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authorByungchul Park <byungchul.park@lge.com>2017-10-25 11:56:05 +0300
committerIngo Molnar <mingo@kernel.org>2017-10-26 08:54:17 +0300
commite319e1fbd9d42420ab6eec0bfd75eb9ad7ca63b1 (patch)
tree8bb9027d1cc2a7cc6153e20f916fb035f79b53eb
parentfd1a5b04dfb899f84ddeb8acdaea6b98283df1e5 (diff)
downloadlinux-e319e1fbd9d42420ab6eec0bfd75eb9ad7ca63b1.tar.xz
block, locking/lockdep: Assign a lock_class per gendisk used for wait_for_completion()
Darrick posted the following warning and Dave Chinner analyzed it: > ====================================================== > WARNING: possible circular locking dependency detected > 4.14.0-rc1-fixes #1 Tainted: G W > ------------------------------------------------------ > loop0/31693 is trying to acquire lock: > (&(&ip->i_mmaplock)->mr_lock){++++}, at: [<ffffffffa00f1b0c>] xfs_ilock+0x23c/0x330 [xfs] > > but now in release context of a crosslock acquired at the following: > ((complete)&ret.event){+.+.}, at: [<ffffffff81326c1f>] submit_bio_wait+0x7f/0xb0 > > which lock already depends on the new lock. > > the existing dependency chain (in reverse order) is: > > -> #2 ((complete)&ret.event){+.+.}: > lock_acquire+0xab/0x200 > wait_for_completion_io+0x4e/0x1a0 > submit_bio_wait+0x7f/0xb0 > blkdev_issue_zeroout+0x71/0xa0 > xfs_bmapi_convert_unwritten+0x11f/0x1d0 [xfs] > xfs_bmapi_write+0x374/0x11f0 [xfs] > xfs_iomap_write_direct+0x2ac/0x430 [xfs] > xfs_file_iomap_begin+0x20d/0xd50 [xfs] > iomap_apply+0x43/0xe0 > dax_iomap_rw+0x89/0xf0 > xfs_file_dax_write+0xcc/0x220 [xfs] > xfs_file_write_iter+0xf0/0x130 [xfs] > __vfs_write+0xd9/0x150 > vfs_write+0xc8/0x1c0 > SyS_write+0x45/0xa0 > entry_SYSCALL_64_fastpath+0x1f/0xbe > > -> #1 (&xfs_nondir_ilock_class){++++}: > lock_acquire+0xab/0x200 > down_write_nested+0x4a/0xb0 > xfs_ilock+0x263/0x330 [xfs] > xfs_setattr_size+0x152/0x370 [xfs] > xfs_vn_setattr+0x6b/0x90 [xfs] > notify_change+0x27d/0x3f0 > do_truncate+0x5b/0x90 > path_openat+0x237/0xa90 > do_filp_open+0x8a/0xf0 > do_sys_open+0x11c/0x1f0 > entry_SYSCALL_64_fastpath+0x1f/0xbe > > -> #0 (&(&ip->i_mmaplock)->mr_lock){++++}: > up_write+0x1c/0x40 > xfs_iunlock+0x1d0/0x310 [xfs] > xfs_file_fallocate+0x8a/0x310 [xfs] > loop_queue_work+0xb7/0x8d0 > kthread_worker_fn+0xb9/0x1f0 > > Chain exists of: > &(&ip->i_mmaplock)->mr_lock --> &xfs_nondir_ilock_class --> (complete)&ret.event > > Possible unsafe locking scenario by crosslock: > > CPU0 CPU1 > ---- ---- > lock(&xfs_nondir_ilock_class); > lock((complete)&ret.event); > lock(&(&ip->i_mmaplock)->mr_lock); > unlock((complete)&ret.event); > > *** DEADLOCK *** The warning is a false positive, caused by the fact that all wait_for_completion()s in submit_bio_wait() are waiting with the same lock class. However, some bios have nothing to do with others, for example in the case of loop devices, there's no direct connection between the bios of an upper device and the bios of a lower device(=loop device). The safest way to assign different lock classes to different devices is to do it for each gendisk. In other words, this patch assigns a lockdep_map per gendisk and uses it when initializing completion in submit_bio_wait(). Analyzed-by: Dave Chinner <david@fromorbit.com> Reported-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Byungchul Park <byungchul.park@lge.com> Reviewed-by: Jens Axboe <axboe@kernel.dk> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: amir73il@gmail.com Cc: axboe@kernel.dk Cc: david@fromorbit.com Cc: hch@infradead.org Cc: idryomov@gmail.com Cc: johan@kernel.org Cc: johannes.berg@intel.com Cc: kernel-team@lge.com Cc: linux-block@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org Cc: linux-mm@kvack.org Cc: linux-xfs@vger.kernel.org Cc: oleg@redhat.com Cc: tj@kernel.org Link: http://lkml.kernel.org/r/1508921765-15396-10-git-send-email-byungchul.park@lge.