From: Jan Kara <jack@suse.cz>
To: Jens Axboe <axboe@kernel.dk>
Cc: Christoph Hellwig <hch@infradead.org>,
<linux-block@vger.kernel.org>, Coly Li <colyli@suse.de>,
linux-bcache@vger.kernel.org, Jan Kara <jack@suse.cz>
Subject: [PATCH 2/2] bcache: Fix bcache device claiming
Date: Wed, 21 Jun 2023 18:23:27 +0200 [thread overview]
Message-ID: <20230621162333.30027-2-jack@suse.cz> (raw)
In-Reply-To: <20230621162024.29310-1-jack@suse.cz>
Commit 2736e8eeb0cc ("block: use the holder as indication for exclusive
opens") introduced a change that blkdev_put() has to get exclusive
holder of the bdev as an argument. However it overlooked that
register_bdev() and register_cache() overwrite the bdev->bd_holder field
in the block device to point to the real owning object which was not
available at the time we called blkdev_get_by_path(). Messing with bdev
internals like this is a layering violation and it also causes
blkdev_put() to issue warning about mismatching holders.
Fix bcache to reopen the block device with appropriate holder once it is
available which also restores the behavior that multiple bcache caches
cannot claim the same device which was also broken by commit
2736e8eeb0cc.
Fixes: 2736e8eeb0cc ("block: use the holder as indication for exclusive opens")
Signed-off-by: Jan Kara <jack@suse.cz>
---
drivers/md/bcache/super.c | 63 ++++++++++++++++++++++-----------------
1 file changed, 36 insertions(+), 27 deletions(-)
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 913dd94353b6..9738e8c0cbfc 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1369,7 +1369,7 @@ static void cached_dev_free(struct closure *cl)
put_page(virt_to_page(dc->sb_disk));
if (!IS_ERR_OR_NULL(dc->bdev))
- blkdev_put(dc->bdev, bcache_kobj);
+ blkdev_put(dc->bdev, dc);
wake_up(&unregister_wait);
@@ -1453,7 +1453,6 @@ static int register_bdev(struct cache_sb *sb, struct cache_sb_disk *sb_disk,
memcpy(&dc->sb, sb, sizeof(struct cache_sb));
dc->bdev = bdev;
- dc->bdev->bd_holder = dc;
dc->sb_disk = sb_disk;
if (cached_dev_init(dc, sb->block_size << 9))
@@ -2218,7 +2217,7 @@ void bch_cache_release(struct kobject *kobj)
put_page(virt_to_page(ca->sb_disk));
if (!IS_ERR_OR_NULL(ca->bdev))
- blkdev_put(ca->bdev, bcache_kobj);
+ blkdev_put(ca->bdev, ca);
kfree(ca);
module_put(THIS_MODULE);
@@ -2345,7 +2344,6 @@ static int register_cache(struct cache_sb *sb, struct cache_sb_disk *sb_disk,
memcpy(&ca->sb, sb, sizeof(struct cache_sb));
ca->bdev = bdev;
- ca->bdev->bd_holder = ca;
ca->sb_disk = sb_disk;
if (bdev_max_discard_sectors((bdev)))
@@ -2359,7 +2357,7 @@ static int register_cache(struct cache_sb *sb, struct cache_sb_disk *sb_disk,
* call blkdev_put() to bdev in bch_cache_release(). So we
* explicitly call blkdev_put() here.
*/
- blkdev_put(bdev, bcache_kobj);
+ blkdev_put(bdev, ca);
if (ret == -ENOMEM)
err = "cache_alloc(): -ENOMEM";
else if (ret == -EPERM)
@@ -2516,10 +2514,11 @@ static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
char *path = NULL;
struct cache_sb *sb;
struct cache_sb_disk *sb_disk;
- struct block_device *bdev;
- void *holder;
+ struct block_device *bdev, *bdev2;
+ void *holder = NULL;
ssize_t ret;
bool async_registration = false;
+ bool quiet = false;
#ifdef CONFIG_BCACHE_ASYNC_REGISTRATION
async_registration = true;
@@ -2548,24 +2547,9 @@ static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
ret = -EINVAL;
err = "failed to open device";
- bdev = blkdev_get_by_path(strim(path), BLK_OPEN_READ | BLK_OPEN_WRITE,
- bcache_kobj, NULL);
- if (IS_ERR(bdev)) {
- if (bdev == ERR_PTR(-EBUSY)) {
- dev_t dev;
-
- mutex_lock(&bch_register_lock);
- if (lookup_bdev(strim(path), &dev) == 0 &&
- bch_is_open(dev))
- err = "device already registered";
- else
- err = "device busy";
- mutex_unlock(&bch_register_lock);
- if (attr == &ksysfs_register_quiet)
- goto done;
- }
+ bdev = blkdev_get_by_path(strim(path), BLK_OPEN_READ, NULL, NULL);
+ if (IS_ERR(bdev))
goto out_free_sb;
- }
err = "failed to set blocksize";
if (set_blocksize(bdev, 4096))
@@ -2582,6 +2566,31 @@ static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
goto out_put_sb_page;
}
+ /* Now reopen in exclusive mode with proper holder */
+ bdev2 = blkdev_get_by_dev(bdev->bd_dev, BLK_OPEN_READ | BLK_OPEN_WRITE,
+ holder, NULL);
+ blkdev_put(bdev, NULL);
+ bdev = bdev2;
+ if (IS_ERR(bdev))
+ ret = PTR_ERR(bdev);
+ if (bdev == ERR_PTR(-EBUSY)) {
+ dev_t dev;
+
+ mutex_lock(&bch_register_lock);
+ if (lookup_bdev(strim(path), &dev) == 0 &&
+ bch_is_open(dev))
+ err = "device already registered";
+ else
+ err = "device busy";
+ mutex_unlock(&bch_register_lock);
+ if (attr == &ksysfs_register_quiet) {
+ quiet = true;
+ ret = size;
+ }
+ }
+ goto out_free_holder;
+ }
+
err = "failed to register device";
if (async_registration) {
@@ -2619,7 +2628,6 @@ static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
goto out_free_sb;
}
-done:
kfree(sb);
kfree(path);
module_put(THIS_MODULE);
@@ -2631,7 +2639,7 @@ static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
out_put_sb_page:
put_page(virt_to_page(sb_disk));
out_blkdev_put:
- blkdev_put(bdev, register_bcache);
+ blkdev_put(bdev, holder);
out_free_sb:
kfree(sb);
out_free_path:
@@ -2640,7 +2648,8 @@ static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
out_module_put:
module_put(THIS_MODULE);
out:
- pr_info("error %s: %s\n", path?path:"", err);
+ if (!quiet)
+ pr_info("error %s: %s\n", path?path:"", err);
return ret;
}
--
2.35.3
next prev parent reply other threads:[~2023-06-21 16:24 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-21 16:23 [PATCH 0/2] bcache: Fix block device claiming Jan Kara
2023-06-21 16:23 ` [PATCH 1/2] bcache: Alloc holder object before async registration Jan Kara
2023-06-21 17:56 ` Kent Overstreet
2023-06-22 10:09 ` Jan Kara
2023-06-22 12:05 ` Kent Overstreet
2023-06-22 15:14 ` Christoph Hellwig
2023-06-21 16:23 ` Jan Kara [this message]
2023-06-22 1:23 ` [PATCH 2/2] bcache: Fix bcache device claiming kernel test robot
2023-06-22 10:26 ` Jan Kara
2023-06-22 1:44 ` kernel test robot
2023-06-22 3:29 ` kernel test robot
2023-06-22 15:12 ` Christoph Hellwig
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