definition seqlock: Fold seqcount_LOCKNAME_t definition seqlock: s/__SEQ_LOCKDEP/__SEQ_LOCK/g hrtimer: Use sequence counter with associated raw spinlock kvm/eventfd: Use sequence counter with associated spinlock userfaultfd: Use sequence counter with associated spinlock NFSv4: Use sequence counter with associated spinlock iocost: Use sequence counter with associated spinlock raid5: Use sequence counter with associated spinlock vfs: Use sequence counter with associated spinlock timekeeping: Use sequence counter with associated raw spinlock xfrm: policy: Use sequence counters with associated lock netfilter: nft_set_rbtree: Use sequence counter with associated rwlock netfilter: conntrack: Use sequence counter with associated spinlock sched: tasks: Use sequence counter with associated spinlock ...

raid5: Use sequence counter with associated spinlock

2020-07-29T14:14:27+00:00

A sequence counter write side critical section must be protected by some form of locking to serialize writers. A plain seqcount_t does not contain the information of which lock must be held when entering a write side critical section. Use the new seqcount_spinlock_t data type, which allows to associate a spinlock with the sequence counter. This enables lockdep to verify that the spinlock used for writer serialization is held when the write side critical section is entered. If lockdep is disabled this lock association is compiled out and has neither storage size nor runtime overhead. Signed-off-by: Ahmed S. Darwish Signed-off-by: Peter Zijlstra (Intel) Acked-by: Song Liu Link: https://lkml.kernel.org/r/20200720155530.1173732-20-a.darwish@linutronix.de