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r--block/bio.c2
-rw-r--r--block/genhd.c10
-rw-r--r--include/linux/genhd.h22
3 files changed, 23 insertions, 11 deletions
diff --git a/block/bio.c b/block/bio.c
index 5e901bfc0576..cc60213e56d8 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -935,7 +935,7 @@ static void submit_bio_wait_endio(struct bio *bio)
*/
int submit_bio_wait(struct bio *bio)
{
- DECLARE_COMPLETION_ONSTACK(done);
+ DECLARE_COMPLETION_ONSTACK_MAP(done, bio->bi_disk->lockdep_map);
bio->bi_private = &done;
bio->bi_end_io = submit_bio_wait_endio;
diff --git a/block/genhd.c b/block/genhd.c
index dd305c65ffb0..630c0da6cfcf 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1354,13 +1354,7 @@ dev_t blk_lookup_devt(const char *name, int partno)
}
EXPORT_SYMBOL(blk_lookup_devt);
-struct gendisk *alloc_disk(int minors)
-{
- return alloc_disk_node(minors, NUMA_NO_NODE);
-}
-EXPORT_SYMBOL(alloc_disk);
-
-struct gendisk *alloc_disk_node(int minors, int node_id)
+struct gendisk *__alloc_disk_node(int minors, int node_id)
{
struct gendisk *disk;
struct disk_part_tbl *ptbl;
@@ -1411,7 +1405,7 @@ struct gendisk *alloc_disk_node(int minors, int node_id)
}
return disk;
}
-EXPORT_SYMBOL(alloc_disk_node);
+EXPORT_SYMBOL(__alloc_disk_node);
struct kobject *get_disk(struct gendisk *disk)
{
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index ea652bfcd675..19d18710546a 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -206,6 +206,7 @@ struct gendisk {
#endif /* CONFIG_BLK_DEV_INTEGRITY */
int node_id;
struct badblocks *bb;
+ struct lockdep_map lockdep_map;
};
static inline struct gendisk *part_to_disk(struct hd_struct *part)
@@ -590,8 +591,7 @@ extern void __delete_partition(struct percpu_ref *);
extern void delete_partition(struct gendisk *, int);
extern void printk_all_partitions(void);
-extern struct gendisk *alloc_disk_node(int minors, int node_id);
-extern struct gendisk *alloc_disk(int minors);
+extern struct gendisk *__alloc_disk_node(int minors, int node_id);
extern struct kobject *get_disk(struct gendisk *disk);
extern void put_disk(struct gendisk *disk);
extern void blk_register_region(dev_t devt, unsigned long range,
@@ -615,6 +615,24 @@ extern ssize_t part_fail_store(struct device *dev,
const char *buf, size_t count);
#endif /* CONFIG_FAIL_MAKE_REQUEST */
+#define alloc_disk_node(minors, node_id) \
+({ \
+ static struct lock_class_key __key; \
+ const char *__name; \
+ struct gendisk *__disk; \
+ \
+ __name = "(gendisk_completion)"#minors"("#node_id")"; \
+ \
+ __disk = __alloc_disk_node(minors, node_id); \
+ \
+ if (__disk) \
+ lockdep_init_map(&__disk->lockdep_map, __name, &__key, 0); \
+ \
+ __disk; \
+})
+
+#define alloc_disk(minors) alloc_disk_node(minors, NUMA_NO_NODE)
+
static inline int hd_ref_init(struct hd_struct *part)
{
if (percpu_ref_init(&part->ref, __delete_partition, 0,