From: Dan Williams <dan.j.williams@intel.com>
Date: Sat, 15 Sep 2018 00:34:35 +0000 (-0700)
Subject: block: fix bdi vs gendisk lifetime mismatch
X-Git-Tag: v4.1.12-124.31.3~448
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=8bd274934987c2af04c2fe862009c026c5ba4910;p=users%2Fjedix%2Flinux-maple.git

block: fix bdi vs gendisk lifetime mismatch

Orabug: 28645416

The name for a bdi of a gendisk is derived from the gendisk's devt.
However, since the gendisk is destroyed before the bdi it leaves a
window where a new gendisk could dynamically reuse the same devt
while a bdi with the same name is still live.  Arrange for the bdi to hold a
reference against its "owner" disk device while it is registered.
Otherwise we can hit sysfs duplicate name collisions like the
following:

WARNING: CPU: 10 PID: 2078 at fs/sysfs/dir.c:31
sysfs_warn_dup+0x64/0x80
sysfs: cannot create duplicate filename
'/devices/virtual/bdi/259:1'

Hardware name: HP ProLiant DL580 Gen8, BIOS P79 05/06/2015
0000000000000286 0000000002c04ad5 ffff88006f24f970 ffffffff8134caec
ffff88006f24f9c0 0000000000000000 ffff88006f24f9b0 ffffffff8108c351
0000001f0000000c ffff88105d236000 ffff88105d1031e0 ffff8800357427f8
Call Trace:
 [<ffffffff8134caec>] dump_stack+0x63/0x87
 [<ffffffff8108c351>] __warn+0xd1/0xf0
 [<ffffffff8108c3cf>] warn_slowpath_fmt+0x5f/0x80
 [<ffffffff812a0d34>] sysfs_warn_dup+0x64/0x80
 [<ffffffff812a0e1e>] sysfs_create_dir_ns+0x7e/0x90
 [<ffffffff8134faaa>] kobject_add_internal+0xaa/0x320
 [<ffffffff81358d4e>] ? vsnprintf+0x34e/0x4d0
 [<ffffffff8134ff55>] kobject_add+0x75/0xd0
 [<ffffffff816e66b2>] ? mutex_lock+0x12/0x2f
 [<ffffffff8148b0a5>] device_add+0x125/0x610
 [<ffffffff8148b788>] device_create_groups_vargs+0xd8/0x100
 [<ffffffff8148b7cc>] device_create_vargs+0x1c/0x20
 [<ffffffff811b775c>] bdi_register+0x8c/0x180
 [<ffffffff811b7877>] bdi_register_dev+0x27/0x30
 [<ffffffff813317f5>] add_disk+0x175/0x4a0

Cc: <stable@vger.kernel.org>
Reported-by: Yi Zhang <yizhan@redhat.com>
Tested-by: Yi Zhang <yizhan@redhat.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Fixed up missing 0 return in bdi_register_owner().

Signed-off-by: Jens Axboe <axboe@fb.com>

(cherrypicked from commit df08c32ce3be5be138c1dbfcba203314a3a7cd6f)
Conflicts: mm/backing-dev.c
           include/linux/backing-dev.h

The patch breaks KABI as-is because of the introduction of a new "owner"
field in struct backing_dev_info. To work around that, use the
UEK_KABI_EXTEND() macro to wrap the "owner" filed with ifdef GENKSYMS.

Signed-off-by: Ashish Samant <ashish.samant@oracle.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>
---

diff --git a/block/genhd.c b/block/genhd.c
index 60db28598670..24fcb43e61ee 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -612,7 +612,7 @@ void add_disk(struct gendisk *disk)
 
 	/* Register BDI before referencing it from bdev */
 	bdi = &disk->queue->backing_dev_info;
-	bdi_register_dev(bdi, disk_devt(disk));
+	bdi_register_owner(bdi, disk_to_dev(disk));
 
 	blk_register_region(disk_devt(disk), disk->minors, NULL,
 			    exact_match, exact_lock, disk);
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index d87d8eced064..3cf1f7409a7c 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -19,6 +19,7 @@
 #include <linux/atomic.h>
 #include <linux/sysctl.h>
 #include <linux/workqueue.h>
+#include <linux/uek_kabi.h>
 
 struct page;
 struct device;
@@ -105,6 +106,7 @@ struct backing_dev_info {
 	struct dentry *debug_dir;
 	struct dentry *debug_stats;
 #endif
+	UEK_KABI_EXTEND(struct device *owner)
 };
 
 struct backing_dev_info *inode_to_bdi(struct inode *inode);
@@ -116,6 +118,7 @@ __printf(3, 4)
 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
 		const char *fmt, ...);
 int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev);
+int bdi_register_owner(struct backing_dev_info *bdi, struct device *owner);
 int __must_check bdi_setup_and_register(struct backing_dev_info *, char *);
 void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
 			enum wb_reason reason);
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 000e7b3b9896..d9ec4976f5f1 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -332,6 +332,20 @@ int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
 }
 EXPORT_SYMBOL(bdi_register_dev);
 
+int bdi_register_owner(struct backing_dev_info *bdi, struct device *owner)
+{
+	int rc;
+
+	rc = bdi_register(bdi, NULL, "%u:%u", MAJOR(owner->devt),
+			  MINOR(owner->devt));
+	if (rc)
+		return rc;
+	bdi->owner = owner;
+	get_device(owner);
+	return 0;
+}
+EXPORT_SYMBOL(bdi_register_owner);
+
 /*
  * Remove bdi from the global list and shutdown any threads we have running
  */
@@ -437,6 +451,11 @@ void bdi_destroy(struct backing_dev_info *bdi)
 		bdi->dev = NULL;
 	}
 
+	if (bdi->owner) {
+		put_device(bdi->owner);
+		bdi->owner = NULL;
+	}
+
 	for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
 		percpu_counter_destroy(&bdi->bdi_stat[i]);
 	fprop_local_destroy_percpu(&bdi->completions);